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  • richardmitnick 12:22 pm on May 11, 2018 Permalink | Reply
    Tags: Astronomers Have Found a Record-Breaking Pair of Stars Orbiting With a Dizzying Speed, , , , , , NASA/NICER,   

    From Goddard via Science Alert: “Astronomers Have Found a Record-Breaking Pair of Stars Orbiting With a Dizzying Speed” 

    NASA Goddard Banner
    From NASA Goddard Space Flight Center

    Science Alert

    11 MAY 2018
    MICHELLE STARR

    1
    Artist’s impression of a rotating neutron star. (Pitris/iStock)

    Astronomers have discovered a record-breaking star system. It’s called IGR J17062-6143, and it’s a very compact binary, where one of the stars is a rapidly spinning, superdense neutron star called an X-ray pulsar.

    The two stars take just 38 minutes to orbit each other. That’s the fastest orbital period of any X-ray pulsar binary ever observed.

    IGR J17062-6143 (or J17062 for short) was only discovered in 2006; it’s very low mass, and very faint, and around 7.3 kiloparsecs, or 23,809 light-years, away.

    It’s been studied fairly extensively, but finding out more about it required some pretty up-to-date technology – NASA’s Neutron star Interior Composition Explorer (NICER), an X-ray detection instrument installed on the International Space Station in June 2017.

    NASA NICER on the ISS

    NASA/NICER

    Previous research had revealed an accretion disc associated with the binary, and that one of the stars was a pulsar, but a 20-minute 2008 observation using NASA’s Rossi X-Ray Timing Explorer could only set a lower limit for the binary’s orbital period.

    NASA/ROSSI

    Neutron stars are also extremely hot, and shine extremely brightly. However, because they’re so small, they’re difficult for us to see – except in X-ray. They can also spin incredibly fast, which creates an electric field that accelerates electrons away from the poles, creating relativistic radiation jets. If this beam passes between us and the pulsar, we can see it flash, or “pulse”, like a cosmic lighthouse.

    In the case of binary X-ray pulsars, these jets are fed by the matter stolen from the donor star. This material falls to the surface of the pulsar, where it travels along its strong magnetic field lines to the poles.

    It was by observing these X-ray jets that the 2008 observation led to the discovery – the J17062 pulsar was rotating 163 times per second, nearly 9,800 revolutions per minute.

    NICER has been able to observe the system for a lot longer – over 7 hours of observing time taken over 5.3 days in August 2017. This has allowed researchers to obtain a lot more detailed information.

    As well as the 38-minute orbital period, researchers were able to ascertain that the two stars are separated by a distance of just 300,000 kilometres (186,000 miles) – less than the distance that separates Earth and the Moon.

    These two factors, and analysis of the spectra produced by the binary, has led the research team on the new paper to the conclusion that the pulsar’s companion star is a very low-mass, low-hydrogen white dwarf, only around 1.5 percent the mass of the Sun. “It’s not possible for a hydrogen-rich star, like our Sun, to be the pulsar’s companion,” said lead researcher Tod Strohmayer, an astrophysicist at NASA Goddard.

    “You can’t fit a star like that into an orbit so small.”

    The pulsar, by comparison, is around 1.4 times the mass of the Sun, but much, much smaller. Neutron stars – of which pulsars are a subset – are the collapsed cores of stars below around three times the mass of the Sun, in the final stage of their life cycle. They’re usually only around 10-20 kilometres in diameter.

    Because they’re so massive, though, neutron stars have a pretty strong gravitational pull – hence the accretion disc, as the J17062 pulsar pulls material from the white dwarf, the binary’s ‘donor star’. That high mass imbalance also means that the central point of the orbit – circular, as the team discovered – is much closer to the pulsar, just 3,000 kilometres (1,900 miles) from it. It’s so close that the white dwarf almost seems to be orbiting a stationary star; but, although faint, it does exert a gravitational pull on the pulsar.

