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The Arkive
 
|| Year Gamma: London: Tuesday: July 03: 2018 ||
First Published: September 24: 2015
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Astrophysics Arkive Year Alpha and Year Beta

 

Astronomers Find Nearby Stars That are Among the Oldest in Our Galaxy

 

|| November 25: 2017: Georgia State University News || ά. Astronomers have discovered some of the oldest stars in our Milky Way galaxy by determining their locations and velocities, according to a study led by scientists at Georgia State University. Just like humans, stars have a life span: birth, youth, adulthood, senior and death. This study focused on old or 'senior citizen' stars, also, known as, cool sub-dwarfs, that are much older and cooler in temperature than the sun. The Milky Way is nearly 14 billion years old and its oldest stars developed in the early stage of the galaxy’s formation, making them about six to nine billion years old.

They’re found in the halo, a roughly spherical component of the galaxy, that formed first, in which old stars move in orbits, that are highly elongated and tilted. Younger stars in the Milky Way rotate together along the galaxy’s disc in roughly circular orbits, much like horses on a merry-go-round. In this study, published in the November 2017 edition of The Astronomical Journal, astronomers conducted a census of our solar neighbourhood to identify how many young, adult and old stars are present. They targeted stars out to a distance of 200 light years, which is relatively nearby considering the galaxy is more than 100,000 light years across.

A light year is how far light can travel in one year. This is farther than the traditional horizon for the region of space that is referred to as 'the solar neighbourhood', which is about 80 light years in radius. “The reason my horizon is more distant is that there are not a lot of senior citizens, old stars in our solar neighbourhood.” said Dr. Wei-Chun Jao, Lead Author of the study and Research Scientist in the Department of Physics and Astronomy at Georgia State. “There are plenty of adult stars in our solar neighbourhood, but there’s not a lot of senior citizens, so we have to reach farther away in the galaxy to find them.”

The astronomers first observed the stars over many years with the 0.9 metre telescope at the United State’s Cerro Tololo Inter-American Observatory in the foothills of the Chilean Andes. They used a technique called astrometry to measure the stars’ positions and were able to determine the stars’ motions across the sky, their distances and whether or not each star had a hidden companion orbiting it.

The team’s work increased the known population of old stars in our solar neighborhood by 25 percent. Among the new sub-dwarfs, the researchers discovered two old binary stars, even though older stars are typically found to be alone, rather than in pairs. “I identified two new possible double stars, called binaries.” Dr Jao said. “It’s rare for senior citizens to have companions. Old folks tend to live by themselves. I then used NASA’s Hubble Space Telescope to detect both stars in one of the binaries and measured the separation between them, which will allow us to measure their masses.”

Dr Jao, also, outlined two methods to identify these rare old stars. One method uses stars’ locations on a fundamental map of stellar astronomy, known as, the Hertzsprung-Russell:H-R Diagram. This is a classic technique that places the old stars below the sequence of dwarf stars such as the sun on the H-R Diagram, hence, the name sub-dwarfs.”

The authors then took a careful look at one particular characteristic of known sub-dwarf stars, how fast they move across the sky. “Every star moves across the sky.” Dr Jao said. “They don’t stay still. They move in three dimensions, with a few stars moving directly toward or away from us, but most moving tangentially across the sky. In my research, I’ve found that if a star has a tangential velocity faster than 200 kilometres per second, it has to be old. So, based on their movements in our galaxy, I can evaluate whether a star is an old sub-dwarf or not. In general, the older a star is, the faster it moves.”

They applied the tangential velocity cut off and compared stars in the sub-dwarf region of the H-R diagram to other existing star databases to identify an additional 29 previously unidentified old star candidates.In 2018, results from the European Space Agency’s Gaia mission, which is measuring accurate positions and distances for millions of stars in the Milky Way, will make finding older stars much easier for astronomers.

Determining the distance of stars is now very labour intensive and requires a lot of telescope time and patience. Because the Gaia mission will provide a much larger sample size, Dr Jao says that the limited sample of sub-dwarfs will grow and the rarest of these rare stars, binary sub-dwarfs, will be revealed.

''Finding old stars could, also, lead to the discovery of new planets.'' Dr Jao said. “Maybe, we can find some ancient civilisations around these old stars.” Dr Jao said. “Maybe, these stars have some planets around them, that we don’t know about.”

Co-authors of the study include Dr Todd J. Henry and Dr Philip A. Ianna of the RECONS Institute, Dr. Jennifer G. Winters of the Harvard-Smithsonian Centre for Astrophysics, Dr. John P. Subasavage of the United States Naval Observatory, Dr. Adric R. Riedel of the Space Telescope Science Institute and graduate student Ms Michele L. Silverstein of Georgia State. The researchers have been visiting astronomers at Cerro Tololo Inter-American Observatory.

The study is supported by Georgia State, the SMARTS Consortium that operates four telescopes in Chile, the National Science Foundation and the Space Telescope Science Institute, which operates the Hubble Space Telescope for NASA.
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The Paper

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The Chemical Make-Up of the Sun and the Perseus Cluster of Galaxies is Similar

 

|| November 15: 2017 || ά. It appears that the hemical make-ups of the Sun and a cluster of galaxies are similar. The observations made by the Soft X-ray Spectrometer:SXS flown on the X-ray astronomical satellite ASTRO-H Hitomi, show that the proportions of iron-peak elements in the Perseus cluster are nearly identical to those measured in the Sun, unlike previously believed. The new research results suggest that the solar abundance of the chemical elements represents the average values of the neighbouring universe.

In addition, this study provides new insights into the mechanism of Type Ia supernova explosions, which are thought to be the major producers of the iron-peak elements. The SXS developed jointly by NASA and the Japan Aerospace Exploration Agency:JAXA and their partners in Europe has provided an unprecedented detail of chemical make-ups of the hot gas in the neighbouring universe.  The results are published in Nature online on November 13. A cluster of galaxies contains hundreds of galaxies orbiting within hot, higher than millions of degrees Kelvin, plasma.

From the beginning of the universe, the hot plasma in the cluster preserves the elements produced in the stars and supernova explosions, indicating that the hot plasma in a cluster can give the average chemical abundance in the current universe. Supernova explosions are categorised into several types. Of these, Type Ia supernova explosions are estimated to comprise 10%-40% of the total number of supernova explosions and are thought to be responsible for producing the majority of the iron-peak elements, including, chromium, manganese, iron and nickel.

Different mechanisms of Type Ia explosions result in different abundance ratios of the iron-peak elements. Therefore, the chemical make-up of the iron-peak elements assists us in understanding the mechanism of Type Ia explosions and their progenitors.

Hot plasma in the clusters of galaxies has been intensively investigated to derive its chemical abundances. However, previous estimations are disputed because existing instruments did not have sufficient spectral resolution and the characteristic X-ray emission of nickel is mixed with the strong characteristic X-ray emission of iron. This hampers the accurate measurements of the abundances of nickel and iron.

A research team led by Hiroya Yamaguchi, University of Maryland and Goddard NASA and Kyoko Matsushita, Tokyo University of Science, analysed data from the centre of the Perseus cluster observed by ASTRO-H and successfully estimated the abundances the iron-peak elements based on the individual strengths of their characteristic X-rays.

The unprecedented high-energy resolution of SXS enabled the resolution of the characteristic X-rays of iron and nickel. Moreover, the research team was able to detect weak chromium and manganese emission lines. The analysis showed that the abundance ratios of silicon, sulfur, argon, calcium, chromium, manganese, iron and nickel were all same as those of the Sun despite these abundance ratios being believed to be higher than the solar value. ω.

The Paper: Solar Abundance Ratios of the Iron-Peak Elements in the Perseus Cluster: Authors: Hitomi collaboration: Responsible author: Hiroya Yamaguchi, Kyoko Matsushita: doi: 10.1038/nature24301

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Every Second Around 50 Trillion Neutrinos From the Sun Pass Through a Human Body: They are the Neutrinos and the Anti-Neutrinos: And Yet They Matter: For The Matter: For The Anti-Matter: For the Making Up and Functioning of the Universe

 The inside of Super-Kamiokande. Image: T2K



|| August 07: 2017: University of Liverpool News || ά. New results from the T2K experiment, which the University of Liverpool is a key partner in, have shown a difference in the way neutrinos and antineutrinos behave, which could help us understand why there is so much matter in the universe, but very little antimatter. The results of the study of neutrino oscillation suggest there could be a difference, or asymmetry, between the behaviour of matter and antimatter. Neutrinos are fundamental particles, that make up our Universe and are among the least understood entities. Yet, every second, around 50 trillion neutrinos from the Sun pass through your body.

Understanding whether neutrinos and antineutrinos behave differently is important, because if all types of matter and antimatter behave the same way, they should have completely wiped each other out shortly after the Big Bang. To explore the changes in neutrinos, known as oscillations, the T2K experiment fires a beam, which can switch from neutrinos to antineutrinos, from the J-PARC laboratory on the eastern coast of Japan. When the beam reaches the Super-Kamiokande detector, 295km away, scientists then look for a difference in the oscillations of neutrinos and anti-neutrinos.

The results indicate a high rate of electron neutrino appearances compared to electron antineutrinos, higher than first expected. Scientists and engineers from the University are heavily involved in the T2K experiment. They designed and constructed a subsystem of the Near Detector:ECAL, which, at 75 tones, is the largest detector ever constructed in the West for an experiment in the Far East. They, also, have responsibilities in running the experiment and analysing the data.

Professor Christos Touramanis, Head of the Liverpool Neutrino group in the University’s Department of Physics, said, “This is very exiting news. T2K was our group’s first major project in this most exciting area of fundamental research.

We led the construction of the photon detector subsystem and we have been leading science exploitation since 2010 with Dr Neil McCauley and Dr Costas Andreopoulos of the Department of Physics, having multiple major roles of responsibility and a large number of outstanding postgraduate students and PDRAs.

The new result offers tantalising hints that new major discovery is around the corner and will be achieved in our next generation of billion-dollar mega-projects in neutrino oscillations, DUNE in the USA and Hyper-K in Japan, where Liverpool, also, has very visible leadership.”

Dr Morgan Wascko, international co-spokesperson for the T2K experiment from Imperial College, said, “The current T2K result shows a fascinating hint that there’s an asymmetry between the behaviour of neutrinos and antineutrinos, in other words, an asymmetry between the behaviour of matter and antimatter.

We now need to collect more data to enhance the significance of our observed asymmetry.” Although, this work is promising, there are still systematic uncertainties, so the T2K team is designing an upgrade to the detector to enhance its sensitivities.

T2K is part-funded by the Science and Technology Facilities Council:STFC.
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The Finding Magnetic: The First-Time Three Dimensional Imaging of Internal Magnetic Patterns

The two PSI-scientists Claire Donnelly and Laura Heyderman and . Image: Paul Scherrer Institute:Markus Fischer


|| July 22: 2017: Paul Scherrer Institute News: Laura Hennemann Writing || ά. Magnets are found in motors, in energy production and in data storage. A deeper understanding of the basic properties of magnetic materials could, therefore, impact our everyday technology. A study by Scientists at the Paul Scherrer Institute:PSI in Switzerland, the ETH Zurich and the University of Glasgow has the potential to further this understanding. The researchers have, for the first time, made visible the directions of the magnetisation inside an object thicker than ever before in three-D and down to details ten thousand times smaller than a millimetre, 100 nanometres.

They were able to map the three dimensional arrangement of the magnetic moments. These can be thought of as tiny magnetic compass needles inside the material, that collectively define its magnetic structure. The scientists achieved their visualisation inside a gadolinium-cobalt magnet, using an experimental imaging technique, called, hard X-ray magnetic tomography, which was developed at PSI. The result showed intriguing intertwining patterns and, within them, so-called, Bloch points. At a Bloch point, the magnetic needles abruptly change their direction. Bloch points were predicted, theoretically, in 1965 but have only now been observed directly with these new measurements. The researchers published their study in the renowned scientific journal Nature.

Laura Heyderman, Claire Donnelly and Sebastian Gliga are part of a team of scientists who for the first time have succeeded in imaging the
internal magnetic structure of a three-D object. Image: Paul Scherrer Institute:Markus Fischer

The studied object was a micrometre-sized pillar, thousandth of a millimetre in diameter, made of the material gadolinium-cobalt, which acts like a ferromagnet. Within it, the scientists visualised the magnetic patterns, that occur on a scale ten thousand times smaller than a millimetre, in other words, the smallest detail they could make visible in their three-D images was around 100 nanometres. The sophisticated imaging was achieved by the use of hard X-ray magnetic tomography, that was newly developed at PSI in the course of this proof-of-principle study.

''Up to now, imaging magnetism and magnetic patterns at this small scale could only be done in thin films or on the surfaces of objects.'' explains Professor Laura Heyderman, Principal Investigator of the study, researcher at PSI and Professor at ETH Zurich. ''We really feel like we are diving inside the magnetic material, seeing and understanding the three-D arrangement of the tiny magnetic compass needles. These tiny needles ‘feel’ each other, and hence, are not oriented randomly, but instead, form well-defined patterns throughout the magnetic object.''

Swirling internal magnetic structure. A section of the investigated sample, which is a gadolinium-cobalt pillar of diameter 0.005 millimetres
05 micrometres, is shown. With magnetic tomography, scientists determined its internal magnetic structure. Here, the magnetisation is
represented by arrows for a horizontal slice within the pillar. In addition, the colour of the arrows indicate whether they are pointing
upwards, orange or downwards, purple. Graphics: Paul Scherrer Institute:Claire Donnelly

''The scientists quickly realised that the magnetic patterns consisted of tangled fundamental magnetic structures: They recognised domains, in other words, regions of homogenous magnetisation and domain walls, the boundaries separating two different domains. They, also, observed magnetic vortices, which have a structure analogous to that of tornadoes and all of these structures intertwined to create a complex and unique pattern. Seeing these basic and well-known structures come together in a complex three-D network made sense and was very beautiful and rewarding.'' says Ms Claire Donnelly, First Author of the study.

''One specific kind of pattern stood out and gave additional significance to the scientists’ results: a pair of magnetic singularities, so-called, Bloch points. Bloch points contain an infinitesimally small region, within which, the magnetic compass needles abruptly change their direction. Singularities, in general, have fascinated scientists in a variety of research fields.

A vertical slice of the internal magnetic structure of a sample section. The sample is 0.005 millimetres, 05 micrometres, in diameter and the section shown here is
0.0036 millimetres, 03.6 micrometres,  high. The internal magnetic structure is represented by arrows for a vertical slice within it. In addition, the colour
of the arrows indicate whether they are pointing towards, orange or away from the viewer, purple. Graphics: Paul Scherrer Institute:Claire Donnelly

Well known examples are black holes in space. In ferromagnets, the magnetisation can, generally,  be considered continuous on the nanoscale. At these singularities, however, this description breaks down.'' says Mr Sebastian Gliga of the University of Glasgow and visiting scientist at PSI. Bloch points constitute monopoles of the magnetisation, and although, they were first predicted over 60 years ago, they have never been directly observed.

The experimental technique of magnetic X-ray tomography employed in this study draws on a basic principle from computer tomography:CT. Similar to medical CT scans, many X-ray images of the sample are taken one after the other from many different directions with a small angle in-between adjacent images. The measurements were carried out at the cSAXS beamline of the synchrotron light source SLS at PSI using advanced instrumentation for X-ray nanotomography under the OMNY project and a recently developed imaging technique, called, ptychography.

Employing computer calculations and a novel reconstruction algorithm, developed at PSI, all of the data collected this way was combined to form the final three-D map of the magnetisation.

''The scientists employed so-called, ‘hard’ X-rays from the SLS at PSI. In comparison with ‘soft’ X-rays, hard X-rays have higher energy. Lower energy soft X-rays have already very successfully been used to achieve a similar map of the magnetic moments.'' Ms Claire Donnelly explains.

''But soft X-rays hardly penetrate such samples so you can only use them to see the magnetisation of a thin film or at the surface of a bulk object. In order to really dive inside their magnet, the PSI scientists chose hard X-rays of higher energy, at the price of obtaining a much weaker signal: Many people did not believe that we would be able to achieve this three-D magnetic imaging with hard X-rays.'' Professor Laura Heyderman recalls.

Representation of a Bloch point which the scientists found in their data. A Bloch point contains a magnetic singularity at
which the magnetisation abruptly changes its direction. Within the Bloch point shown here, this change of direction
is from upward pointing magnetic needles, visualised by arrows, to downward pointing ones. This singularity
is surrounded by a swirling magnetisation pattern which is analogous to the structure of a tornado.
Graphics: Paul Scherrer Institute:Claire Donnelly


The researchers see their achievement as a contribution to a deeper understanding of the basic properties of magnetic materials. Moreover, the ability to image inside magnets could be applied to many of today’s technological problems: Magnets are found in motors, in energy production and in data storage, creating better magnets, thus, has a huge potential of improving many every-day applications.

About PSI: The Paul Scherrer Institute PSI develops, builds and operates large, complex research facilities and makes them available to the national and international research community. The institute's own key research priorities are in the fields of matter and materials, energy and environment and human health. PSI is committed to the training of future generations. Therefore about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether PSI employs 2100 people, thus being the largest research institute in Switzerland. The annual budget amounts to approximately CHF 380 million. PSI is part of the ETH Domain, with the other members being the two Swiss Federal Institutes of Technology, ETH Zurich and EPFL Lausanne, as well as , Swiss Federal Institute of Aquatic Science and Technology:Eawag, Swiss Federal Laboratories for Materials Science and Technology:Empa and Swiss Federal Institute for Forest, Snow and Landscape Research:WSL. ω.

Contact: Claire Donnelly: Laboratory for Multiscale materials experiments: Paul Scherrer Institute: Switzerland: e-mail: claire.donnelly at psi.ch: Language: English.
Laura Heyderman: Head of Laboratory for Multiscale materials experiments: Paul Scherrer Institute: Switzerland: e-mail: laura.heyderman at psi.ch Languages: German, English, French

The Paper: Three-dimensional magnetisation structures revealed with X-ray vector nanotomography: Claire Donnelly, Manuel Guizar-Sicairos, Valerio Scagnoli, Sebastian Gliga, Mirko Holler, Jörg Raabe, Laura J. Heyderman: Nature: June 20, 2017: DOI: 10.1038/nature23006
 

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New Particle Discovered at CERN But It's Name is Too Out of This World So We Call It Emchestercle So to Eliminate the Man But Appreciate the Great Work at the University of Manchester

Image: University of Manchester



|| July 10: 2017: University of Manchester News || ά. New Particle Discovered at CERN But It's Name is Too Out of This World So We Call It Emchestercle So to Eliminate the Man But Appreciate the Great Work at the University of Manchester. A University of Manchester physicist is part of an international team of scientists, that has discovered a new subatomic particle at CERN’s Large Hadron Collider:LHC. The new heavy particle, named Xi-cc++, pronounced Ksī-CC plus-plus, was discovered by LHCb experiment and is part of a family of 'doubly charmed baryons'. Baryons are subatomic particles made up of quarks. Protons and neutrons are the most common baryons. Quarks are even smaller particles, that come in six types, two common types, that are light and four heavier types.

The particle has long been predicted to exist by the Standard Model theory of particle physics, but this is the first time scientists have been able to confirm their existence. Professor Chris Parkes, Deputy Spokesperson for LHCb and Head of Accelerator, Nuclear and Particle Physics at the University of Manchester, said, “This discovery opens up a new field of particle physics research. An entire family of doubly charmed baryons, related to this particle, now await discovery!" Nearly all the matter, that we see around us is made of baryons, which are common particles composed of three quarks, the best-known being, protons and neutrons.

But there are six types of existing quarks, and theoretically, many different potential combinations could form other kinds of baryons. Baryons so far observed are all made of, at most, one heavy quark such as a bottom or charm quark.

University of Glasgow Physicist Dr Patrick Spradlin, who led the research and announced the findings at the European Physical Society Conference on High Energy Physics in Venice, said, ''The properties of the newly discovered baryon shed light on a longstanding puzzle surrounding the experimental status of baryons containing two charm quarks, opening an exciting new branch of investigation for LHCb.”

The observation of this new baryon proved to be challenging and has been made possible owing to the high production rate of heavy quarks at the LHC and to the unique capabilities of the LHCb, one of the four main experiments at CERN solving the mysteries of our universe, which can identify the decay products with excellent efficiency. The Ξ_cc^:++ baryon was identified via its decay into a Λc+ baryon and three lighter mesons K-, π+ and π+.

The observation of the Ξ_cc^:++ in LHCb raises raises expectations that other representatives of the doubly charmed baryon family could be detected. They will now be searched for at the LHC. The Large Hadron Collider, located in a 27-kilometre:16.8-mile tunnel beneath the Swiss-French border, was instrumental in the discovery of the Higgs boson.
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You Have Scientifically Found a Demon: No a Hypothetical One: So the Hypothesis was Wrong: No It Needed a Little Fixing: It Will Take a Lot More Than a Little Fixing to Get a Demon to Exist Scientifically

Image: Anja Schmidt:University of Leeds

 



|| July 06: 2017: University of Exeter News || ά. New research offers a fascinating view into the inner workings of the mind of ‘Maxwell’s Demon’, a famous thought experiment in physics. An international research team, including Dr Janet Anders  from the University of Exeter, have used superconducting circuits to bring the ‘demon’ to life. The demon, first proposed by James Clerk Maxwell in 1867, is a hypothetical being, that can gain more useful energy from a thermodynamic system than one of the most fundamental laws of physics, the second law of thermodynamics, should allow.

The team not only directly observed the gained energy for the first time, they were able to track how information gets stored in the demon’s memory. The research is published in the leading scientific journal Proceedings of the National Academy of Sciences. The original thought experiment was first proposed by mathematical physicist James Clerk Maxwell, one of the most influential scientists in history, 150 years ago. He hypothesised that gas particles in two adjacent boxes could be filtered by a ‘demon’ operating a tiny door, that allowed only fast energy particles to pass in one direction and low energy particles the opposite way.

As a result, one box gains a higher average energy than the other, which creates a pressure difference. This non-equilibrium situation can be used to gain energy, not unlike the energy obtained when water stored behind a dam is released. So, although, the gas was initially in equilibrium, the demon can create a non-equilibrium situation and extract energy, by passing the second law of thermodynamics.

Dr Anders, a leading theoretical physicist from the University of Exeter’s physics department says, “In the 1980s it was discovered that this is not the full story. The information about the particles’ properties remains stored in the memory of the demon. This information leads to an energetic cost, which then reduces the demon’s energy gain to null, resolving the paradox.”

In this research, the team created a quantum Maxwell demon, manifested as a microwave cavity, that draws energy from a superconducting qubit. The team was able to fully map out the memory of the demon after its intervention, unveiling the stored information about the qubit state.

Dr Anders says, “The fact that the system behaves quantum mechanically means that the particle can have a high and low energy at the same time, not only either of these choices as considered by Maxwell.”

This ground-breaking experiment gives a fascinating peek into the interplay between quantum information and thermodynamics and is an important step in the current development of a theory for nanoscale thermodynamic processes.
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Uniformly Moving Charged Particle with Rather Low Velocity Could Radiate Electromagnetic Waves

Numerical simulation of CR with electron energy of 0.1keV. Image: Tsinghua University
 

|| April 18: 2017: Tsinghua University News || ά. On April 11, Associate Professor Fang Liu and Professor Yidong Huang, Department of Electronic Engineering, Tsinghua University and their colleges, published a paper, 'Integrated Cherenkov Radiation Emitter Eliminating the Electron Velocity Threshold' in Nature Photonics. This work provides a way to realise threshold-less Cherenkov Radiation:CR, opening up the possibility of exploring high performance integrated free-electron light source and offering a platform to study the interaction of flying electrons with nanostructures on chip.

CR is the electromagnetic radiation, emitted by a moving charge passing through a dielectric medium with a uniform velocity above a certain threshold. In the early 20th century, the discovery and explanation of CR overturned the knowledge, that no material body can move at a velocity exceeding light speed in a media and a uniformly moving charged particle cannot radiate electromagnetic waves. Pavel A. Cherenkov and other two scientists were awarded the Nobel Prize in Physics in 1958 for their outstanding work in this area. After its discovery, CR has played a key role in discovering some fundamental particles and physical phenomena, such as anti-proton, J-particle and neutrino oscillations.

To generate CR, the velocity of a charge should be higher than the phase velocity of light in the medium. In an initial experiment, Cherenkov generated the radiation in water with electron velocity of 0.7c, corresponding to energy of about 300 thousands eV, where c is the light speed in vacuum. Although various approaches were adopted, high-energy electrons, tens of thousands of eV, were still required to generate CR experimentally in the visible:infrared light region.

In terms of application, CR is one of the approaches to realising free-electron light source, which is rather important in the field of fundamental physics, military, biology, information science and so on. Similar to other methods, the electrons should be accelerated to an ultra-high velocity, which requires large volume, several to thousands of metres, equipment. Decreasing the threshold of electron energy for CR remained a basic scientific problem remaining for many years.

Professor Huang’s group began the research on micro and nano optoelectronic devices, since 2004 and accumulated rich experiences on fabrication and measurement of optoelectronic devices. Group members, Fang Liu, Long Xiao, PhD candidate and other colleges made an important discovery in theory when they studied the CR in multilayer hyperbolic metamaterial:HMM. In theory that the CR could be excited in HMM no matter how slow the electrons move, namely threshold-less CR.

To verify this theoretical result, in following two years they overcame lots of difficulties in experiment, such as the fabrication of planar electron emitter on chip, the multilayer HMM with thickness of ten nanometres for each layer, the plasmonic nano-slits and the measurement of CR in HMM. Finally, they succeeded in observing the threshold-less CR by extracting the free electrons from nano-scale Mo tip and having the electrons fly a distance of 200 micron above parallel to the surface of HMM with height of only 40nm.

The wavelength of CR ranges from 500~900nm and the electron energy is only 250~1400eV, which is two to three orders of magnitude lower than previous reports. The measured output light power reaches 200nW, which is two orders of magnitude higher than free electron light source by using other nanostructures.

This work has solved the problem of generating CR with rather low electron energy and realised the first integrated free-electron light source on chip. Eliminating the threshold of charge velocity and high radiation efficiency opens the possibilities of wideband radiation sources from UV light to THz by designing proper HMM structures.

Moreover, such an integrated CR emitter brings CR from the field of high-energy physics to integrated devices. It, also, provides a platform for studying the interaction between the flying electrons and various kinds of artificial nanostructures on chip and more integrated vacuum optoelectronic devices can be expected in future.

Associate Professor Fang Liu, the First and Corresponding Author, PhD student Long Xiao being the Co-first Author and Professor Yidong Huang is the Corresponding Author. This work was supported by the National Basic Research Programmes of China, the National Natural Science Foundation of China. ω.

The Paper: Published in Nature Photonics on April 11.

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Super Pressure Balloon Flight Enables Pioneering Infrasound Study: But Make Sure Santa Barbara Keeping a Watch

The Compton Spectrometer and Imager:COSI payload, just prior to launch from Wanaka, New Zealand, on a NASA super pressure balloon in May 2016.
The Carolina Infrasound payload hitched a ride on the mission on a pioneering study to measure infrasound from the stratosphere. Image: NASA:Bill Rodman
 

|| April 06: 2017 || ά. It's all about that bass and lots of it. Deep, deep base, sound at frequencies too low for the human ear to pick-up. It's called, infrasound, low-frequency soundwaves, formed by events as diverse as ocean waves crashing together, volcanic eruptions and earthquakes to rocket launches. These soundwaves, capable of travelling around the world multiple times, have never been recorded from the stratosphere for more than a day and a half and never over the ocean. That is, not until this past year. NASA's 2016 Super Pressure Balloon flight from Wanaka, New Zealand, carried the Compton Spectrometer and Imager:COSI payload, a gamma ray telescope.

Tucked behind one of COSI's solar panels was the Carolina Infrasound instrument, a three-kilogram payload resembling a small styrofoam ice chest on the outside but with a trio of InfraBSU infrasound microphones on the inside. A Boise State University team led by Associate Professor Jeff Johnson, originally designed the microphones to record volcanic explosions but the sensors have found an unexpected new use in the stratosphere. The balloon and payload took flight May 16, 2016, on a journey, that went around the world amassing some 46 days of flight time.

All the while, the University of North Carolina at Chapel Hill team who built the instrument monitored the flight nervously. If the balloon flight was terminated over sea, there would be no way to retrieve the infrasound data as the instrument had no telemetry connection for beaming data back to a control station. Fortunately, some relief came when controllers terminated the balloon flight along the coast of Peru.

