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  • richardmitnick 8:12 am on May 3, 2019 Permalink | Reply
    Tags: "Have scientists observed a black hole swallowing a neutron star?", , , , , , , , , Virgo collaboration   

    From Cardiff University: “Have scientists observed a black hole swallowing a neutron star?” 

    Cardiff University

    From Cardiff University

    3 May 2019

    Professor Mark Hannam
    Head of Gravitational Physics Group
    Director of the Gravity Exploration Institute

    1
    Now iconic image NSF/LIGO/Sonoma State University/A. Simonnet

    Within weeks of switching their machines back on to scour the sky for more sources of gravitational waves, scientists are poring over data in an attempt to further understand an unprecedented cosmic event.

    Astronomers working at the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the European-based Virgo detector have reported the possible detection of gravitational waves emanating from the collision of a neutron star and a black hole.


    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

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

    Localizations of gravitational-wave signals detected by LIGO in 2015 (GW150914, LVT151012, GW151226, GW170104), more recently, by the LIGO-Virgo network (GW170814, GW170817). After Virgo came online in August 2018


    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)

    The signal, detected on 26 April, came just weeks after the teams turned the updated detectors back on to start their third observation run, named “O3”.

    “The universe is keeping us on our toes,” says Patrick Brady, spokesperson for the LIGO Scientific Collaboration and a professor of physics at the University of Wisconsin-Milwaukee. “We’re especially curious about the April 26 candidate. Unfortunately, the signal is rather weak. It’s like listening to somebody whisper a word in a busy café; it can be difficult to make out the word or even to be sure that the person whispered at all. It will take some time to reach a conclusion about this candidate.”

    The possible detection not only throws light on an event that up until now has never been observed, but also confirms the unprecedented accuracy with which the gravitational wave detectors are now operating.

    Included in the latest batch of discoveries is another possible merger between two neutron stars – potentially the second time this has been observed by the LIGO and Virgo teams – as well as a further three interesting black hole mergers.

    Professor Mark Hannam, a member of the LIGO team and Director of Cardiff University’s Gravity Exploration Institute said: “Yet again the LIGO and Virgo detectors have surpassed expectations. Our most optimistic estimates were for a detection every week, and the first month of the run gave us five candidates.”

    Dr Vivien Raymond, from Cardiff University’s Gravity Exploration Institute, said: “LIGO-Virgo’s third observing run has already proven to be more interesting than we expected, barely a month after it started. It’s exciting to think about the next surprises in the Universe for us to discover.”

    Gravitational waves are ripples in space produced by massive cosmic events such as the collision of black holes or the explosion of supernovae.

    Research undertaken by Cardiff University’s Gravity Exploration Institute has laid the foundations for how we go about detecting gravitational waves with the development of novel algorithms and software that have now become standard tools for detecting the elusive signals.

    The Institute also includes world-leading experts in the collision of black holes, who have produced large-scale computer simulations of what is to be expected and observed when these violent events occur, as well as experts in the design of gravitational-wave detectors.

    The twin detectors of LIGO—one in Washington and one in Louisiana—along with Virgo, located at the European Gravitational Observatory (EGO) in Italy, resumed operations on 1 April , after undergoing a series of upgrades to increase their sensitivities to gravitational waves—ripples in space and time.

    Each detector now surveys larger volumes of the universe than before, searching for extreme events such as smash-ups between black holes and neutron stars.

    In total, since making history with the first-ever direct detection of gravitational waves in 2015, the network has spotted evidence for two neutron star mergers; 13 black hole mergers; and one possible black hole-neutron star merger.

    See the full article here .


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    Please help promote STEM in your local schools.

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    Cardiff Unversity is an ambitious and innovative university with a bold and strategic vision located in a beautiful and thriving capital city. Our research is world-leading and we provide an educationally outstanding experience for our students.

    Driven by creativity and curiosity, we strive to fulfil our social, cultural and economic obligations to Cardiff, Wales, and the world.

     
  • richardmitnick 2:26 pm on December 14, 2018 Permalink | Reply
    Tags: A Jet from Neutron Star Merger GW170817, , , , , , , , Virgo collaboration   

    From AAS NOVA: ” A Jet from Neutron Star Merger GW170817″ 

    AASNOVA

    From AAS NOVA

    14 December 2018
    Kerry Hensley

    1
    This artist’s impression of a black hole that formed after two neutron stars collided shows an accretion disk and a narrow jet. [NASA/CXC/M.Weiss]

    Just last year, the three observatories of the Laser Interferometer Gravitational-Wave Observatory (LIGO)–Virgo Collaboration detected the gravitational-wave signature of two neutron stars colliding. What can we learn from the months of observations made since?


    2
    On 17 August, 2017, LIGO detected this “chirp” as two neutron stars spiraled inward and collided. This brief gravitational-wave blip, known as GW170817, has been followed up with months of multiwavelength observations. [LSC/Alex Nitz]

    When Worlds Collide

    Immediately following the detection of gravitational-wave event GW170817, teams of astronomers around the world rushed to pinpoint and characterize the electromagnetic radiation from the source.

    These early observations were hugely important for validating our understanding of what happens when neutron stars collide, but the work didn’t end there; in the months that followed, repeated measurements of the flux across the electromagnetic spectrum have provided us with the tools to probe what happened in the aftermath of the merger.

    These late-time observations should allow us to distinguish between two competing post-merger scenarios, in which the resultant relativistic jet either pushes past the previously ejected material surrounding the remnant (the “jet-dominated outflow” model) or fails to escape the slow-moving shroud of material (the “cocoon-dominated outflow” model) and is choked.

    3
    Radio spectral indices from 6 to 10 months post merger. Combining all the radio data gives a spectral index of -0.53. The black line shown for reference is the radio-to-X-ray spectral index measurement. [Mooley et al. 2018]

    Tuning in to GW170817

    In order to characterize the nature of the outflow and determine which scenario describes GW170817, a team led by Kunal Mooley (National Radio Astronomy Observatory/Caltech) analyzed the decline of GW170817’s radio emission over time. The authors combined data from multiple radio sources — MeerKAT, Very Large Array (VLA), Giant Metrewave Radio Telescope (uGMRT), and the Australia Telescope Compact Array (ATCA) — to cover the radio emission from 0.65 to 12 GHz.

    SKA Meerkat telescope, 90 km outside the small Northern Cape town of Carnarvon, SA

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    Giant Metrewave Radio Telescope, an array of thirty telecopes, located near Pune in India

    CSIRO Australia Compact Array, six radio telescopes at the Paul Wild Observatory, is an array of six 22-m antennas located about twenty five kilometres (16 mi) west of the town of Narrabri in Australia.

    After steadily rising for 5–6 months after the event, the radio emission peaked and quickly began to decline, making the transition from rising to falling in just a few weeks. The authors focused on two important features of the radio light curve: how rapidly the flux density decreases after the peak (the power-law decay index) and how “sharp” the peak of the light curve is.

    4
    Radio data used in this study. All measurements have been scaled to 3 GHz. The black line is the best-fit model. [Mooley et al. 2018]

    Jet vs. Cocoon

    Models tell us that if GW170817’s jet were choked by a slow-moving cocoon of material, the radio observations would reveal a power-law decay index of -0.88. If instead the jet punches free of the material as in the jet-dominated outflow model, its flux density would decrease much more rapidly, exhibiting a power-law decay index of -2.17.
    So which model do the radio observations of GW170817 support? All of the post-peak data are well-described by a single power-law decay with an index of -2.4. This strongly supports the jet model over the cocoon model, and it suggests that the majority of the energy in the post-merger outflow is carried away by the jet.

    The sharpness of the light-curve peak is dependent upon the viewing angle and the width of the jet. Based on a simple jet model, the authors find that the jet is likely very narrow (with an opening angle of less than 10°) and the viewing angle is less than 28°. Future modeling will explore the effects that structure in the jet can have on how sharply peaked the radio light curve is and further our understanding of these highly energetic collisions.

    Citation

    “A Strong Jet Signature in the Late-time Light Curve of GW170817,” K. P. Mooley et al 2018 ApJL 868 L11.
    http://iopscience.iop.org/article/10.3847/2041-8213/aaeda7/meta

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Societyis to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 3:34 pm on December 11, 2018 Permalink | Reply
    Tags: , , , , , Five Surprising Truths About Black Holes From LIGO, , Virgo collaboration   

    From Ethan Siegel: “Five Surprising Truths About Black Holes From LIGO” 

    From Ethan Siegel
    Dec 11, 2018

    1
    A still image of a visualization of the merging black holes that LIGO and Virgo have observed so far. As the horizons of the black holes spiral together and merge, the emitted gravitational waves become louder (larger amplitude) and higher pitched (higher in frequency). The black holes that merge range from 7.6 solar masses up to 50.6 solar masses, with about 5% of the total mass lost during each merger. (TERESITA RAMIREZ/GEOFFREY LOVELACE/SXS COLLABORATION/LIGO-VIRGO COLLABORATION)

    With a total of 10 black holes detected, what we’ve learned about the Universe is truly amazing.