    “The distance between us and the pulsar is not constant,” Strohmayer said. “It’s varying by this orbital motion. When the pulsar is closer, the X-ray emission takes a little less time to reach us than when it’s further away.” “This time delay is small, only about 8 milliseconds for J17062’s orbit, but it’s well within the capabilities of a sensitive pulsar machine like NICER.”

    The team’s research has been published in The Astrophysical Journal Letters.

    See the full article here.

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    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


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  • richardmitnick 4:30 pm on March 22, 2018 Permalink | Reply
    Tags: , , , , , NASA/NICER, , , Squishy or Solid? A Neutron Star’s Insides Open to Debate   

    From Quanta Magazine: “Squishy or Solid? A Neutron Star’s Insides Open to Debate” 

    Quanta Magazine
    Quanta Magazine

    October 30, 2017 [Just now in social media]
    Joshua Sokol

    The core of a neutron star is such an extreme environment that physicists can’t agree on what happens inside. But a new space-based experiment — and a few more colliding neutron stars — should reveal whether neutrons themselves break down.

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    Maciej Rebisz for Quanta Magazine

    The alerts started in the early morning of Aug. 17. Gravitational waves produced by the wreck of two neutron stars — dense cores of dead stars — had washed over Earth. The thousand-plus physicists of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) rushed to decode the space-time vibrations that rolled across the detectors like a drawn-out peal of thunder. Thousands of astronomers scrambled to witness the afterglow. But officially, all this activity was kept secret. The data had to be collected and analyzed, the papers written. The outside world wouldn’t know for two more months.

    See https://sciencesprings.wordpress.com/2017/10/20/from-ucsc-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/

    The strict ban put Jocelyn Read and Katerina Chatziioannou, two members of the LIGO collaboration, in a bit of an awkward situation. In the afternoon on the 17th, the two were scheduled to lead a panel at a conference dedicated to the question of what happens under the almost unfathomable conditions in a neutron star’s interior. Their panel’s topic? What a neutron-star merger would look like. “We sort of went off at the coffee break and sat around just staring at each other,” said Read, a professor at California State University, Fullerton. “OK, how are we going to do this?”

    Physicists have spent decades debating whether or not neutron stars contain new forms of matter, created when the stars break down the familiar world of protons and neutrons into new interactions between quarks or other exotic particles. Answering this question would also illuminate astronomical mysteries surrounding supernovas and the production of the universe’s heavy elements, such as gold.

    In addition to watching for collisions using LIGO, astrophysicists have been busy developing creative ways to probe neutron stars from the outside. The challenge is then to infer something about the hidden layers within. But this LIGO signal and those like it — emitted as two neutron stars pirouette around their center of mass, pull on each other like taffy, and finally smash together — offers a whole new handle on the problem.

    Strange Matter

    A neutron star is the compressed core of a massive star — the super dense cinders left over after a supernova. It has the mass of the sun, but squeezed into a space the width of a city. As such, neutron stars are the densest reservoirs of matter in the universe — the “last stuff on the line before a black hole,” said Mark Alford, a physicist at Washington University in St. Louis.

    To drill into one would bring us to the edge of modern physics. A centimeter or two of normal atoms — iron and silicon, mostly — encrusts the surface like the shiny red veneer on the universe’s densest Gobstopper. Then the atoms squeeze so close together that they lose their electrons, which fall into a shared sea. Deeper, the protons inside nuclei start turning into neutrons, which cluster so close together that they start to overlap.

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    Lucy Reading-Ikkanda/Quanta Magazine; Source: Feryal Özel

    But theorists argue about what happens farther in, when densities creep past two or three times higher than the density of a normal atomic nucleus. From the perspective of nuclear physics, neutron stars could just be protons and neutrons — collectively called nucleons — all the way in. “Everything can be explained by variations of nucleons,” said James Lattimer, an astrophysicist at Stony Brook University.

    Other astrophysicists suspect otherwise. Nucleons aren’t elementary particles. They’re made up of three quarks. Under immense pressure, these quarks might form a new state of quark matter. “Nucleons are not billiard balls,” said David Blaschke, a physicist at the University of Wroclaw in Poland. “They are like cherries. So you can compress them a little bit, but at some point you smash them.”