Still, the team waited another five months before the infrasound experiment was returned to its principal investigator, Danny Bowman, University of North Carolina at Chapel Hill and his Ph.D. Advisor Jonathan Lees. All the while, one question loomed overhead: did it work? "My payload was untested and I didn't know how long the batteries would last." said Bowman. "Actually, I didn't know, if it would even turn on."

With the instrument back home, Bowman quickly discovered that the recorder had turned on and stayed on for nearly 19 days. "The experiment worked perfectly." said Bowman. The raw result: over two weeks of continuous recording of infrasound from the stratosphere. During one portion of the flight, the balloon was able to fill a 7,000 km gap in ground station coverage. Wind noise, a pervasive issue on ground-based stations, was entirely absent. The sheer time span of the recording was novel in itself.

"To have a continuous, multi-week recording is probably unheard of." said Bowman. "One of the coolest things is that we can hear ocean waves crashing together, turning entire regions of sea into subwoofers." said Bowman. "The distant roaring sound is the ocean waves colliding." Aside from the waves, Bowman continues to examine the data to identify the sources of infrasound he recorded. In the meantime, the instrument has already increased the time duration of available stratospheric acoustic data by an order of magnitude.

Months after the flight, Bowman discussed how he had a stowaway on his payload. "When I started graduate school, my godmother sent me a retablo of Santa Barbara, patron saint of volcanoes and earthquakes." said Bowman. "Santa Barbara watched over me in the lab for a few years." And, who better to watch over Bowman than the patron saint of some of the various sources of infrasound he has dedicated years to studying.

In the lab, Bowman engineered his payload to the greatest extent he could with the resources available. The rest, he handed over to faith. "I put Santa Barbara in, the payload, figuring I needed all the help I could get." said Bowman.

Back in his office, Bowman, now a Senior Scientist at Sandia National Laboratories, Albuquerque, New Mexico, continues the task of unravelling the mystery behind the infrasound recording with the globetrotting retablo of Santa Barbara nearby, watching over him.

: Editor: Jeremy Eggers: NASA: ω.

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Now Resolve This Quantum Conundrum: Or Rather Deal with This Quantum Entanglement

Image: University of Strathclyde

|| April 04: 2017: University of East Anglia News || ά.  Scientists have discovered a new mechanism that is involved in the creation of paired light particles, which could have significant impact on the study of quantum physics. Researchers at the University of East Anglia:UEA have shown that when photons, the fundamental particles of light, are created in pairs, they can emerge from different, rather than the same, location. The ground-breaking research could have significant implications for quantum physics, the theoretical basis of modern physics. Until now, the general assumption was that such photon pairs necessarily originate from single points in space.

Quantum entanglement, when particles are linked so closely that what affects one directly affects the other, is widely used in labs in numerous processes from quantum cryptography to quantum teleportation. The UEA team was studying a process, called, spontaneous parametric down-conversion:SPDC, in which photon beams are passed through a crystal to generate entangled pairs of photons. Professor David Andrews in UEA’s School of Chemistry, said, “When the emergent pairs equally share the energy of the input, this is known as degenerate down-conversion or DDC.

Until now, it has been assumed that such paired photons come from the same location. Now, the identification of a new delocalised mechanism shows that each photon pair can be emitted from spatially separated points, introducing a new positional uncertainty of a fundamental quantum origin.”

The entanglement of the quantum states in each pair has important applications in quantum computing, theoretical computation systems, that could potentially process big data problems at incredible speeds, as well as other areas of quantum physics.

The findings are, additionally, significant because they place limits on spatial resolution. Professr Andrews said, “Everything has a certain quantum ‘fuzziness’ to it and photons are not the hard little bullets of light, that are popularly imagined.”

The study ‘Nonlocalised generation of correlated photon pairs in degenerate down-conversion’ by Kayn A. Forbes, Jack S. Ford, and David L. Andrews is published in the journal Physical Review Letters. ω.

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The Mozart of Ultra High Temperature Energy Storage and Conversion Arising Out of a Scientific Aria Called the Carnot Theorem: One Day Humanity Will Come to Call This Branch of Science Thermoseismodynamics Because This Will Lift Humanity Out of the Stranglehold of the Heat Barrier

Well, you must start, even an orchestra: And here, they met at the UPM Madrid: We call them the Amdadeus Orchestra of Thermoseismoquantumdynamics



|| April 03: 2017: Universidad Politecnica de Madrid News || ά.  Under the co-ordination of the Technical University of Madrid:UPM, a team of seven European Research and Development institutions have started the Horizon-2020 Research Project AMADEUS, aiming to the development of a new generation of ultra-compact energy storage devices based in molten silicon and solid state heat-to-power converters. And The Humanion envisions, this project, will begin a new branch of science, what we would like to call Thermoseismicquantumdynamics for this has the potential to lift humanity out of the existing stranglehold of heat barriers. What is and must be an absolute urgency to seek to and break this barrier for whatever we build currently is liable to be melted away even before it could do greater things. For imagine, one day, we are able to create devices, that are capable of being able to maintain themselves and work much, much closer to the sun or on places like Mercury or Venus. What is hypothetically possible is, this development of thermoseismicquantumdynamics will offer the other end of the scientific basis of creating devices and mechanisms, that would work in the extreme opposite of heat, as in extreme cold, such as -1000, -2000 degrees etc.

Further, The Humanion always hypothesised that the darkness itself is an energy but we are probably few hundred years away from being able to develop the science, mathematics and technology to be able to tap into and convert that infinity of darkness into any energy we want. And The Humanion has always hypothesised that like heat, cold itself is an energy and it could be converted into any energy we want except we are nowhere near there to be able to do that for imagine how much cold is out there and how much heat we are losing to cold? This branch of science, Thermoseismoquantumdynamics will have these fields and areas to develop and this will be the theory of relativity for the next few centuries. If you do not seem to share this vision, you are welcome to write this down on paper and place it in an envelop, sealing it send it to Cartagena Science Museum, asking them to keep it sealed for a couple of centuries and then let them open it and see.

The storage of energy at temperatures higher than 1000°C using molten silicon-based alloys is the objective of the project AMADEUS, the first European project of the kind. The team of experts will seek for a new generation of extremely compact and lower cost energy storage devices, with potential application into different sectors.

Direct storage of solar energy in thermal solar power plants, or the integration of both electric power storage and cogeneration in the housing sector and urban areas, are just some examples of the potential applications of the devices to be developed by the Project. AMADEUS has been granted with the funding allocated for the Future Emerging Technologies:FET Call of the European Horizon 2020 Programme, which constitutes an achievement in itself when considering that only 4 out of 100 proposals were granted in this call, one of the most competitive ones of the whole programme.

Counting on a total budget of € 03,3 M for the next three years, AMADEUS or Next Generation Materials and Solid State Devices for Ultra High Temperature Energy Storage and Conversion will search for new materials and devices allowing the energy storage at temperatures in a range among 1000 and 2000°C , thus, breaking the 600°C mark, rarely exceeded by current state of the art concentrated solar power:CSP systems.

To that end, the research team will work with different silicon and boron metal alloys melting at temperatures higher than 1385°C, and allowing for the storage of amounts in the range of 02-04 MJ:kg, an order of magnitude higher than to those of currently used salts. In addition, the Project will search for a material able to contain these molten metals over long periods, along with achieving a good thermal isolation. Devices able to achieve an efficient conversion of heat into electricity will also be studied.

To this development, the Project will work on a new concept combining thermionic and photovoltaic effects to achieve direct conversion of heat into electricity. Unlike conventional heat engines, this system does not require physical contact with the heat source, as it is based on direct emission of electrons, thermionic effect and photons, thermo-photovoltaic effect, enabling an ultra high temperature operation.

Besides the capability of operation at high temperatures, these new devices would also lead to the simplification of the whole system as well as an important cost reduction. This is mainly because the use of the most expensive elements of the currently used systems, such as pipes, heat exchangers or heat transfer fluids, would be avoided.

The Project counts on seven partners from six European countries, with a high experience in the field of metallurgy, thermal isolation, fluid dynamics and solid state heat-to-power conversion.

The research consortium, coordinated by Alejandro Datas and Antonio Martí, both from UPM , will count on the participation of the National Research Council, Italy, Foundry Research Institute, Poland, Norwegian University of Science and Technology, Norway, The Centre for Research and Technology, Hellas, Greece, University of Stuttgart, Germany and IONVAC Process SRL, Italy. ω.

The Paper: A.Datas, et.al, 'Ultra high temperature latent heat energy storage and thermophotovoltaic energy conversion', Energy, Vol. 107, 2016: A. Datas 'Hybrid Thermionic-Photovoltaic converter' Appl. Phys. Lett. 108, 143503 2016

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USTC Proposes Noble-Metal-Free Scheme for Water Splitting Hydrogen Energy Production

Illustration for the noble metal-free Z-scheme materials towards broadband photocatalytic water splitting. Image: Xiong Yujie and Angewandte Chemie

 

|| April 02: 2017: University of Science and Technology of China News || ά.   Photocatalytic water splitting producing hydrogen and oxygen with solar light is a sustainable energy technology. The research group led by Professor Xiong Yujie at the University of Science and Technology of China:USTC has developed a class of noble-metal-free Z-scheme photocatalysts, which exhibit the enhanced performance in photocatalytic hydrogen production, based on a facile cation-exchange approach.

The photocatalytic water splitting is a promising approach to the conversion from solar to hydrogen energy by harvesting solar light to produce hydrogen and oxygen. The breakthrough enables development of hydrogen energy production, among various new sustainable energy technologies, meeting the global energy demand. To harvest and utilise broadband light, various all-solid-state artificial Z-scheme photocatalytic systems have been developed based on two semiconductors with staggered-aligned band structures and different bandgaps.

Two structural characteristics are necessary for an ideal Z-scheme system. The first characteristic is the system must contain well-defined interfaces for efficient interfacial charge transfer. Secondly, the system must include exposed surfaces of both semiconductors for surface reduction and oxidation half reactions.

Noble metals should be excluded from their interfaces as cocatalysts to promote hydrogen evolution for the concern of reducing costs, though they are commonly used as electron mediators to facilitate the charge transfer between semiconductors in Z scheme. The exclusion of noble metals from Z scheme can also eliminate the possible backward reactions over metal surface back to water.

To meet the requirements, Xiong research group has developed a facile cation-exchange approach to form Janus-like structures between γ-MnS and Cu7S4 with exposed surfaces and high-quality interfaces without the need of using noble metals. The γ-MnS and Cu7S4 can complementarily absorb light to exhibit the dramatically enhanced photocatalytic hydrogen performance in full solar spectrum.

This work provides insights into the surface and interface design of hybrid photocatalysts, and offers a noble metal-free approach to broadband photocatalytic hydrogen production.

Professor Junfa Zhu made an important contribution to the synchrotron radiation-based photoelectron spectroscopy characterizations in this work. It was published titled as 'Noble-Metal-Free Janus-likeStructures by Cation Exchange for Z-SchemePhotocatalytic Water Splitting underBroadbandLight Irradiation'. This work was financially supported by the 973 Programme, NSFC and CAS Key Research Programne of Frontier Sciences.

The Paper: This work has been published in Angewandte Chemie, Angew. Chem. Int. Ed. DOI: 10.1002/anie.201700150

Contact: Professor Xiong Yujie: School of Chemistry and Material Sciences: emaill: yjxiong at ustc.edu.cn: ω.

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The Eternal Law: Nothing is Lost But Changes Forms: Where Does the Laser Energy Go After Being Fired Into Plasma

Image: University of Strathclyde

 

|| March 31: 2017: University of Strathclyde News || ά.  An outstanding conundrum on what happens to the laser energy after beams are fired into plasma has been solved in newly-published research at the University of Strathclyde. The study discovered that the same forces that produce a bubble in plasma in the laser-plasma wakefield accelerator produce two additional low-energy but high-charge electron beams simultaneously with a low charge high energy beam. These high charge beams can have a thousand times more charge than the high energy beam.

Plasma, the state in which nearly all of the universe exists, can support electric fields that are 1,000 to 10,000 times higher than in conventional accelerators, simply by separating the positive and negative charged particles that makes up the plasma medium, which is quasi-neutral. This can easily be achieved using an intense laser pulse, the light pressure of which pushes electrons out of its way, leaving behind the much heavier ions, which remain in place and exert an attractive force on the displaced electrons. The displaced electrons then oscillate around the stationary ions resulting in a wake behind the laser pulse, in a similar manner to the wake behind a boat.

Because the laser pulse travels at a velocity close to that of light in vacuum, the wake can track and accelerate charged particles rapidly to very high energies, over extremely short lengths. The research paper, entitled Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question, has been published in Scientific Reports.

Professor Dino Jaroszynski, of Strathclyde’s Department of Physics, led the study. He said, “The intense laser pulse we used and the acceleration of the wake it creates, lead to a very compact laser wakefield accelerator, which is millimetres long, rather than tens of metres long, for an equivalent conventional accelerator. The plasma wake forms into something like a bubble-shaped, laser-powered miniature Van de Graaf accelerator, which travels at close to the speed of light.

Some of the laser energy is converted to electrostatic energy of the plasma bubble, which has a diameter of several microns. Conventional accelerators store their microwave energy in copper or superconducting cavities, which have limited power-carrying capability. An interesting conundrum that has not been considered before is the question of where laser energy goes after being deposited in plasma. We know where some of this energy goes because of the presence of high-energy electrons emitted in a narrow, forward directed beam.

One of these beams is emitted by a sling-shot action into a broad forward-directed cone, with several mega electron volt:MeV energies and nanocoulomb-level charge. Paradoxically, another beam is emitted in the backward direction, which has similar charge but an energy of around 200 kilo electron volt:keV. These beams carry off a significant amount of energy from the plasma bubble.

It is interesting to observe that answering a very basic question, where does the laser energy go, yields surprising and paradoxical answers. Introducing a new technology, such as the laser-wakefield accelerator, can change the way we think about accelerators. The result is a very novel source of several charge particle beams emitted simultaneously.

My research group has shown that the wakefield accelerator produces three beams, two of which are low energy and high charge, and the third, high energy and low charge.”

Dr Enrico Brunetti, a Research Fellow in Strathclyde’s Department of Physics and a member of the research group, said: “These beams can provide a useful high flux of electrons or bremsstrahlung photons over a large area, which can be used for imaging applications, or for investigating radiation damage in materials. If not properly dumped, they can, however, have undesirable side-effects, such as causing damage to equipment placed close to the accelerator.

This is a particular concern for longer accelerators, which often use plasma wave guides based on capillaries to guide the laser beam over long distances. These low energy, high charge beams also carry a large amount of energy away from the plasma, setting a limit to the efficiency of laser-wakefield accelerators. This is an issue, which needs to be taken into account in the future design and construction of laser-wakefield accelerators.”

The Research Excellence Framework 2014, the comprehensive rating of UK universities’ research, ranked the University of Strathclyde’s Physics research first in the UK, with 96% of output assessed as world-leading or internationally excellent. ω.

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The Photonarine-Song: I Will Continue to Sing So Long There Remains the Light-Firefly Crafting the Darkness of the Universe Into an Eternal Dawn-Sojourn

Image: Mika Kanerva


|| March 29: 2017: Tampere University of Technology News: Leena Koskenlaakso Writing || ά. Tampere University of Technology:TUT has embarked on the development of light-controlled materials. The idea is to produce mechanical movement by changing the length and thickness of these materials, thus enabling the creation of microrobots and tunable optical materials. At best, this new material concept could one day be utilised in several fields and across disciplinary borders. “I am a dedicated fan of fundamental research and the force that drives me the most is scientific curiosity. This should be supported in the university world, as it spawns technological advancement.'' says Academy Research Fellow, Assistant Professor Arri Priimägi from TUT’s Department of Chemistry and Bioengineering.

And he cannot emphasise this enough: it is absolutely vital that universities support, nurture, foster and inspire 'fundamental' research because the fact is, though terribly sad, in a lot of places, institutions seem to have entered a 'safe', 'cut-out' and 'clichéd' world of 'research', where they are 'curtailing' and effectively 'killing' off the human minds into wasting their lives in the worthless clichéd pursuits of so called research. Yet, the world and humanity have infinite needs to find answers, seek solutions and create advances in both knowledge and innovations and that must be done with the finite resources that are available to us and therefore, we do not, cannot waste this scarce resources into worthless clichéd pursuits.

Without light, we would not have the fast Internet connections enabled by optical fibres, we would not have home entertainment as we know it today, and we would also lack many modern medical tools. New lighting solutions, such as LED lights, along with solar cells, are key light-based technologies whose significance is only about to grow in the years to come. “Last year was proclaimed as the International Year of Light. Also, technological gurus have predicted that the 2000s will become the century of light and that light-based technologies will revolutionize our lifestyle as we know it.'' says Academy Research Fellow, Assistant Professor Arri Priimägi from TUT’s Department of Chemistry and Bioengineering.

Photonics, i.e. the science of light, studies how light can be produced, manipulated and detected. In practice, photonics is, also, often dubbed optics. Priimägi is heading a new five-year ‘Tunable Photonic Structures via Photomechanical Actuation’ project for which he received a 01.5 million euro funding from the European Research Council. Consisting of chemists and physicists, Priimägi’s research group studies and develops functional light-controlled materials whose length and thickness can be altered to generate mechanical movement.

Certain properties of functional materials can be changed with specific external stimuli. In this case, the stimulus is light. “Light is a convenient stimulus for designing functional materials in that it is easily available, cheap and environmentally friendly. The materials can be remotely controlled with a laser or a LED, for example. The properties of light, such as colour, intensity, polarisation or the duration of a light pulse, can be controlled with great accuracy. Therefore, many things can be done with light that cannot be done with other stimuli.” Priimägi continues.

The aim is to develop techniques and methods for managing light-controlled changes in the length and thickness of polymeric substrates and thin films, respectively. “The light control is enabled by molecular switches, which are molecules approximately a single nanometre in length. A human hair could fit roughly 50,000 of them side by side. Light allows us to tune the molecules so that they transform and change in length.” The molecular switches are very intriguing, as they can do great things regardless of their nanoscale size. The power of the mass is the key.

“Instead of using single switches, we put millions or billions of them together. Together they cooperate and intensify the desired property. When a nanoscale phenomenon is intensified this way, all kinds of mechanical macro-scale movements may result – microrobots of sorts.” According to Priimägi, it is possible to attain forces of similar scope in the studied materials with light as generated by a human muscle when contracted.

“Light-based movements have been used for moving small particles from one place to another, for example. The particles moved have been dozens of times heavier than the microrobot causing the movement. This type of robotics could perhaps be used for super-precise light-controlled placement and disposition of small items, for example.” Priimägi envisions. “In wilder visions, a tiny light-controlled microrobot could move from one place to another on a surface in a controlled manner and transmit information or move materials between different parts of a microcircuit.”

Since these developments concern fundamental research and they are still largely based on hypotheses, it is impossible to list practical applications at this point. “Our actual goal is a kind of a future technology platform, or a material concept that could be used for many types of purposes across disciplinary borders. This is why interdisciplinary cooperation within TUT and both nationally and internationally is needed to find applications.” Priimägi says.

The research of light-based technologies goes hand in hand with materials development, and TUT has strong merits in both. In addition, there is great bioengineering expertise at TUT. Light-controlled materials could possibly be used in the field of bioengineering, for example, to improve the detection of various molecules, viruses and bacteria in test samples. In principle, the technique Priimägi studies can be applied to any chemical.

“As regards organic electronics, we intend to study if quantities such as conductivity or capacitance can be controlled with light. If we succeed, this could be a link to more advanced applications.” Different materials interact in different ways with light, and different molecules can be detected more effectively with different colour light sources. A small laser with an adjustable colour could be useful in sensor applications and developing one is, in fact, included in the goals of the project.

Light control also enables controlling the friction properties and wettability of a surface and producing externally-controlled self-cleaned surfaces. “In industrial measurements, light-based technologies can be controlled remotely. Therefore, they can be applied in places where electric control cannot be used.” The most tremendous visions speculate on the harnessing of sunlight and turning it into kinetic energy to be utilized in various technological applications in the energy branch.

“This is definitely worth looking into, and the idea is indeed being studied elsewhere. But we have a long way to go before we can actually harness sunlight-driven movement for something useful in the materials we study. I believe that the first potential applications will be rather found on the micro-scale and that the light control will be implemented with lasers or LEDs.” Priimägi notes.

“We must combine chemistry and physics in order to learn how to both manufacture these materials and transform them in a way that allows us to harness light energy for generating movement. For the most part, we can study these materials with the existing equipment.” Arri Priimägi’s career with light-controlled materials began a decade ago. He already studied similar materials in his master’s thesis, but from a whole different perspective. The vast potential of the field keep the scientist intrigued.

“I would not say that I sought this area of research. It was the topic that picked me.” Priimägi says. “The further you dive into a research topic, the more widely it reveals itself. But at the core of it all are the tiny little molecule switches – they have companied with me throughout the journey. They are truly fascinating.”

Photonics employs widely around Europe. Photonics employs approximately 290,000 people directly and 30 million people indirectly around Europe. The annual worldwide turnover of light-based technologies is 300 billion euros. The share of Europe in the worldwide turnover is 20 per cent, i.e. approx. 60 billion euros. In certain sectors, such as lighting, Europe makes up 40 per cent. The annual growth forecast for light-based technologies is 08 per cent. ω.

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CERN Experiment Discovers Five New Particles

Image: Swansea University

 

|| March 24: 2017: University of Liverpool News || ά. A new group of particles which have long been hiding in plain sight have finally been discovered thanks to the incredibly sensitive LHCb experiment at CERN. LHCb, otherwise known as the Large Hadron Collider beauty experiment, is one of seven experiments collecting data at the Large Hadron Collider at CERN. UK participation in the experiment is funded by STFC. In a paper released on March 21, the LHCb collaboration has announced an exceptional and unique observation of five new baryons, particles composed of three quarks.

Tara Shears, Professor of Physics at University of Liverpool, is Liverpool’s LHCb group lead. She explains why this discovery is significant, “These particles have been hiding in plain sight for years, but it’s taken the exquisite sensitivity of LHCb’s particle detectors to bring them to our attention.” These new baryons are high-energy excited states of the Omega_c baryon, a particle made of two ‘strange’ and one ‘charm’ quark. Quarks are one of the fundamental building blocks for matter, combining to make hadrons. There are six types of quark. ‘up’, ‘down’, ‘strange’, ‘charm’, ‘top’ and ‘bottom’.

LHCb scientists reconstructed the short-lived Omega-c baryon from its decay to a Xi baryon, a particle containing a ‘charm’, a ‘strange’ and an ‘up’ quark and a kaon K-, a particle made up of a ‘strange’ quark and an ‘up’ antiquark. The Xi baryon then decayed further into a proton, a kaon K- and a pion. By studying the trajectories and energies deposited by all the particles, LHCb scientists uncovered the Omega_c baryon. They found not one but five distinct new excited Omega_c baryon states.

Professor Shears explained how the UK’s future involvement will be vital, “We need the precision trajectory information from the VELO detector to reconstruct the trail of particles these new baryons produce, and information from the RICH detectors to know what these particles are both detectors that the UK helped build. If we’re uncovering these new particles now, who knows what else is in our data waiting to be discovered?”

Using the vast amounts of data collected during the operational life of the Large Hadron Collider, and the fantastic precision of LHCb’s detectors, scientists have been able to confirm the discovery is not just a fluke. Physicists will now determine the precise properties of these new particles, which will contribute to our understanding of how quarks are bound inside a baryon using the strong nuclear force, otherwise known as ‘the strong interaction’.

Professor Tim Gershon, Professor of Physics at University of Warwick and UK spokesperson for the LHCb experiment, explained what will come next for the LHCb experiment, “After the LHCb experiment is upgraded in the next long shutdown of the LHC during 2019-20, it will be able to move to the next stage in the search for new particles: namely, doubly heavy baryons.

These states, which contain two charm quarks or two beauty quarks or one of each, have long been predicted, but never yet observed. Their discovery will help to address important unsolved questions about how hadrons are bound together by the strong interaction.”

LHCb is one of the four main experiments at the Large Hadron Collider at CERN. LHCb was built in a cavern 100m below ground near Ferney-Voltaire in France. It is investigating the subtle differences between matter and antimatter in a bid to answer one of the most fundamental questions, why is our Universe made of matter? UK participation in LHCb is funded by STFC, with contributions from the participating institutes, the Royal Society and European Union.

The UK participation in the international LHCb experiment is from eleven institutes. University of Birmingham, University of Bristol, University of Cambridge, University of Edinburgh, University of Glasgow, Imperial College London, University of Liverpool, University of Manchester, University of Oxford, STFC Rutherford Appleton Laboratory, University of Warwick.
ω.

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Unravelling Earth’s Magnetic Field

Magnetic anomaly: Bangui: Latest map of the lithospheric magnetic field by Swarm shows detailed variations in this field more precisely
than previous satellite-based reconstructions, caused by geological structures in Earth’s crust. One of these anomalies occurs in
Central African Republic, centred on the city of Bangui, where the magnetic field is significantly sharper and stronger. The cause for
this anomaly is still unknown, but some scientists speculate that it may be the result of a meteorite impact more than 540 million
years ago. Image: ESA:DTU Space:DLR
 

|| March 21: 2017 || ά. ESA’s Swarm satellites are seeing fine details in one of the most difficult layers of Earth’s magnetic field to unpick, as well as our planet’s magnetic history imprinted on Earth’s crust. Earth’s magnetic field can be thought of as a huge cocoon, protecting us from cosmic radiation and charged particles that bombard our planet in solar wind. Without it, life as we know it would not exist.

Most of the field is generated at depths greater than 3000 km by the movement of molten iron in the outer core. The remaining 06% is partly due to electrical currents in space surrounding Earth, and partly due to magnetised rocks in the upper lithosphere, the rigid outer part of Earth, consisting of the crust and upper mantle. Although this ‘lithospheric magnetic field’ is very weak and therefore difficult to detect from space, the Swarm trio is able to map its magnetic signals. After three years of collecting data, the highest resolution map of this field from space to date has been released.

“By combining Swarm measurements with historical data from the German CHAMP satellite, and using a new modelling technique, it was possible to extract the tiny magnetic signals of crustal magnetisation.” explained Nils Olsen from the Technical University of Denmark, one of the scientists behind the new map.   ESA’s Swarm mission Manager, Rune Floberghagen, added, “Understanding the crust of our home planet is no easy feat. We can’t simply drill through it to measure its structure, composition and history.

Measurements from space have great value as they offer a sharp global view on the magnetic structure of our planet’s rigid outer shell.” Presented at this week’s Swarm Science Meeting in Canada, the new map shows detailed variations in this field more precisely than previous satellite-based reconstructions, caused by geological structures in Earth’s crust.

One of these anomalies occurs in Central African Republic, centred around the city of Bangui, where the magnetic field is significantly sharper and stronger. The cause for this anomaly is still unknown, but some scientists speculate that it may be the result of a meteorite impact more than 540 million years ago. The magnetic field is in a permanent state of flux. Magnetic north wanders, and every few hundred thousand years the polarity flips so that a compass would point south instead of north.

When new crust is generated through volcanic activity, mainly along the ocean floor, iron-rich minerals in the solidifying magma are oriented towards magnetic north, thus capturing a ‘snapshot’ of the magnetic field in the state it was in when the rocks cooled.

Since magnetic poles flip back and forth over time, the solidified minerals form ‘stripes’ on the seafloor and provide a record of Earth’s magnetic history.  The latest map from Swarm gives us an unprecedented global view of the magnetic stripes associated with plate tectonics reflected in the mid-oceanic ridges in the oceans.

“These magnetic stripes are evidence of pole reversals and analysing the magnetic imprints of the ocean floor allows the reconstruction of past core field changes. They also help to investigate tectonic plate motions.” said Dhananjay Ravat from the University of Kentucky in the USA.

“The new map defines magnetic field features down to about 250 km and will help investigate geology and temperatures in Earth’s lithosphere.”
ω.

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Magnify Time and See How Things Work

Image: Tampere University of Technology

 

|| March 12: 2017: Tampere University of Technology News || ά.  Researchers from the Photonics Laboratory of the Tampere University of Technology, working in collaboration with colleagues from France, Ireland and Canada, have used a novel measurement technique, that magnifies time to reveal how ultrafast intense pulses of light can be generated from noise on a laser as it propagates in optical fibre. These experiments confirm theoretical predictions made decades ago and may have implications in understanding the science of giant rogue waves on the ocean and the formation of other extreme events in nature.