    On September 14th, 2015, just days after LIGO first turned on at its new-and-improved sensitivity, a gravitational wave passed through Earth. Like the billions of similar waves that had passed through Earth over the course of its history, this one was generated by an inspiral, merger, and collision of two massive, ultra-distant objects from far beyond our own galaxy. From over a billion light years away, two massive black holes had coalesced, and the signal — moving at the speed of light — finally reached Earth.

    But this time, we were ready. The twin LIGO detectors saw their arms expand-and-contract by a subatomic amount, but that was enough for the laser light to shift and produce a telltale change in an interference pattern. For the first time, we had detected a gravitational wave. Three years later, we’ve detected 11 of them, with 10 coming from black holes. Here’s what we’ve learned.

    2
    The 30-ish solar mass binary black holes first observed by LIGO are very difficult to form without direct collapse. Now that it’s been observed twice, these black hole pairs are thought to be quite common. But the question of whether black hole mergers emit electromagnetic emission is not yet settled. (LIGO, NSF, A. SIMONNET (SSU))

    There have been two “runs” of LIGO data: a first one from September 12, 2015 to January 19, 2016 and then a second one, at somewhat improved sensitivity, from November 30, 2016 to August 25, 2017. That latter run was, partway through, joined by the VIRGO detector in Italy, which added not only a third detector, but significantly improved our ability to pinpoint the location of where these gravitational waves occurred. LIGO is currently shut down right now, as it’s undergoing upgrades that will make it even more sensitive, as it prepares to begin a new data-taking observing run in the spring of 2019.

    On November 30th, the LIGO scientific collaboration released the results of their improved analysis, which is sensitive to the final stages of mergers between objects between about 1 and 100 solar masses.

    3
    The 11 gravitational wave events detected by LIGO and Virgo, with their names, mass parameters, and other essential information encoded in Table form. Note how many events came in the last month of the second run: when LIGO and Virgo were operating simultaneously. (THE LIGO SCIENTIFIC COLLABORATION, THE VIRGO COLLABORATION; ARXIV:1811.12907)

    The 11 detections that have been made so far are shown above, with 10 of them representing black hole-black hole mergers, and only GW170817 representing a neutron star-neutron star merger. Those merging neutron stars was the closest event at a mere 130–140 million light years away. The most massive merger seen — GW170729 — comes to us from a location that, with the expansion of the Universe, is now 9 billion light years away.

    These two detections are also the lightest and heaviest gravitational wave mergers ever detected, with GW170817 colliding a 1.46 and a 1.27 solar mass neutron star, and GW170729 colliding a 50.6 and a 34.3 solar mass black hole together.

    Here are the five surprising truths that we’ve learned from all of these detections combined.

    4
    LIGO, as designed, should be sensitive to black holes of a particular mass range that inspiral and merge: from 1 up to a few hundred solar masses. The fact that what we observe appears to be capped at 50 solar masses places severe constraints on black hole merger rates above that figure. (NASA / DANA BERRY (SKYWORKS DIGITAL))

    1.) The largest merging black holes are the easiest to see, and they don’t appear to get larger than about 50 solar masses. One of the best things about looking for gravitational waves is that it’s easier to see them from farther away than it is for a light source. Stars appear dimmer in proportion to their distance squared: a star 10 times the distance is just one-hundredth as bright. But gravitational waves are dimmer in direct proportion to distance: merging black holes 10 times as far away produce 10% the signal.

    As a result, we can see very massive objects to very great distances, and yet we don’t see black holes merging with 75, 100, 150, or 200+ solar masses. 20-to-50 solar masses are common, but we haven’t seen anything above that yet. Perhaps the black holes arising from ultra-massive stars truly are rare.

    6
    Aerial view of the Virgo gravitational-wave detector, situated at Cascina, near Pisa (Italy). Virgo is a giant Michelson laser interferometer with arms that are 3 km long, and complements the twin 4 km LIGO detectors. (NICOLA BALDOCCHI / VIRGO COLLABORATION)

    2.) Adding in a third detector both improves our ability to pinpoint their positions and increases the detection rate significantly. LIGO ran for about 4 months during its first run and 9 months during its second. Yet, fully half of their detections came in the final month: when VIRGO was running alongside it, too. In 2017, gravitational wave events were detected on:

    July 29th (50.6 and 34.3 solar mass black holes),
    August 9th (35.2 and 23.8 solar mass black holes),
    August 14th (30.7 and 25.3 solar mass black holes),
    August 17th (1.46 and 1.27 solar mass neutron stars),
    August 18th (35.5 and 26.8 solar mass black holes), and
    August 23rd (39.6 and 29.4 solar mass black holes).

    During this final month of observing, we were detecting more than one event per week. It’s possible that, as we becomes sensitive to greater distances and smaller-amplitude, lower-mass signals, we may begin seeing as many as one event per day in 2019.

    4
    Cataclysmic events occur throughout the galaxy and across the Universe, from supernovae to active black holes to merging neutron stars and more. When two black holes merge, their peak brightness is enough, for a few short milliseconds, to outshine all the stars in the observable Universe combined. (J. WISE/GEORGIA INSTITUTE OF TECHNOLOGY AND J. REGAN/DUBLIN CITY UNIVERSITY)

    3.) When the black holes we’ve detected collide, they release more energy at their peak than all the stars in the Universe combined. Our Sun is the standard by which we came to understand all other stars. It shines so brightly that its total energy energy output — 4 × 10²⁶ W — is equivalent to converting four million tons of matter into pure energy with every second that goes by.

    With an estimated ~10²³ stars in the observable Universe, the total power output of all the stars shining throughout the sky is greater than 10⁴⁹ W at any given time: a tremendous amount of energy spread out over all of space. But for a brief few milliseconds during the peak of a binary black hole merger, every one of the observed 10 events outshone, in terms of energy, all the stars in the Universe combined. (Although it’s by a relatively small amount.) Unsurprisingly, the most massive merger tops the charts.

    5
    Even though black holes should have accretion disks, there aren’t any significant electromagnetic signals expected to be generated by a black hole-black hole merger. Their energy instead gets converted into gravitational radiation: ripples in the fabric of space itself. We see this radiation, and it’s the most energetic event to occur in the Universe when it happens. (AEI POTSDAM-GOLM)

    4.) About 5% of the total mass of both black holes gets converted into pure energy, via Einstein’s E = mc², during these mergers. The ripples in space that these black hole mergers produce need to get their energy from somewhere, and realistically, that has to come out of the mass of the merging black holes themselves. On average, based on the magnitude of the gravitational wave signals we’ve seen and the reconstructed distances to them, black holes lose about 5% of their total mass — having it converted into gravitational wave energy — when they merge.

    GW170608, the lowest mass black hole merger (of 10.9 and 7.6 solar masses), converted 0.9 solar masses into energy.
    GW150914, the first black hole merger (of 35.6 and 30.6 solar masses), converted 3.1 solar masses into energy.
    And GW170729, the most massive black hole merger (at 50.6 and 34.3 solar masses), converted 4.8 solar masses into energy.

    These events, creating ripples in spacetime, are the most energetic events we know of since the Big Bang. They produce more energy than any neutron star merger, gamma-ray burst, or supernova ever created.

    6
    Illustrated here is the range of Advanced LIGO and its capability of detecting merging black holes. Merging neutron stars may have only one-tenth the range and 0.1% the volume, but we caught one, last year, just 130 million light years away. Additional black holes are likely present and merging, and perhaps run III of LIGO will find them.(LIGO COLLABORATION / AMBER STUVER / RICHARD POWELL / ATLAS OF THE UNIVERSE)

    5.) With everything we’ve seen so far, we fully expect there are lower-mass, more frequent black hole mergers just waiting to be seen. The most massive black hole mergers produce the largest-amplitude signals, and so are the easiest to spot. But with the way volume and distance are related, going twice as distant means encompassing eight times the volume. As LIGO gets more sensitive, it’s easier to spot massive objects at greater distances than low-mass objects that are close by.

    We know there are black holes of 7, 10, 15, and 20 solar masses out there, but it’s easier for LIGO to spot a more massive one farther away. We expect there are black hole binaries with mismatched masses: where one is much more massive than the other. As our sensitivities improve, we expect there are more of these out there to find, but the most massive ones are easier to find. We expect the most massive ones to dominate the early searches, just as “hot Jupiters” dominated early exoplanet searches. As we get better at finding them, expect there to be greater numbers of lower-mass black holes out there.