    But to some, the prospect of a quark jam like this is a relatively vanilla scenario. Theorists have long speculated that layers of other weird particles might arise inside a neutron star. As neutrons are jostled closer together, all that extra energy might go into creating heavier particles that contain not just the “up” and “down” quarks that exclusively make up protons and neutrons, but heavier and more exotic “strange” quarks.

    For example, neutrons might be replaced by hyperons, three-quark particles that include at least one strange quark. Laboratory experiments can make hyperons, but they vanish almost immediately. Deep inside neutron stars, they might be stable for millions of years.

    Alternatively, the hidden depths of neutron stars might be filled with kaons — also made with strange quarks — that collect into a single lump of matter sharing the same quantum state.

    For decades, though, the field has been stuck. Theorists invent ideas about what might be going on inside neutron stars, but that environment is so extreme and unfamiliar that experiments here on Earth can’t reach the right conditions. At Brookhaven National Laboratory and CERN, for example, physicists smash together heavy nuclei like those of gold and lead.

    That creates a soupy state of matter made up of released quarks, known as a quark-gluon plasma. But this stuff is rarefied, not dense, and at billions or trillions of degrees, it’s far hotter than the inside of neutron star, which sits in the comparatively chilly millions.

    Quark gluon plasma. Duke University

    Even the decades-old theory of quarks and nuclei — “quantum chromodynamics,” or QCD — can’t really provide answers. The computations needed to study QCD in relatively cold, dense environments are so devastatingly difficult that not even computers can calculate the results. Researchers are forced to resort to oversimplification and shortcuts.

    The only other option is for astronomers to study neutron stars themselves. Unfortunately, neutron stars are distant, thus dim, and difficult to measure for anything but the very basic bulk properties. Even worse, the truly interesting physics is happening under the surface. “It’s a bit like there’s this lab that’s doing amazing things,” Alford said, “but all you’re allowed to do is see the light coming out of the window.”

    With a new generation of experiments coming online, though, theorists might soon get their best look yet.

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    The NICER instrument, shown here before it was launched to the International Space Station, monitors the X-ray emissions of neutron stars. NASA/Goddard/Keith Gendreau

    Squishy or Hard?

    Whatever might be inside the core of a neutron star — loose quarks, or kaon condensates, or hyperons, or just regular old nucleons — the material must be able to hold up to the crushing weight of more than a sun’s worth of gravity. Otherwise, the star would collapse into a black hole. But different materials will compress to different degrees when squeezed by gravity’s vise, determining how heavy the star can be at a given physical size.

    Stuck on the outside, astronomers work backwards to figure out what neutron stars are made of. For this purpose, it helps to know how squishy or stiff they are when squeezed. And for that, astronomers need to measure the masses and radii of various neutron stars.

    In terms of mass, the most easily weighed neutron stars are pulsars: neutron stars that rotate quickly, sweeping a radio beam across Earth with each spin. About 10 percent of the 2,500 known pulsars belong to binary systems. As these pulsars move with their partners, what should be a constant tick-tock of pulses hitting Earth will vary, betraying the pulsar’s motion and its location in its orbit. And from the orbit, astronomers can use Kepler’s laws and the additional rules imposed by Einstein’s general relativity to solve for the masses of the pair.

    So far, the biggest breakthrough has been the discovery of surprisingly hefty neutron stars. In 2010, a team led by Scott Ransom at the National Radio Astronomy Observatory in Virginia announced that they had measured a pulsar weighing about two solar masses — making it far bigger than any previously seen. Some people doubted whether such a neutron star could exist; that it does has had immense consequences for our understanding of how nuclei behave. “Now it’s like the most cited observational pulsar paper ever, because of the nuclear physicists,” Ransom said.