The work is published in the journal Nature Communications last December. Instability and chaos are common in natural systems, that are highly sensitive to initial conditions. where a small change in the input can lead to dramatic consequences. To understand chaos under controlled conditions, scientists have often used experiments with light and optics, that allow the study of even the most complex dynamics on a benchtop. A serious limitation of these existing experiments in optics, however, is that the chaotic behaviour is often seen on ultrafast picosecond timescales, a millionth of a millionth of a second, that is simply too fast to measure in real time, using ordinary experimental equipment.

The recent experiments reported in the Nature Communications article by the team of Professor Goëry Genty in collaboration with teams in France, Ireland and Canada have now overcome this limitation, using a novel experimental technique known as a time lens to magnify picosecond chaotic pulses by over 100 times so that they can be conveniently measured, using a much slower ordinary electronic detector.

The particular phenomenon that was studied is known as modulation instability, an optical Butterfly Effect, that amplifies microscopic noise on a laser beam to create giant pulses of light with intensity over 1000 times, that of the initial fluctuations. The experimental results have confirmed theoretical studies dating back to the 1980s.

The results are, also, important in providing new insights into modulation instability, an ubiquitous noise amplification process considered as one of the possible mechanisms for describing giant rogue waves on the ocean but also relevant to many other areas of physics, including plasma dynamics in the early universe.

Professor Goëry Genty says that these experiments are remarkable not only because they have allowed for a better understanding of modulation instability and extreme events in general but also because they have now opened a new avenue to study, in real-time, chaotic dynamics on ultra-short time scales." ω.

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Antimatter Research Receives a Major Funding Boost

Image: Swansea University

 

|| March 10: 2017: University of Liverpool News || ά. The ALPHA collaboration, in which the University is a partner, has been awarded a new four-year research grant from the Engineering and Physical Sciences Research Council:EPSRC, worth almost £05 million. ALPHA studies the properties of antihydrogen with the goal of understanding the fundamental properties of antimatter. The ALPHA collaboration covers 14 institutes worldwide and over 50 people. The UK collaboration involves the University of Liverpool, as well as Manchester and Swansea Universities.

ALPHA carries out its experiments at CERN and has been very successful in its studies of antihydrogen over recent years with seven papers in Nature Journals and four in Physical Review Letters. Amongst those was the first observation of the 1S to 2S transition in antihydrogen. Professor Paul Nolan, who leads the Liverpool ALPHA group, said, This new grant will allow more data to be collected to improve the precision of our experiments and to measure the line width of the transition. This will allow a very accurate comparison with the properties of the same transition in hydrogen and hence a direct comparison between matter and antimatter.”

Liverpool is responsible for the silicon vertex detector that plays a vital role in ALPHA to determine when antihydrogen has been formed within the apparatus. This detection system was constructed in the Liverpool Semiconductor Detector Centre and mechanical workshop.

The detector and its electronic readout system was designed and is maintained by the highly experienced staff in the nuclear physics research cluster. The new EPSRC grant provides around £840,000 for research by the Liverpool ALPHA group.

The Head of the Physics Department, Professor Carsten Welsch, who is also a Co-investigator on the new grant added, We are absolutely delighted about this excellent news. The EPSRC funding provides important support for ALPHA and will allow us to continue to address some of the most fundamental questions in physics.“

The Liverpool effort at CERN and the data analysis part of the project are the responsibility of Dr Petteri Pusa and research student Mostafa Ahmadi. Antimatter research is a very important element of RD in the physics department. In addition to its involvement in ALPHA, Liverpool, also, has a lead role in the European network AVA. ω.

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A New Laser Spectroscopy Technique to Understand Atomic and Nuclear Structure of Radioactive Atoms

These, however, are  not  spectroscopic images, but the beautiful images of a bridge that the Finns have built. Images: University of Jyväskylä

 

|| March 05: 2017: University of Jyväskylä Finland News || ά. Researchers at the University of Jyväskylä participated in an international collaboration with research groups from five countries, Belgium, Finland, France, Germany and Russia, applying high-resolution laser ionisation of radioactive atoms in a supersonic gas jet to probe the properties of heavy elements. The results have been recently published in Nature Communications. Laser spectroscopy experiments have been used for the first time to obtain a thorough understanding of the atomic and nuclear structure of the short-lived heaviest atoms at the far end of Mendeleev’s periodic table.

“The vast majority of the actinide and transactinide elements do not occur in nature and are difficult to produce artificially in weighable quantities.” says Iain Moore, Professor at the University of Jyväskylä. “Performing spectroscopy of these elements therefore, necessitated the development of a new, extremely sensitive and accurate technique, based on laser ionisation spectroscopy of radioactive atoms in a gas jet moving at supersonic velocities.” he adds. This new technique has been applied to study the nuclear structure of actinium atoms, produced at the Leuven Isotope Separator On-line:LISOL facility in Louvain-la-Neuve, Belgium.''

Actinium, with 89 protons, is the first and eponymous element of the actinide group. It has only one long-lived isotope, 227Ac with a lifetime of 21.8 years, limiting our knowledge of the atomic transitions in this element and thus, making laser spectroscopy experiments very difficult. At the cyclotron in Louvain-la-Neuve, actinium atoms were produced in a nuclear-fusion reaction by bombarding a thin gold foil with neon nuclei.

The actinium atoms were then stopped in the surrounding argon gas and transported in the cold supersonic jet of a "de Laval" nozzle, a miniaturised version, resembling the exhaust of rocket engines, towards a laser interaction zone. In such conditions, resonance laser ionisation is used to ionise the atoms and perform spectroscopy studies. Pure ion beams of actinium are finally separated according to their mass to gain isotopic selection and are electrostatically guided to a detector array.

"With this new technique, which is generally applicable, the spectral resolution is improved by more than an order of magnitude without loss of efficiency and detailed experiments now become possible on nuclei produced at a rate of only one atom every ten seconds." says KU Leuven scientist Dr. Rafael Ferrer, who led the experiment. ω.

Further information: Professor Iain D Moore, Department of Physics, University of Jyväskylä: Tel: +358 40 8054103, iain.d.moore at jyu.fi

The Paper: R. Ferrer et al. 'Towards high-resolution laser ionization spectroscopy of the heaviest elements in supersonic gas jet expansion', Nat. Commun. 8, 14520 doi:10.1038/ncomms14520 2017.

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Physicists Discover a New Form of Light With Its Own Angular Momentum Amounting to Half of Planck's Constant


|| February 18: 2017: Trinity College University of Dublin News || ά. If, a story or news, has not been read or seen by a reader, it remains new to that reader until she:he reads it, regardless of how long ago this news was first published. This story was published on May 11, 2016, we treat it as such a story that many people outside the very and immediate reach of this beautiful institution and those who are immediately involved in this field, would have read about. And here it is for another reason for anything that speaks of any kind of light, The Humanion will seek it and speak about it. And this story involves the light. Physicists from Trinity College Dublin’s School of Physics and the CRANN Institute, Trinity College, have discovered a new form of light, which will impact our understanding of the fundamental nature of light.

One of the measurable characteristics of a beam of light is known as angular momentum. Until now, it was thought that in all forms of light the angular momentum would be a multiple of Planck’s constant, the physical constant that sets the scale of quantum effects. Now, recent PhD graduate Kyle Ballantine and Professor Paul Eastham, both from Trinity College Dublin’s School of Physics, along with Professor John Donegan from CRANN, have demonstrated a new form of light where the angular momentum of each photon, a particle of visible light, takes only half of this value. This difference, though small, is profound. These results were recently published in the online journal Science Advances.

Commenting on their work, Assistant Professor Paul Eastham said, “We’re interested in finding out how we can change the way light behaves and how that could be useful. What I think is so exciting about this result is that even this fundamental property of light, that physicists have always thought was fixed, can be changed.”

Professor John Donegan said, “My research focuses on nanophotonics, which is the study of the behaviour of light on the nanometer scale. A beam of light is characterised by its colour or wavelength and a less familiar quantity known as angular momentum. Angular momentum measures how much something is rotating. For a beam of light, although travelling in a straight line, it can also be rotating around its own axis.

So when light from the mirror hits your eye in the morning, every photon twists your eye a little, one way or another. Our discovery will have real impacts for the study of light waves in areas such as secure optical communications.”

Professor Stefano Sanvito, Director of CRANN, said, “The topic of light has always been one of interest to physicists, while also being documented as one of the areas of physics that is best understood. This discovery is a breakthrough for the world of physics and science alike. I am delighted to, once again, see CRANN and Physics in Trinity producing fundamental scientific research that challenges our understanding of light.”

To make this discovery, the team involved used an effect discovered in the same institution almost 200 years before. In the 1830s, mathematician William Rowan Hamilton and physicist Humphrey Lloyd found that, upon passing through certain crystals, a ray of light became a hollow cylinder. The team used this phenomenon to generate beams of light with a screw-like structure.

Analysing these beams within the theory of quantum mechanics they predicted that the angular momentum of the photon would be half-integer and devised an experiment to test their prediction. Using a specially constructed device they were able to measure the flow of angular momentum in a beam of light. They were also able, for the first time, to measure the variations in this flow caused by quantum effects. The experiments revealed a tiny shift, one-half of Planck’s constant, in the angular momentum of each photon.

Theoretical physicists since the 1980s have speculated how quantum mechanics works for particles that are free to move in only two of the three dimensions of space. They discovered that this would enable strange new possibilities, including particles whose quantum numbers were fractions of those expected. This work shows, for the first time, that these speculations can be realised with light. The journal article can be read here. ω.

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How Do You Observe and Measure the Optical Spectrum of an Anti-Hydrogen Atom: Well, Build a Sophisticated Refrigerator to Begin with

Rob Thompson, right, department head and professor in the Department of Physics and Astronomy in the Faculty of Science
and a longtime member of ALPHA, with UCalgary PhD student Andrew Evans. Image: Riley Brandt, University of Calgary
 

|| February 12: 2017: University of Calgary Canada News:  Mark Lowey Writing || ά. An international collaboration that includes University of Calgary scientists has measured a frequency of light or optical 'fingerprint' of antimatter for the first time. The ALPHA collaboration, in an experiment done at the CERN particle physics laboratory in Geneva, Switzerland, used a laser to observe and measure the optical spectrum of an antihydrogen atom. This spectroscopic measurement, which allows the light spectrum of matter and antimatter to be compared for the first time, brings scientists a significant step closer to unravelling the mystery of antimatter and how our universe formed.

“ALPHA is testing the very foundation of physics. We’re trying to see if there’s anything missing in our understanding of the world around us.” says Rob Thompson, department Head and Professor in the Department of Physics and Astronomy in the Faculty of Science and a longtime member of ALPHA. Based on the new finding, 'so far, our fundamental theories in physics are consistent.” he says. The team’s research, 'Observation of the 1S-2S Transition in Trapped Antihydrogen' is published in the Journal Nature.

Physics is governed by a set of fundamental theories or symmetries, which requires equal amounts of matter and antimatter to have been produced in the Big Bang that created the universe. These symmetries also require matter and antimatter to be identical mirror images of each other. The paired subatomic particles that make up matter have, respectively, a positive and a negative electrical charge. So the paired particles that make up antimatter should have the opposite charge, the mirror image.

The mystery is that everything in the observable universe appears to be made of matter. So is the antimatter hiding somewhere or does the universe actually consist mostly of matter? “In either case, it suggests there’s something missing in our understanding of the physical world.” says Thompson, a member of the University of Calgary’s Quantum Optics Research Group. “The goal of ALPHA from its launch over a decade ago was and continues to be to test and measure that ‘mirror image-ness’ of matter and antimatter.”

The ALPHA collaboration includes about 50 scientists, about one-third from Canada, from 14 institutions in seven countries. To achieve its newest milestone, the ALPHA team first spent years figuring out how to make, trap and finally study antimatter by manipulating its subatomic particles, called antiprotons and positrons.

By 2011, the team had built and used an apparatus called ALPHA-1 to successfully trap and hold antihydrogen in magnetic confinement fields for 15 minutes or more. The team then built a second-generation apparatus, called ALPHA-2, which enabled them to use a laser beam to measure a precisely tuned frequency of light, called a spectral line, absorbed by the antihydrogen.

The researchers found no difference between the antihydrogen and the equivalent spectral line in hydrogen. Both the antimatter and the matter absorb light at the same frequency, indicating that to a precision of a few parts in 10 billion, the current laws of physics hold. “We now know how to measure this property in antimatter and we know the techniques we can use to continue to push the precision frontier further and further.” Thompson notes.

Doing so may reveal whether there are any differences between matter and antimatter. Even small differences will open up a whole new realm of physics. A key to ALPHA’s successful experiment was being able to cool the fast-moving antiprotons and positrons that constitute antimatter, sufficiently slowing down these particles to make antihydrogen and trap it long enough to be studied.

An essential component required to accomplish this extreme cooling is a sophisticated ‘refrigerator’ or cooling device called a cryostat, mostly fabricated in the Faculty of Science’s Science Workshop. The device was designed at ALPHA-Canada’s home institution TRIUMF, Canada’s national subatomic physics laboratory located in Vancouver.

Using liquid helium as a coolant in a vacuum-tight chamber, the cryostat chills the experimental ALPHA apparatus from 20 degrees Celsius to close to minus 270 degrees C or nearly absolute zero degrees Kelvin. “That allows us to start with the antimatter particles cold enough that we can then use other techniques to cool them further so we can trap and study them.” Thompson says. “We couldn’t have done the experiments without the cryostat.”

The ALPHA team is now designing and constructing ALPHA-g, a new vertical apparatus to measure whether dropped antimatter will fall exactly like matter in Earth’s gravity. The University of Calgary is leading this multinational Canada Foundation for Innovation project, with about 80 per cent of the funding provided by Canada including contributions from provincial partners Alberta, British Columbia and Ontario. ω.

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The Matters and Their Anti: New Breakthrough Opens the Path for Atomic Antimatter Study 

Image: Swansea University

|| February 02: 2017: Swansea University News || ά. Swansea University scientists working at CERN have made a landmark finding, taking them one step closer to answering the question of why matter exists and illuminating the mysteries of the Big Bang and the birth of the Universe. In their paper published in Nature the physicists from the University’s College of Science, working with an international collaborative team at CERN, describe the first precision study of antihydrogen, the antimatter equivalent of hydrogen.

Professor Mike Charlton said: “The existence of antimatter is well established in physics, and it is buried deep in the heart of some of the most successful theories ever developed. But we have yet to answer a central question of why didn’t matter and antimatter, which it is believed were created in equal amounts when the Big Bang started the Universe, mutually self-annihilate? We also have yet to address why there is any matter left in the Universe at all. This conundrum is one of the central open questions in fundamental science, and one way to search for the answer is to bring the power of precision atomic physics to bear upon antimatter.”

It has long been established that any excited atom will reach its lowest state by emitting photons and the spectrum of light emitted from them represents a kind of atomic fingerprint and it is a unique identifier. The most familiar everyday example is the orange of the sodium streetlights.

Hydrogen has its own spectrum and as the simplest and most abundant atom in the Universe, it holds a special place in physics. The properties of the hydrogen atom are known with high accuracy, and one in particular, the so-called 1S-2S transition has been determined with a precision close to one part in a hundred trillion, equivalent to knowing the distance between Swansea and London to about a billionth of a metre!

Now in these latest experiments, the team have replaced the proton nucleus of the ordinary atom by an antiproton, and the electron substitute is the positron. By shining laser light at a well-defined frequency onto antihydrogen atoms held in a trap, they have seen that some of them get excited to an upper level, and in so doing leave the trap. This very first experiment has already determined the frequency of the antihydrogen transition to a few parts in a tenth of a billion.

Professor Mike Charlton added, “To get some sense of the importance of this discovery, we need to understand that it has been 30 years in the making and represents the collaborative work of hundreds of researchers over the years. Enquiries into this area of physics started in the 1980s and this landmark achievement has now opened the door to precision studies of atomic antimatter, which will hopefully bring us closer to answering the question of why matter exists to help solve the mystery as to how the Universe came about.”

The Swansea team are: Academic: Professor Mike Charlton, Dr Stefan Eriksson, Dr Aled Isaac, Professor Niels Madsen, Professor Dirk Peter van der Werf. Research Fellows: Dr Chris Baker and Dr Dan Maxwell. Post-Graduate students: Steven Armstrong Jones and Muhammed Sameed. ω.

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The Hubble Constant: The New Challenge for the Current Universe-View

The H0LiCOW Group, Dr Thomas Collett, second from the left. Image: University of Portsmouth

 

|| January 29: 2017: University of Portsmouth News || ά. An international group of astronomers, including one from the University of Portsmouth, has used galaxies as giant gravitational lenses to calculate a faster than expected expansion of the Universe. The team used the Hubble Space Telescope and other telescopes in space and on the ground to observe five galaxies to calculate the independent measure of the Hubble constant, the unit of measurement used to describe the expansion of the Universe.

The findings agree with other measurements of the Hubble constant in the local Universe, which used stars and supernovae as points of reference. However, they differ from those made by the European Space Agency:ESA Planck satellite, which measured the Hubble constant for the early Universe by observing the cosmic microwave background. This means there is a serious discrepancy, which lies at the heart of our astronomical understanding. Astrophysicist Dr Thomas Collett, from the University of Portsmouth’s Institute of Cosmology and Gravitation, is a member of the H0LiCOW collaboration, the group of astronomers who conducted the research.

Dr Thomas said, “We’ve measured how fast the Universe is expanding today, and it’s faster than we had expected. When we take measurements from the edge of the Universe made by ESA’s Planck satellite and extrapolate to today, we expect the expansion to be five per cent slower than measured from these lenses. Astronomers using other methods have independently got similar results that agree with ours, so this discrepancy with Planck might be a sign that the standard cosmological model is missing something new and important.”

Dr Collett developed algorithms to account for the effect of the weak deflections caused by the other galaxies near the line of sight of the primary lens. He was also responsible for combining the measured distance with the Planck constraints to test which extensions to the standard cosmological model might explain the discrepancy between the two results.

He said, “While the value for the Hubble constant determined by the ESA Planck satellite fits with our current understanding of the cosmos, the values obtained by the different groups of astronomers for the local Universe are in disagreement with our accepted theoretical model of the Universe.”

The H0LiCOW collaboration is led by Sherry Suyu, Max Planck TUM Professor at the Technical University Munich and the Max Planck Institute for Astrophysics in Germany. Professor Suyu said, “The expansion rate of the Universe is now starting to be measured in different ways with such high precision that actual discrepancies may possibly point towards new physics beyond our current knowledge of the Universe.”

The study targeted massive galaxies positioned between Earth and very distant quasars, incredibly luminous galaxy cores. Strong gravitational lensing causes the light from the more distant quasars to be bent around the huge masses of the galaxies. This creates multiple images of the background quasar.

Dr Collett explains the method, “Each of the images of the background quasar travels on a different path past the lens galaxy and through the Universe. These paths have different lengths, so the light takes a few weeks more or less to reach us. These ‘time-delays’ can be measured because the background quasar flickers. Once we have measured the time-delays, which has taken the team several years of monitoring, we can convert them into a measurement of the Hubble constant using our model of how the matter is distributed in the lens.”

Co-Lead Frédéric Courbin from École Polytechnique Fédérale de Lausanne:EPFL, Switzerland, said, ''Our method is the most simple and direct way to measure the Hubble constant as it only uses geometry and General Relativity, and no other assumptions.”

Using the accurate measurements of the time delays between the multiple images, as well as computer models, has allowed the team to determine the Hubble constant to an impressively high precision of 03.8 per cent.

Professor Suyu added, “The Hubble constant is crucial for modern astronomy as it can help to confirm or refute whether our picture of the Universe, composed of dark energy, dark matter and normal matter, is actually correct, or if we are missing something fundamental.” ω.

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As a Matter of Fact Matters are Getting Closer to Antimatter

 

|| December 19: 2016: University of Manchester News || ά.  A researcher from the University of Manchester has played a key role in a major breakthrough to help solve one of the great unsolved mysteries in modern science – the puzzling imbalance between matter and antimatter in the visible Universe. Dr Will Bertsche, a lecturer at Manchester’s School of Physics and Astronomy, plays a leading role in the international ALPHA collaboration which has achieved a breakthrough development in precision measurement of atomic antimatter.

The observed asymmetry of matter and antimatter in the visible Universe is a long standing and unsolved problem in physics since the first proposal and subsequent observation of antimatter which occurred in the early 20th century, spanning the 1920s and 1930s. The use of neutral antimatter atomic systems to test matter:antimatter asymmetry has been a goal for the past 40 years. The new research, supported by Dr Bertsche, has been published in a paper entitled ‘Observation of the 1S-2S transition in trapped antihydrogen’ by prestigious journal Nature and it represents the first significant milestone on precision CPT, Charge, Parity and Time, tests with atomic antimatter.

“The published result is the first of its kind, light of a specific colour was used to resonantly excite an antihydrogen atom from its ground state to an excited state. The question being asked is whether the colour of light required to accomplish this for antihydrogen is different from that of hydrogen as a test of observed matter and antimatter symmetry in the Universe.” explained Dr Bertsche.

“Any minute difference found between these would have profound consequences to our understanding of the Universe. For this initial measurement, the difference between the two has been limited to approximately 200 parts per trillion of the frequency. The goal of antihydrogen spectroscopy is to ultimately test matter:antimatter symmetry at high precision in order to try to understand why there is so little antimatter left in the Universe today.

“This is an important measurement in the field as it represents a landmark achievement from which many new measurements will be possible.”

Dr Bertsche is a key member of the international team of researchers that operate the ALPHA antimatter experiment based at CERN, the research powerhouse that is home to world-leading physicists and engineers probing the fundamental structure of our Universe.

He has served as the Technical Co-ordinator of the ALPHA collaboration for the last five years and consequently managed and organised the realisation of the apparatus used to make this measurement, known as ALPHA-2. ω.  

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Researchers Discovered Elusive Half-Quantum Vortices in Superfluid Helium

A half-quantum vortex combines circular spin flow and circular mass flow, leading to the formation of vortex
pairs that can be observed experimentally. Image: Ella Maru Studio.
 

|| December 19: 2016: Aalto University News || ά. Researchers in Aalto University, Finland, and P.L. Kapitza Institute in Moscow have discovered half-quantum vortices in superfluid helium. This vortex is a topological defect, exhibited in superfluids and superconductors, which carries a fixed amount of circulating current.

‘This discovery of half-quantum vortices culminates a long search for these objects originally predicted to exist in superfluid helium in 1976.’ says Samuli Autti, Doctoral Candidate at Aalto University in Finland. ‘In the future, our discovery will provide access to the cores of half-quantum vortices, hosting isolated Majorana modes, exotic solitary particles. Understanding these modes is essential for the progress of quantum information processing, building a quantum computer.’ Autti continues.

Macroscopic coherence in quantum systems such as superfluids and superconductors provides many possibilities, and some central limitations. For instance, the strength of circulating currents in these systems is limited to certain discrete values by the laws of quantum mechanics.

A half-quantum vortex overcomes that limitation using the non-trivial topology of the underlying material, a topic directly related to the 2016 Nobel Prize in physics.

Among the emerging properties is one analogous to the so-called Alice string in high-energy physics, where a particle on a route around the string flips the sign of its charge. In general the quantum character of these systems is already utilized in ultra-sensitive SQUID amplifiers and other important quantum devices.

The research article has been published on December 14 in the online version of Physical Review Letters. The article has also been highlighted in online publication Physics:DOI: 10.1103/Physics.9.148: Experiments were done in the Low Temperature Laboratory at the national OtaNano infrastructure. The research group is part of the Centre of Excellence in Low Temperature Quantum Phenomena and Devices at Aalto University.

For more information: Samuli Autti, Doctoral Candidate: Aalto University, Dept. of Physics: samuli.autti at aalto.fi: +358 400 458 345

Rota Superfluids research group

Article: S. Autti, V.V. Dmitriev, J.T. Mäkinen, A.A. Soldatov, G.E. Volovik, A.N. Yudin V.V. Zavjalov, and V.B. Eltsov: Observation of Half-Quantum Vortices in Topological Superfluid 3He. Physical Review Letters 2016. DOI: 10.1103/PhysRevLett.117.255301. ω.  

Whatever Your Field of Work and Wherever in the World You are, Please, Make a Choice to Do All You Can to Seek and Demand the End of Death Penalty For It is Your Business What is Done in Your Name. The Law That Makes Humans Take Part in Taking Human Lives and That Permits and Kills Human Lives is No Law. It is the Rule of the Jungle Where Law Does Not Exist. The Humanion

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Electrifying Spacecraft Propulsion

Neil Wallace: Electric Propulsion Engineer: Image: ESA

 

|| December 04: 2016: Neil Wallace: Electric Propulsion Engineer Writing || ά. Electric propulsion has been around for a long time, 1920s rocket pioneer Robert Goddard wrote about it. Perhaps it was an idea ahead of its time, because when I got into the space industry the thinking was that chemical thrusters were good enough, certainly for telecom missions. The platforms were small, working lifetimes were limited, power availability was constrained and electronics didn’t last that long then either. All that started to change around the turn of the century, with a creeping up of mass, lifetime and power that made the various electric propulsion technologies more attractive.

From Ariane five rockets to small onboard thrusters, standard chemical thrusters work in the same way, squirting together chemicals that react in the form of heat, sending out exhaust to trigger an acceleration. These face a fundamental upper limit on performance however, set by the amount of energy in the chemical reaction that heats the ejected propellant, producing the thrust. Electric propulsion pumps extra energy into the thrust reaction to reach much higher propellant velocities, up to an order of magnitude or so more, because their propellant is accelerated using electrical energy generated by the spacecraft solar arrays.

There are a wide range of different engine designs, starting with resistojets that simply use a heater on exhaust gases, to arcjets that pass a current through them, to Hall effect thrusters, a Russian speciality which has found commercial success, based on ionising propellant and then the highest-efficiency gridded ion thruster I’ve done a lot of work with, and has been applied to ESA’s GOCE and now BepiColombo missions. Gridded ion thrusters reach very high exhaust speeds, typically an order of magnitude greater than chemical thrusters – because ionised propellant is accelerated through a set of high-voltage grids using electrical energy, freely available from solar arrays.

Much less propellant is required, although the down side is that thrust levels are much lower and therefore the initial spacecraft acceleration is also low, around the the weight of a Euro coin to start off with – meaning the thrusters have to keep firing for long periods to be effective. However, in space there is nothing to slow a spacecraft down, so the craft’s velocity ends up increasing dramatically. Assuming the same propellant mass, our T6 thrusters can accelerate BepiColombo to a speed 15 times greater than an equivalent chemical thruster.

The difficulty has been developing them, of course. There’s a physics side to understand and then an engineering side as well, to optimise the materials, achieve stable gas discharges and so on. What was originally the UK’s Farnborough Royal Aircraft Establishment, now the QinetiQ company has been researching electric propulsion since the early 1960s. These high-temperature thrusters require utmost reliability through thousands of on:off cycles, amounting to tens of thousands of hours of testing. 

The initial result was the 10-cm diameter T5 thruster, which became a key enabling technology for ESA’s gravity-mapping GOCE mission. Because GOCE stayed in the lowest possible orbit for maximum gravitational sensitivity, it needed a continuously throttling thruster to overcome constantly-varying drag from the thin vestiges of atmosphere. GOCE’s drag compensation system operated continuously throughout its four-year lifetime, responding in tenths of a second, the mission only ending when its xenon fuel finally ran out. Then came the scaled-up 22-cm T6, four of which will propel BepiColombo into Mercury orbit after its 2018 launch. The mission would not be realisable in its current form without them.

What’s needed next is a shift in scale. It took four years to build these four BepiColombo flight models, the real challenge would be to speed up production so the technology could be routinely available for missions, including large scale mega-constellations to come. ω.