    7
    LIGO and Virgo have discovered a new population of black holes with masses that are larger than what had been seen before with X-ray studies alone (purple). This plot shows the masses of all ten confident binary black hole mergers detected by LIGO/Virgo (blue). Also shown are neutron stars with known masses (yellow), and the component masses of the binary neutron star merger GW170817 (orange).(LIGO/VIRGO/NORTHWESTERN UNIV./FRANK ELAVSKY)

    When the first gravitational wave detection was announced, it was heralded as the birth of gravitational wave astronomy. People likened it to when Galileo first pointed his telescope at the skies, but it was so much more than that. It was as though our view of the gravitational wave sky had always been shrouded in clouds, and for the first time, we had developed a device to see through them if we got a bright enough gravitational source: merging black holes or neutron stars. The future of gravitational wave astronomy promises to revolutionize our Universe by letting us see it in a whole new way. And that future has already arrived; we are seeing the first fruits of our labor.

    8
    This visualization shows the coalescence of two orbiting neutron stars. The right panel contains a visualization of the matter of the neutron stars. The left panel shows how space-time is distorted near the collisions. For black holes, there is no matter-generated signal expected, but thanks to LIGO and Virgo, we can still see the gravitational waves. (KARAN JANI/GEORGIA TECH)

    As our technology improves, we gain an ever-improved ability to see through those clouds: to see fainter, lower-mass, and more distant gravitational sources. When LIGO starts taking data again in 2019, we fully expect greater rates of ~30 solar mass black holes merging, but we hope to finally know what the lower-mass black holes are doing. We hope to see neutron star-black hole mergers. And we hope to go even farther out into the distant reaches of the Universe.

    Now that we’ve made it into the double digits for the number of detected events, it’s time to go even farther. With LIGO and VIRGO fully operational, and at better sensitivities than ever, we’re ready to go one step deeper in our exploration of the gravitational wave Universe. These merging, massive stellar remnants were just the start. It’s time to visit the stellar graveyard, and find out what the skeletons are truly like.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 7:09 am on October 17, 2017 Permalink | Reply
    Tags: , , , , , , , Virgo collaboration   

    From STFC: “Crashing neutron stars unlock secrets of the Universe – thanks to UK tech” 


    STFC

    16 October 2017
    Jake Gilmore; STFC Media Manager – 07970994586
    jake.gilmore@stfc.ac.uk

    Mike Bishop; Senior Communications Officer, Cardiff University – Tel: 02920 874499 / 07713 325300
    bishopm1@cardiff.ac.uk

    Luke Sullivan; Communications Manager (Science), University of Birmingham – Tel: 0121 414 5134 / 07789 921165
    l.harrison.1@bham.ac.uk

    Liz Buie; Communications and Public Affairs Office, University of Glasgow – 0141 330 2702 / 07527 335373
    Liz.Buie@glasgow.ac.uk

    Ather Mirza; Division of External Relations, University of Leicester – Tel: +44 (0)116 2523335 / m: +44 (0) 7711 927821
    am47@leicester.ac.uk

    Emma Gallagher; Communications Officer, Queen’s University Belfast – Tel: 028 9097 5384
    emma.gallagher@qub.ac.uk

    Tom Frew; Senior Press and Media Relations Manager, University of Warwick – Tel: 02476575910 / 07785433155
    a.t.frew@warwick.ac.uk

    1
    Cataclysmic collision. (Credit: NSF/LIGO/Sonoma State University/A. Simonnet)

    In a galaxy far away, two dead stars begin a final spiral into a massive collision. The resulting explosion unleashes a huge burst of energy, sending ripples across the very fabric of space. In the nuclear cauldron of the collision, atoms are ripped apart to form entirely new elements and scattered outward across the Universe.

    It could be a scenario from science fiction, but it really happened 130 million years ago — in the NGC 4993 galaxy in the Hydra constellation, at a time here on Earth when dinosaurs still ruled and flowering plants were only just evolving.

    Today, dozens of UK scientists and their international collaborators representing 70 observatories worldwide announced the detection of this event and the significant “scientific firsts” it has revealed about our Universe.

    Those ripples in space finally reached Earth at 1.41pm UK time, on Thursday 17 August 2017, and were recorded by the twin detectors of the US-based Laser Interferometer Gravitational-wave Observatory (LIGO) and its European counterpart Virgo.


    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

    1
    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)

    A few seconds later, the gamma-ray burst from the collision was recorded by two specialist space telescopes, and over following weeks, other space- and ground-based telescopes recorded the aftermath of the massive explosion. UK developed engineering and technology is at the heart of many of the instruments used for the detection and analysis.

    Dr John Veitch, who is co-chair of LIGO’s Compact Binary Coalescence Search Group and Research Fellow at the University of Glasgow’s School of Physics and Astronomy and played a leading role in the GW170817 data analysis said: “One key difference between the gravitational wave signals from binary black holes and binary neutron stars is that neutron stars are many times lighter than black holes. This means that the gravitational wave signal from neutron stars linger for a much greater period in the detector – for around 100 seconds as opposed to just a fraction of a second for binary black holes. A longer signal means we can glean much more information about the source.”

    Studying the data confirmed scientists’ initial conclusion that the event was the collision of a pair of neutron stars – the remnants of once gigantic stars, but collapsed down into approximately the size of a city.

    UK Science Minister, Jo Johnson, said “Today’s announcement of the latest detection of gravitational waves is another important development in our understanding of the universe which has been made possible by UK research and technology.

    “The recent awarding of the Nobel Prize for Physics to gravitational waves research is clear recognition of the importance of this area. The UK plays a significant role in these detections, enabling us to continue building our reputation as a world leader in science and innovation which is a core part of our Industrial Strategy.”

    There are a number of “firsts” associated with this event, including the first detection of both gravitational waves and electromagnetic radiation (EM) – while existing astronomical observatories “see” EM across different frequencies (eg, optical, infra-red, gamma ray etc), gravitational waves are not EM but instead ripples in the fabric of space requiring completely different detection techniques. An analogy is that LIGO and Virgo “hear” the Universe.

    The announcement also confirmed the first direct evidence that short gamma ray bursts are linked to colliding neutron stars. The shape of the gravitational waveform also provided a direct measure of the distance to the source, and it was the first confirmation and observation of the previously theoretical cataclysmic aftermaths of this kind of merger – a kilonova.

    Additional research papers on the aftermath of the event have also produced new understanding of how heavy elements such as gold and platinum are created by supernova and stellar collisions and then spread through the Universe. More such original science results are still under current analysis.

    By combining gravitational-wave and electromagnetic signals together, researchers also used a new technique to measure the expansion rate of the Universe. This technique was first proposed in 1986 by University of Cardiff’s Professor Bernard Schutz.

    UK astronomers using the VISTA telescope in Chile were among the first to locate the new source.


    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    “We were really excited when we first got notification that a neutron star merger had been detected by LIGO,” said Professor Nial Tanvir from the University of Leicester, who leads a paper in [The] Astrophysical Journal Letters today. “We immediately triggered observations on several telescopes in Chile to search for the explosion that we expected it to produce. In the end we stayed up all night analysing the images as they came in, and it was remarkable how well the observations matched the theoretical predictions that had been made.”

    Dr Kate Maguire, from Queen’s University Belfast was part of the team studying the burst of light from the smashing together of the two neutron stars “Using rapid-response triggering at some of the world’s best telescopes, we have discovered that this neutron-star merger scattered heavy chemical elements, such as gold and platinum, out into space at high speeds. These new results have significantly contributed to solving the long-debated mystery of the origin of elements heavier than iron in the periodic table.”

    Once the location of the collision was pin-pointed, scientists quickly maneuvered the Swift satellite to examine the aftermath with its X-ray and UV/optical telescopes.

    NASA/SWIFT Telescope

    “We didn’t detect any X-rays from the object, which was surprising given the gamma ray detection,” said Dr Phil Evans from the University of Leicester, lead-author of a paper published today in Science. “But we did find bright ultra-violet emission, which most people were not expecting. This discovery helped us to pin down what happened after the neutron star collision was detected by LIGO and Virgo.”

    4
    Artists impression of merging neutron stars
    (Credit: ESO/L. Calçada/M. Kornmesser)

    Professor Alberto Vecchio from the University of Birmingham’s Institute of Gravitational Wave Astronomy said: “Detecting for the first time gravitational waves from the coalescence of a binary neutron star is fantastic, and even more so that we could do it almost in real time and precisely locate this source in the sky. If fact, telescopes around the world could then point at that little patch in the sky and show us over hours, days and weeks extra-ordinary events set in motion by this cataclysmic collision as the emerging radiation swept the whole electromagnetic spectrum.”

    Chief Executive Designate of UK Research and Innovation, Sir Mark Walport said: “Over a hundred years ago Einstein introduced his revolutionary General Theory of Relativity. In this, space and time were no longer absolute, no longer a fixed background to events, he proposed the existence of gravitational waves as a way to understanding the origins of the Universe.