    According to some neutron-star models, which hold that gravity should strongly compress neutron stars, an object at that mass should collapse all the way into a black hole. That would be bad news for kaon condensates, which would be especially squishy, and it bodes poorly for some versions of quark matter and hyperons that would also compress too much. The measurement has been confirmed with the discovery of another neutron star of two solar masses in 2013.

    Radii are trickier. Astrophysicists like Feryal Özel at the University of Arizona have devised various tricks to calculate the physical size of neutron stars by observing the X-rays emitted at their surfaces. Here’s one way: You can look at the overall X-ray emission, use it to estimate the temperature of the surface, and then figure out how big the neutron star needs to be to emit the observed light (correcting for how the light bends through space-time warped by gravity). Or you can look for hot spots on the neutron star’s surface that spin in and out of view. The neutron star’s strong gravitational field will modify the pulses of light from these hot spots. And once you understand the star’s gravitational field, you can reconstruct its mass and radius.

    Taken at face value, these X-ray measurements suggest that even though neutron stars can be heavy, they are on the small end of predictions: only about 20 to 22 kilometers wide, according to Özel.

    Accepting that neutron stars are both small and massive “kind of locks you in, in a good way,” Özel said. Neutron stars stuffed with interacting quarks would look like this, she said, while neutron stars made up of only nucleons would have larger radii.

    But Lattimer, among other critics, has reservations about the assumptions that go into the X-ray measurements, which he calls flawed. He thinks they make the radii look smaller they really are.

    Both sides expect that a resolution to the dispute will soon arrive. This past June, SpaceX’s 11th resupply mission to the International Space Station brought with it a 372-kilogram box containing an X-ray telescope called the Neutron Star Interior Composition Explorer (NICER).

    7
    NICER before launch.

    Now taking data, NICER is designed to find the size of neutron stars by watching for hot spots on their surfaces. The experiment should produce better radii measurements of neutron stars, including pulsars that have already had their masses measured.

    “We look so much forward to it,” Blaschke said. A well-measured mass and radius for even a single neutron star would knock out many possible theories of their interior structure, keeping in play only the ones that could produce that particular combination of size and weight.

    And now, finally chiming in, there’s LIGO.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

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    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    As a first pass, the signal that Read huddled over coffee to discuss on Aug. 17 had been processed as if it were a merger of two black holes, not two neutron stars. This wasn’t unreasonable. LIGO’s previous signals had all come from black holes, which are more tractable beasts from a computational standpoint. But this signal involved lighter objects and went on for much longer than the black hole mergers. “It’s immediately obvious that this was not the same kind of system that we were practiced on,” Read said.

    When two black holes spiral together, they bleed orbital energy into space-time as gravitational waves. But in the final second or so of the new 90-second-long LIGO signal, each object did something black holes don’t do: It deformed. The pair started to stretch and squeeze each other’s matter, generating tides that stole energy from their orbits. This drove them to collide faster than they would have otherwise.

    After a frantic few months of running computer simulations, Read’s group inside LIGO has released their first measurement of the effect of those tides on the signal. So far, the team can set only an upper limit — meaning the tides have a weak or even unnoticeable effect. In turn, that means that neutron stars are physically small, with their matter held very tightly around their centers and thus more resistant to getting yanked by tides. “I think the first gravitational-wave measurement is in a sense really kind of confirming the kinds of things that X-ray observations have been saying,” Read said. But this isn’t the last word. She expects that more sophisticated modeling of the same signal will yield a more precise estimate.

    With NICER and LIGO both offering new ways to look at neutron-star stuff, many experts are optimistic that the next few years will provide unambiguous answers to the question of how the material stands up to gravity. But theorists like Alford caution that measuring neutron-star matter’s squishiness alone won’t fully reveal what it is.

    Perhaps other signatures can say more. Ongoing observations of the rate at which neutron stars cool, for example, should let astrophysicists speculate about the particles inside them and their ability to radiate away energy. Or observations of how their spins slow over time could help determine the viscosity of their insides.

    Ultimately, just knowing when dense matter changes phase and what it changes into is a worthy goal, Alford argues. “Mapping the properties of matter under different conditions,” he said, “kind of is physics”.