Whatever Your Field of Work and Wherever in the World You are, Please, Make a Choice to Do All You Can to Seek and Demand the End of Death Penalty For It is Your Business What is Done in Your Name. The Law That Makes Humans Take Part in Taking Human Lives and That Permits and Kills Human Lives is No Law. It is the Rule of the Jungle Where Law Does Not Exist. The Humanion

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ESA Calls for Mission-Concepts for the Next Step Towards a Gravitational-Wave Observatory in Space: Deadline November 15

Artist's impression of two black holes as they spiral towards each other before merging, releasing gravitational waves, fluctuations in
the fabric of spacetime. Image: ESA:C.Carreau

 

|| October 25: 2016 || ά.  Today, ESA has invited European scientists to propose concepts for the third large mission in its science programme, to study the gravitational Universe. A spaceborne observatory of gravitational waves, ripples in the fabric of spacetime created by accelerating massive objects, was identified in 2013 as the goal for the third large mission, L-Three in ESA’s Cosmic Vision plan. A Gravitational Observatory Advisory Team was appointed in 2014, composed of independent experts.

The team completed its final report earlier this year, further recommending ESA to pursue the mission having verified the feasibility of a multisatellite design with free-falling test masses linked over millions of kilometres by lasers. Now, following the first detection of the elusive waves with ground-based experiments and the successful performance of ESA’s LISA Pathfinder mission, which demonstrated some of the key technologies needed to detect gravitational waves from space, the agency is inviting the scientific community to submit proposals for the first space mission to observe gravitational waves.

“Gravitational waves promise to open a new window for astronomy, revealing powerful phenomena across the Universe that are not accessible via observations of cosmic light.” says Alvaro Gimenez, ESA’s Director of Science. Predicted a century ago by Albert Einstein’s general theory of relativity, gravitational waves remained elusive until the first direct detection by the ground-based Laser Interferometer Gravitational-Wave Observatory and Virgo collaborations, made in September 2015 and announced earlier this year.

The signal originated from the coalescence of two black holes, each with some 30 times the mass of the Sun and about 01.3 billion light-years away. A second detection was made in December 2015 and announced in June, and revealed gravitational waves from another black hole merger, this time involving smaller objects with masses around seven and 14 solar masses. Meanwhile, the LISA Pathfinder mission was launched in December 2015 and started its scientific operations in March this year, testing some of the key technologies that can be used to build a space observatory of gravitational waves.

Data collected during its first two months showed that it is indeed possible to eliminate external disturbances on test masses placed in freefall at the level of precision required to measure passing gravitational waves disturbing their motion. While ground-based detectors are sensitive to gravitational waves with frequencies of around 100 Hz or a hundred oscillation cycles per second, an observatory in space will be able to detect lower-frequency waves, from 01 Hz down to 0.1 mHz. Gravitational waves with different frequencies carry information about different events in the cosmos, much like astronomical observations in visible light are sensitive to stars in the main stages of their lives while X-ray observations can reveal the early phases of stellar life or the remnants of their demise.

In particular, low-frequency gravitational waves are linked to even more exotic cosmic objects than their higher-frequency counterparts: supermassive black holes, with masses of millions to billions of times that of the Sun, that sit at the centre of massive galaxies. The waves are released when two such black holes are coalescing during a merger of galaxies, or when a smaller compact object, like a neutron star or a stellar-mass black hole, spirals towards a supermassive black hole.

Observing the oscillations in the fabric of spacetime produced by these powerful events will provide an opportunity to study how galaxies have formed and evolved over the lifetime of the Universe, and to test Einstein’s general relativity in its strong regime. Concepts for ESA’s L-Three mission will have to address the exploration of the Universe with low-frequency gravitational waves, complementing the observations performed on the ground to fully exploit the new field of gravitational astronomy. The planned launch date for the mission is 2034.

Lessons learned from LISA Pathfinder will be crucial to developing this mission, but much new technology will also be needed to extend the single-satellite design to multiple satellites. For example, lasers much more powerful than those used on LISA Pathfinder, as well as highly stable telescopes, will be necessary to link the freely falling masses over millions of kilometres.

Large missions in ESA’s Science Programme are ESA-led, but also allow for international collaboration. The first large-class mission is Juice, the JUpiter ICy moons Explorer, planned for launch in 2022, and the second is Athena, the Advanced Telescope for High-ENergy Astrophysics, an X-ray observatory to investigate the hot and energetic Universe, with a planned launch date in 2028.

Letters of intent for ESA’s new gravitational-wave space observatory must be submitted by November 15, and the deadline for the full proposal is January 16, 2017. The selection is expected to take place in the first half of 2017, with a preliminary internal study phase planned for later in the year. More information visit: ω.

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University of Portsmouth Presents the Largest Ever Map of Voids and Superclusters

Figure Two: The cosmic microwave background over the whole sky, with the unusual ‘Cold Spot’ feature circled at the lower right.

|| October 12: 2016: University of Portsmouth News || ά. A team of astrophysicists at the University of Portsmouth have created the largest ever map of voids and superclusters in the Universe, which helps solve a long-standing cosmological mystery. The map of the positions of cosmic voids, large empty spaces which contain relatively few galaxies, and superclusters, huge regions with many more galaxies than normal, can be used to measure the effect of dark energy ‘stretching’ the Universe. The results confirm the predictions of Einstein’s theory of gravity. Lead author Dr Seshadri Nadathur from the University’s Institute of Cosmology and Gravitation said: “We used a new technique to make a very precise measurement of the effect that these structures have on photons from the cosmic microwave background:CMB light left over from shortly after the Big Bang, passing through them.

Light from the CMB travels through such voids and superclusters on its way to us. According to Einstein’s General Theory of Relativity, the stretching effect of dark energy causes a tiny change in the temperature of CMB light depending on where it came from. Photons of light travelling through voids should appear slightly colder than normal and those arriving from superclusters should appear slightly hotter. This is known as the integrated Sachs-Wolfe:ISW effect.

When this effect was studied by astronomers at the University of Hawai’i in 2008 using an older catalogue of voids and superclusters, the effect seemed to be five times bigger than predicted. This has been puzzling scientists for a long time, so we looked at it again with new data.”

Figure One: The effect of voids and superclusters seen in patches of the cosmic microwave background:CMB. Photons of the CMB that have travelled through void regions on average appear slightly colder than average, left panel, and those coming from supercluster regions appear slightly hotter, right panel. The colour scale shows the temperature differences, with blue being coldest and red hottest. The circles show the regions over which the effect is expected to be important.

To create the map of voids and superclusters, the Portsmouth team used more than three-quarters of a million galaxies identified by the Sloan Digital Sky Survey. This gave them a catalogue of structures more than 300 times bigger than the one previously used.

The scientists then used large computer simulations of the Universe to predict the size of the ISW effect. Because the effect is so small, the team had to develop a powerful new statistical technique to be able to measure the CMB data.

They applied this technique to CMB data from the Planck satellite, and were able to make a very precise measurement of the ISW effect of the voids and superclusters. Unlike in the previous work, they found that the new result agreed extremely well with predictions using Einstein’s gravity.

Dr Nadathur said: “Our results resolve one long-standing cosmological puzzle, but doing so has deepened the mystery of a very unusual ‘Cold Spot’ in the CMB. It has been suggested that the Cold Spot could be due to the ISW effect of a gigantic ‘supervoid’ which has been seen in that region of the sky. But if Einstein’s gravity is correct, the supervoid isn’t big enough to explain the Cold Spot.

It was thought that there was some exotic gravitational effect contradicting Einstein which would simultaneously explain both the Cold Spot and the unusual ISW results from Hawai’i. But this possibility has been set aside by our new measurement, and so the Cold Spot mystery remains unexplained.”

The paper is published today in the Astrophysical Journal Letters. ω.

Images: University of Portsmouth
 

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David J. Thouless,  F. Duncan M. Haldane and J. Michael Kosterlitz Awarded The Nobel Prize in Physics 2016

Image:L-R: 01: David J. Thouless, Trinity Hall, Cambridge University. Image: Kiloran Howard: 02: F. Duncan M. Haldane,
Princeton University, Comms. Office, Image: D. Applewhite: 03: J. Michael Kosterlitz: Image Ill: N. Elmehed at the Nobel Media 2016
 

|| October 04: 2016|| ά. The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2016 with one half to David J. Thouless, University of Washington, Seattle, WA, USA and the other half to F. Duncan M. Haldane, Princeton University, NJ, USA and J. Michael Kosterlitz, Brown University, Providence, RI, USA ”for theoretical discoveries of topological phase transitions and topological phases of matter”. They revealed the secrets of exotic matter

This year’s Laureates opened the door on an unknown world where matter can assume strange states. They have used advanced mathematical methods to study unusual phases, or states, of matter, such as superconductors, superfluids or thin magnetic films. Thanks to their pioneering work, the hunt is now on for new and exotic phases of matter. Many people are hopeful of future applications in both materials science and electronics.

The three Laureates’ use of topological concepts in physics was decisive for their discoveries. Topology is a branch of mathematics that describes properties that only change step-wise. Using topology as a tool, they were able to astound the experts. In the early 1970s, Michael Kosterlitz and David Thouless overturned the then current theory that superconductivity or suprafluidity could not occur in thin layers. They demonstrated that superconductivity could occur at low temperatures and also explained the mechanism, phase transition, that makes superconductivity disappear at higher temperatures.

In the 1980s, Thouless was able to explain a previous experiment with very thin electrically conducting layers in which conductance was precisely measured as integer steps. He showed that these integers were topological in their nature. At around the same time, Duncan Haldane discovered how topological concepts can be used to understand the properties of chains of small magnets found in some materials.

We now know of many topological phases, not only in thin layers and threads, but also in ordinary three-dimensional materials. Over the last decade, this area has boosted frontline research in condensed matter physics, not least because of the hope that topological materials could be used in new generations of electronics and superconductors, or in future quantum computers. Current research is revealing the secrets of matter in the exotic worlds discovered by this year’s Nobel Laureates.

David J. Thouless, born 1934 in Bearsden, UK. Ph.D. 1958 from Cornell University, Ithaca, NY, USA. Emeritus Professor at the University of Washington, Seattle, WA, USA.

F. Duncan M. Haldane, born 1951 in London, UK. Ph.D. 1978 from Cambridge University, UK. Eugene Higgins Professor of Physics at Princeton University, NJ, USA.

J. Michael Kosterlitz, born 1942 in Aberdeen, UK. Ph.D. 1969 from Oxford University, UK. Harrison E. Farnsworth Professor of Physics at Brown University, Providence, RI, USA. ω.

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NASA's Fermi Mission Expands Its Search for Dark Matter

The Small Magellanic Cloud:SMC, at centre, is the second-largest satellite galaxy orbiting our own. This image superimposes a photograph of the SMC with one half of a model of its dark matter, right of centre. Lighter colours indicate greater density and show a strong concentration toward the galaxy's centre. Ninety-five percent of the dark matter is contained within a circle tracing the outer edge of the model shown. In six years of data, Fermi finds no indication of gamma rays from the SMC's dark matter. Image: Dark matter, R. Caputo et al. 2016; background, Axel Mellinger, Central Michigan University

 

|| August 14: 2016|| ά. Dark matter, the mysterious substance that constitutes most of the material universe, remains as elusive as ever. Although experiments on the ground and in space have yet to find a trace of dark matter, the results are helping scientists rule out some of the many theoretical possibilities. Three studies published earlier this year, using six or more years of data from NASA's Fermi Gamma-ray Space Telescope, have broadened the mission's dark matter hunt using some novel approaches.

“We've looked for the usual suspects in the usual places and found no solid signals, so we've started searching in some creative new ways," said Julie McEnery, Fermi project scientist at NASA's Goddard Space Flight Centre in Greenbelt, Maryland. "With these results, Fermi has excluded more candidates, has shown that dark matter can contribute to only a small part of the gamma-ray background beyond our galaxy, the Milky Way, and has produced strong limits for dark matter particles in the second-largest galaxy orbiting it."

Dark matter neither emits nor absorbs light, primarily interacts with the rest of the universe through gravity, yet accounts for about 80 percent of the matter in the universe. Astronomers see its effects throughout the cosmos, in the rotation of galaxies, in the distortion of light passing through galaxy clusters, and in simulations of the early universe, which require the presence of dark matter to form galaxies at all.

The leading candidates for dark matter are different classes of hypothetical particles. Scientists think gamma rays, the highest-energy form of light, can help reveal the presence of some of types of proposed dark matter particles. Previously, Fermi has searched for tell-tale gamma-ray signals associated with dark matter in the center of our galaxy and in small dwarf galaxies orbiting our own. Although no convincing signals were found, these results eliminated candidates within a specific range of masses and interaction rates, further limiting the possible characteristics of dark matter particles.

Among the new studies, the most exotic scenario investigated was the possibility that dark matter might consist of hypothetical particles called axions or other particles with similar properties. An intriguing aspect of axion-like particles is their ability to convert into gamma rays and back again when they interact with strong magnetic fields. These conversions would leave behind characteristic traces, like gaps or steps, in the spectrum of a bright gamma-ray source.

Manuel Meyer at Stockholm University led a study to search for these effects in the gamma rays from NGC 1275, the central galaxy of the Perseus galaxy cluster, located about 240 million light-years away. High-energy emissions from NGC 1275 are thought to be associated with a supermassive black hole at its center. Like all galaxy clusters, the Perseus cluster is filled with hot gas threaded with magnetic fields, which would enable the switch between gamma rays and axion-like particles. This means some of the gamma rays coming from NGC 1275 could convert into axions, and potentially back again, as they make their way to us.

Meyer's team collected observations from Fermi's Large Area Telescope:LAT and searched for predicted distortions in the gamma-ray signal. The findings, published April 20 in Physical Review Letters, exclude a small range of axion-like particles that could have comprised about 4 percent of dark matter. "While we don't yet know what dark matter is, our results show we can probe axion-like models and provide the strongest constraints to date for certain masses," Meyer said. "Remarkably, we reached a sensitivity we thought would only be possible in a dedicated laboratory experiment, which is quite a testament to Fermi."

Another broad class of dark matter candidates are called Weakly Interacting Massive Particles:WIMPs. In some versions, colliding WIMPs either mutually annihilate or produce an intermediate, quickly decaying particle. Both scenarios result in gamma rays that can be detected by the LAT.

Regina Caputo at the University of California, Santa Cruz, sought these signals from the Small Magellanic Cloud:SMC, which is located about 200,000 light-years away and is the second-largest of the small satellite galaxies orbiting the Milky Way. Part of the SMC's appeal for a dark matter search is that it lies comparatively close to us and its gamma-ray emission from conventional sources, like star formation and pulsars, is well understood.

Most importantly, astronomers have high-precision measurements of the SMC's rotation curve, which shows how its rotational speed changes with distance from its centre and indicates how much dark matter is present. In a paper published in Physical Review D on March 22, Caputo and her colleagues modelled the dark matter content of the SMC, showing it possessed enough to produce detectable signals for two WIMP types.

"The LAT definitely sees gamma rays from the SMC, but we can explain them all through conventional sources," Caputo said. "No signal from dark matter annihilation was found to be statistically significant." In the third study, researchers led by Marco Ajello at Clemson University in South Carolina and Mattia Di Mauro at SLAC National Accelerator Laboratory in California took the search in a different direction. Instead of looking at specific astronomical targets, the team used more than 6.5 years of LAT data to analyze the background glow of gamma rays seen all over the sky.

The nature of this light, called the extragalactic gamma-ray background:EGB has been debated since it was first measured by NASA's Small Astronomy Satellite 02 in the early 1970s. Fermi has shown that much of this light arises from unresolved gamma-ray sources, particularly galaxies called blazars, which are powered by material falling toward gigantic black holes. Blazars constitute more than half of the total gamma-ray sources seen by Fermi, and they make up an even greater share in a new LAT catalogue of the highest-energy gamma rays.

Some models predict that EGB gamma rays could arise from distant interactions of dark matter particles, such as the annihilation or decay of WIMPs. In a detailed analysis of high-energy EGB gamma rays, published April 14 in Physical Review Letters, Ajello and his team show that blazars and other discrete sources can account for nearly all of this emission.

"There is very little room left for signals from exotic sources in the extragalactic gamma-ray background, which in turn means that any contribution from these sources must be quite small," Ajello said. "This information may help us place limits on how often WIMP particles collide or decay." Although these latest studies have come up empty-handed, the quest to find dark matter continues both in space and in ground-based experiments. Fermi is joined in its search by NASA's Alpha Magnetic Spectrometer, a particle detector on the International Space Station.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

By Francis Reddy: NASA's Goddard Space Flight Center, Greenbelt, Md.

:Editor: Ashley Morrow:NASA: ω.

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Dark Matter Particle Remains Elusive


The photon sensors inside LUX: Image: C.H. Faham

|| July 24: 2016: UCL News || ά. The Large Underground Xenon:LUX dark matter experiment has yielded no trace of a dark matter particle after completing its final 20-month long search of the universe, according to LUX collaboration scientists including UCL researchers.  LUX’s sensitivity far exceeded the goals for the project and the team are confident that if dark matter particles had interacted with the LUX’s Xenon target, the detector would almost certainly have seen it. This finding enables scientists to confidently eliminate many potential models for dark matter particles, offering critical guidance for the next generation of experiments.

“The discovery of the nature of the elusive dark matter that accounts for more than four-fifths of the mass of the universe is internationally recognised as one of the highest priorities in science, and the LUX experiment is the world-leading experiment in the direct search of it,” explained UCL LUX collaboration scientist Dr Cham Ghag, UCL Physics & Astronomy.

Scientists are confident that dark matter exists because the effects of its gravity can be seen in the rotation of galaxies and in the way light bends as it travels through the universe, but experiments have yet to make direct contact with a particle.

Dr Ghag added: “We’ve probed previously unexplored regions of parameter space with the aim of making the first definitive discovery of dark matter. Though a positive signal would have been welcome, nature was not so kind! Nonetheless, a null result is significant as it changes the landscape of the field by constraining models for what dark matter could be beyond anything that existed previously.”

UCL researchers played a significant role in the LUX experiment since 2012 by performing key data analyses, as well as being part of the maintenance and calibrations effort on-site at the Sanford Underground Research Facility a mile beneath rock in in the Black Hills of South Dakota.

The LUX experiment was designed to look for weakly interacting massive particles, or WIMPs – the leading theoretical candidate for a dark matter particle. If the WIMP idea is correct, billions of these particles pass through your hand every second, and also through the Earth and everything on it. But because WIMPs interact so weakly with ordinary matter, this ghostly traverse goes entirely unnoticed.

“We’ve worked on identifying and classifying pulses in the raw data collected by LUX to select candidate pulse signal events which could indicate weakly interacting massive particles, or WIMPs,” said collaborator UCL PhD student, Sally Shaw, UCL High Energy Physics.

“Pulse selection and identification is a vital part of the experiment as we’re looking for an extremely rare event, so it’s important to remove noise and events that do not exhibit signatures we expect to see from WIMP dark matter. We then used our findings to determine how efficient the detector is, and found that if a dark matter particle had hit the detector, we would have identified it.”

Over the next few months, LUX scientists will continue to analyse the crucial data that LUX was able to provide, in hope of helping future experiments that finally pin down a dark matter particle. To continue the hunt for a dark matter particle, the UCL team is now working on the LUX-ZEPLIN:(LZ experiment that will succeed LUX and is presently under construction. LZ will be over 70 times more sensitive than LUX.

Dr Jim Dobson, UCL Physics & Astronomy, said: “We’re responsible for ensuring the LZ experiment is constructed to unprecedented radio-purity requirements that limit background to extremely low levels in order to expose any signal from WIMPs hiding underneath. We must also accurately characterise the background pulses that do remain because before we can say we have detected WIMPs, we must know precisely what we expect from everything else. This will be crucial to ensure any future discoveries of dark matter are valid.”

The LUX scientific collaboration is supported by the US Department of Energy and National Science Foundation and includes 20 research universities and national laboratories in the United States, the United Kingdom, and Portugal.
ω.

Dr Cham Ghag's academic profile

Dr Jim Dobson's academic profile

UCL High Energy Physics

UCL Physics & Astronomy

LUX Dark Matter Experiment

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The Largest Galactic Map Will Throw Light on ‘Dark Energy’

A slice through the map of the large-scale structure of the Universe from the Sloan Digital Sky Survey and its Baryon Oscillation Spectroscopic Survey. Each dot in this picture indicates the position of a galaxy six billion years into the past. The image covers about 1/20th of the sky, a slice of the Universe 6 billion light-years wide, 4.5 billion light-years high, and 500 million light-years thick. Colour indicates distance from Earth, ranging from yellow on the near side of the slice to purple on the far side. Image courtesy: Daniel Eisenstein and SDSS-III.




|| July 14: 2016: University of Portsmouth News || ά. An international team of astronomers has created the largest ever three-dimensional map of distant galaxies in a bid to help them understand one of the most mysterious forces in the universe. Scientists including a team led by Dr Florian Beutler at the University of Portsmouth’s Institute of Cosmology and Gravitation have spent a decade collecting measurements of 1.2 million galaxies as part of the Sloan Digital Sky Survey III:SDSS-III.

This will allow them to make the most precise measurements to date of ‘dark energy’, the force that is driving the accelerated expansion of the universe. Dr Beutler said: “This extremely detailed three-dimensional map represents a colossal amount of work. The University of Portsmouth has worked with partner institutions for ten years, helping to gather measurements of galaxies making up a quarter of the sky.

“Using this map we will now be able to make the most accurate possible measurements of dark energy, and the part it plays in the expansion of the universe.”

The new measurements were carried out by the Baryon Oscillation Spectroscopic Survey:BOSS program of SDSS-III.

Shaped by a continuous tug-of-war between dark matter and dark energy, the map revealed by BOSS allows astronomers to measure the expansion rate of the universe and thus determine the amount of matter and dark energy that make up the present-day universe.

A collection of papers describing these results was submitted this week to the Monthly Notices of the Royal Astronomical Society. BOSS measures the expansion rate of the Universe by determining the size of the baryonic acoustic oscillations:BAO in the three-dimensional distribution of galaxies.

 

Dr Florian Beutler, of the Institute of Cosmology and Gravitation. Image courtesy: ICRAR

The original BAO size is determined by pressure waves that travelled through the young universe up to when it was only 400,000 years old, the Universe is presently 13.8 billion years old, at which point they became frozen in the matter distribution of the Universe.

Measuring the distribution of galaxies since that time allows astronomers to measure how dark matter and dark energy have competed to govern the rate of expansion of the Universe.

To measure the size of these ancient giant waves to such sharp precision, BOSS had to make an unprecedented and ambitious galaxy map, many times larger than previous surveys.

At the time the BOSS program was planned, dark energy had been previously determined to significantly influence the expansion of the Universe starting about 5 billion years ago. BOSS was thus designed to measure the BAO feature from before this point, 7 billion years ago, out to near the present day, 2 billion years ago.

Dr Beutler said: “If dark energy has been driving the expansion of the Universe over that time, our maps tells us that it is evolving very slowly, if at all. The change is at most 20 per cent over the past seven billion years.”

Dr Rita Tojeiro, of the University of St Andrews, a partner in the project, added: “We see a dramatic connection between the sound wave imprints seen in the cosmic microwave background 400,000 years after the Big Bang to the clustering of galaxies 7-12 billion years later.

“The ability to observe a single well-modelled physical effect from recombination until today is a great boon for cosmology.”

The map also reveals the distinctive signature of the coherent movement of galaxies toward regions of the universe with more matter, due to the attractive force of gravity. Crucially, the observed amount of infall is explained well by the predictions of general relativity. This agreement supports the idea that the acceleration of the expansion rate is driven by a phenomenon at the largest cosmic scales, such as dark energy, rather than a breakdown of gravitational theory.

Dr Jeremy Tinker, of New York University, added: “BOSS has marked an important cosmological milestone, combining precise clustering measurements of an enormous volume with extensive observations of the primary cosmic microwave background to produce a firm platform for the search for extensions to the standard cosmological model.

“We look forward to seeing this programme extended with the coming decade of large spectroscopic surveys.”

Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III website: ω.

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New Modelling of the Universe the Very Way Einstein Saw It

Dr Marco Bruni: Modelling Universe

|| June 24: 2016 || ά. Research teams in Europe and the USA, including a cosmologist from the University of Portsmouth, have begun modelling the universe for the first time using Einstein’s full general theory of relativity. The teams have independently created two new computer codes, which, they say, will lead to the most accurate possible models of the universe and provide new insights into gravity and its effects.

One hundred years since it was developed, Einstein’s theory remains the best theory of gravity, consistently passing high-precision tests in the solar system and successfully predicting phenomena such as gravitational waves, discovered earlier this year. But because the equations involved are so complex, physicists, until now, have been forced to simplify the theory when applying it to the universe. The two new codes are the first to use Einstein’s complete general theory of relativity to account for the effects of the clumping of matter in some regions and the lack of matter in others.

Dr Marco Bruni

Dr Marco Bruni, of the Institute of Cosmology and Gravitation, Portsmouth, said: “This is a really exciting development that will help cosmologists create the most accurate possible model of the universe.

Over the next decade we expect a deluge of new data coming from next generation galaxy surveys, which use extremely powerful telescopes and satellites to obtain high-precision measurements of cosmological parameters, an area where ICG researchers play a leading role. To match this precision we need theoretical predictions that are not only equally precise, but also accurate at the same level.

These new computer codes apply general relativity in full and aim precisely at this high level of accuracy, and in future they should become the benchmark for any work that makes simplifying assumptions.”

Work by the two teams, one team from Case Western Reserve University and Kenyon College, Ohio, the other, a partnership between Dr Bruni, a Reader in cosmology and gravitation, and Eloisa Bentivegna, a senior researcher at the University of Catania, Italy, will be highlighted today as Editors’ Suggestion by Physical Review Letters and Physical Review D and in a Synopsis on the American Physical Society Physics website.

Both groups of physicists were trying to answer the question of whether small-scale structures in the universe produce effects on larger distance scales. Both found that to be the case; however, they present concrete tests that show a departure from a purely averaged model.

The researchers say computer simulations employing the full power of general relativity are the key to producing more accurate results and perhaps new or deeper understanding.

Professor Glenn Starkman, of the American team, said: “No one has modelled the full complexity of the problem before. These papers are an important step forward, using the full machinery of general relativity to model the universe, without unwarranted assumptions of symmetry or smoothness. The universe doesn’t make these assumptions, neither should we.”

Both groups independently created software applying the Einstein Field Equations, which describe the complicated relationships between the matter content of the universe and the curvature of space and time, at billions of places and times over the history of the universe.

Comparing the outcomes of these new simulations to the outcomes of traditional simplified models, the researchers found that approximations break down. Dr Bruni said: “Much more work will be needed in future to fully comprehend the importance of the differences between simulations based on Einstein equations and those making simplifying assumptions. In the end, as always in physics, it will be the interplay between theory and observations that will further our understanding of the universe.”

PhD student James Martens took the lead in developing and implementing the numerical techniques for the US team, working with Tom Giblin, the Harvey F Lodish Development Professor of Natural Science at Kenyon College and an adjunct associate professor of physics at Case Western Reserve, and Glenn Starkman, professor of physics and director of the Institute for the Science of Origins at Case Western Reserve.  ω.

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NASA’s Van Allen Probes Reveal Long-term Behaviour of Earth’s Ring Current

During periods when there are no geomagnetic storms affecting the area around Earth (left image), high-energy protons (with energy of hundreds of thousands of electronvolts, or keV; shown here in orange) carry a substantial electrical current that encircles the planet, also known as the ring current. During periods when geomagnetic storms affect Earth (right), new low-energy protons (with energy of tens of thousands of electronvolts, or keV; shown here in magenta) enter the near-Earth region, enhancing the pre-existing ring current. Credits: Johns Hopkins APL


|| May 20: 2016 || ά. New findings based on a year's worth of observations from NASA’s Van Allen Probes have revealed that the ring current – an electrical current carried by energetic ions that encircles our planet – behaves in a much different way than previously understood.

The ring current has long been thought to wax and wane over time, but the new observations show that this is true of only some of the particles, while other particles are present consistently. Using data gathered by the Radiation Belt Storm Probes Ion Composition Experiment, or RBSPICE, on one of the Van Allen Probes, researchers have determined that the high-energy protons in the ring current change in a completely different way from the current’s low-energy protons. Such information can help adjust our understanding and models of the ring current – which is a key part of the space environment around Earth that can affect our satellites.

The findings were published in Geophysical Research Letters.

“We study the ring current because, for one thing, it drives a global system of electrical currents both in space and on Earth’s surface, which during intense geomagnetic storms can cause severe damages to our technological systems," said lead author of the study Matina Gkioulidou, a space physicist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “It also modifies the magnetic field in near-Earth space, which in turn controls the motion of the radiation belt particles that surround our planet. That means that understanding the dynamics of the ring current really matters in helping us understand how radiation belts evolve as well.”