    “The latest gravitational waves announcement, today, includes the first direct evidence that short gamma ray bursts are linked to colliding neutron stars and is the result of outstanding international collaboration. This spectacular discovery is built on ambition and tenacity of international partnerships. I am proud that UK Science is at the heart of many of the instruments and detectors used for today’s historic announcement”

    Dr Brian Bowsher, Chief Executive of the UK’s Science and Technology Facilities Council, said: “This new gravitational wave discovery will inspire many young people into the world of science as it reinforces the fact that there is still so much we can learn about how the Universe works. It offers new insights into the field of astronomy as well as showcasing how technological breakthroughs made by UK engineers and scientists made this latest understanding possible.”

    For science papers see https://sciencesprings.wordpress.com/2017/10/16/from-hubble-nasa-missions-catch-first-light-from-a-gravitational-wave-event/

    See the full article here .

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    STFC Hartree Centre

    Helping build a globally competitive, knowledge-based UK economy

    We are a world-leading multi-disciplinary science organisation, and our goal is to deliver economic, societal, scientific and international benefits to the UK and its people – and more broadly to the world. Our strength comes from our distinct but interrelated functions:

    Universities: we support university-based research, innovation and skills development in astronomy, particle physics, nuclear physics, and space science
    Scientific Facilities: we provide access to world-leading, large-scale facilities across a range of physical and life sciences, enabling research, innovation and skills training in these areas
    National Campuses: we work with partners to build National Science and Innovation Campuses based around our National Laboratories to promote academic and industrial collaboration and translation of our research to market through direct interaction with industry
    Inspiring and Involving: we help ensure a future pipeline of skilled and enthusiastic young people by using the excitement of our sciences to encourage wider take-up of STEM subjects in school and future life (science, technology, engineering and mathematics)

    We support an academic community of around 1,700 in particle physics, nuclear physics, and astronomy including space science, who work at more than 50 universities and research institutes in the UK, Europe, Japan and the United States, including a rolling cohort of more than 900 PhD students.

    STFC-funded universities produce physics postgraduates with outstanding high-end scientific, analytic and technical skills who on graduation enjoy almost full employment. Roughly half of our PhD students continue in research, sustaining national capability and creating the bedrock of the UK’s scientific excellence. The remainder – much valued for their numerical, problem solving and project management skills – choose equally important industrial, commercial or government careers.

    Our large-scale scientific facilities in the UK and Europe are used by more than 3,500 users each year, carrying out more than 2,000 experiments and generating around 900 publications. The facilities provide a range of research techniques using neutrons, muons, lasers and x-rays, and high performance computing and complex analysis of large data sets.

    They are used by scientists across a huge variety of science disciplines ranging from the physical and heritage sciences to medicine, biosciences, the environment, energy, and more. These facilities provide a massive productivity boost for UK science, as well as unique capabilities for UK industry.

    Our two Campuses are based around our Rutherford Appleton Laboratory at Harwell in Oxfordshire, and our Daresbury Laboratory in Cheshire – each of which offers a different cluster of technological expertise that underpins and ties together diverse research fields.

    The combination of access to world-class research facilities and scientists, office and laboratory space, business support, and an environment which encourages innovation has proven a compelling combination, attracting start-ups, SMEs and large blue chips such as IBM and Unilever.

    We think our science is awesome – and we know students, teachers and parents think so too. That’s why we run an extensive Public Engagement and science communication programme, ranging from loans to schools of Moon Rocks, funding support for academics to inspire more young people, embedding public engagement in our funded grant programme, and running a series of lectures, travelling exhibitions and visits to our sites across the year.

    Ninety per cent of physics undergraduates say that they were attracted to the course by our sciences, and applications for physics courses are up – despite an overall decline in university enrolment.

     
  • richardmitnick 5:36 pm on October 16, 2017 Permalink | Reply
    Tags: , , , , , , , , , Virgo collaboration   

    From UCSC: “A UC Santa Cruz special report: Neutron stars, gravitational waves, and all the gold in the universe” 

    UC Santa Cruz

    UC Santa Cruz

    10.16.17
    Tim Stephens

    2

    Astronomer Ryan Foley says observing the explosion of two colliding neutron stars–the first visible event ever linked to gravitational waves–is probably the biggest discovery he’ll make in his lifetime. That’s saying a lot for a young assistant professor who presumably has a long career still ahead of him.

    1

    So what makes this strange cataclysm in another galaxy so exciting to astronomers? And what the heck is a neutron star, anyway?

    A neutron star forms when a massive star runs out of fuel and explodes as a supernova, throwing off its outer layers and leaving behind a collapsed core composed almost entirely of neutrons. Neutrons are the uncharged particles in the nucleus of an atom, where they are bound together with positively charged protons. In a neutron star, they are packed together just as densely as in the nucleus of an atom, resulting in an object with one to three times the mass of our sun but only about 12 miles wide.

    “Basically, a neutron star is a gigantic atom with the mass of the sun and the size of a city like San Francisco or Manhattan,” said Foley, an assistant professor of astronomy and astrophysics at UC Santa Cruz.

    These objects are so dense, a cup of neutron star material would weigh as much as Mount Everest, and a teaspoon would weigh a billion tons. It’s as dense as matter can get without collapsing into a black hole.

    THE MERGER

    Like other stars, neutron stars sometimes occur in pairs, orbiting each other and gradually spiraling inward. Eventually, they come together in a catastrophic merger that distorts space and time (creating gravitational waves) and emits a brilliant flare of electromagnetic radiation, including visible, infrared, and ultraviolet light, x-rays, gamma rays, and radio waves. Merging black holes also create gravitational waves, but there’s nothing to be seen because no light can escape from a black hole.

    Foley’s team was the first to observe the light from a neutron star merger that took place on August 17, 2017, and was detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (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

    1
    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)

    Now, for the first time, scientists can study both the gravitational waves (ripples in the fabric of space-time), and the radiation emitted from the violent merger of the densest objects in the universe.

    3
    The UC Santa Cruz team found SSS17a by comparing a new image of the galaxy N4993 (right) with images taken four months earlier by the Hubble Space Telescope (left). The arrows indicate where SSS17a was absent from the Hubble image and visible in the new image from the Swope Telescope. (Image credits: Left, Hubble/STScI; Right, 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley)


    Carnegie Institution Swope telescope at Las Campanas, Chile

    It’s that combination of data, and all that can be learned from it, that has astronomers and physicists so excited. The observations of this one event are keeping hundreds of scientists busy exploring its implications for everything from fundamental physics and cosmology to the origins of gold and other heavy elements.


    A small team of UC Santa Cruz astronomers were the first team to observe light from two neutron stars merging in August. The implications are huge.

    All THE GOLD IN THE UNIVERSE

    It turns out that the origins of the heaviest elements, such as gold, platinum, uranium—pretty much everything heavier than iron—has been an enduring conundrum. All the lighter elements have well-explained origins in the nuclear fusion reactions that make stars shine or in the explosions of stars (supernovae). Initially, astrophysicists thought supernovae could account for the heavy elements, too, but there have always been problems with that theory, says Enrico Ramirez-Ruiz, professor and chair of astronomy and astrophysics at UC Santa Cruz.

    5
    The violent merger of two neutron stars is thought to involve three main energy-transfer processes, shown in this diagram, that give rise to the different types of radiation seen by astronomers, including a gamma-ray burst and a kilonova explosion seen in visible light. (Image credit: Murguia-Berthier et al., Science)

    A theoretical astrophysicist, Ramirez-Ruiz has been a leading proponent of the idea that neutron star mergers are the source of the heavy elements. Building a heavy atomic nucleus means adding a lot of neutrons to it. This process is called rapid neutron capture, or the r-process, and it requires some of the most extreme conditions in the universe: extreme temperatures, extreme densities, and a massive flow of neutrons. A neutron star merger fits the bill.

    Ramirez-Ruiz and other theoretical astrophysicists use supercomputers to simulate the physics of extreme events like supernovae and neutron star mergers. This work always goes hand in hand with observational astronomy. Theoretical predictions tell observers what signatures to look for to identify these events, and observations tell theorists if they got the physics right or if they need to tweak their models. The observations by Foley and others of the neutron star merger now known as SSS17a are giving theorists, for the first time, a full set of observational data to compare with their theoretical models.

    According to Ramirez-Ruiz, the observations support the theory that neutron star mergers can account for all the gold in the universe, as well as about half of all the other elements heavier than iron.

    RIPPLES IN THE FABRIC OF SPACE-TIME

    Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity, but until recently they were impossible to observe. LIGO’s extraordinarily sensitive detectors achieved the first direct detection of gravitational waves, from the collision of two black holes, in 2015. Gravitational waves are created by any massive accelerating object, but the strongest waves (and the only ones we have any chance of detecting) are produced by the most extreme phenomena.

    Two massive compact objects—such as black holes, neutron stars, or white dwarfs—orbiting around each other faster and faster as they draw closer together are just the kind of system that should radiate strong gravitational waves. Like ripples spreading in a pond, the waves get smaller as they spread outward from the source. By the time they reached Earth, the ripples detected by LIGO caused distortions of space-time thousands of times smaller than the nucleus of an atom.