    See the full article here .

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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
  • richardmitnick 11:14 am on January 11, 2018 Permalink | Reply
    Tags: , , , , , NASA Team First to Demonstrate X-ray Navigation in Space, NASA/NICER, NASA/Sextant   

    From Goddard: “NASA Team First to Demonstrate X-ray Navigation in Space” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    Jan. 11, 2018
    Lori Keesey
    Clare Skelly
    Goddard Space Flight Center

    1
    This illustration shows the NICER mission at work aboard the International Space Station. Credits: NASA’s Goddard Space Flight Center.

    In a technology first, a team of NASA engineers has demonstrated fully autonomous X-ray navigation in space — a capability that could revolutionize NASA’s ability in the future to pilot robotic spacecraft to the far reaches of the solar system and beyond.

    The demonstration, which the team carried out with an experiment called Station Explorer for X-ray Timing and Navigation Technology, or SEXTANT, showed that millisecond pulsars could be used to accurately determine the location of an object moving at thousands of miles per hour in space — similar to how the Global Positioning System, widely known as GPS, provides positioning, navigation, and timing services to users on Earth with its constellation of 24 operating satellites.

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    NASA Sextant.

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    NICER’s mirror assemblies concentrate X-rays onto silicon detectors to gather data that probes the interior makeup of neutron stars, including those that appear to flash regularly, called pulsars. Credits: NASA’s Goddard Space Flight Center/Keith Gendreau.

    “This demonstration is a breakthrough for future deep space exploration,” said SEXTANT Project Manager Jason Mitchell, an aerospace technologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “As the first to demonstrate X-ray navigation fully autonomously and in real-time in space, we are now leading the way.”

    This technology provides a new option for deep space navigation that could work in concert with existing spacecraft-based radio and optical systems.

    Although it could take a few years to mature an X-ray navigation system practical for use on deep-space spacecraft, the fact that NASA engineers proved it could be done bodes well for future interplanetary space travel. Such a system provides a new option for spacecraft to autonomously determine their locations outside the currently used Earth-based global navigation networks because pulsars are accessible in virtually every conceivable fight regime, from low-Earth to deepest space.

    Exploiting NICER Telescopes

    The SEXTANT technology demonstration, which NASA’s Space Technology Mission Directorate had funded under its Game Changing Program, took advantage of the 52 X-ray telescopes and silicon-drift detectors that make up NASA’s Neutron-star Interior Composition Explorer, or NICER.

    NASA/NICER

    Since its successful deployment as an external attached payload on the International Space Station in June, it has trained its optics on some of the most unusual objects in the universe.

    “We’re doing very cool science and using the space station as a platform to execute that science, which in turn enables X-ray navigation,” said Goddard’s Keith Gendreau, the principal investigator for NICER, who presented the findings Thursday, Jan. 11, at the American Astronomical Society meeting in Washington. “The technology will help humanity navigate and explore the galaxy.”

    NICER, an observatory about the size of a washing machine, currently is studying neutron stars and their rapidly pulsating cohort, called pulsars. Although these stellar oddities emit radiation across the electromagnetic spectrum, observing in the X-ray band offers the greatest insights into these unusual, incredibly dense celestial objects, which, if compressed any further, would collapse completely into black holes. Just one teaspoonful of neutron star matter would weigh a billion tons on Earth.

    Although NICER is studying all types of neutron stars, the SEXTANT experiment is focused on observations of pulsars. Radiation emanating from their powerful magnetic fields is swept around much like a lighthouse. The narrow beams are seen as flashes of light when they sweep across our line of sight. With these predictable pulsations, pulsars can provide high-precision timing information similar to the atomic-clock signals supplied through the GPS system.