The ring current lies at a distance of approximately 6,200 to 37,000 miles:10,000 to 60,000 km from Earth. The ring current was hypothesized in the early 20th century to explain observed global decreases in the Earth’s surface magnetic field, which can be measured by ground magnetometers. Such changes of the ground magnetic field are described by what's called the Sym-H index.

“Previously, the state of the ring current had been inferred from the variations of the Sym-H index, but as it turns out, those variations represent the dynamics of only the low-energy protons,” said Gkioulidou. “When we looked at the high-energy proton data from the RBSPICE instrument, however, we saw that they were behaving in a very different way, and the two populations told very different stories about the ring current.”

The Van Allen Probes, launched in 2012, offer scientists the first chance in recent history to continuously monitor the ring current with instruments that can observe ions with an extremely wide range of energies. The RBSPICE instrument has captured detailed data of all types of these energetic ions for several years. “We needed to have an instrument that measures the broad energy range of the particles that carry the ring current, within the ring current itself, for a long period of time,” Gkioulidou said. A period of one year from one of the probes was used for the team’s research.

“After looking at one year of continuous ion data it became clear to us that there is a substantial, persistent ring current around the Earth even during non-storm times, which is carried by high-energy protons. During geomagnetic storms, the enhancement of the ring current is due to new, low-energy protons entering the near-Earth region. So trying to predict the storm-time ring current enhancement while ignoring the substantial pre-existing current is like trying to describe an elephant after seeing only its feet,” Gkioulidou said.

The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, built and operates the Van Allen Probes for NASA's Science Mission Directorate. RBSPICE is operated by the New Jersey Institute of Technology in Newark, New Jersey. The mission is the second mission in NASA's Living With a Star program, managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Geoffrey Brown: Johns Hopkins University Applied Physics Laboratory, Laurel, Md.

Karen C. Fox: NASA's Goddard Space Flight Center, Greenbelt, Md.

:Editor: Rob Garner:NASA: ω.

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Comet 252P: The Rotating Jet

Comet 252P:LINEAR as it passed by Earth. Credits: NASA, ESA, and J.-Y. Li: Planetary Science Institute

 

|| May 14: 2016 || The images were taken on April 4, 2016, roughly two weeks after the icy visitor made its closest approach to Earth on March 21. The comet traveled within 3.3 million miles of Earth, or about 14 times the distance between our planet and the moon. These observations also represent the closest celestial object Hubble has observed, other than the moon.

The images reveal a narrow, well-defined jet of dust ejected by the comet’s icy, fragile nucleus. The nucleus is too small for Hubble to resolve. Astronomers estimate that it is less than one mile across. A comet produces jets of material as it travels close to the sun in its orbit. Sunlight warms ices in a comet’s nucleus, resulting in large amounts of dust and gas being ejected, sometimes in the form of jets. The jet in the Hubble images is illuminated by sunlight.

The jet also appears to change direction in the images, which is evidence that the comet’s nucleus is spinning. The spinning nucleus makes the jet appear to rotate like the water jet from a rotating lawn sprinkler. The images underscore the dynamics and volatility of a comet’s fragile nucleus.

Comet 252P/LINEAR is traveling away from Earth and the sun; its orbit will bring it back to the inner solar system in 2021, but not anywhere close to the Earth.

These visible-light images were taken with Hubble’s Wide Field Camera 3.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

For images, video, and more information about Comet 252P/LINEAR and Hubble, visit http://hubblesite.org/news/2016/14 http://www.nasa.gov/hubble

Donna Weaver / Ray Villard: Space Telescope Science Institute, Baltimore, Maryland: 410-338-4493 / 410-338-4514: dweaver@stsci.edu / villard@stsci.edu

Jian-Yang Li: Planetary Science Institute, Tucson, Arizona: 571-488-9999: jyli@psi.edu

:Editor: Ashley Morrow: NASA:

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MMS Reporting on Magnetic Reconnection

Karen C. Fox Writing

The four Magnetospheric Multiscale, or MMS, spacecraft (shown here in an artist's concept) have now made more than 4,000 trips through the boundaries of Earth's magnetic field, gathering observations of our dynamic space environment.

|| May 12: 2016 || Like sending sensors up into a hurricane, NASA has flown four spacecraft through an invisible maelstrom in space, called magnetic reconnection. Magnetic reconnection is one of the prime drivers of space radiation and so it is a key factor in the quest to learn more about our space environment and protect our spacecraft and astronauts as we explore farther and farther from our home planet.

Space is a better vacuum than any we can create on Earth, but it does contain some particles — and it's bustling with activity. It overflows with energy and a complex system of magnetic fields. Sometimes, when two sets of magnetic fields connect, an explosive reaction occurs: As the magnetic fields re-align and snap into a new formation they send particles zooming off in jets.

A new paper printed on May 12, 2016, in Science provides the first observations from inside a magnetic reconnection event. The research shows that magnetic reconnection is dominated by the physics of electrons — thus providing crucial information about what powers this fundamental process in nature.

The effects of this sudden release of particles and energy — such as giant eruptions on the sun, the aurora, radiation storms in near-Earth space, high energy cosmic particles that come from other galaxies — have been observed throughout the solar system and beyond. But we have never been able to witness the phenomenon of magnetic reconnection directly. Satellites have observed tantalizing glances of particles speeding by, but not the impetus — like seeing the debris flung out from a tornado, but never seeing the storm itself.

"We developed a mission, the Magnetospheric Multiscale mission, that for the first time would have the precision needed to gather observations in the heart of magnetic reconnection," said Jim Burch, the principal investigator for MMS at the Southwest Research Institute in San Antonio, Texas, and the first author of the Science paper. "We received results faster than we could have expected. By seeing magnetic reconnection in action, we have observed one of the fundamental forces of nature."

MMS is made of four identical spacecraft that launched in March 2015. They fly in a pyramid formation to create a full 3-D map of any phenomena they observe. On Oct. 16, 2015, the spacecraft traveled straight through a magnetic reconnection event at the boundary where Earth’s magnetic field bumps up against the sun’s magnetic field. In only a few seconds, the 25 sensors on each of the spacecraft collected thousands of observations. This unprecedented time cadence opened the door for scientists to track better than ever before how the magnetic and electric fields changed, as well as the speeds and direction of the various charged particles.

The science of reconnection springs from the basic science of electromagnetics, which dominates most of the universe and is a force as fundamental in space as gravity is on Earth. Any set of magnetic fields can be thought of as a row of lines. These field lines are always anchored to some body — a planet, a star — creating a giant magnetic network surrounding it. It is at the boundaries of two such networks where magnetic reconnection happens.

Imagine rows of magnetic field lines moving toward each other at such a boundary. (The boundary that MMS travels through, for example, is the one where Earth's fields meet the sun's.) The field lines are sometimes traveling in the same direction, and don't have much effect on each other, like two water currents flowing along side each other.

But if the two sets of field lines point in opposite directions, the process of realigning is dramatic. It can be hugely explosive, sending particles hurtling off at near the speed of light. It can also be slow and steady. Either way it releases a huge amount of energy.

"One of the mysteries of magnetic reconnection is why it’s explosive in some cases, steady in others, and in some cases, magnetic reconnection doesn’t occur at all," said Tom Moore, the mission scientist for MMS at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Whether explosive or steady, the local particles are caught up in the event, hurled off to areas far away, crossing magnetic boundaries they never could have crossed otherwise. At the edges of Earth's magnetic environment, the magnetosphere, such events allow solar radiation to enter near-Earth space.

"From previous satellites' measurements, we know that the magnetic fields act like a slingshot, sending the protons accelerating out," said Burch. "The decades-old mystery is what do the electrons do, and how do the two magnetic fields interconnect. Satellite measurements of electrons have been too slow by a factor of 100 to sample the magnetic reconnection region. The precision and speed of the MMS measurements, however, opened up a new window on the universe, a new 'microscope' to see reconnection."

With this new set of observations, MMS tracked what happens to electrons during magnetic reconnection. As the four spacecraft flew across the magnetosphere's boundary they flew directly through what's called the dissipation region where magnetic reconnection occurred. The observations were able to track how the magnetic fields suddenly shifted, and also how the particles moved away.

The observations show that the electrons shot away in straight lines from the original event at hundreds of miles per second, crossing the magnetic boundaries that would normally deflect them. Once across the boundary, the particles curved back around in response to the new magnetic fields they encountered, making a U-turn. These observations align with a computer simulation known as the crescent model, named for the characteristic crescent shapes that the graphs show to represent how far across the magnetic boundary the electrons can be expected to travel before turning around again.

A surprising result was that at the moment of interconnection between the sun’s magnetic field lines and those of Earth the crescents turned abruptly so that the electrons flowed along the field lines. By watching these electron tracers, MMS made the first observation of the predicted breaking and interconnection of magnetic fields in space.

"The data showed the entire process of magnetic reconnection to be fairly orderly and elegant," said Michael Hesse, a space scientist at Goddard who first developed the crescent model. "There doesn't seem to be much turbulence present, or at least not enough to disrupt or complicate the process."

Spotting the persistent characteristic crescent shape in the electron distributions suggests that it is the physics of electrons that is at the heart of understanding how magnetic field lines accelerate the particles.

"This shows us that the electrons move in such a way that electric fields are established and these electric fields in turn produce a flash conversion of magnetic energy,” said Roy Torbert, a scientist at the Space Science Center at the University of New Hampshire in Durham, who is a co-author on the paper. “The encounter that our instruments were able to measure gave us a clearer view of an explosive reconnection energy release and the role played by electron physics."

Since it launched, MMS has made more than 4,000 trips through the magnetic boundaries around Earth, each time gathering information about the way the magnetic fields and particles move. After its first direct observation of magnetic reconnection, it has flown through such an event five more times, providing more information about this fundamental process.

As the mission continues, the team can adjust the formation of the MMS spacecraft bringing them closer together, which provides better viewing of electron paths, or further apart, which provides better viewing of proton paths. Each set of observations contributes to explaining different aspects of magnetic reconnection. Together, such information will help scientists map out the details of our space environment — crucial information as we journey ever farther beyond our home planet.

By Karen C. Fox: NASA’s Goddard Space Flight Centre, Greenbelt, Md. Last Updated: May 12, 2016

: Editor: Rob Garner: NASA:

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Powerful Winds from an Ultra-luminous X-ray Binary

Powerful winds from an ultra-luminous X-ray binary: Artist’s impression depicting a compact object – either a black hole or a neutron star – feeding on gas from a companion star in a binary system. Since gas cannot fall in from all directions in a rotating system, it forms a swirling disc around the compact object. This causes matter to heat up and emit light at many wavelengths, especially X-rays. However, not all the gas in the disc is swallowed, and some of it is blown away in the form of winds or jets. Scientists using ESA's XMM-Newton have discovered gas streaming away at a quarter of the speed of light from two very bright X-ray binaries, known as ultra-luminous X-ray sources, that are located in nearby galaxies. The discovery confirms that these sources conceal a compact object accreting matter at extraordinarily high rates. Released 28/04/2016 10:00 am: Copyright ESA–C. Carreau


|| May 01: 2016 || ESA’s XMM-Newton has discovered gas streaming away at a quarter of the speed of light from very bright X-ray binaries in two nearby galaxies. At X-ray wavelengths, the celestial sky is dominated by two types of astronomical objects: supermassive black holes, sitting at the centres of large galaxies and ferociously devouring the material around them, and binary systems, consisting of a stellar remnant – a white dwarf, neutron star or black hole – feeding on gas from a companion star.

In both cases, the gas forms a swirling disc around the compact and very dense central object: friction in the disc causes the gas to heat up and emit light at many wavelengths, with a peak in X-rays.

Not all of the gas is swallowed by the central object though, and some of it might even be pushed away by powerful winds and jets.

But an intermediate class of objects was discovered in the 1980s and is still not well understood. Ten to a hundred times brighter than ordinary X-ray binaries, these sources are nevertheless too faint to be linked to accreting supermassive black holes, and in any case, are usually found far from the centre of their host galaxy.

“We think these ‘ultra-luminous X-ray sources’ are somewhat special binary systems, sucking up gas at a much higher rate than an ordinary X-ray binary,” explains Ciro Pinto from the Institute of Astronomy in Cambridge, UK.

“Some host highly magnetised neutron stars, while others might conceal the long-sought-after intermediate-mass black holes, which have masses around 1000 times the mass of the Sun. But in the majority of cases, the reason for their extreme behaviour is still unclear.”

 Ciro is the lead author of a new study, based on observations from ESA’s XMM-Newton, revealing for the first time strong winds gusting at very high speed from two of these exotic objects. The discovery, published in this week’s issue of the journal Nature, confirms that these sources conceal a compact object accreting matter at extraordinarily high rates.

Ciro and his colleagues delved into the XMM-Newton archives and collected several days’ worth of observations of three ultra-luminous X-ray sources, all hosted in nearby galaxies located less than 22 million light-years from our Milky Way.

The data were obtained over several years with the Reflection Grating Spectrometer, a highly sensitive instrument that allowed them to spot very subtle features in the spectrum of the X-rays from the sources.

 In all three sources, the scientists were able to identify X-ray emission from gas in the outer portions of the disc surrounding the central compact object, slowly flowing towards it.

But two of the three sources – known as NGC 1313 X-1 and NGC 5408 X-1 – also show clear signs of X-rays being absorbed by gas that is streaming away from the central source at an extremely rapid 70 000 km/s – almost a quarter of the speed of light.

“This is the first time we’ve seen winds streaming away from ultra-luminous X-ray sources,” says Ciro.

“And there's more, since the very high speed of these outflows is telling us something about the nature of the compact objects in these sources, which are frantically devouring matter.”

While the hot gas is pulled inwards by the central object’s gravity, it also shines brightly, and the pressure exerted by the radiation pushes it outwards. This is a balancing act: the greater the mass, the faster it draws the surrounding gas. But this also causes the gas to heat up faster, emitting more light and increasing the pressure that blows the gas away.

There is a theoretical limit to how much matter can be accreted by an object of a given mass, called the ‘Eddington luminosity’. It was first calculated for stars by astronomer Arthur Eddington, but it can also be applied to compact objects like black holes and neutron stars.

Eddington’s calculation refers to an ideal case in which both the matter being accreted onto the central object and the radiation being emitted by it do so equally in all directions.

But the sources studied by Ciro and his collaborators are being fed through an accretion disc that is likely being puffed up by internal pressure of the gas flowing at a fast pace towards the central object.

In such a configuration, the material in the disc can shine 10 times or more above the Eddington limit and, as part of the gas eludes the gravitational grasp from the central object, very high-speed winds can arise like the ones observed by XMM-Newton.

“By observing X-ray sources that are radiating beyond the Eddington limit, it is possible to study their accretion process in great detail, investigating by how much the limit can be exceeded and what exactly triggers the outflow of such powerful winds,” says Norbert Schartel, ESA XMM-Newton Project Scientist.

The nature of the compact objects hosted at the core of the sources observed in this study is, however, still uncertain, although the scientists suspect it might be stellar-mass black holes, with masses of several to a few dozen times that of the Sun.

To investigate further, the team is still scrutinising the data archive of XMM-Newton, searching for more sources of this type, and are also planning future observations, in X-rays as well as at optical and radio wavelengths.

“With a broader sample of sources and multi-wavelength observations, we hope to finally uncover the physical nature of these powerful, peculiar objects,” concludes Ciro.

Resolved atomic lines reveal outflows in two ultraluminous X-ray sources,” by C. Pinto et al., is published in the journal Nature.

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JAXA Sadly Declares X-ray Astronomy Satelite Hitomi ASTRO-H Lost

Image: JAXA


|| April 30: 2016 || The Japan Aerospace Exploration Agency (JAXA) established the emergency headquarters led by President Okumura and has been doing its utmost to understand the anomaly of the X-ray Astronomy Satellite ASTRO-H ("Hitomi"). We have made every effort to confirm the status of ASTRO-H and to regain its functions. Unfortunately, based on our rigorous technical investigation, we had to conclude as follows.

(1) Most of our analyses including simulations on the mechanisms of object separation, it is highly likely that both solar array paddles had broken off at their bases where they are vulnerable to rotation.

(2) Originally, we had some hopes to restore communication with ASTRO-H since we thought we received signals from ASTRO-H three times after object separation. However, we had to conclude that the received signals were not from ASTRO-H due to the differences in frequencies as a consequence of technological study.

JAXA has also received information from several overseas organizations that indicated the separation of the two solar array paddles from ASTRO-H. Considering this information, we have determined that we cannot restore the ASTRO-H's functions.

Accordingly, JAXA will cease the efforts to restore ASTRO-H and will focus on the investigation of anomaly causes. We will carefully review all phases from design, manufacturing, verification, and operations to identify the causes that may have led to this anomaly including background factors.

JAXA expresses the deepest regret for the fact that we had to discontinue the operations of ASTRO-H and extends our most sincere apologies to everyone who has supported ASTRO-H believing in the excellent results ASTRO-H would bring, to all overseas and domestic partners including NASA, and to all foreign and Japanese astrophysicists who were planning to use the observational results from ASTRO-H for their studies.

JAXA also would like to take this opportunity to send our profound appreciation to all overseas and domestic organizations for all of their help in confirming the status of ASTRO-H through ground-based observations and other means.

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Once Upon a Time, 10 Billion Years Ago, There Created a Thing Called Neutrinos Now You Do Find
 

Francis Reddy Writing


|| April 28, 2016 ||  Nearly 10 billion years ago, the black hole at the center of a galaxy known as PKS B1424-418 produced a powerful outburst. Light from this blast began arriving at Earth in 2012. Now astronomers using data from NASA's Fermi Gamma-ray Space Telescope and other space- and ground-based observatories have shown that a record-breaking neutrino seen around the same time likely was born in the same event.

"Neutrinos are the fastest, lightest, most unsociable and least understood fundamental particles, and we are just now capable of detecting high-energy ones arriving from beyond our galaxy," said Roopesh Ojha, a Fermi team member at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and a coauthor of the study. "Our work provides the first plausible association between a single extragalactic object and one of these cosmic neutrinos."

Although neutrinos far outnumber all the atoms in the universe, they rarely interact with matter, which makes detecting them quite a challenge. But this same property lets neutrinos make a fast exit from places where light cannot easily escape -- such as the core of a collapsing star -- and zip across the universe almost completely unimpeded. Neutrinos can provide information about processes and environments that simply aren't available through a study of light alone.

The IceCube Neutrino Observatory, built into a cubic kilometer of clear glacial ice at the South Pole, detects neutrinos when they interact with atoms in the ice. This triggers a cascade of fast-moving charged particles that emit a faint glow, called Cerenkov light, as they travel, which is picked up by thousands of optical sensors strung throughout IceCube. Scientists determine the energy of an incoming neutrino by the amount of light its particle cascade emits.

To date, the IceCube science team has detected about a hundred very high-energy neutrinos and nicknamed some of the most extreme events after characters on the children's TV series "Sesame Street." On Dec. 4, 2012, IceCube detected an event known as Big Bird, a neutrino with an energy exceeding 2 quadrillion electron volts (PeV). To put that in perspective, it's more than a million million times greater than the energy of a dental X-ray packed into a single particle thought to possess less than a millionth the mass of an electron. Big Bird was the highest-energy neutrino ever detected at the time and still ranks second.

Where did it come from? The best IceCube position only narrowed the source to a patch of the southern sky about 32 degrees across, equivalent to the apparent size of 64 full moons.

Enter Fermi. Starting in the summer of 2012, the satellite's Large Area Telescope (LAT) witnessed a dramatic brightening of PKS B1424-418, an active galaxy classified as a gamma-ray blazar. An active galaxy is an otherwise typical galaxy with a compact and unusually bright core. The excess luminosity of the central region is produced by matter falling toward a supermassive black hole weighing millions of times the mass of our sun. As it approaches the black hole, some of the material becomes channeled into particle jets moving outward in opposite directions at nearly the speed of light. In blazars, one of these jets happens to point almost directly toward Earth.

During the year-long outburst, PKS B1424-418 shone between 15 and 30 times brighter in gamma rays than its average before the eruption. The blazar is located within the Big Bird source region, but then so are many other active galaxies detected by Fermi.

The scientists searching for the neutrino source then turned to data from a long-term observing program named TANAMI. Since 2007, TANAMI has routinely monitored nearly 100 active galaxies in the southern sky, including many flaring sources detected by Fermi. The program includes regular radio observations using the Australian Long Baseline Array (LBA) and associated telescopes in Chile, South Africa, New Zealand and Antarctica. When networked together, they operate as a single radio telescope more than 6,000 miles across and provide a unique high-resolution look into the jets of active galaxies.

Three radio observations of PKS B1424-418 between 2011 and 2013 cover the period of the Fermi outburst. They reveal that the core of the galaxy's jet had brightened by about four times. No other galaxy observed by TANAMI over the life of the program has exhibited such a dramatic change.

"We combed through the field where Big Bird must have originated looking for astrophysical objects capable of producing high-energy particles and light," said coauthor Felicia Krauss, a doctoral student at the University of Erlangen-Nuremberg in Germany. "There was a moment of wonder and awe when we realized that the most dramatic outburst we had ever seen in a blazar happened in just the right place at just the right time."

In a paper published Monday, April 18, in Nature Physics, the team suggests the PKS B1424-418 outburst and Big Bird are linked, calculating only a 5-percent probability the two events occurred by chance alone. Using data from Fermi, NASA’s Swift and WISE satellites, the LBA and other facilities, the researchers determined how the energy of the eruption was distributed across the electromagnetic spectrum and showed that it was sufficiently powerful to produce a neutrino at PeV energies.

"Taking into account all of the observations, the blazar seems to have had means, motive and opportunity to fire off the Big Bird neutrino, which makes it our prime suspect," said lead author Matthias Kadler, a professor of astrophysics at the University of Wuerzburg in Germany.

Francis Halzen, the principal investigator of IceCube at the University of Wisconsin–Madison, and not involved in this study, thinks the result is an exciting hint of things to come. "IceCube is about to send out real-time alerts when it records a neutrino that can be localized to an area a little more than half a degree across, or slightly larger than the apparent size of a full moon," he said. "We're slowly opening a neutrino window onto the cosmos."

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

For more information about NASA's Fermi, visit

By Francis Reddy: NASA's Goddard Space Flight Center, Greenbelt, Md.

( Editor: Ashley Morrow: NASA)

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Microscopic "Timers" Reveal Likely Source of Galactic Space Radiation

Karen C. Fox

This is a mosaic image-- one of the largest ever taken by NASA's Hubble Space Telescope -- of the Crab Nebula, a six-light-year-wide expanding remnant of a star's supernova explosion. Recent research shows that galactic cosmic rays flowing into our solar system originate in clusters like these. Credits: NASA/ESA/Arizona State University

|| April 23, 2016 || Most of the cosmic rays that we detect at Earth originated relatively recently in nearby clusters of massive stars, according to new results from NASA's Advanced Composition Explorer (ACE) spacecraft. ACE allowed the research team to determine the source of these cosmic rays by making the first observations of a very rare type of cosmic ray that acts like a tiny timer, limiting the distance the source can be from Earth.

"Before the ACE observations, we didn't know if this radiation was created a long time ago and far, far away, or relatively recently and nearby," said Eric Christian of NASA's Goddard Space Flight Center in Greenbelt, Maryland. Christian is co-author of a paper on this research published April 21 in Science.

Cosmic rays are high-speed atomic nuclei with a wide range of energy -- the most powerful race at almost the speed of light. Earth's atmosphere and magnetic field shield us from less-energetic cosmic rays, which are the most common. However, cosmic rays will present a hazard to unprotected astronauts traveling beyond Earth's magnetic field because they can act like microscopic bullets, damaging structures and breaking apart molecules in living cells. NASA is currently researching ways to reduce or mitigate the effects of cosmic radiation to protect astronauts traveling to Mars.

Cosmic rays are produced by a variety of violent events in space. Most cosmic rays originating within our solar system have relatively low energy and come from explosive events on the sun, like flares and coronal mass ejections. The highest-energy cosmic rays are extremely rare and are thought to be powered by massive black holes gorging on matter at the center of other galaxies. The cosmic rays that are the subject of this study come from outside our solar system but within our Galaxy and are called galactic cosmic rays. They are thought to be generated by shock waves from exploding stars called supernovae.

The galactic cosmic rays detected by ACE that allowed the team to estimate the age of the cosmic rays, and the distance to their source, contain a radioactive form of iron called Iron-60 (60Fe). It is created inside massive stars when they explode and then blasted into space by the shock waves from the supernova. Some 60Fe in the debris from the destroyed star is accelerated to cosmic-ray speed when another nearby massive star in the cluster explodes and its shock wave collides with the remnants of the earlier stellar explosion.

60Fe galactic cosmic rays zip through space at half the speed of light or more, about 90,000 miles per second. This seems very fast, but the 60Fe cosmic rays won't travel far on a galactic scale for two reasons. First, they can't travel in straight lines because they are electrically charged and respond to magnetic forces. Therefore they are forced to take convoluted paths along the tangled magnetic fields in our Galaxy. Second, 60Fe is radioactive and over a period of about 2.6 million years, half of it will self-destruct, decaying into other elements (Cobalt-60 and then Nickel-60). If the 60Fe cosmic rays were created hundreds of millions of years or more ago, or very far away, eventually there would be too little left for the ACE spacecraft to detect.

"Our detection of radioactive cosmic-ray iron nuclei is a smoking gun indicating that there has likely been more than one supernova in the last few million years in our neighborhood of the Galaxy," said Robert Binns of Washington University, St. Louis, Missouri, lead author of the paper.

"In 17 years of observing, ACE detected about 300,000 galactic cosmic rays of ordinary iron, but just 15 of the radioactive Iron-60," said Christian. "The fact that we see any Iron-60 at all means these cosmic ray nuclei must have been created fairly recently (within the last few million years) and that the source must be relatively nearby, within about 3,000 light years, or approximately the width of the local spiral arm in our Galaxy." A light year is the distance light travels in a year, almost six trillion miles. A few thousand light years is relatively nearby because the vast swarm of hundreds of billions of stars that make up our Galaxy is about 100,000 light years wide.

There are more than 20 clusters of massive stars within a few thousand light years, including Upper Scorpius (83 stars), Upper Centaurus Lupus (134 stars), and Lower Centaurus Crux (97 stars). These are very likely major contributors to the 60Fe that ACE detected, owing to their size and proximity, according to the research team.

ACE was launched on August 25, 1997 to a point 900,000 miles away between Earth and the sun where it has acted as a sentinel, detecting space radiation from solar storms, the Galaxy, and beyond. This research was funded by NASA's ACE program.

Additional co-authors on this paper were: Martin Israel and Kelly Lave at Washington University, St. Louis, Missouri; Alan Cummings, Rick Leske, Richard Mewaldt and Ed Stone at Caltech in Pasadena, California; Georgia de Nolfo and Tycho von Rosenvinge at Goddard; and Mark Wiedenbeck at NASA's Jet Propulsion Laboratory in Pasadena, California.

Karen C. Fox: NASA Goddard Space Flight Center, Greenbelt, Maryland: 301-286-6284: karen.c.fox@nasa.gov
( Editor: Bill Steigerwald: NASA)

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Massive Bodies Warp Space-Time

Image Credit: T. Pyle/Caltech/MIT/LIGO Lab

||April 18, 2016|| How our sun and Earth warp space and time, or spacetime, is represented here with a green grid. As Albert Einstein demonstrated in his theory of general relativity, the gravity of massive bodies warps the fabric of space and time—and those bodies move along paths determined by this geometry. His theory also predicted the existence of gravitational waves , which are ripples in space and time. These waves, which move at the speed of light, are created when massive bodies accelerate through space and time.

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NASA's Fermi Telescope Poised to Pin Down Gravitational Wave Sources

Francis Reddy Writing

An artist's impression of gravitational waves generated by binary neutron stars. Credits: R. Hurt/Caltech-JPL

||April 18, 2016||  On Sept. 14, waves of energy travelling for more than a billion years gently rattled space-time in the vicinity of Earth. The disturbance, produced by a pair of merging black holes, was captured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Hanford, Washington, and Livingston, Louisiana. This event marked the first-ever detection of gravitational waves and opens a new scientific window on how the universe works.