    The rarefied signals recorded by LIGO’s detectors not only prove the existence of gravitational waves, they also provide crucial information about the events that produced them. Combined with the telescope observations of the neutron star merger, it’s an incredibly rich set of data.

    LIGO can tell scientists the masses of the merging objects and the mass of the new object created in the merger, which reveals whether the merger produced another neutron star or a more massive object that collapsed into a black hole. To calculate how much mass was ejected in the explosion, and how much mass was converted to energy, scientists also need the optical observations from telescopes. That’s especially important for quantifying the nucleosynthesis of heavy elements during the merger.

    LIGO can also provide a measure of the distance to the merging neutron stars, which can now be compared with the distance measurement based on the light from the merger. That’s important to cosmologists studying the expansion of the universe, because the two measurements are based on different fundamental forces (gravity and electromagnetism), giving completely independent results.

    “This is a huge step forward in astronomy,” Foley said. “Having done it once, we now know we can do it again, and it opens up a whole new world of what we call ‘multi-messenger’ astronomy, viewing the universe through different fundamental forces.”

    LIGO can tell scientists the masses of the merging objects and the mass of the new object created in the merger, which reveals whether the merger produced another neutron star or a more massive object that collapsed into a black hole. To calculate how much mass was ejected in the explosion, and how much mass was converted to energy, scientists also need the optical observations from telescopes. That’s especially important for quantifying the nucleosynthesis of heavy elements during the merger.

    Published research

    Credits

    Writing: Tim Stephens
    Header image: Illustration by Robin Dienel courtesy of the Carnegie Institution for Science
    Design and development: Rob Knight
    Project managers: Sherry Main, Scott Hernandez-Jason, Tim Stephens

    See the full article here .

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    UCO Lick Shane Telescope
    UCO Lick Shane Telescope interior
    Shane Telescope at UCO Lick Observatory, UCSC

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    UC Santa Cruz campus
    The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

    UCSC is the home base for the Lick Observatory.

    Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
    Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

    Search for extraterrestrial intelligence expands at Lick Observatory
    New instrument scans the sky for pulses of infrared light
    March 23, 2015
    By Hilary Lebow
    1
    The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch) UCSC Lick Nickel telescope

    Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

    “Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

    Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

    Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

    5
    UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch)

    Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

    “The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

    The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

    Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

    “We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

    Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

    “This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

    NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

    “Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

    NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

    The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

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  • richardmitnick 12:37 pm on October 16, 2017 Permalink | Reply
    Tags: , , , , , , , Virgo collaboration   

    From CfA: “CfA Scientists Weigh in on Historic Gravitational Wave Discovery” and the Press Release 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    October 16, 2017

    Scientists have detected gravitational waves and electromagnetic radiation, or light, from the same event for the first time, as described in our latest press release [see below].

    Thousands of scientists around the world have worked on this result, with researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., playing a pivotal role. A series of eight papers led by CfA astronomers and their colleagues detail the complete story of the aftermath of this event and reveal clues about its origin.

    We conducted interviews with four CfA scientists about their work on this discovery: Professor Edo Berger, who led the work, postdoctoral fellow Matt Nicholl, and graduate students Kate Alexander and Philip Cowperthwaite. Here they describe their reactions to the exciting news that Advanced LIGO had detected gravitational waves from a neutron star merger, and they discuss unanswered questions and prospects for future work.

    How did you hear about LIGO’s detection of a neutron star merger and what were your first thoughts?

    Kate Alexander:

    I saw the e-mail from the LIGO collaboration when I woke up in the morning, and no one was expecting it because LIGO was a week away from shutting down from its current observing run. We all just kind of went “Wow. Oh my goodness! This is actually happening.” Edo called a meeting and we all rushed into his office to prepare our plans for following it up.


    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

    1
    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)

    Edo Berger:

    So, we first got an alert from LIGO on the morning of August 17th. I was actually in the middle of a boring committee meeting. My office phone started ringing, and I ignored it. Then my cell phone started ringing and I ignored it. Then text messages started coming in. At that point I knew that I couldn’t ignore it anymore, so I kicked everybody out of the office and started catching up on this new alert that came from the LIGO observatory saying that they detected the first merger of a neutron star binary system.

    Matt Nicholl:

    As soon as we started observing the sky in Chile we were transferring these images back to computers at Harvard as soon as they came in and we all frantically brought them up on our computer screens and looked for new sources that appeared. Really what we expected was that we wouldn’t find anything in real time and that we’d spend the whole day next day processing these images trying to find some sort of faint little detections of possible candidates. But what actually happened was that one of the first giant galaxies we looked had an obvious new source popping right out at us. This was an incredible moment. I think one of my collaborators saw it first and sent an email that I can’t quite repeat but I will never forget. After that our email inboxes exploded. Every team in the world was looking at this thing and trying to compete to say things first. It was a night unlike any other I’ve had in my career.

    Phil Cowperthwaite:

    I actually heard about it through a very informal email from a colleague. I just woke up that morning and it was there on my phone: “Oh we have a binary neutron star in LIGO with a coincident Fermi detection. It’s insane. It took a moment to process – it didn’t seem real because that was the goal we never expected to happen.”

    What are some unanswered questions and the prospects for future work?

    Kate Alexander:

    The VLA has been invaluable to the science so far.

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    This is going to continue to be a very interesting target for radio observations going forward. The radio emission that we’re observing is likely to continue to be observable with the VLA for the next several weeks to months, and we’ll be very eager to monitor the radio emission we’ve seen as it slowly fades away. We also predict that several years from now the source should brighten in the radio again as all of the slower moving material that produced the optical light eventually starts producing a shock wave [akin to a sonic boom] with the surrounding medium. Then we’ll have a completely independent second chance to figure out all of these properties of the environment around the neutron star. We don’t know exactly when this will happen, but we certainly will continue to look at it with the VLA for years to come.

    Edo Berger:

    In studying both the gravitational wave signal and the electromagnetic signal what we hope to do is understand the detailed composition of neutron stars. What are they exactly made of? What do they look like on the inside? The only way we get to see the inside of a neutron star is when it collides with another neutron star and then material from the inside spills out. This is what we see in our observations. We also want to understand how pairs of neutron stars actually come into being. How are they actually formed? How are these systems born? How was their life before they ended it in that final catastrophic collision?

    One of the particularly exciting aspects of studying the collisions of neutron stars in both gravitational waves and electromagnetic radiation is that it gives us a completely new way of measuring the Hubble Constant, which is the measurement of how fast the Universe is expanding. So far, we’ve been studying the Hubble Constant using different techniques: supernova explosions or the cosmic microwave background [leftover radiation from the Big Bang].

    CMB per ESA/Planck

    ESA/Planck

    But here, for the first time, we have a completely independent new way of measuring the Hubble Constant. We can measure the distance to the object from the gravitational wave signal and we can then measure the amount of redshifting which tells us how fast the universe is expanding from the electromagnetic signal. And by combining these two measurements we can directly measure the Hubble Constant.

    Matt Nicholl:

    I think the big outstanding questions now are first of all how typical was this event of the general population of neutron star mergers? Maybe we got lucky and we found a very bright one. Maybe the others aren’t going to be so great. But we’ll find this out in the next few years as LIGO detects more and more of these sources. By detecting more sources we can also measure the rate at which they occur. The combination of those two things is very powerful. If we know how diverse they are and how often they occur we can work out the total production of heavy elements in the universe. If we compare this production of heavy elements to the abundances that we measure in our local environment we can show definitively whether all heavy elements come from neutron star mergers.

    Phil Cowperthwaite:

    You can do all kinds of science that you could not do with just a gravitational wave detection. The gravitational wave detection is great for telling you about the binary, the objects that merged and their properties, but it can’t do other things. For instance, LIGO can’t give you a precise location on the sky. It can do very well, especially with Virgo, but once you have an optical counterpart you know exactly where that event occurred. And then you can do all kinds of other exciting science. We can associate the source with a galaxy. We can learn about where these objects come from. What are their homes like? Understanding all this information will help us understand the behavior of the merger: how much material is produced, which is important for understanding whether or not these events can truly be the source of heavy element production. So, it really is necessary to maximize the science goals.

    Press release:
    Astronomers See Light Show Associated With Gravitational Waves
    October 16, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Marking the beginning of a new era in astrophysics, scientists have detected gravitational waves and electromagnetic radiation, or light, from the same event for the first time. This historic discovery reveals the merger of two neutron stars, the dense cores of dead stars, and resolves the debate about how the heaviest elements such as platinum and gold were created in the Universe.

    To achieve this remarkable result, thousands of scientists around the world have worked feverishly using data from telescopes on the ground and in space. Researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., have played a pivotal role. A series of eight papers led by CfA astronomers and their colleagues detail the complete story of the aftermath of this event and examine clues about its origin.

    “It’s hard to describe our sense of excitement and historical purpose over the past couple of months,” said the leader of the team, CfA’s Edo Berger. “This is a once in a career moment — we have fulfilled a dream of scientists that has existed for decades.”