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    This animation shows how NICER scans the sky and highlights the mission’s main features. Credits: NASA’s Goddard Space Flight Center

    Veteran’s Day Demonstration

    n the SEXTANT demonstration that occurred over the Veteran’s Day holiday in 2017, the SEXTANT team selected four millisecond pulsar targets — J0218+4232, B1821-24, J0030+0451, and J0437-4715 — and directed NICER to orient itself so it could detect X-rays within their sweeping beams of light. The millisecond pulsars used by SEXTANT are so stable that their pulse arrival times can be predicted to accuracies of microseconds for years into the future.

    During the two-day experiment, the payload generated 78 measurements to get timing data, which the SEXTANT experiment fed into its specially developed onboard algorithms to autonomously stitch together a navigational solution that revealed the location of NICER in its orbit around Earth as a space station payload. The team compared that solution against location data gathered by NICER’s onboard GPS receiver.

    “For the onboard measurements to be meaningful, we needed to develop a model that predicted the arrival times using ground-based observations provided by our collaborators at radio telescopes around the world,” said Paul Ray, a SEXTANT co-investigator with the U. S. Naval Research Laboratory. “The difference between the measurement and the model prediction is what gives us our navigation information.”

    The goal was to demonstrate that the system could locate NICER within a 10-mile radius as the space station sped around Earth at slightly more than 17,500 mph. Within eight hours of starting the experiment on November 9, the system converged on a location within the targeted range of 10 miles and remained well below that threshold for the rest of the experiment, Mitchell said. In fact, “a good portion” of the data showed positions that were accurate to within three miles.

    “This was much faster than the two weeks we allotted for the experiment,” said SEXTANT System Architect Luke Winternitz, who works at Goddard. “We had indications that our system would work, but the weekend experiment finally demonstrated the system’s ability to work autonomously.”

    Although the ubiquitously used GPS system is accurate to within a few feet for Earth-bound users, this level of accuracy is not necessary when navigating to the far reaches of the solar system where distances between objects measure in the millions of miles. “In deep space, we hope to reach accuracies in the hundreds of feet,” Mitchell said.

    Next Steps and the Future

    Now that the team has demonstrated the system, Winternitz said the team will focus on updating and fine-tuning both flight and ground software in preparation for a second experiment later in 2018. The ultimate goal, which may take years to realize, would be to develop detectors and other hardware to make pulsar-based navigation readily available on future spacecraft. To advance the technology for operational use, teams will focus on reducing the size, weight, and power requirements and improving the sensitivity of the instruments. The SEXTANT team now also is discussing the possible application of X-ray navigation to support human spaceflight, Mitchell added.

    If an interplanetary mission to the moons of Jupiter or Saturn were equipped with such a navigational device, for example, it would be able to calculate its location autonomously, for long periods of time without communicating with Earth.

    Mitchell said that GPS is not an option for these far-flung missions because its signal weakens quickly as one travels beyond the GPS satellite network around Earth.

    “This successful demonstration firmly establishes the viability of X-ray pulsar navigation as a new autonomous navigation capability. We have shown that a mature version of this technology could enhance deep-space exploration anywhere within the solar system and beyond,” Mitchell said. “It is an awesome technology first.”

    NICER is an Astrophysics Mission of Opportunity within NASA’s Explorers program, which provides frequent flight opportunities for world-class scientific investigations from space utilizing innovative, streamlined and efficient management approaches within the heliophysics and astrophysics science areas. NASA’s Space Technology Mission Directorate funds the SEXTANT component of the mission through its Game Changing Development Program.

    Related Links:

    NASA’s NICER mission website
    More information on SEXTANT
    Download NICER-SEXTANT multimedia resources

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


    NASA/Goddard Campus

     
  • richardmitnick 12:40 pm on August 26, 2017 Permalink | Reply
    Tags: , , , , , NASA/NICER,   

    From Spaceflight Insider: “NICER and LISA could confirm or disprove predictions of general relativity” 

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    Spaceflight Insider

    Two astrophysical missions, NICER and LISA, could soon change humanity’s understanding of the universe. Scientists hope both instruments will help answer fundamental questions about the universe, testing many aspects of Einstein’s theory of general relativity.