Less than half a second later, the Gamma-ray Burst Monitor (GBM) on NASA's Fermi Gamma-ray Space Telescope picked up a brief, weak burst of high-energy light consistent with the same part of the sky. Analysis of this burst suggests just a 0.2-percent chance of simply being random coincidence. Gamma-rays arising from a black hole merger would be a landmark finding because black holes are expected to merge “cleanly,” without producing any sort of light.

“This is a tantalizing discovery with a low chance of being a false alarm, but before we can start rewriting the textbooks we’ll need to see more bursts associated with gravitational waves from black hole mergers,” said Valerie Connaughton, a GBM team member at the National Space, Science and Technology Center in Huntsville, Alabama, and lead author of a paper on the burst now under review by The Astrophysical Journal.

Detecting light from a gravitational wave source will enable a much deeper understanding of the event. Fermi's GBM sees the entire sky not blocked by Earth and is sensitive to X-rays and gamma rays with energies between 8,000 and 40 million electron volts (eV). For comparison, the energy of visible light ranges between about 2 and 3 eV.

With its wide energy range and large field of view, the GBM is the premier instrument for detecting light from short gamma-ray bursts (GRBs), which last less than two seconds. They are widely thought to occur when orbiting compact objects, like neutron stars and black holes, spiral inward and crash together. These same systems also are suspected to be prime producers of gravitational waves.

"With just one joint event, gamma rays and gravitational waves together will tell us exactly what causes a short GRB," said Lindy Blackburn, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and a member of the LIGO Scientific Collaboration. "There is an incredible synergy between the two observations, with gamma rays revealing details about the source's energetics and local environment and gravitational waves providing a unique probe of the dynamics leading up to the event." He will be discussing the burst and how Fermi and LIGO are working together in an invited talk at the American Physical Society meeting in Salt Lake City on Tuesday.

Currently, gravitational wave observatories possess relatively blurry vision. This will improve in time as more facilities begin operation, but for the September event, dubbed GW150914 after the date, LIGO scientists could only trace the source to an arc of sky spanning an area of about 600 square degrees, comparable to the angular area on Earth occupied by the United States.

“That's a pretty big haystack to search when your needle is a short GRB, which can be fast and faint, but that’s what our instrument is designed to do," said Eric Burns, a GBM team member at the University of Alabama in Huntsville. "A GBM detection allows us to whittle down the LIGO area and substantially shrinks the haystack."

Less than half a second after LIGO detected gravitational waves, the GBM picked up a faint pulse of high-energy X-rays lasting only about a second. The burst effectively occurred beneath Fermi and at a high angle to the GBM detectors, a situation that limited their ability to establish a precise position. Fortunately, Earth blocked a large swath of the burst’s likely location as seen by Fermi at the time, allowing scientists to further narrow down the burst’s position.

The GBM team calculates less than a 0.2-percent chance random fluctuations would have occurred in such close proximity to the merger. Assuming the events are connected, the GBM localization and Fermi's view of Earth combine to reduce the LIGO search area by about two-thirds, to 200 square degrees. With a burst better placed for the GBM’s detectors, or one bright enough to be seen by Fermi’s Large Area Telescope, even greater improvements are possible.

The LIGO event was produced by the merger of two relatively large black holes, each about 30 times the mass of the sun. Binary systems with black holes this big were not expected to be common, and many questions remain about the nature and origin of the system.

Black hole mergers were not expected to emit significant X-ray or gamma-ray signals because orbiting gas is needed to generate light. Theorists expected any gas around binary black holes would have been swept up long before their final plunge. For this reason, some astronomers view the GBM burst as most likely a coincidence and unrelated to GW150914. Others have developed alternative scenarios where merging black holes could create observable gamma-ray emission. It will take further detections to clarify what really happens when black holes collide.

Albert Einstein predicted the existence of gravitational waves in his general theory of relativity a century ago, and scientists have been attempting to detect them for 50 years. Einstein pictured these waves as ripples in the fabric of space-time produced by massive, accelerating bodies, such as black holes orbiting each other. Scientists are interested in observing and characterizing these waves to learn more about the sources producing them and about gravity itself.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

For more information about NASA's Fermi Gamma-ray Space Telescope, please visit

Francis Reddy: NASA's Goddard Space Flight Center, Greenbelt, Maryland

( Editor: Ashley Morrow: NASA)

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It's a Matter of Dark Matter: A Black Hole May Make an Ideal Dark Matter Lab

 

 

 

 

 

 

 

 

 

 

 

 

 

 

April 07, 2016: A new NASA computer simulation shows that dark matter particles colliding in the extreme gravity of a black hole can produce strong, potentially observable gamma-ray light. Detecting this emission would provide astronomers with a new tool for understanding both black holes and the nature of dark matter, an elusive substance accounting for most of the mass of the universe that neither reflects, absorbs nor emits light.

"While we don't yet know what dark matter is, we do know it interacts with the rest of the universe through gravity, which means it must accumulate around supermassive black holes," said Jeremy Schnittman, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "A black hole not only naturally concentrates dark matter particles, its gravitational force amplifies the energy and number of collisions that may produce gamma rays."

In a study published in The Astrophysical Journal on June 23, Schnittman describes the results of a computer simulation he developed to follow the orbits of hundreds of millions of dark matter particles, as well as the gamma rays produced when they collide, in the vicinity of a black hole. He found that some gamma rays escaped with energies far exceeding what had been previously regarded as theoretical limits.

In the simulation, dark matter takes the form of Weakly Interacting Massive Particles, or WIMPS, now widely regarded as the leading candidate of what dark matter could be. In this model, WIMPs that crash into other WIMPs mutually annihilate and convert into gamma rays, the most energetic form of light. But these collisions are extremely rare under normal circumstances.

Over the past few years, theorists have turned to black holes as dark matter concentrators, where WIMPs can be forced together in a way that increases both the rate and energies of collisions. The concept is a variant of the Penrose process, first identified in 1969 by British astrophysicist Sir Roger Penrose as a mechanism for extracting energy from a spinning black hole. The faster it spins, the greater the potential energy gain.

In this process, all of the action takes place outside the black hole's event horizon, the boundary beyond which nothing can escape, in a flattened region called the ergosphere. Within the ergosphere, the black hole's rotation drags space-time along with it and everything is forced to move in the same direction at nearly speed of light. This creates a natural laboratory more extreme than any possible on Earth.

The faster the black hole spins, the larger its ergosphere becomes, which allows high-energy collisions further from the event horizon. This improves the chances that any gamma rays produced will escape the black hole.

"Previous work indicated that the maximum output energy from the collisional version of the Penrose process was only about 30 percent higher than what you start with," Schnittman said. In addition, only a small portion of high-energy gamma rays managed to escape the ergosphere. These results suggested that clear evidence of the Penrose process might never be seen from a supermassive black hole.

But the earlier studies included simplifying assumptions about where the highest-energy collisions were most likely to occur. Moving beyond this initial work meant developing a more complete computational model, one that tracked large numbers of particles as they gathered near a spinning black hole and interacted among themselves.

Schnittman's computer simulation does just that. By tracking the positions and properties of hundreds of millions of randomly distributed particles as they collide and annihilate each other near a black hole, the new model reveals processes that produce gamma rays with much higher energies, as well as a better likelihood of escape and detection, than ever thought possible. He identified previously unrecognized paths where collisions produce gamma rays with a peak energy 14 times higher than that of the original particles.

Using the results of this new calculation, Schnittman created a simulated image of the gamma-ray glow as seen by a distant observer looking along the black hole's equator. The highest-energy light arises from the center of a crescent-shaped region on the side of the black hole spinning toward us. This is the region where gamma rays have the greatest chance of exiting the ergosphere and being detected by a telescope.

The research is the beginning of a journey Schnittman hopes will one day culminate with the incontrovertible detection of an annihilation signal from dark matter around a supermassive black hole.

"The simulation tells us there is an astrophysically interesting signal we have the potential of detecting in the not too distant future, as gamma-ray telescopes improve," Schnittman said. "The next step is to create a framework where existing and future gamma-ray observations can be used to fine-tune both the particle physics and our models of black holes."

Francis Reddy: NASA's Goddard Space Flight Center, Greenbelt, Md.

( Editor: Karl Hille: NASA)

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Search Up and Down, Search High and Low, Search Far and Wide, Search All Nooks and Crannies: You Won't Find Any Sign of Gamma Rays

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Gamma-ray observatory: ESA’s Integral observatory is able to detect gamma-ray bursts, the most energetic phenomena in the Universe. Released 29/06/2011 4:45 pm: Copyright ESA/Medialab

March 30, 2016:  Following the discovery of gravitational waves from the merging of two black holes, ESA’s Integral satellite has revealed no simultaneous gamma rays, just as models predict.

On 14 September, the terrestrial Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves – fluctuations in the fabric of spacetime – produced by a pair of black holes as they spiralled towards each other before merging. The signal lasted less than half a second. The discovery was the first direct observation of gravitational waves, predicted by Albert Einstein a century ago.

Two days after the detection, the LIGO team alerted a number of ground- and space-based astronomical facilities to look for a possible counterpart to the source of gravitational waves. The nature of the source was unclear at the time, and it was hoped that follow-up observations across the electromagnetic spectrum might provide valuable information about the culprit. Gravitational waves are released when massive bodies are accelerated, and strong emission should occur when dense stellar remnants such as neutron stars or black holes spiral towards each other before coalescing.

 Models predict that the merging of two stellar-mass black holes would not produce light at any wavelength, but if one or two neutron stars were involved in the process, then a characteristic signature should be observable across the electromagnetic spectrum. Another possible source of gravitational waves would be an asymmetric supernova explosion, also known to emit light over a range of wavelengths. It was not possible to pinpoint the LIGO source – its position could only be narrowed down to a very long strip across the sky.

Observatories searched their archives in case data had been serendipitously collected anywhere along this strip around the time of the gravitational wave detection. They were also asked to point their telescopes to the same region in search for any possible ‘afterglow’ emission. Integral is sensitive to transient sources of high-energy emission over the whole sky, and thus a team of scientists searched through its data, seeking signs of a sudden burst of hard X-rays or gamma rays that might have been recorded at the same time as the gravitational waves were detected.

“We searched through all the available Integral data, but did not find any indication of high-energy emission associated with the LIGO detection,” says Volodymyr Savchenko of the François Arago Centre in Paris, France. Volodymyr is the lead author of a paper reporting the results, published today in Astrophysical Journal Letters.  The team analysed data from the Anti-Coincidence Shield on Integral’s SPI instrument. The shield helps to screen out radiation and particles coming from directions other than that where the instrument is pointing, as well as to detect transient high-energy sources across the whole sky.

The team also looked at data from Integral’s IBIS instrument, although at the time it was not pointing at the strip where the source of gravitational waves was thought to be located. “The source detected by LIGO released a huge amount of energy in gravitational waves, and the limits set by the Integral data on a possible simultaneous emission of gamma rays are one million times lower than that,” says co-author Carlo Ferrigno from the Integral Science Data Centre at the University of Geneva, Switzerland.

Subsequent analysis of the LIGO data has shown that the gravitational waves were produced by a pair of coalescing black holes, each with a mass roughly 30 times that of our Sun, located about 1.3 billion light years away. Scientists do not expect to see any significant emission of light at any wavelength from such events, and thus Integral’s null detection is consistent with this scenario. Similarly, nothing was seen by the great majority of the other astronomical facilities making observations from radio and infrared to optical and X-ray wavelengths.

The only exception was the Gamma-Ray Burst Monitor on NASA’s Fermi Gamma-Ray Space Telescope, which observed what appears to be a sudden burst of gamma rays about 0.4 seconds after the gravitational waves were detected. The burst lasted about one second and came from a region of the sky that overlaps with the strip identified by LIGO. This detection sparked a bounty of theoretical investigations, proposing possible scenarios in which two merging black holes of stellar mass could indeed have released gamma rays along with the gravitational waves.

However, if this gamma-ray flare had had a cosmic origin, either linked to the LIGO gravitational wave source or to any other astrophysical phenomenon in the Universe, it should have been detected by Integral as well. The absence of any such detection by both instruments on Integral suggests that the measurement from Fermi could be unrelated to the gravitational wave detection. “This result highlights the importance of synergies between scientists and observing facilities worldwide in the quest for as many cosmic messengers as possible, from the recently-detected gravitational waves to particles and light across the spectrum,” says Erik Kuulkers, Integral project scientist at ESA.

This will become even more important when it becomes possible to observe gravitational waves from space. This has been identified as the goal for the L3 mission in ESA’s Cosmic Vision programme, and the technology for building it is currently being tested in space by ESA’s LISA Pathfinder mission. Such an observatory will be capable of detecting gravitational waves from the merging of supermassive black holes in the centres of galaxies for months prior to the final coalescence, making it possible to locate the source much more accurately and thus provide astronomical observatories with a place and a time to look out for associated electromagnetic emission.

“We are looking forward to further collaborations and discoveries in the newly-inaugurated era of gravitational astronomy,” concludes Erik.

Integral Upper Limits On Gamma-Ray Emission Associated With The Gravitational Wave Event GW150914,” by V. Savchenko et al. is published in Astrophysical Journal Letters.

For further information, please contact:

Markus Bauer: ESA Science Communication Officer: Tel: +31 71 565 6799: Mob: +31 61 594 3 954: Email: markus.bauer@esa.int

Volodymyr Savchenko: François Arago Center: APC - Astroparticule et Cosmologie: Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire De Paris, Sorbonne Paris Cité: Paris, France: Email: savchenk@apc.in2p3.fr

Carlo Ferrigno: Integral Science Data Centre: University of Geneva, Switzerland: Email: Carlo.Ferrigno@unige.ch

Erik Kuulkers: ESA Integral Project Scientist: Email: Erik.Kuulkers@esa.int
 

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Caught For The First Time: The Early Flash of an Exploding Star

H. Pat Brennan and Michele Johnson Writing

Image: Credits: Credit: NASA Ames, STScI/G. Bacon

March 21, 2016: The brilliant flash of an exploding star’s shockwave—what astronomers call the “shock breakout”—has been captured for the first time in the optical wavelength or visible light by NASA's planet-hunter, the Kepler space telescope.

An international science team led by Peter Garnavich, an astrophysics professor at the University of Notre Dame in Indiana, analyzed light captured by Kepler every 30 minutes over a three-year period from 500 distant galaxies, searching some 50 trillion stars. They were hunting for signs of massive stellar death explosions known as supernovae.

In 2011, two of these massive stars, called red supergiants, exploded while in Kepler’s view. The first behemoth, KSN 2011a, is nearly 300 times the size of our sun and a mere 700 million light years from Earth. The second, KSN 2011d, is roughly 500 times the size of our sun and around 1.2 billion light years away.

“To put their size into perspective, Earth's orbit about our sun would fit comfortably within these colossal stars,” said Garnavich.

Whether it’s a plane crash, car wreck or supernova, capturing images of sudden, catastrophic events is extremely difficult but tremendously helpful in understanding root cause. Just as widespread deployment of mobile cameras has made forensic videos more common, the steady gaze of Kepler allowed astronomers to see, at last, a supernova shockwave as it reached the surface of a star. The shock breakout itself lasts only about 20 minutes, so catching the flash of energy is an investigative milestone for astronomers.

“In order to see something that happens on timescales of minutes, like a shock breakout, you want to have a camera continuously monitoring the sky,” said Garnavich. “You don’t know when a supernova is going to go off, and Kepler's vigilance allowed us to be a witness as the explosion began.”

Supernovae like these — known as Type II — begin when the internal furnace of a star runs out of nuclear fuel causing its core to collapse as gravity takes over.

The two supernovae matched up well with mathematical models of Type II explosions reinforcing existing theories. But they also revealed what could turn out to be an unexpected variety in the individual details of these cataclysmic stellar events.

While both explosions delivered a similar energetic punch, no shock breakout was seen in the smaller of the supergiants. Scientists think that is likely due to the smaller star being surrounded by gas, perhaps enough to mask the shockwave when it reached the star's surface.

“That is the puzzle of these results,” said Garnavich. “You look at two supernovae and see two different things. That’s maximum diversity.”

Understanding the physics of these violent events allows scientists to better understand how the seeds of chemical complexity and life itself have been scattered in space and time in our Milky Way galaxy

"All heavy elements in the universe come from supernova explosions. For example, all the silver, nickel, and copper in the earth and even in our bodies came from the explosive death throes of stars," said Steve Howell, project scientist for NASA's Kepler and K2 missions at NASA’s Ames Research Center in California's Silicon Valley. "Life exists because of supernovae."

Garnavich is part of a research team known as the Kepler Extragalactic Survey or KEGS. The team is nearly finished mining data from Kepler’s primary mission, which ended in 2013 with the failure of reaction wheels that helped keep the spacecraft steady. However, with the reboot of the Kepler spacecraft as NASA's K2 mission, the team is now combing through more data hunting for supernova events in even more galaxies far, far away.

"While Kepler cracked the door open on observing the development of these spectacular events, K2 will push it wide open observing dozens more supernovae," said Tom Barclay, senior research scientist and director of the Kepler and K2 guest observer office at Ames. "These results are a tantalizing preamble to what's to come from K2!"

In addition to Notre Dame, the KEGS team also includes researchers from the University of Maryland in College Park; the Australian National University in Canberra, Australia; the Space Telescope Science Institute in Baltimore, Maryland; and the University of California, Berkeley.

The research paper reporting this discovery has been accepted for publication in the Astrophysical Journal.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

Authors: H. Pat Brennan/JPL and Michele Johnson/Ames

Michele Johnson: Ames Research Center, Moffett Field, Calif.
650-604-6982: michele.johnson@nasa.gov

( Editor: Michele Johnson:NASA)

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Mind in Microgravity?

In this April 8, 2010 photograph, from left STS-131 mission specialists Stephanie Wilson of NASA, Naoko Yamazaki of the Japanese Aerospace Exploration Agency (JAXA), Dorothy Metcalf-Lindenburger of NASA, and Expedition 23 flight engineer Tracy Caldwell Dyson (top left) work at the robotics workstation on the International Space Station, in support of transfer operations using the station's Canadarm2 robotic arm to move cargo from the Multi-Purpose Logistics Module. Image: NASA

March 20, 2016: In space, astronauts do not walk on the floor like people on Earth do. They float around inside their spacecraft. That is because of microgravity. Microgravity is when things seem to be weightless. "Micro-" means "very small."

Microgravity is when the pull of gravity is not very strong. In microgravity, it is easy to move heavy objects. Astronauts can even move things that weigh hundreds of pounds with just the tips of their fingers.


How Does Gravity Work?

Gravity is what pulls people down toward Earth. When you jump, gravity makes you come back down. When you are walking, it holds you on the ground.


Is There Gravity in Space?

Some people think that there is no gravity in space. But small amounts of gravity are everywhere. Gravity keeps the moon in orbit around Earth. It keeps Earth in orbit around the sun. The pull of gravity gets weaker the farther apart two objects are. A spacecraft could go so far from Earth that a person would feel very little gravity. But this is not why things float on the International Space Station. The space station orbits Earth at about 200 to 250 miles high. At that height, Earth's gravity is still very strong. In fact, a person who weighs 100 pounds on the ground would weigh 90 pounds there.


Why Do Objects Float in Orbit?

So why do astronauts float in space? The answer is that they are in free fall. Gravity pulls all objects the same way, even if they are different sizes. If you drop a hammer and a feather on Earth, the hammer will fall faster. But that is not because gravity pulls them differently. Air makes the feather fall more slowly. If there were no air, they would fall together at the same speed. Some amusement parks have free-fall rides. On those rides, a cabin falls along a tall tower. If you let go of a ball at the start of the fall, you and the ball would fall together. The ball would appear to float in front of you! That is what happens in a spacecraft. The spacecraft, its crew and everything aboard are all falling around Earth. Since they are all falling together, the crew and objects appear to float.


How Can Spacecraft Fall Around Earth?

What does it mean to "fall around Earth"? Earth's gravity pulls objects toward the surface. Gravity pulls on the space station, too. As a result, it is falling toward Earth's surface. The station also is moving very fast. It moves so fast it matches the way Earth's surface curves. If you throw a baseball, gravity will cause it to curve down. It will hit the ground soon.

A spacecraft in orbit moves at the right speed so that the curve of its fall matches the curve of Earth. For the space station, that speed is 17,500 miles per hour. The spacecraft keeps falling toward the ground but never hits it. Instead, it falls around the planet. The moon stays in orbit around Earth for this same reason. The moon also is falling around Earth.


Why Does NASA Study Microgravity?

NASA studies microgravity. The studies help show what happens to people and other things in space. Microgravity does things to the human body. For example, muscles and bones can get weaker. Astronauts on the space station spend months in microgravity. Astronauts who travel to Mars would have to live even longer in microgravity. That is because it will take a long time to get there and back. NASA must learn what microgravity does to astronauts. NASA will use this information to find ways to keep them safe and healthy.

Other things seem to act differently in microgravity, too. Fire burns in a different shape. Without gravity, flames are more round. Crystals grow better. Their shapes are more perfect without gravity. NASA performs science experiments in microgravity. They help NASA learn things that would be hard to learn on Earth.


Can Microgravity Be Found on Earth?

Microgravity can be found on Earth, too. NASA uses airplanes to create microgravity for a short time. The airplane does this by flying in up-and-down parabolas. At the top of the parabola, people and things inside the airplane are in free fall for about 20-30 seconds. NASA also uses drop towers to study microgravity. Objects are dropped from the top of these towers. The objects are in free fall as they drop. You can even experience microgravity yourself. How? You can go over a big hill on a roller coaster or ride on a free-fall ride at an amusement park.

( Editor: Sandra May: NASA)

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To Find Bose-Einstein Condensates

Elizabeth Landau Writing

JPL's David Aveline and Anita Sengupta are seen with the physics package for the Cold Atom Laboratory, which includes a vacuum chamber where ultra-cold quantum gases are made. Credits: NASA/JPL-Caltech

March 17, 2016: On a sun-drenched hill in Southern California's San Gabriel Mountains, researchers are making progress on an experimental facility that could create the coldest known place in the universe.

The Cold Atom Laboratory (CAL), developed at NASA's Jet Propulsion Laboratory, Pasadena, California, will probe the wonders of quantum physics when it launches to the International Space Station. The CAL facility recently hit a milestone of making an ultra-cold quantum gas with potassium, a high-tech feat that puts it on track for launch next year. The planned flight to space is in August 2017.

"Studying gases that have been cooled down to extreme temperatures is key to understanding how complexity arises in the universe, and allows us to test the fundamental laws of physics in a whole new way," said Robert Thompson, project scientist for the Cold Atom Laboratory at JPL.

Researchers with CAL are interested in a state of matter called a Bose-Einstein condensate, which happens when all the atoms in a very cold gas have the same energy levels. Like dancers in a chorus line, the atoms become synchronized and behave like one continuous wave instead of discrete particles.

On Earth, gravity limits how long scientists can study Bose-Einstein condensates because this form of matter falls to the bottom of any apparatus used to study it. In microgravity, such condensates can be observed for longer periods of time. This would allow scientists to better understand the properties of particles in this state and their uses for tests of fundamental physics. Ultra-cold atoms in microgravity may also be key to a wide variety of advanced quantum sensors, and exquisitely sensitive measurements of quantities such as gravity, rotations and magnetic fields.

Using lasers, magnetic traps and an electromagnetic "knife" to remove warm particles, CAL will take atoms down to the coldest temperatures ever achieved.

In February, the team created their first ultra-cold quantum gas made from two elemental species: rubidium and potassium. Previously, in 2014, CAL researchers made Bose-Einstein condensates using rubidium, and were able to reliably create them in a matter of seconds. This time, the cooled rubidium was used to bring potassium-39 down to ultra-cold temperatures.

"This marks an important step for the project, as we needed to verify that the instrument could create this two-species ultra-cold gas on Earth before doing so in space," said Anita Sengupta, the project manager for CAL, based at JPL.

“We were able to cool the gases down to about a millionth of a degree Kelvin above absolute zero, the point at which atoms would be close to motionless,” said JPL's David Aveline, the CAL testbed lead.

That sounds inconceivably cold to mere mortals, but such temperatures are like tropical beach afternoons compared to the ultimate goal of CAL. Researchers hope to cool atoms down to a billionth of a degree above absolute zero when the experimental facility gets to space.

One area of science to which CAL will contribute is called Efimov physics, which makes fascinating predictions about the ways that a small number of particles interact. Isaac Newton had fundamental insights into how two bodies interact -- for example, Earth and the moon -- but the rules that govern them are more complicated when a third body, such as the sun, is introduced. The interactions become even more complex in a system of three atoms, which behave according to the odd laws of quantum mechanics.

Under the right conditions, ultra-cold gases that CAL produces contain molecules with three atoms each, but are a thousand times bigger than a typical molecule. This results in a low-density, "fluffy" molecule that quickly falls apart unless it is kept extremely cold.

"The way atoms behave in this state gets very complex, surprising and counterintuitive, and that's why we're doing this," said Eric Cornell, a physicist at the University of Colorado and the National Institute of Standards and Technology, both in Boulder, and member of the CAL science team. Cornell shared the 2001 Nobel Prize in physics for creating Bose-Einstein condensates.

At a recent meeting at JPL, researchers associated with the mission gathered to discuss ongoing developments and their scientific goals, which range from dark matter detection to atom lasers. They included Cornell, who, along with co-investigator Peter Engels of Washington State University, is leading one of the CAL experiments. "CAL science investigators could open new doors into the quantum world and will demonstrate new technologies for future NASA missions," said CAL Deputy Project Manager Kamal Oudrhiri at JPL.

"CAL's investigation will generate scientific data that could rewrite textbooks for generations," said Mark Lee, senior program scientist for fundamental physics at NASA Headquarters.

For more information about the Cold Atom Laboratory visit:

http://coldatomlab.jpl.nasa.gov

Elizabeth Landau: NASA's Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425: Elizabeth.Landau@jpl.nasa.gov

( Editor: Martin Perez:NASA)

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Rosetta Discovered Diamagnetic Cavity on Comet 67P

Magnetic field-free cavity at comet: Released 11/03/2016 10:00 am: Copyright ESA–C.Carreau

March 11, 2016: ESA’s Rosetta spacecraft has revealed a surprisingly large region around its host comet devoid of any magnetic field.

When ESA’s Giotto flew past Comet Halley three decades ago, it found a vast magnetic-free region extending more than 4000 km from the nucleus. This was the first observation of something that scientists had until then only thought about but had never seen.

Interplanetary space is pervaded by the solar wind, a flow of electrically charged particles streaming from the Sun and carrying its magnetic field across the Solar System. But a comet pouring lots of gas into space obstructs the solar wind.

At the interface between the solar wind and the coma of gas around the active comet, particle collisions as well as sunlight can knock out electrons from the molecules in the coma, which are ionised and picked up by the solar wind. This process slows the solar wind, diverting its flow around the comet and preventing it from directly impacting the nucleus.

Along with the solar wind, its magnetic field is unable to penetrate the environment around the comet, creating a region devoid of magnetic field called a diamagnetic cavity.

Prior to Rosetta arriving at Comet 67P/Churyumov-Gerasimenko, scientists had hoped to observe such a magnetic field-free region in the environment of this comet. The spacecraft carries a magnetometer as part of the Rosetta Plasma Consortium suite of sensors (RPC-MAG), whose measurements were already used to demonstrate that the comet nucleus is not magnetised.

However, since Rosetta’s comet is much less active than Comet Halley, the scientists predicted that a diamagnetic cavity could form only in the months around perihelion – the closest point to the Sun on the comet’s orbit – but that it would extend only 50–100 km from the nucleus.

During 2015, the increased amounts of dust dragged into space by the outflowing gas became a significant problem for navigation close to the comet. To keep Rosetta safe, trajectories were chosen such that by the end of July 2015, a few weeks before perihelion, it was some 170 km away from the nucleus. As a result, scientists considered that detecting signs of the magnetic field-free bubble would be impossible.

“We had almost given up on Rosetta finding the diamagnetic cavity, so we were astonished when we eventually found it,” says Charlotte Götz of the Institute for Geophysics and extraterrestrial Physics in Braunschweig, Germany.

Discovery of diamagnetic cavity

Charlotte is the lead author of a new study, published in the journal Astronomy and Astrophysics, presenting the detection of a diamagnetic cavity obtained by RPC-MAG on 26 July. The paper describes one of the most spectacular measurements from almost 700 detections of regions with no magnetic field made by Rosetta at the comet since June 2015.

“We were able to detect the cavity, and on many occasions, because it is much bigger and dynamic than we had expected,” adds Charlotte.