    Gravitational waves are ripples in space-time caused by the accelerated motion of massive celestial objects. They were first predicted by Einstein’s General Theory of Relativity. The Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first direct detection of gravitational waves in September 2015, when the merger of two stellar-mass black holes was discovered.

    On 8:41 am EDT August 17, 2017, LIGO detected a new gravitational wave source, dubbed GW170817 to mark its discovery date. Just two seconds later NASA’s Fermi satellite detected a weak pulse of gamma rays from the same location of the sky. Later that morning, LIGO scientists announced that two merging neutron stars produced the gravitational waves from GW170817.

    “Imagine that gravitational waves are like thunder. We’ve heard this thunder before, but this is the first time we’ve also been able to see the lightning that goes with it,” said Philip Cowperthwaite of the CfA. “The difference is that in this cosmic thunderstorm, we hear the thunder first and then get the light show afterwards.”

    A few hours after the announcement, as night set in Chile, Berger’s team used the powerful Dark Energy Camera on the Blanco telescope to search the region of sky from which the gravitational waves emanated. In less than an hour they located a new source of visible light in the galaxy NGC 4993 at a distance of about 130 million light years.

    “One of the first giant galaxies we looked at had an obvious new source of light popping right out at us, and this was an incredible moment,” said Matt Nicholl of the CfA. “We thought it would take days to locate the source but this was like X marks the spot.”

    The CfA team and collaborators then launched a series of observations that spanned the electromagnetic spectrum from X-rays to radio waves to study the aftermath of the neutron star merger.

    In their set of papers, the CfA scientists report their studies of the brightness and spectrum of the optical and infrared light and how it changed over time. They show that the light is caused by the radioactive glow when heavy elements in the material ejected by the neutron star merger are produced in a process called a kilonova.

    “We’ve shown that the heaviest elements in the periodic table, whose origin was shrouded in mystery until today are made in the mergers of neutron stars,” said Edo Berger. “Each merger can produce more than an Earth’s mass of precious metals like gold and platinum and many of the rare elements found in our cellphones.”

    The material observed in the kilonova is moving at high speeds, suggesting that it was expelled during the head-on collision of two neutron stars. This information, independent of the gravitational wave signature, suggests that two neutron stars were involved in GW170817, rather than a black hole and a neutron star.

    Radio observations with the Very Large Array in New Mexico helped confirm that the merger of the two neutron stars triggered a short gamma ray burst (GRB), a brief burst of gamma rays in a jet of high-energy particles. The properties match those predicted by theoretical models of a short GRB that was viewed with the jet initially pointing at a large angle away from Earth. Combining the radio data with observations from NASA’s Chandra X-ray Observatory shows that the jet pointed about 30 degrees away from us.

    “This object looks far more like the theories than we had any right to expect,” said the CfA’s Kate Alexander who led the teams’ VLA observations. “We will continue to track the radio emission for years to come as the material ejected from the collision slams into the surrounding medium,” she continued.

    An analysis of the host galaxy, NGC 4993, and the environment of the cataclysmic merger shows that the neutron star binary most likely formed more than 11 billion years ago.

    “The two neutron stars formed in supernova explosions when the universe was only two billion years old, and have spent the rest of cosmic history getting closer and closer to each other until they finally smashed together,” said Peter Blanchard of the CfA.

    A long list of observatories were used to study the kilonova, including the SOAR and Magellan telescopes, the Hubble Space Telescope, the Dark Energy Camera on the Blanco, and the Gemini-South telescope.

    The series of eight papers describing these results appeared in the Astrophysical Journal Letters on October 16th. The four papers with first authors from CfA are led by Philip Cowperthwaite about the changes with time of light from the kilonova, one led by Matt Nicholl about the changes with time of the kilonova’s spectrum, another led by Kate Alexander about the VLA observations, and another led by Peter Blanchard about how long the merger took to unfold and the properties of the host galaxy.

    Completing the series of eight papers, Marcelle Soares-Santos from Brandeis University in Waltham MA led a paper about the discovery of the optical counterpart; Ryan Chornock from Ohio University in Athens, OH, led a paper about the kilonova’s infrared spectra, Raffaella Margutti from Northwestern University in Evanston, IL, led a paper about the Chandra observations of the jet, and Wen-fai Fong also from Northwestern led a paper about the comparison between GW170817 and previous short GRBs.

    Graphics and other additional information on this result can be found at http://www.kilonova.org.

    Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

    See the full main article here .
    See the press release here .

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    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 12:04 pm on October 16, 2017 Permalink | Reply
    Tags: , , , , , , , Virgo collaboration   

    From ESO: “ESO Telescopes Observe First Light from Gravitational Wave Source” 

    ESO 50 Large

    European Southern Observatory

    16 October 2017
    Stephen Smartt
    Queen’s University Belfast
    Belfast, United Kingdom
    Tel: +44 7876 014103
    Email: s.smartt@qub.ac.uk

    Elena Pian
    Istituto Nazionale di Astrofisica (INAF)
    Bologna, Italy
    Tel: +39 051 6398701
    Email: elena.pian@inaf.it

    Andrew Levan
    University of Warwick
    Coventry, United Kingdom
    Tel: +44 7714 250373
    Email: A.J.Levan@warwick.ac.uk

    Nial Tanvir
    University of Leicester
    Leicester, United Kingdom
    Tel: +44 7980 136499
    nrt3@leicester.ac.uk

    Stefano Covino
    Istituto Nazionale di Astrofisica (INAF)
    Merate, Italy
    Tel: +39 02 72320475
    Cell: +39 331 6748534
    stefano.covino@brera.inaf.it

    Marina Rejkuba
    ESO Head of User Support Department
    Garching bei München, Germany
    Tel: +49 89 3200 6453
    mrejkuba@eso.org

    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    rhook@eso.org

    1
    ESO’s fleet of telescopes in Chile have detected the first visible counterpart to a gravitational wave source. These historic observations suggest that this unique object is the result of the merger of two neutron stars. The cataclysmic aftermaths of this kind of merger — long-predicted events called kilonovae — disperse heavy elements such as gold and platinum throughout the Universe. This discovery, published in several papers in journals [listed below], also provides the strongest evidence yet that short-duration gamma-ray bursts are caused by mergers of neutron stars.

    For the first time ever, astronomers have observed both gravitational waves and light (electromagnetic radiation) from the same event, thanks to a global collaborative effort and the quick reactions of both ESO’s facilities and others around the world.

    On 17 August 2017 the NSF’s Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, working with the Virgo Interferometer in Italy, detected gravitational waves passing the Earth.


    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

    1
    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)

    This event, the fifth ever detected, was named GW170817. About two seconds later, two space observatories, NASA’s Fermi Gamma-ray Space Telescope and ESA’s INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL), detected a short gamma-ray burst from the same area of the sky.

    NASA/Fermi Telescope


    NASA/Fermi LAT

    ESA/Integral

    The LIGO–Virgo observatory network positioned the source within a large region of the southern sky, the size of several hundred full Moons and containing millions of stars [1]. As night fell in Chile many telescopes peered at this patch of sky, searching for new sources. These included ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) and VLT Survey Telescope (VST) at the Paranal Observatory, the Italian Rapid Eye Mount (REM) telescope at ESO’s La Silla Observatory, the LCO 0.4-meter telescope at Las Cumbres Observatory,

    LCOGT Las Cumbres Observatory Global Telescope Network, Haleakala Hawaii, USA

    and the American DECam at Cerro Tololo Inter-American Observatory.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    The Swope 1-metre telescope was the first to announce a new point of light. It appeared very close to NGC 4993, a lenticular galaxy in the constellation of Hydra, and VISTA observations pinpointed this source at infrared wavelengths almost at the same time. As night marched west across the globe, the Hawaiian island telescopes Pan-STARRS and Subaru also picked it up and watched it evolve rapidly.

    Carnegie Institution Swope telescope at Las Campanas, Chile

    Pan-STARRS1 located on Haleakala, Maui, HI, USA


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    “There are rare occasions when a scientist has the chance to witness a new era at its beginning,” said Elena Pian, astronomer with INAF, Italy, and lead author of one of the Nature papers. “This is one such time!”

    ESO launched one of the biggest ever “target of opportunity” observing campaigns and many ESO and ESO-partnered telescopes observed the object over the weeks following the detection [2]. ESO’s Very Large Telescope (VLT), New Technology Telescope (NTT), VST, the MPG/ESO 2.2-metre telescope, and the Atacama Large Millimeter/submillimeter Array (ALMA) [3] all observed the event and its after-effects over a wide range of wavelengths. About 70 observatories around the world also observed the event, including the NASA/ESA Hubble Space Telescope.

    Distance estimates from both the gravitational wave data and other observations agree that GW170817 was at the same distance as NGC 4993, about 130 million light-years from Earth. This makes the source both the closest gravitational wave event detected so far and also one of the closest gamma-ray burst sources ever seen [4].