    NASA’s Neutron star Interior Composition Explorer (NICER) is already in space. It was launched to the International Space Station (ISS) on June 3, 2017, and is mounted on one of the outpost’s external platforms. The instrument studies the densest observable objects in the universe.

    NASA/NICER

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    An artist’s rendering of the NICER experiment on the International Space Station. Image Credit: NASA

    ESA’s Laser Interferometer Space Antenna (LISA), planned to be launched in 2034, will detect and observe gravitational waves emitted during the most powerful events in the universe. It will focus on finding gravitational radiation from astronomical sources, testing the fundamental theories of gravitation.

    ESA/eLISA the future of gravitational wave research

    Nicolas Yunes, a Montana State University (MSU) gravitational physicist, believes NICER and LISA will play a key role in improving knowledge about the universe.

    “The X-rays emitted by pulsars (rotating neutron stars) that NICER will detect and the gravitational waves emitted in the coalescence of supermassive black holes that LISA will detect will allow us to test Einstein’s theory of general relativity more stringently than ever before in a regime that has not yet been fully explored,” Yunes told Astrowatch.net

    Yunes is a founding member of the MSU eXtreme Gravity Institute, known as XGI, and an associate professor in the department of physics in MSU’s College of Letters and Science. He leads the scientific project known as Exploring Extreme Gravity: Neutron Stars, Black Holes and Gravitational Waves. Recently, this project received a $750,000 grant from NASA’s Established Program to Stimulate Competitive Research, or EPSCoR, to continue the works aiming to answer fundamental questions about the universe.

    Backed by the funding, Yunes and his team will be able to focus on improving and developing tools to extract as much astrophysics information as possible from X-ray data obtained with NICER. They will also work to create a framework to test Einstein’s theory of general relativity using X-ray data from the space-based instrument, as well as gravitational wave data gathered by LISA. Moreover, this grant will allow him to grow his research group within the XGI.

    “The NASA award I received is crucial to expand my research endeavor and address fundamental questions about gravity with astrophysical observations,” Yunes said. “The award will allow us to grow [our] research group by hiring many more graduate students and one more postdoctoral researcher. This research group will lay the foundations of the theoretical and fundamental physics implications that could be extracted given future data from NASA missions, such as NICER and LISA.”

    Yunes said NASA funding will allow his team to develop new tools and methods to extract the most theoretical physics from future observations with NICER and LISA. This information will allow them to test many aspects of Einstein’s theory of general relativity.

    “These tests will confirm or disprove predictions of Einstein’s theory, such as the idea that gravitational waves move at the speed of light, that the graviton is massless, that gravity is parity invariant, and that the strong equivalence principle holds,” Yunes said. “Any deviation from Einstein’s predictions would be groundbreaking.”

    For instance, NICER will detect the X-rays emitted by hot spots on the surface of neutron stars. The X-ray pulse profile detected will depend on the properties of the star, such as its mass, radius and moment of inertia. By measuring these quantities and modeling the pulse profile, Yunes’ team expects to be able to test Einstein’s general theory of relativity at these extremes.

    When it comes to LISA, this instrument could allow the scientists to fully understand the gravitational wave universe, since ground-based detectors cannot operate at the low frequencies that LISA would operate at. The most powerful sources of gravitational waves mostly emit their radiation at very low frequencies, below 10 millihertz, or less than one oscillation every 100 seconds.

    See the full article here .

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    Stem Education Coalition

    SpaceFlight Insider reports on events taking place within the aerospace industry. With our team of writers and photographers, we provide an “insider’s” view of all aspects of space exploration efforts. We go so far as to take their questions directly to those officials within NASA and other space-related organizations. At SpaceFlight Insider, the “insider” is not anyone on our team, but our readers.

    Our team has decades of experience covering the space program and we are focused on providing you with the absolute latest on all things space. SpaceFlight Insider is comprised of individuals located in the United States, Europe, South America and Canada. Most of them are volunteers, hard-working space enthusiasts who freely give their time to share the thrill of space exploration with the world.

     
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