To investigate why the magnetic field-free cavity is so much bigger than predicted, Charlotte and her colleagues looked at measurements performed around the same time by other instruments, such as Rosetta's scientific camera, OSIRIS, and the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument, ROSINA, to verify whether any anomalous changes in the comet's activity could be pushing the cavity away from the nucleus.

While one of the cavity detections, on 29 July, occurred in conjunction with a strong outburst of gas and dust recorded by other instruments on Rosetta, this seems to be an isolated case. Almost all of the other observations of magnetic field-free regions, including the one recorded on 26 July, were not accompanied by any appreciable increase of outgassing.

“To account for such a big cavity in the simulations, we would need the outgassing rate to be 10 times higher than was measured at the comet by ROSINA,” says co-author Karl-Heinz Glassmeier from Technische Universität Braunschweig, Germany, principal investigator of RPC-MAG.

The most likely explanation seems to lie, instead, in the dynamical nature of the cavity boundary.

Boundaries between plasma regions with different properties are often unstable, and small oscillations can arise in the pile-up region of the solar wind, where it encounters the magnetic field-free region, on the Sun-facing side of the comet. If these oscillations propagate and get amplified along the boundary, in the direction opposite the Sun, they could easily cause the cavity to grow in size.

Such a moving instability would also explain why the measurements of magnetic field-free regions are sporadic and mainly span several minutes, with the 26 July one lasting 25 minutes and the longest one, recorded in November, about 40 minutes. The short duration of the detections is not a result of Rosetta crossing the cavity – the spacecraft moves much too slowly with respect to the comet – but of the magnetic field-free regions repeatedly passing through the spacecraft.

“What we are seeing is not the main part of the cavity but the smaller pockets at the cavity boundary, which are occasionally pushed farther away from the nucleus by the waves propagating along the boundary,” adds Charlotte.

Scientists are now busy analysing all the magnetic field-free events recorded by Rosetta, to learn more about the properties of the plasma in the comet environment and its interaction with the solar wind. After perihelion, as the comet moved away from the Sun and its outgassing and dust production rate declined, the spacecraft was able to move closer to the nucleus, and the magnetometer continued detecting magnetic field-free regions for several months, until the latest detection in February 2016.
Comet Halley close up

“Three decades ago, Giotto’s detection at Comet Halley was a great success, because it was the first confirmation of the existence of a diamagnetic cavity at a comet,” says Matt Taylor, Rosetta Project Scientist at ESA.

“But that was only one measurement, while now we have seen the cavity at Rosetta’s comet come and go hundreds of times over many months. This is why Rosetta is there, living with the comet and studying it up close.”

First detection of a diamagnetic cavity at comet 67P/Churyumov-Gerasimenko,” by C. Götz et al. is published in the journal Astronomy & Astrophysics. The results will be presented at the 50th ESLAB Symposium “From Giotto to Rosetta”, held 14–18 March in Leiden, the Netherlands.

For more information contact:

Charlotte Götz
Institute for Geophysics and extraterrestrial Physics
Technische Universität Braunschweig, Germany
Email: c.goetz@tu-bs.de

Karl-Heinz Glassmeier
RPC-MAG principal investigator
Institute for Geophysics and extraterrestrial Physics
Technische Universität Braunschweig, Germany
Email: kh.glassmeier@tu-bs.de

Matt Taylor
ESA Rosetta Project Scientist
Email: matt.taylor@esa.int

Markus Bauer








ESA Science Communication Officer









Tel: +31 71 565 6799









Mob: +31 61 594 3 954









Email: markus.bauer@esa.int
 

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Pulsar Web Could Detect Low-Frequency Gravitational Waves

Elizabeth Ferrara Writing

Gravitational waves are ripples in space-time, represented by the green grid, produced by accelerating bodies such as interacting supermassive black holes. These waves affect the time it takes for radio signals from pulsars to arrive at Earth.
Credits: David Champion



The recent detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) came from two black holes, each about 30 times the mass of our sun, merging into one. Gravitational waves span a wide range of frequencies that require different technologies to detect. A new study from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has shown that low-frequency gravitational waves could soon be detectable by existing radio telescopes.

"Detecting this signal is possible if we are able to monitor a sufficiently large number of pulsars spread across the sky," said Stephen Taylor, lead author of the paper published this week in The Astrophysical Journal Letters. He is a postdoctoral researcher at NASA's Jet Propulsion Laboratory, Pasadena, California. "The smoking gun will be seeing the same pattern of deviations in all of them." Taylor and colleagues at JPL and the California Institute of Technology in Pasadena have been studying the best way to use pulsars to detect signals from low-frequency gravitational waves. Pulsars are highly magnetized neutron stars, the rapidly rotating cores of stars left behind when a massive star explodes as a supernova.

Einstein's general theory of relativity predicts that gravitational waves -- ripples in spacetime -- emanate from accelerating massive objects. Nanohertz gravitational waves are emitted from pairs of supermassive black holes orbiting each other, each of which contain millions or a billion times more mass than those detected by LIGO. These black holes each originated at the center of separate galaxies that collided. They are slowly drawing closer together and will eventually merge to create a single super-sized black hole.

As they orbit each other, the black holes pull on the fabric of space and create a faint signal that travels outward in all directions, like a vibration in a spider's web. When this vibration passes Earth, it jostles our planet slightly, causing it to shift with respect to distant pulsars. Gravitational waves formed by binary supermassive black holes take months or years to pass Earth and require many years of observations to detect.

"Galaxy mergers are common, and we think there are many galaxies harboring binary supermassive black holes that we should be able to detect," said Joseph Lazio, one of Taylor's co-authors, also based at JPL. "Pulsars will allow us to see these massive objects as they slowly spiral closer together."

Once these gigantic black holes get very close to each other, the gravitational waves are too short to detect using pulsars. Space-based laser interferometers like eLISA, a mission being developed by the European Space Agency with NASA participation, would operate in the frequency band that can detect the signature of supermassive black holes merging. The LISA Pathfinder mission, which includes a stabilizing thruster system managed by JPL, is currently testing technologies necessary for the future eLISA mission.

Finding evidence for supermassive black hole binaries has been a challenge for astronomers. The centers of galaxies contain many stars, and even monstrous black holes are quite small -- comparable to the size of our solar system. Seeing visible signatures of these binaries amid the glare of the surrounding galaxy has been difficult for astronomers.

Radio astronomers search instead for the gravitational signals from these binaries. In 2007, NANOGrav began observing a set of the fastest-rotating pulsars to try to detect tiny shifts caused by gravitational waves.

Pulsars emit beams of radio waves, some of which sweep across Earth once every rotation. Astronomers detect this as a rapid pulse of radio emission. Most pulsars rotate several times a second. But some, called millisecond pulsars, rotate hundreds of times faster.

"Millisecond pulsars have extremely predictable arrival times, and our instruments are able to measure them to within a ten-millionth of a second," said Maura McLaughlin, a radio astronomer at West Virginia University in Morgantown and member of the NANOGrav team. "Because of that, we can use them to detect incredibly small shifts in Earth's position."

But astrophysicists at JPL and Caltech caution that detecting faint gravitational waves would likely require more than a few pulsars. "We're like a spider at the center of a web," said Michele Vallisneri, another member of the JPL/Caltech research group. "The more strands we have in our web of pulsars, the more likely we are to sense when a gravitational wave passes by."

Vallisneri said accomplishing this feat will require international collaboration. "NANOGrav is currently monitoring 54 pulsars, but we can only see some of the southern hemisphere. We will need to work closely with our colleagues in Europe and Australia in order to get the all-sky coverage this search requires."

The feasibility of this approach was recently called into question when a group of Australian pulsar researchers reported that they were unable to detect such signals when analyzing a set of pulsars with the most precise timing measurements. After studying this result, the NANOGrav team determined that the reported non-detection was not a surprise, and resulted from the combination of optimistic gravitational wave models and analysis of too few pulsars. Their one-page response was released recently via the arXiv electronic print service.

Despite the technical challenges, Taylor is confident their team is on the right track. "Gravitational waves are washing over Earth all the time," Taylor said. "Given the number of pulsars being observed by NANOGrav and other international teams, we expect to have clear and convincing evidence of low-frequency gravitational waves within the next decade."

NANOGrav is a collaboration of over 60 scientists at more than a dozen institutions in the United States and Canada. The group uses radio pulsar timing observations acquired at NRAO's Green Bank Telescope in West Virginia and at Arecibo Radio Observatory in Puerto Rico to search for ripples in the fabric of spacetime. In 2015, NANOGrav was awarded $14.5 million by the National Science Foundation to create and operate a Physics Frontiers Center.

"With the recent detection of gravitational waves by LIGO, the outstanding work of the NANOGrav collaboration is particularly relevant and timely," said Pedro Marronetti, National Science Foundation program director for gravitational wave research. "This NSF-funded Physics Frontier Center is poised to complement LIGO observations, extending the window of gravitational wave detection to very low frequencies."

For additional information, visit
Written by Elizabeth Ferrara of NANOGrav

Elizabeth Landau : Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
elizabeth.landau@jpl.nasa.gov

Elizabeth Ferrara: NANOGrav press officer
elizabeth.ferrara@nanograv.org

(Editor: Tony Greicius:NASA)
 

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NASA’s IBEX Observations Pin Down Interstellar Magnetic Field

Sarah Frazier Writing

(Artist concept) Far beyond the orbit of Neptune, the solar wind and the interstellar medium interact to create a region known as the inner heliosheath, bounded on the inside by the termination shock, and on the outside by the heliopause. Image: NASA/IBEX/Adler Planetarium

February 26, 2016: Immediately after its 2008 launch, NASA’s Interstellar Boundary Explorer, or IBEX, spotted a curiosity in a thin slice of space: More particles streamed in through a long, skinny swath in the sky than anywhere else. The origin of the so-called IBEX ribbon was unknown – but its very existence opened doors to observing what lies outside our solar system, the way drops of rain on a window tell you more about the weather outside.

Now, a new study uses IBEX data and simulations of the interstellar boundary – which lies at the very edge of the giant magnetic bubble surrounding our solar system called the heliosphere – to better describe space in our galactic neighborhood. The paper, published Feb. 8, 2016, in The Astrophysical Journal Letters, precisely determines the strength and direction of the magnetic field outside the heliosphere. Such information gives us a peek into the magnetic forces that dominate the galaxy beyond, teaching us more about our home in space.

The new paper is based on one particular theory of the origin of the IBEX ribbon, in which the particles streaming in from the ribbon are actually solar material reflected back at us after a long journey to the edges of the sun’s magnetic boundaries. A giant bubble, known as the heliosphere, exists around the sun and is filled with what’s called solar wind, the sun’s constant outflow of ionized gas, known as plasma. When these particles reach the edges of the heliosphere, their motion becomes more complicated.  

“The theory says that some solar wind protons are sent flying back towards the sun as neutral atoms after a complex series of charge exchanges, creating the IBEX ribbon,” said Eric Zirnstein, a space scientist at the Southwest Research Institute in San Antonio, Texas, and lead author on the study. “Simulations and IBEX observations pinpoint this process – which takes anywhere from three to six years on average – as the most likely origin of the IBEX ribbon.”

Outside the heliosphere lies the interstellar medium, with plasma that has different speed, density, and temperature than solar wind plasma, as well as neutral gases. These materials interact at the heliosphere’s edge to create a region known as the inner heliosheath, bounded on the inside by the termination shock – which is more than twice as far from us as the orbit of Pluto – and on the outside by the heliopause, the boundary between the solar wind and the comparatively dense interstellar medium.

Some solar wind protons that flow out from the sun to this boundary region will gain an electron, making them neutral and allowing them to cross the heliopause. Once in the interstellar medium, they can lose that electron again, making them gyrate around the interstellar magnetic field. If those particles pick up another electron at the right place and time, they can be fired back into the heliosphere, travel all the way back toward Earth, and collide with IBEX’s detector. The particles carry information about all that interaction with the interstellar magnetic field, and as they hit the detector they can give us unprecedented insight into the characteristics of that region of space.

“Only Voyager 1 has ever made direct observations of the interstellar magnetic field, and those are close to the heliopause, where it’s distorted,” said Zirnstein. “But this analysis provides a nice determination of its strength and direction farther out.”

The directions of different ribbon particles shooting back toward Earth are determined by the characteristics of the interstellar magnetic field. For instance, simulations show that the most energetic particles come from a different region of space than the least energetic particles, which gives clues as to how the interstellar magnetic field interacts with the heliosphere.

For the recent study, such observations were used to seed simulations of the ribbon’s origin. Not only do these simulations correctly predict the locations of neutral ribbon particles at different energies, but the deduced interstellar magnetic field agrees with Voyager 1 measurements, the deflection of interstellar neutral gases, and observations of distant polarized starlight.

However, some early simulations of the interstellar magnetic field don’t quite line up. Those pre-IBEX estimates were based largely on two data points – the distances at which Voyagers 1 and 2 crossed the termination shock.

“Voyager 1 crossed the termination shock at 94 astronomical units, or AU, from the sun, and Voyager 2 at 84 AU,” said Zirnstein. One AU is equal to about 93 million miles, the average distance between Earth and the sun. “That difference of almost 930 million miles was mostly explained by a strong, very tilted interstellar magnetic field pushing on the heliosphere.”

But that difference may be accounted for by considering a stronger influence from the solar cycle, which can lead to changes in the strength of the solar wind and thus change the distance to the termination shock in the directions of Voyager 1 and 2. The two Voyager spacecraft made their measurements almost three years apart, giving plenty of time for the variable solar wind to change the distance of the termination shock.

“Scientists in the field are developing more sophisticated models of the time-dependent solar wind,” said Zirnstein.

The simulations generally jibe well with the Voyager data.

“The new findings can be used to better understand how our space environment interacts with the interstellar environment beyond the heliopause,” said Eric Christian, IBEX program scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in this study. “In turn, understanding that interaction could help explain the mystery of what causes the IBEX ribbon once and for all.”

The Southwest Research Institute leads IBEX with teams of national and international partners. NASA Goddard manages the Explorers Program for the agency’s Heliophysics Division within the Science Mission Directorate in Washington.

IBEX mission website

Article: The Astrophysical Journal Letters - "Local Interstellar Magnetic Field Determined From the Interstellar Boundary Explorer Ribbon"

Sarah Frazier: NASA’s Goddard Space Flight Center, Greenbelt, Md.
( Editor: Rob Garner: NASA)

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NASA's WFIRST A Wider Set of Eyes on the Universe

NASA's Wide Field Infrared Survey Telescope (WFIRST), illustrated here, will carry a Wide Field Instrument to capture Hubble-quality images covering large swaths of sky, enabling cosmic evolution studies. Its Coronagraph Instrument will directly image exoplanets and study their atmospheres. Credits: NASA/GSFC/Conceptual Image Lab

 

After years of preparatory studies, NASA is formally starting an astrophysics mission designed to help unlock the secrets of the universe -- the Wide Field Infrared Survey Telescope (WFIRST).

With a view 100 times bigger than that of NASA’s Hubble Space Telescope, WFIRST will aid researchers in their efforts to unravel the secrets of dark energy and dark matter, and explore the evolution of the cosmos. It also will discover new worlds outside our solar system and advance the search for worlds that could be suitable for life.

NASA's Agency Program Management Council, which evaluates the agency's programs and projects on content, risk management, and performance, made the decision to move forward with the mission on Wednesday.

“WFIRST has the potential to open our eyes to the wonders of the universe, much the same way Hubble has,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate at Headquarters in Washington. "This mission uniquely combines the ability to discover and characterize planets beyond our own solar system with the sensitivity and optics to look wide and deep into the universe in a quest to unravel the mysteries of dark energy and dark matter.”

WFIRST is the agency's next major astrophysics observatory, following the launch of the James Webb Space Telescope in 2018. The observatory will survey large regions of the sky in near-infrared light to answer fundamental questions about the structure and evolution of the universe, and expand our knowledge of planets beyond our solar system – known as exoplanets.

It will carry a Wide Field Instrument for surveys, and a Coronagraph Instrument designed to block the glare of individual stars and reveal the faint light of planets orbiting around them. By blocking the light of the host star, the Coronagraph Instrument will enable detailed measurements of the chemical makeup of planetary atmospheres. Comparing these data across many worlds will allow scientists to better understand the origin and physics of these atmospheres, and search for chemical signs of environments suitable for life.

"WFIRST is designed to address science areas identified as top priorities by the astronomical community," said Paul Hertz, director of NASA's Astrophysics Division in Washington. “The Wide-Field Instrument will give the telescope the ability to capture a single image with the depth and quality of Hubble, but covering 100 times the area. The coronagraph will provide revolutionary science, capturing the faint, but direct images of distant gaseous worlds and super-Earths."

The telescope’s sensitivity and wide view will enable a large-scale search for exoplanets by monitoring the brightness of millions of stars in the crowded central region of our galaxy. The survey will net thousands of new exoplanets similar in size and distance from their star as those in our own solar system, complementing the work started by NASA's Kepler mission and the upcoming work of the Transiting Exoplanet Survey Satellite.

Employing multiple techniques, astronomers also will use WFIRST to track how dark energy and dark matter have affected the evolution of our universe. Dark energy is a mysterious, negative pressure that has been speeding up the expansion of the universe. Dark matter is invisible material that makes up most of the matter in our universe.

By measuring the distances of thousands of supernovae, astronomers can map in detail how cosmic expansion has increased with time. WFIRST also can precisely measure the shapes, positions and distances of millions of galaxies to track the distribution and growth of cosmic structures, including galaxy clusters and the dark matter accompanying them.

"In addition to its exciting capabilities for dark energy and exoplanets, WFIRST will provide a treasure trove of exquisite data for all astronomers," said Neil Gehrels, WFIRST project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "This mission will survey the universe to find the most interesting objects out there."

WFIRST is slated to launch in the mid-2020s. The observatory will begin operations after travelling to a gravitational balance point known as Earth-Sun L2, which is located about one million miles from Earth in a direction directly opposite the Sun.

WFIRST is managed at Goddard, with participation by the Jet Propulsion Laboratory (JPL) in Pasadena, California, the Space Telescope Science Institute in Baltimore, the Infrared Processing and Analysis Center, also in Pasadena, and a science team comprised of members from U.S. research institutions across the country.

For more information about NASA's WFIRST mission

Felicia Chou
Headquarters, Washington
202-358-0257
felicia.chou@nasa.gov

Lynn Chandler
Goddard Space Flight Center, Greenbelt, Md.
301-286-2806
lynn.chandler-1@nasa.gov
 

( Editor: Karen Northon: NASA)

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Wait, Here; LISA Will Show You the Way Soon

Artist's impression of LISA Pathfinder: LISA Pathfinder will test in flight the concept of low-frequency gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall, and control and measure their motion with unprecedented accuracy. To do this it will use inertial sensors, a laser metrology system, a drag-free control system and an ultra-precise micro-propulsion system.

LISA Pathfinder carries two advanced instruments: The LTP (LISA Technology Package), a payload developed by European institutes and industry. It contains two identical proof masses in the form of 46 mm cubes made of gold-platinum, each suspending in its own vacuum can. They shall simulate the observational arrangement for the LISA mission, with the difference that the distance between the proof masses is reduced from 5 million kilometres to 35 centimetres.

The Disturbance Reduction System (DRS) is an experiment provided by NASA's Jet Propulsion Laboratory in California, which includes also a set of micro-rockets that aim to control the spacecraft’s position to within a millionth of a millimetre. Released 14/11/2013 1:49 pm: Copyright ESA–D. Ducros, 2010

16 February 2016: ESA’s LISA Pathfinder has released both of its gold–platinum cubes, and will shortly begin its demanding science mission, placing these test masses in the most precise freefall ever obtained to demonstrate technologies for observing gravitational waves from space.

Launched on 3 December, LISA Pathfinder reached its operational location on 22 January, some 1.5 million km from Earth in the direction of the Sun.

As tests on the spacecraft and its precious payload continue, a major milestone was reached today. For the first time, the two masses – a pair of identical 46 mm gold–platinum cubes – in the heart of the spacecraft are floating freely, several millimetres from the walls of their housings. The cubes sit 38 cm apart linked only by laser beams.

Throughout LISA Pathfinder’s ground handling, launch, the burns that raised its orbit, and the six-week cruise to its work site, each cube was held firmly in place by eight ‘fingers’ pressing on its corners.

On 3 February, the locking fingers were retracted and a valve was opened to allow any residual gas molecules around the cubes to vent to space.

Each cube remained in the centre of its housing held by a pair of rods softly pushing on two opposite sides.

The rods were finally released from one test mass yesterday and from the other today, leaving the cubes floating freely, with no mechanical contact with the spacecraft.

“This is why we sent the test cubes into space: to recreate conditions that are impossible to achieve in the gravitational field of our planet,” says Paul McNamara, ESA’s project scientist.

“Only under these conditions is it possible to test freefall in the purest achievable form. We can’t wait to start running experiments with this amazing gravity laboratory.”

It will be another week before the cubes are left completely at the mercy of gravity, with no other forces acting on them. Before then, minute electrostatic forces are being applied to move them around and make them follow the spacecraft as its flight through space is slightly perturbed by outside forces such as pressure from sunlight.

 On 23 February, the team will switch LISA Pathfinder to science mode for the first time, and the opposite will become true: the cubes will be in freefall and the spacecraft will start sensing any motions towards them owing to external forces. Microthrusters will make minuscule shifts in order to keep the craft centred on one mass.

Then the scientists will be in a position to run several months of experiments to determine how accurately the two freely-flying test masses can be kept positioned relative to each other, making measurements with the laser that links them.

Roughly speaking, the required accuracy is on the order of a millionth of a millionth of a metre.

“The release of the test masses was clearly the most critical operation throughout the mission, as it was not possible to test it fully on the ground due to the small forces and movements involved. We are ecstatic with this world-class achievement,” says César García Marirrodriga, ESA’s project manager.

“This is a testament to the innovation and dedication of the large team of people that put together this outstanding space laboratory.”

After final checks, LISA Pathfinder will begin its science mission on 1 March, validating a key technology for observing gravitational waves from space.

Gravitational waves are minute fluctuations in the fabric of spacetime, predicted by Albert Einstein’s general theory of relativity and directly observed for the first time recently by the Laser Interferometer Gravitational-Wave Observatory – an announcement that created a worldwide sensation last week.
 

 As this discovery confirmed, ground-based experiments can detect high-frequency gravitational waves from cosmic events such as the coalescence of a pair of stellar remnants, like neutron stars or black holes. However, to observe lower-frequency gravitational waves emitted by different astronomical sources, such as the merging of supermassive black holes at the centre of large galaxies, it is necessary to move the search into space.

There, a future gravitational wave observatory, already identified as the goal for the L3 mission in ESA’s Cosmic Vision programme, will measure distortions in the fabric of spacetime on the inconceivably tiny scale of a few millionths of a millionth of a metre over a distance of a million kilometres.

“Releasing LISA Pathfinder's test masses is another step forward in gravitational wave astronomy within this memorable month: the test masses are, for the first time, suspended in orbit and subject to measurements,” says Stefano Vitale of University of Trento, Italy, Principal Investigator of the LISA Technology Package.

In the coming months, LISA Pathfinder will verify the fundamental condition needed for a future gravitational wave observatory in space: putting test masses into freefall at unprecedented levels of accuracy, by isolating the two cubes from all external and internal forces except one: gravity. Stay tuned!

For more information, please contact:
Markus Bauer
ESA Science and Robotic Exploration Communication Officer









Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int

Paul McNamara
LISA Pathfinder Project Scientist
Scientific Support Office
Directorate of Science
European Space Agency
Phone: +31 71 565 8239
Email: paul.mcnamara@esa.int

César García Marirrodriga
LISA Pathfinder Project Manager


Projects Department
Directorate of Science
European Space Agency
Tel: +31 71 565 5172
Email: cesar.garcia@esa.int

Stefano Vitale
LISA Technology Package Principal Investigator
University of Trento, Italy
Tel: +39 046 128 1568
Email: stefano.vitale@unitn.it
 

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Particles in Love: Quantum Mechanics Explored in New Study

Technology used to study the "love" between particles is also being used in research to improve communications between space and Earth.

Credits: NASA/JPL-Caltech

 

Here's a love story at the smallest scales imaginable: particles of light. It is possible to have particles that are so intimately linked that a change to one affects the other, even when they are separated at a distance.

This idea, called "entanglement," is part of the branch of physics called quantum mechanics, a description of the way the world works at the level of atoms and particles that are even smaller. Quantum mechanics says that at these very tiny scales, some properties of particles are based entirely on probability. In other words, nothing is certain until it happens.

Testing Bell's Theorem

Albert Einstein did not entirely believe that the laws of quantum mechanics described reality. He and others postulated that there must be some hidden variables at work, which would allow quantum systems to be predictable. In 1964, however, John Bell published the idea that any model of physical reality with such hidden variables also must allow for the instantaneous influence of one particle on another. While Einstein proved that information cannot travel faster than the speed of light, particles can still affect each other when they are far apart according to Bell.

Scientists consider Bell's theorem an important foundation for modern physics. While many experiments have taken place to try to prove his theorem, no one was able to run a full, proper test of the experiment Bell would have needed until recently. In 2015, three separate studies were published on this topic, all consistent with the predictions of quantum mechanics and entanglement.

"What's exciting is that in some sense, we're doing experimental philosophy," said Krister Shalm, physicist with the National Institute of Standards and Technology (NIST), Boulder, Colorado. Shalm is lead author on one of the 2015 studies testing Bell's theorem. "Humans have always had certain expectations of how the world works, and when quantum mechanics came along, it seemed to behave differently."

How 'Alice and Bob' Test Quantum Mechanics

The paper by Shalm, Marsili and colleagues was published in the journal Physical Review Letters, with the mind-bending title "Strong Loophole-Free Test of Local Realism."

“Our paper and the other two published last year show that Bell was right: any model of the world that contains hidden variables must also allow for entangled particles to influence one another at a distance," said Francesco Marsili of NASA's Jet Propulsion Laboratory in Pasadena, California, who collaborated with Shalm.

An analogy helps to understand the experiment, which was conducted at a NIST laboratory in Boulder:

Imagine that A and B are entangled photons. A is sent to Alice and B is sent to Bob, who are located 607 feet (185 meters) apart.

Alice and Bob poke and prod at their photons in all kinds of ways to get a sense of their properties. Without talking to each other, they then each randomly decide how to measure their photons, using random number generators to guide their decisions. When Alice and Bob compare notes, they are surprised to find that the results of their independent experiments are correlated. In other words, even at a distance, measuring one photon of the entangled pair affects the properties of the other photon.

"It's as if Alice and Bob try to tear the two photons apart, but their love still persists," Shalm said. In other words, the entangled photons behave as if they are two parts of a single system, even when separated in space.

Alice and Bob -- representing actual photon detectors -- then repeat this with many other pairs of entangled photons, and the phenomenon persists.

In reality, the photon detectors are not people, but superconducting nanowire single photon detectors (SNSPDs). SNSPDs are metal strips that are cooled until they become "superconducting," meaning they lose their electric resistance. A photon hitting this strip causes it to turn into a normal metal again momentarily, so the resistance of the strip jumps from zero to a finite value. This change in resistance allows the researchers to record the event.

To make this experiment happen in a laboratory, the big challenge is to avoid losing photons as they get sent to the Alice and Bob detectors through an optical fiber. JPL and NIST developed SNSPDs with worldrecord performance, demonstrating more than 90 percent efficiency and low "jitter," or uncertainty on the time of arrival of a photon. This experiment would not have been possible without SNSPDs.

Why This is Useful

The design of this experiment could potentially be used in cryptography -- making information and communications secure -- as it involves generating random numbers.

"The same experiment that tells us something deep about how the world is constructed also can be used for these applications that require you to keep your information safe," Shalm said.

Cryptography isn't the only application of this research. Detectors similar to those used for the experiment, which were built by JPL and NIST, could eventually also be used for deep-space optical communication. With a high efficiency and low uncertainty about the time of signal arrival, these detectors are well-suited for transmitting information with pulses of light in the optical spectrum.

"Right now we have the Deep Space Network to communicate with spacecraft around the solar system, which encodes information in radio signals. With optical communications, we could increase the data rate of that network 10- to 100-fold," Marsili said.