    The ripples in spacetime known as gravitational waves are created by moving masses, but only the most intense, created by rapid changes in the speed of very massive objects, can currently be detected. One such event is the merging of neutron stars, the extremely dense, collapsed cores of high-mass stars left behind after supernovae [5]. These mergers have so far been the leading hypothesis to explain short gamma-ray bursts. An explosive event 1000 times brighter than a typical nova — known as a kilonova — is expected to follow this type of event.

    The almost simultaneous detections of both gravitational waves and gamma rays from GW170817 raised hopes that this object was indeed a long-sought kilonova and observations with ESO facilities have revealed properties remarkably close to theoretical predictions. Kilonovae were suggested more than 30 years ago but this marks the first confirmed observation.

    Following the merger of the two neutron stars, a burst of rapidly expanding radioactive heavy chemical elements left the kilonova, moving as fast as one-fifth of the speed of light. The colour of the kilonova shifted from very blue to very red over the next few days, a faster change than that seen in any other observed stellar explosion.

    “When the spectrum appeared on our screens I realised that this was the most unusual transient event I’d ever seen,” remarked Stephen Smartt, who led observations with ESO’s NTT as part of the extended Public ESO Spectroscopic Survey of Transient Objects (ePESSTO) observing programme. “I had never seen anything like it. Our data, along with data from other groups, proved to everyone that this was not a supernova or a foreground variable star, but was something quite remarkable.”

    Spectra from ePESSTO and the VLT’s X-shooter instrument suggest the presence of caesium and tellurium ejected from the merging neutron stars. These and other heavy elements, produced during the neutron star merger, would be blown into space by the subsequent kilonova. These observations pin down the formation of elements heavier than iron through nuclear reactions within high-density stellar objects, known as r-process nucleosynthesis, something which was only theorised before.

    “The data we have so far are an amazingly close match to theory. It is a triumph for the theorists, a confirmation that the LIGO–VIRGO events are absolutely real, and an achievement for ESO to have gathered such an astonishing data set on the kilonova,” adds Stefano Covino, lead author of one of the Nature Astronomy papers.

    “ESO’s great strength is that it has a wide range of telescopes and instruments to tackle big and complex astronomical projects, and at short notice. We have entered a new era of multi-messenger astronomy!” concludes Andrew Levan, lead author of one of the papers.
    Notes

    [1] The LIGO–Virgo detection localised the source to an area on the sky of about 35 square degrees.

    [2 The galaxy was only observable in the evening in August and then was too close to the Sun in the sky to be observed by September.

    [3] On the VLT, observations were taken with: the X-shooter spectrograph located on Unit Telescope 2 (UT2); the FOcal Reducer and low dispersion Spectrograph 2 (FORS2) and Nasmyth Adaptive Optics System (NAOS) – Near-Infrared Imager and Spectrograph (CONICA) (NACO) on Unit Telescope 1 (UT1); VIsible Multi-Object Spectrograph (VIMOS) and VLT Imager and Spectrometer for mid-Infrared (VISIR) located on Unit Telescope 3 (UT3); and the Multi Unit Spectroscopic Explorer (MUSE) and High Acuity Wide-field K-band Imager (HAWK-I) on Unit Telescope 4 (UT4). The VST observed using the OmegaCAM and VISTA observed with the VISTA InfraRed CAMera (VIRCAM). Through the ePESSTO programme, the NTT collected visible spectra with the ESO Faint Object Spectrograph and Camera 2 (EFOSC2) spectrograph and infrared spectra with the Son of ISAAC (SOFI) spectrograph. The MPG/ESO 2.2-metre telescope observed using the Gamma-Ray burst Optical/Near-infrared Detector (GROND) instrument.

    [4] The comparatively small distance between Earth and the neutron star merger, 130 million light-years, made the observations possible, since merging neutron stars create weaker gravitational waves than merging black holes, which were the likely case of the first four gravitational wave detections.

    [5] When neutron stars orbit one another in a binary system, they lose energy by emitting gravitational waves. They get closer together until, when they finally meet, some of the mass of the stellar remnants is converted into energy in a violent burst of gravitational waves, as described by Einstein’s famous equation E=mc2.
    More information

    This research was presented in a series of papers to appear in Nature, Nature Astronomy and The Astrophysical Journal Letters.

    [see https://sciencesprings.wordpress.com/2017/10/16/from-hubble-nasa-missions-catch-first-light-from-a-gravitational-wave-event/ for science papers.]

    The extensive list of team members is available in this PDF file

    See the full article here .

    Please help promote STEM in your local schools.
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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

     
  • richardmitnick 11:33 am on October 16, 2017 Permalink | Reply
    Tags: , , , , , , , , Virgo collaboration   

    From LBNL: “Scientists Decode the Origin of Universe’s Heavy Elements in the Light from a Neutron Star Merger” 

    Berkeley Logo

    Berkeley Lab

    October 16, 2017
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    2
    When Neutron Stars Collide: (Credit: Caltech)

    Sometimes – even in matters of science – you have to be lucky.

    On Aug. 17, scientists around the globe were treated to near-simultaneous observations by separate instruments: One set of Earth-based detectors measured the signature of a cataclysmic event sending ripples through the fabric of space-time, and a space-based detector measured the gamma-ray signature of a high-energy outburst emanating from the same region of the sky.

    These parallel detections led astronomers and astrophysicists on an all-out hunt for more detailed measurements explaining this confluence of signals, which would ultimately be confirmed as the first measurement of the merger of two neutron stars and its explosive aftermath.

    Just a week earlier, Daniel Kasen, a scientist in the Nuclear Science Division at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and an associate professor of physics and astronomy at UC Berkeley was attending a science conference in Seattle.

    A hypothetical question was posed to attendees as to when would astronomers detect an astrophysical source that produced both a strong disruption in the space-time continuum – in the form of gravitational waves – and see an associated burst of light.

    2
    This image, from a simulation showing the formation of a cocoon-like release in the merger of two neutron stars, illustrates energy density nine seconds after the merger, with higher density shown in yellower shades. (Caltech)

    The likely target would be the violent merger of a neutron star, which is the ultradense remnant of an exploded star, with another neutron star or a black hole. Such events have been theorized to seed the universe with heavy elements like gold, platinum, and radioactive elements like uranium.

    Most scientists in the room expected that, based on the planned sensitivity of future instruments, and the presumed rarity of neutron star mergers, such a historic discovery might – with some luck – be more than a decade away.

    So Kasen, who had been working for years on models and simulations to help understand the likely signals from merging neutron stars, was stunned when data on a neutron star merger and its aftermath began to pour in just a week later.

    “It seemed too good to be true,” said Kasen. “Not only had they detected gravitational waves, but from a neutron star merger that was so close, it was practically in our backyard. Almost everybody on Earth with a telescope started pointing at the same part of the sky.”

    LIGO and VIRGO – a network of Earth-based gravitational wave detectors capable of observing some of the universe’s most violent events by detecting ever-so-slight changes in laser-measured distances caused by passing gravitational waves – had picked up an event.


    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

    1
    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)

    A couple of seconds later, a brief burst of gamma rays were detected by an instrument aboard the Fermi Gamma-ray Space Telescope. Less than 12 hours after that, astronomers spotted the first glimpse of visible light from the event.

    When Kasen saw the email alerts rolling in about the various observations, he couldn’t help but feel a sense of unease. “For years we had been studying what colliding neutron stars would look like, with nothing to go on but our theoretical imagination and computer modeling,” he said. “Now, real data was flooding in, and it was going to test everything we had predicted.”

    Over the following days and weeks, an influx of observations provided data confirming that the brilliant burst behaved remarkably like the theorized merger of two neutron stars.

    Computer simulations had suggested that, during such a merger, a small fraction of neutron star matter would be flung into surrounding space. Models predicted that this cloud of exotic debris would assemble into heavy elements and give off a radioactive glow over 10 million times brighter than the sun. The phenomenon is called a kilonova or macronova.

    3
    An animation for a model of a kilonova associated with a neutron star merger (right), showing fast effects in blue and slower effects in red, and associated graph that shows how the model matches with data from the observed kilonova. (Credit: Daniel Kasen/Berkeley Lab, UC Berkeley)

    Jennifer Barnes, an Einstein postdoctoral fellow at Columbia University, who as a UC Berkeley graduate student worked with Kasen to compute some of the first detailed model predictions of kilonovae, said, “We expected from theory and simulations that kilonovae would be tinged red if heavy elements were produced, and would shine blue if they weren’t.

    She added, “Understanding this relationship allowed us to more confidently interpret the emission from this event and diagnose the presence of heavy elements in the merger debris.”

    Kasen, Barnes, and two other Berkeley Lab scientists were among the co-authors of several papers published today in the journals Nature, Science, and The Astrophysical Journal. The publications detailed the discovery, follow-up observations, and theoretical interpretation of this event.

    See https://sciencesprings.wordpress.com/2017/10/16/from-hubble-nasa-missions-catch-first-light-from-a-gravitational-wave-event/ for science papers.