Deep space optical communication using technology similar to the detectors in Marsili's experiment was demonstrated with NASA's Lunar Atmosphere Dust and Environment Explorer (LADEE) mission, which orbited the moon from October 2013 to April 2014. A technology mission called the Lunar Laser Communication Demonstration, with components on LADEE and on the ground, downlinked data encoded in laser pulses, and made use of ground receivers based on SNSPDs.

NASA's Space Technology Mission Directorate is working on the Laser Communications Relay Demonstration (LCRD) mission. The mission proposes to revolutionize the way we send and receive data, video and other information, using lasers to encode and transmit data at rates 10 to 100 times faster than today's fastest radio-frequency systems, using significantly less mass and power.

"Information can never travel faster than the speed of light -- Einstein was right about that. But through optical communications research, we can increase the amount of information we send back from space," Marsili said. "The fact that the detectors from our experiment have this application creates great synergy between the two endeavors."

And so, what began as the study of "love" between particles is contributing to innovations in communications between space and Earth. "Love makes the world go 'round," and it may, in a sense, help us learn about other worlds.

Elizabeth Landau
NASA's Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
Elizabeth.Landau@jpl.nasa.gov

( Editor: Tony Greicius: NASA)

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Einstein's Gravitational Waves Detected

An artist's impression of gravitational waves generated by binary neutron stars. Credits: R. Hurt/Caltech-JPL

 

Feb. 11, 2016: The National Science Foundation (NSF) has announced the detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of ground-based observatories in Hanford, Washington, and Livingston, Louisiana.

Albert Einstein predicted the existence of gravitational waves in his general theory of relativity a century ago, and scientists have been attempting to detect them for 50 years. Einstein pictured these waves as ripples in the fabric of space-time produced by massive, accelerating bodies, such as black holes orbiting each other. Scientists are interested in observing and characterizing these waves to learn more about the sources producing them and about gravity itself.

Gravitational Waves

Released 11/02/2016 6:00 pm: Copyright ESA–C.Carreau

Gravitational waves are ripples in the fabric of spacetime produced by accelerating massive bodies to Albert Einstein’s general theory of relativity.

In general relativity, gravity manifests itself as massive objects bending the structure of spacetime. In addition, something else happens if the gravitational field varies, for example when two massive objects orbit each other.

The motion of massive bodies through spacetime perturbs its very fabric, imprinting a signal that travels away as a disturbance to the structure of spacetime itself: gravitational waves. The animation visualises the effect of these oscillations, which consist of sequential stretches and compressions of spacetime, rhythmically increasing and reducing the distance between particles as a wave propagates through the surroundings. Readmore

The LIGO detections represent a much-awaited first step toward opening a whole new branch of astrophysics. Nearly everything we know about the universe comes from detecting and analyzing light in all its forms across the electromagnetic spectrum – radio, infrared, visible, ultraviolet, X-rays and gamma rays. The study of gravitational waves opens a new window on the universe, one that scientists expect will provide key information that will complement what we can learn through electromagnetic radiation.   

Just as in other areas of astronomy, astronomers need both ground-based and space-based observatories to take full advantage of this new window. LIGO is sensitive to gravitational waves within the range of 10 to 1,000 cycles per second (10 to 1,000 Hz). A space-based system would be able to detect waves at much lower frequencies, from 0.0001 to 0.1 Hz, and detect different types of sources. NASA is working closely with the European Space Agency (ESA) to develop a concept for a space-based gravitational wave observatory.

ESA is currently leading the LISA Pathfinder mission, launched last December and now in its commissioning phase, to demonstrate technologies that could be used for a future space-based gravitational wave observatory. NASA contributed its ST-7 Disturbance Reduction System to the payload as part of that demonstration.

NASA missions are searching the sky for fleeting X-ray and gamma-ray signals from LIGO events. Detecting the light emitted by a gravitational wave source would enable a much deeper understanding of the event than through either technique alone.  

For more information, please visit:

Francis Reddy: NASA's Goddard Space Flight Center, Greenbelt, Md.

Felicia Chou: NASA Headquarters, Washington, D.C.

(Editor: Ashley Morrow: NASA)

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Galaxy Clusters Reveal New Dark Matter Insights

This image from NASA's Hubble Space Telescope shows the inner region of Abell 1689, an immense cluster of galaxies. Scientists say the galaxy clusters we see today have resulted from fluctuations in the density of matter in the early universe.
Credits: NASA/ESA/JPL-Caltech/Yale/CNRS

 

Dark matter is a mysterious cosmic phenomenon that accounts for 27 percent of all matter and energy. Though dark matter is all around us, we cannot see it or feel it. But scientists can infer the presence of dark matter by looking at how normal matter behaves around it.

Galaxy clusters, which consist of thousands of galaxies, are important for exploring dark matter because they reside in a region where such matter is much denser than average. Scientists believe that the heavier a cluster is, the more dark matter it has in its environment. But new research suggests the connection is more complicated than that.

"Galaxy clusters are like the large cities of our universe. In the same way that you can look at the lights of a city at night from a plane and infer its size, these clusters give us a sense of the distribution of the dark matter that we can't see," said Hironao Miyatake at NASA's Jet Propulsion Laboratory, Pasadena, California.

A new study in Physical Review Letters, led by Miyatake, suggests that the internal structure of a galaxy cluster is linked to the dark matter environment surrounding it. This is the first time that a property besides the mass of a cluster has been shown to be associated with surrounding dark matter.

Researchers studied approximately 9,000 galaxy clusters from the Sloan Digital Sky Survey DR8 galaxy catalog, and divided them into two groups by their internal structures: one in which the individual galaxies within clusters were more spread out, and one in which they were closely packed together. The scientists used a technique called gravitational lensing -- looking at how the gravity of clusters bends light from other objects -- to confirm that both groups had similar masses.

But when the researchers compared the two groups, they found an important difference in the distribution of galaxy clusters. Normally, galaxy clusters are separated from other clusters by 100 million light-years on average. But for the group of clusters with closely packed galaxies, there were fewer neighboring clusters at this distance than for the sparser clusters. In other words, the surrounding dark-matter environment determines how packed a cluster is with galaxies.

"This difference is a result of the different dark-matter environments in which the groups of clusters formed. Our results indicate that the connection between a galaxy cluster and surrounding dark matter is not characterized solely by cluster mass, but also its formation history," Miyatake said.

Study co-author David Spergel, professor of astronomy at Princeton University in New Jersey, added, “Previous observational studies had shown that the cluster’s mass is the most important factor in determining its global properties. Our work has shown that ‘age matters': Younger clusters live in different large-scale dark-matter environments than older clusters.”

The results are in line with predictions from the leading theory about the origins of our universe. After an event called cosmic inflation, a period of less than a trillionth of a second after the big bang, there were small changes in the energy of space called quantum fluctuations. These changes then triggered a non-uniform distribution of matter. Scientists say the galaxy clusters we see today have resulted from fluctuations in the density of matter in the early universe.

"The connection between the internal structure of galaxy clusters and the distribution of surrounding dark matter is a consequence of the nature of the initial density fluctuations established before the universe was even one second old," Miyatake said.

Researchers will continue to explore these connections.

“Galaxy clusters are remarkable windows into the mysteries of the universe. By studying them, we can learn more about the evolution of large-scale structure of the universe, and its early history, as well as dark matter and dark energy," Miyatake said.

Elizabeth Landau
NASA's Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425 Elizabeth.Landau@jpl.nasa.gov

( Editor: Tony Greicius: NASA)

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LISA Has Arrived at the Middle of Nowhere in L1, at 1.5 Million KM from Earth Towards the Sun, to Be Precise

Module separation: Released 22/01/2016 4:15 pm: Copyright ESA/C.Carreau. LISA Pathfinder, ESA's mission to test technology for future gravitational-wave observatories in space, depicted after the separation of the propulsion module. LISA Pathfinder launched on 3 December 2015, and used its propulsion module to raise its orbit six times and embark on the path to its operational orbit. After releasing the propulsion module on 22 January, the science module will enter its final orbit around the first Sun–Earth Lagrangian point L1, 1.5 million km from Earth in the direction of the Sun.

 

22 January 2016: After a six-week journey, LISA Pathfinder arrived at its destination today, an orbit around a point of balance in space where it will soon start testing technologies crucial for exploring the gravitational Universe.

LISA Pathfinder is testing the key elements that could be used for a future mission to detect gravitational waves – ripples in spacetime predicted by Albert Einstein in his General Theory of Relativity.

To this end, it will release two test masses into near-perfect free fall and measure their motion with unprecedented accuracy.

LISA Pathfinder was launched on 3 December 2015 and arrived today in its orbit around ‘L1’, the first libration point of the Sun-Earth system, a virtual point in space some 1.5 million km from Earth towards the Sun.

LISA Pathfinder’s arrival came after a final thruster burn using the spacecraft’s hard-working propulsion module on 20 January. The small, 64-second firing was designed to slightly change its speed and just barely tip the craft onto its new orbit about L1.

Since launch, the propulsion module raised the orbit around Earth six times, the last of which kicked it towards L1.

“We had planned two burns to get us into final orbit at L1, but only one was needed,” says Ian Harrison, Spacecraft Operations Manager at ESA’s ESOC operations centre in Darmstadt, Germany.

The propulsion module separated from the science section at 11:30 GMT (12:30 CET) today after the combination was set spinning for stability.

“Heat and vibration from the regular, hot thrusters on the propulsion module would cause too much disturbance during the spacecraft’s delicate technology demonstration mission,” notes Ian. “Primary propulsion during the rest of the mission will be provided by cold-gas microthrusters to keep us at L1.”

These small thrusters were used in the hours after separation to kill the spin and stabilise the spacecraft.

 Today’s operations were monitored by the mission control and science teams at ESOC in real time via the Agency’s deep-space station at Malargüe, Argentina.

During this evening, the craft will be slowly turned to point towards Earth and, around midnight, establish a full communications link via ESA’s New Norcia ground station, Australia.

Next week, LISA Pathfinder’s trajectory will be fine-tuned with a series of three microthruster bursts, taking it onto its final orbit, a 500 000 × 800 000 km orbit around L1.

L1 was chosen because it is a quiet place in space, far away from large bodies such as Earth and is ideal for communications.

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Dark Energy, Dark Matter


In the early 1990s, one thing was fairly certain about the expansion of the Universe. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. Granted, the slowing had not been observed, but, theoretically, the Universe had to slow. The Universe is full of matter and the attractive force of gravity pulls all matter together. Then came 1998 and the Hubble Space Telescope (HST) observations of very distant supernovae that showed that, a long time ago, the Universe was actually expanding more slowly than it is today. So the expansion of the Universe has not been slowing due to gravity, as everyone thought, it has been accelerating. No one expected this, no one knew how to explain it. But something was causing it.

Eventually theorists came up with three sorts of explanations. Maybe it was a result of a long-discarded version of Einstein's theory of gravity, one that contained what was called a "cosmological constant." Maybe there was some strange kind of energy-fluid that filled space. Maybe there is something wrong with Einstein's theory of gravity and a new theory could include some kind of field that creates this cosmic acceleration. Theorists still don't know what the correct explanation is, but they have given the solution a name. It is called dark energy.

What Is Dark Energy?

More is unknown than is known. We know how much dark energy there is because we know how it affects the Universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 68% of the Universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the Universe. Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the Universe.

One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the Universe to expand faster and faster. Unfortunately, no one understands why the cosmological constant should even be there, much less why it would have exactly the right value to cause the observed acceleration of the Universe. 

Another explanation for how space acquires energy comes from the quantum theory of matter. In this theory, "empty space" is actually full of temporary ("virtual") particles that continually form and then disappear. But when physicists tried to calculate how much energy this would give empty space, the answer came out wrong - wrong by a lot. The number came out 10120 times too big. That's a 1 with 120 zeros after it. It's hard to get an answer that bad. So the mystery continues.

Another explanation for dark energy is that it is a new kind of dynamical energy fluid or field, something that fills all of space but something whose effect on the expansion of the Universe is the opposite of that of matter and normal energy. Some theorists have named this "quintessence," after the fifth element of the Greek philosophers. But, if quintessence is the answer, we still don't know what it is like, what it interacts with, or why it exists. So the mystery continues.

A last possibility is that Einstein's theory of gravity is not correct. That would not only affect the expansion of the Universe, but it would also affect the way that normal matter in galaxies and clusters of galaxies behaved. This fact would provide a way to decide if the solution to the dark energy problem is a new gravity theory or not: we could observe how galaxies come together in clusters. But if it does turn out that a new theory of gravity is needed, what kind of theory would it be? How could it correctly describe the motion of the bodies in the Solar System, as Einstein's theory is known to do, and still give us the different prediction for the Universe that we need? There are candidate theories, but none are compelling. So the mystery continues.

The thing that is needed to decide between dark energy possibilities - a property of space, a new dynamic fluid, or a new theory of gravity - is more data, better data.

What Is Dark Matter?

By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?

We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.

However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs". But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles).

Recent Discoveries


March 26, 2015 Hubble and Chandra Find Clues that May Help Identify Dark Matter

June 24, 2014 Mysterious X-ray Signal Intrigues Astronomers (Perseus Cluster)

June 6, 2014 Cosmic Collision in the Bullet Group (Bullet Group)

May 5, 2014 The Scale of the Universe (NGC 4605)

April 3, 2014 Fermi Data Tantalize with New Clues to Dark Matter
November 30, 2012 'Dark Core' May Not be so Dark After All

April 12, 2012 DLSCL J0916.2+2951: Discovery of the Musket Ball Cluster

April 2, 2012 Fermi Observations of Dwarf Galaxies Provide New Insights on Dark Matter

March 14, 2012 Mapping the Dark Matter in Abell 383

March 2, 2012 Dark Matter Core Defies Explanation

January 10, 2012 El Gordo

January 10, 2012 Farthest Protocluster of Galaxies Ever Seen

( From NASA)

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Posted: December 21, 2015

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If Eyes Could See Gravitational Waves

If our eyes could see gravitational waves: Released 28/09/2015 12:52 pm
Copyright NASA/C. Henze
 


Picture the scene: two gigantic black holes, each one a good fraction of the size of our Solar System spiralling around each other. Closer and closer they draw until they touch and merge into a single, even more gigantic gravitational prison.

But what would you actually see? For such a cataclysmic event, it might all take place with remarkable stealth because black holes by their very nature emit no light at all. Rather than light, it would be a different story if our eyes could see gravitational waves.

This is what the merger of two black holes would look like. It is a computer simulation of the gravitational waves that would ripple away from the titanic collision, a bit like the ripples on a pond when a pebble drops into the water.

In the case of gravitational waves, the disturbances are not in water but in the spacetime continuum. This is the mathematical ‘fabric' of space and time that Albert Einstein used to explain gravity.

Gravitational radiation has been indirectly observed but never seen directly. Its detection would open a whole new way of studying the Universe. As a result, astronomers are working on both ground-based and space-based detectors. And it is a real challenge.

Gravitational radiation is incredibly difficult to measure. The ripples cause atoms to ‘bob’ about to just 1 part in 1000 000 000 000 000 000 000. Building a detector to notice this is like measuring the distance from Earth to the Sun to the accuracy of the size of a hydrogen atom.

Following decades of technology development and experiments, detectors on the ground are nearing the required sensitivity. The first detections are expected in the next few years. But these detectors can see only half of the picture. The mass of the colliding black holes determines the frequency of the gravitational radiation.

The merger of small black holes, each about a few times the mass of the Sun, will create high-frequency gravitational waves that could be seen from the ground. But the giant black holes that sit at the heart of galaxies with masses of a million times that of the Sun will generate gravitational waves of much lower frequency. These cannot be detected with ground-based systems because seismic interference and other noise will overwhelm the signals. Hence, spaceborne observatories are needed.

ESA has selected the gravitational Universe as the focus for the third large mission in the Cosmic Vision plan, with a launch date of around 2034.

Unlocking the gravitational Universe will require a highly ambitious mission. In preparation, ESA will launch LISA-Pathfinder this November to test some of the essential technologies needed to build confidence in future spaceborne gravitational wave observatories.

This image is from a simulation of two black holes merging and the resulting emission of gravitational radiation, published by NASA in 2012.

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Posted: December 7, 2015

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LISA The Pathfinder: Off She Goes Today

There are two webcasts providing in-depth coverage of LISA Pathfinder on 3 December.

First, coverage of our LISA Pathfinder launch starts at 03:44 GMT (04:44 CET) with commentary from experts at Europe’s Spaceport in Kourou.

A second webcast will provide coverage of the media briefing at ESA’s ESOC spacecraft operations centre, Darmstadt, Germany, with project managers, scientists and mission control experts. This will start at 05:30 GMT (06:30 CET).

The media briefing will begin while Vega is still in flight, just prior to separation and the critical first receipt of signals from LISA Pathfinder, expected around 05:51 GMT (06:51 CET).
 

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Posted on: December 3, 2015

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Gravitational Waves Dents in Spacetime

Searching for gravitational waves with LISA:  LISA will be the first space-based mission to attempt the detection of gravitational waves. These are ripples in space that are emitted by exotic objects such as black holes. Copyright ESA


Gravitational waves are fundamentally different from, for example, electromagnetic waves. The acceleration of electric charges creates electromagnetic waves, propagating in space and time. However, gravitational waves, created by the acceleration of mass, are waves of the spacetime ‘fabric’ itself.

According to Newton’s theory of gravity, the gravitational interaction between two bodies is instantaneous. However, Einstein’s Special Relativity says nothing can travel faster than the speed of light. If an object changes shape as a result of a mass pulling on it, the resulting change in the force field would spread outwards at the speed of light.

In 1805, Laplace said that if gravity propagates with finite speed, the force in a binary star system should not point along the line connecting the stars, and the angular momentum of the system must slowly decrease with time.
Albert Einstein, 1879 - 1955
Albert Einstein, 1879 - 1955

Today’s scientists would say that binary stars lose energy and angular momentum by emitting ‘gravitational waves’. In the late 1970s, indirect proof was found for the existence of gravitational waves by observing the binary pulsar PSR 1913+16. However, scientists are still waiting to detect gravitational waves directly.

Forty years after Einstein’s work on gravitational waves, relativity theorists like H. Bondi proved that gravitational radiation was physically observable, that gravitational waves carry energy, and that a system emitting gravitational waves should lose energy.

General Relativity implies accepting that space and time do not have an independent existence, but rather are in intense interaction with the physical world. Massive objects produce ‘dents’ in the fabric of spacetime. Other objects move in this curved spacetime taking the shortest path, like billiard balls on a springy surface. So spacetime is an ‘elastic medium’.

If an object changes shape asymmetrically, the spacetime ‘dents’ travel outwards like ripples in spacetime called ‘gravitational waves’. Gravitational effects that are spherically symmetric will not produce gravitational radiation. A perfectly symmetrical collapse of a supernova will produce no waves, but a non-spherical one will emit gravitational radiation. A binary system will always radiate.

Gravitational waves distort spacetime: they change the distances between large, free objects. A gravitational wave passing through the Solar System creates a time-varying strain in space that periodically changes the distances between all bodies in the Solar System (this strain changes distances perpendicularly to the direction in which the wave moves).

However, the relative change in length due to the passage of a gravitational wave is extremely small. For example, in the case of a typical white dwarf binary at a typical distance of 160 light-years, it is only 10–10 m. Measuring distances this small between objects far apart presents a challenge.

Although a supernova in a distant galaxy would bathe Earth with gravitational radiation as strong as several kilowatts per square metre, the resulting length changes will always be very small. Spacetime is an elastic medium that remains stubbornly stiff.
Gigantic black holes

As far as a LISA-like mission is concerned, gravitational waves arise from two main sources: galactic binaries and the massive black holes (MBHs) which are expected to exist in the centres of most galaxies.

Observing binaries is limited to our Galaxy. LISA-like missions will be able to detect several types of galactic sources. Some galactic binaries are so well studied, especially the X-ray binary 4U1820-30, that it is one of the most reliable sources.

If a LISA-like mission does not detect the gravitational waves from known binaries with the intensity and polarisation predicted by General Relativity, it would shake the very foundations of gravitational physics.
Searching for gravitational waves with LISA

Learning about the formation, growth, space density and surroundings of MBHs is also very important. Scientists suspect that there are MBHs with masses of one million to 100 million times the mass of our Sun in the centres of most galaxies, including our own. Observations of signals from merging MBHs in distant galaxies would test General Relativity, and particularly black-hole theory, to unprecedented accuracy.

ESA Article

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Posted on : November 29, 2015

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LISA's on Her Way: LISA Pathfinder Launch

LISA Pathfinder launch sequence. Copyright ESA/ATG medialab


Scheduled for launch in late 2015, ESA’s LISA Pathfinder will test key technologies for space-based observation of gravitational waves – ripples in the fabric of spacetime that are predicted by Albert Einstein’s general theory of relativity. Produced by massive accelerating bodies, these perturbations are expected to be abundant across the Universe, but they are yet to be detected directly.

Although not aiming at detecting gravitational waves, LISA Pathfinder will test the approach that could be used for this daunting endeavour. In particular, the goal is to achieve the best free-fall ever, reducing all the non-gravitational forces acting on two test masses and controlling any residual effect with unprecedented accuracy.

LISA Pathfinder will operate from a special location in the Sun–Earth system: the Lagrange point L1, 1.5 million km from Earth towards the Sun. After launch, it will take the spacecraft about eight weeks to cruise towards its operational orbit around L1.

First, it will lift off on a Vega rocket from Europe’s Spaceport in French Guiana, as shown in the left frame of this illustrated sequence. The Vega rocket, which is specially designed to take small payloads into low Earth orbit, will place LISA Pathfinder into an elliptical orbit.

The upper right frame shows the spacecraft riding the final stage of the Vega rocket, while the fairing is being released.

After the final stage of the Vega rocket is jettisoned, LISA Pathfinder will continue on its own, as shown in the lower right frame of the sequence. During this phase, the spacecraft will use its separable propulsion module to perform six manoeuvres, gradually raising the apogee of the initial orbit.

Eventually, LISA Pathfinder will cruise towards its final orbiting location, discarding the propulsion system along the way, one month after the last burn. Once orbiting L1, LISA Pathfinder will begin six months of demonstrating the technology for future gravitational-wave observatories in space.

LISA Pathfinder

LISA Pathfinder, die ESA-Mission zur Demonstration von Technologie zum Aufspüren von Gravitationswellen, soll am Mittwoch, 2. Dezember 2015, um 05:15 MEZ an Bord einer Vega-Trägerrakete vom Europäischen Weltraumbahnhof in Kourou, Französisch-Guayana starten. 

Details

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Posted on : November 24, 2015

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Accident Proved to Be Beneficial for Einstein and Relativity in the Galileo Constellation

Albert Einstein predicted a century ago that time would pass more slowly close to a massive object. Although the satellites’ orbits have been adjusted, they remain elliptical, with each satellite climbing and falling some 8500 km twice per day.

Europe’s fifth and sixth Galileo satellites – subject to complex salvage manoeuvres following their launch last year into incorrect orbits – will help to perform an ambitious year-long test of Einstein’s most famous theory.

Galileos 5 and 6 were launched together by a Soyuz rocket on 22 August 2014. But the faulty upper stage stranded them in elongated orbits that blocked their use for navigation.

ESA’s specialists moved into action and oversaw a demanding set of manoeuvres to raise the low points of their orbits and make them more circular.

“The satellites can now reliably operate their navigation payloads continuously, and the European Commission, with the support of ESA, is assessing their eventual operational use,” explains ESA’s senior satnav advisor Javier Ventura-Traveset.
Albert Einstein

“In the meantime, the satellites have accidentally become extremely useful scientifically, as tools to test Einstein’s General Theory of Relativity by measuring more accurately than ever before the way that gravity affects the passing of time.”
 


 

Although the satellites’ orbits have been adjusted, they remain elliptical, with each satellite climbing and falling some 8500 km twice per day.

It is those regular shifts in height, and therefore gravity levels, that are valuable to researchers.
Corrected Galileo orbits

Albert Einstein predicted a century ago that time would pass more slowly close to a massive object. It has been verified experimentally, most significantly in 1976 when a hydrogen maser atomic clock on Gravity Probe A was launched 10 000 km into space, confirming the prediction to within 140 parts in a million.

Atomic clocks on navigation satellites have to take into account they run faster in orbit than on the ground – a few tenths of a microsecond per day, which would give us navigation errors of around 10 km per day.

“Now, for the first time since Gravity Probe A, we have the opportunity to improve the precision and confirm Einstein’s theory to a higher degree,” comments Javier.
Passive hydrogen maser
Galileo maser clock

This new effort takes advantage of the passive hydrogen maser atomic clock aboard each Galileo, the elongated orbits creating varying time dilation, and the continuous monitoring thanks to the global network of ground stations.

“Moreover, while the Gravity Probe A experiment involved a single orbit of Earth, we will be able to monitor hundreds of orbits over the course of a year,” explains Javier.
Gravity Probe A

“This opens up the prospect of gradually refining our measurements by identifying and removing systematic errors. Eliminating those errors is actually one of the big challenges.

“For that we count on the support of Europe’s best experts plus precise tracking from the International Global Navigation Satellite System Service, along with tracking to centimetre accuracy by laser.”

The results are expected in about one year, projected to quadruple the accuracy on the Gravity Probe A results.

The two teams devising the experiments are Germany's ZARM Center of Applied Space Technology and Microgravity, and France's SYRTE Systèmes de Référence Temps-Espace, both specialists in fundamental physics research. 

ESA’s forthcoming Atomic Clock Ensemble in Space experiment, planned to fly on the International Space Station in 2017, will go on to test Einstein’s theory down to 2–3 parts per million.

For more information, please contact:

Javier Ventura-Traveset
ESA Global Navigation Satellite Systems Senior Advisor
Email: Javier.ventura-traveset@esa.int

Pacôme Delva
SYRTE, Observatoire de Paris
Email: pacome.delva@obspm.fr

Sven Hermann
ZARM Center of Applied Space Technology and Microgravity
Email: sven.herrmann@zarm.uni-bremen.de
 

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Posted on: November 10, 2015

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Earth's Dark Hairy Dark Matter

This artist's rendering zooms in on what dark matter "hairs" might look like around Earth. Credits: NASA/JPL-Caltech

Neither dark matter nor dark energy has ever been directly detected, although many experiments are trying to unlock the mysteries of dark matter, whether from deep underground or in space.

Based on many observations of its gravitational pull in action, scientists are certain that dark matter exists, and have measured how much of it there is in the universe to an accuracy of better than one percent. The leading theory is that dark matter is "cold," meaning it doesn't move around much, and it is "dark" insofar as it doesn't produce or interact with light.

Galaxies, which contain stars made of ordinary matter, form because of fluctuations in the density of dark matter. Gravity acts as the glue that holds both the ordinary and dark matter together in galaxies.

According to calculations done in the 1990s and simulations performed in the last decade, dark matter forms "fine-grained streams" of particles that move at the same velocity and orbit galaxies such as ours.

"A stream can be much larger than the solar system itself, and there are many different streams crisscrossing our galactic neighborhood," Prézeau said.

Prézeau likens the formation of fine-grained streams of dark matter to mixing chocolate and vanilla ice cream. Swirl a scoop of each together a few times and you get a mixed pattern, but you can still see the individual colors.

"When gravity interacts with the cold dark matter gas during galaxy formation, all particles within a stream continue traveling at the same velocity," Prézeau said.

But what happens when one of these streams approaches a planet such as Earth? Prézeau used computer simulations to find out.

His analysis finds that when a dark matter stream goes through a planet, the stream particles focus into an ultra-dense filament, or "hair," of dark matter. In fact, there should be many such hairs sprouting from Earth.

A stream of ordinary matter would not go through Earth and out the other side. But from the point of view of dark matter, Earth is no obstacle. According to Prézeau's simulations, Earth's gravity would focus and bend the stream of dark matter particles into a narrow, dense hair.

Hairs emerging from planets have both "roots," the densest concentration of dark matter particles in the hair, and "tips," where the hair ends. When particles of a dark matter stream pass through Earth’s core, they focus at the "root" of a hair, where the density of the particles is about a billion times more than average. The root of such a hair should be around 600,000 miles (1 million kilometers) away from the surface, or twice as far as the moon. The stream particles that graze Earth's surface will form the tip of the hair, about twice as far from Earth as the hair’s root.

"If we could pinpoint the location of the root of these hairs, we could potentially send a probe there and get a bonanza of data about dark matter," Prézeau said.

A stream passing through Jupiter's core would produce even denser roots: almost 1 trillion times denser than the original stream, according to Prézeau's simulations.

"Dark matter has eluded all attempts at direct