    Simulations related to the event were carried out at the Lab’s National Energy Research Scientific Computing Center (NERSC).

    NERSC Cray Cori II supercomputer

    LBL NERSC Cray XC30 Edison supercomputer

    NERSC Hopper Cray XE6 supercomputer

    Peter Nugent, a senior staff scientist in the Computational Research Division at Berkeley Lab and an adjunct professor of astronomy at UC Berkeley, also closely followed the alerts related to the Aug. 17 observations.

    At the time, he was assisting with the final preparations for the startup of the Zwicky Transient Facility (ZTF) at the Palomar Observatory in Southern California. Berkeley Lab is a member of the collaboration for ZTF, which is designed to discover supernovae and also to search for rare and exotic events such as those that occur during the aftermath of neutron star mergers.

    5
    The arrow in the left image points to light associated with matter expelled from a neutron star merger, as recorded by the Dark Energy Camera. (Credit: DECam/DES Collaboration)

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    “This event happened too early by three months,” Nugent said, as the soon-to-launch ZTF is designed to quickly follow up on LIGO/VIRGO gravitational wave measurements to look for their visible counterparts in the sky.

    Nugent said that, at first, he thought that the multiple observations of the object (known as an optical transient) associated with the neutron star merger and gamma-ray burst was just a common supernova. But the object was evolving too quickly and had an incredibly blue light signature that pointed to a different type of event than the supernovae normally associated with the type of galaxy hosting this event.

    Also, Nugent said, “We didn’t expect an event this close. It’s almost akin to having a supernova blow up in Andromeda,” which is about 2.5 million light years away from our Milky Way galaxy. “We hope this means there are going to be more of these events. We now know the rate is not zero.”

    Nugent contributed to an analysis in one of the papers in the journal Science that concludes there may be “many more events” like the observed merger, and that neutron star mergers are likely “the main production sites” for heavy elements in the Milky Way. The observation could also provide valuable clues about how scientists might look for other neutron star mergers in optical surveys without a LIGO/VIRGO detection.

    “How the heaviest elements came to be has been one of the longest standing questions of our cosmic origins,” Kasen said. “Now we have for the first time directly witnessed a cloud of freshly made precious metals right at their production site.”

    The debris cloud from the merger mushroomed from about the size of a city shortly after the merger to about the size of a solar system after only one day, Kasen said. It is also likely that only a few percent of the matter in the merging neutron stars escaped the central site of the merger; the rest likely collapsed to form a black hole.

    It is expected that the escaping debris will be very long-lived, diffusing across the galaxy over a billion years and enriching stars and planets with the heavy elements like those we find on Earth today.

    “For me, it is the astronomical event of a lifetime,” Kasen said “It’s also an incredible moment for the field of scientific computing. Simulations succeeded in modeling what would happen in an incredibly complex phenomenon like a neutron star merger. Without the models, we all probably all would have been mystified by exactly what we were seeing in the sky.”

    Future advances in computing, and new insights from the Facility for Rare Isotope Beams (FRIB) at Michigan State University on exotic reactions that produce heavy nuclei, should provide even more insight as to how the heavy elements came to be, and the extreme physics of matter and gravity that occurs in mergers.

    Kasen is also the lead investigator on a DOE Exascale Computing Project that is developing high-performance astrophysical simulation codes that will run on the next generation of U.S. supercomputers. He is also a member of a DOE-supported SciDAC (Scientific Discovery through Advanced Computing) collaboration that is using computing to simulate supernovae, neutron star mergers, and related high-energy events.

    “Before these observations, the signals from neutron star mergers were mainly theoretical speculation,” Kasen said. “Now, it has suddenly become a major new field of astrophysics.”

    The National Energy Research Scientific Computing Center is a DOE Office of Science User Facility.

    Berkeley Lab’s contributions to the simulations and observations were supported by the U.S. Department of Energy’s Office of Science.

    View a related UC Berkeley video:

    See the full article here .

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  • richardmitnick 10:46 am on October 16, 2017 Permalink | Reply
    Tags: , , , , , , , , , Virgo collaboration   

    From Hubble: “NASA Missions Catch First Light From a Gravitational-Wave Event” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Oct 16, 2017

    Christine Pulliam
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4366
    cpulliam@stsci.edu

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

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

    Dewayne Washington
    Goddard Space Flight Center, Greenbelt, Maryland
    301-286-0040
    dewayne.a.washington@nasa.gov

    1
    Neutron Star Collision Cooks Up Exotic Elements, Gravitational Waves

    For the first time, NASA scientists have detected light tied to a gravitational-wave event, thanks to two merging neutron stars in the galaxy NGC 4993, located about 130 million light-years from Earth in the constellation Hydra.

    Shortly after 8:41 a.m. EDT on Aug. 17, NASA’s Fermi Gamma-ray Space Telescope picked up a pulse of high-energy light from a powerful explosion, which was immediately reported to astronomers around the globe as a short gamma-ray burst.

    NASA/Fermi Telescope

    NASA/Fermi LAT

    The scientists at the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves dubbed GW170817 from a pair of smashing stars tied to the gamma-ray burst, encouraging astronomers to look for the aftermath of the explosion. Shortly thereafter, the burst was detected as part of a follow-up analysis by ESA’s (European Space Agency’s) INTEGRAL satellite.

    ESA/Integral


    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

    1
    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)

    NASA’s Swift, Hubble, Chandra, and Spitzer missions, along with dozens of ground-based observatories, including the NASA-funded PanSTARRS survey, later captured the fading glow of the blast’s expanding debris.

    NASA/Chandra Telescope

    NASA/Spitzer Infrared Telescope

    PanSTARRS telescope, U Hawaii, Mauna Kea, Hawaii, USA

    “This is extremely exciting science,” said Paul Hertz, director of NASA’s Astrophysics Division at the agency’s headquarters in Washington. “Now, for the first time, we’ve seen light and gravitational waves produced by the same event. The detection of a gravitational-wave source’s light has revealed details of the event that cannot be determined from gravitational waves alone. The multiplier effect of study with many observatories is incredible.”

    Neutron stars are the crushed, leftover cores of massive stars that previously exploded as supernovas long ago. The merging stars likely had masses between 10 and 60 percent greater than that of our Sun, but they were no wider than Washington, D.C. The pair whirled around each other hundreds of times a second, producing gravitational waves at the same frequency. As they drew closer and orbited faster, the stars eventually broke apart and merged, producing both a gamma-ray burst and a rarely seen flare-up called a “kilonova.”

    “This is the one we’ve all been waiting for,” said David Reitze, executive director of the LIGO Laboratory at Caltech in Pasadena, California. “Neutron star mergers produce a wide variety of light because the objects form a maelstrom of hot debris when they collide. Merging black holes — the types of events LIGO and its European counterpart, Virgo, have previously seen — very likely consume any matter around them long before they crash, so we don’t expect the same kind of light show.”

    “The favored explanation for short gamma-ray bursts is that they’re caused by a jet of debris moving near the speed of light produced in the merger of neutron stars or a neutron star and a black hole,” said Eric Burns, a member of Fermi’s Gamma-ray Burst Monitor team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “LIGO tells us there was a merger of compact objects, and Fermi tells us there was a short gamma-ray burst. Together, we know that what we observed was the merging of two neutron stars, dramatically confirming the relationship.”

    Within hours of the initial Fermi detection, LIGO and the Virgo detector at the European Gravitational Observatory near Pisa, Italy, greatly refined the event’s position in the sky with additional analysis of gravitational wave data. Ground-based observatories then quickly located a new optical and infrared source — the kilonova — in NGC 4993.

    To Fermi, this appeared to be a typical short gamma-ray burst, but it occurred less than one-tenth as far away as any other short burst with a known distance, making it among the faintest known. Astronomers are still trying to figure out why this burst is so odd, and how this event relates to the more luminous gamma-ray bursts seen at much greater distances.

    NASA’s Swift, Hubble and Spitzer missions followed the evolution of the kilonova to better understand the composition of this slower-moving material, while Chandra searched for X-rays associated with the remains of the ultra-fast jet.

    NASA/SWIFT Telescope

    When Swift turned to the galaxy shortly after Fermi’s gamma-ray burst detection, it found a bright and quickly fading ultraviolet (UV) source.

    “We did not expect a kilonova to produce bright UV emission,” said Goddard’s S. Bradley Cenko, principal investigator for Swift. “We think this was produced by the short-lived disk of debris that powered the gamma-ray burst.”

    Over time, material hurled out by the jet slows and widens as it sweeps up and heats interstellar material, producing so-called afterglow emission that includes X-rays. But the spacecraft saw no X-rays — a surprise for an event that produced higher-energy gamma rays.

    NASA’s Chandra X-ray Observatory clearly detected X-rays nine days after the source was discovered. Scientists think the delay was a result of our viewing angle, and it took time for the jet directed toward Earth to expand into our line of sight.

    “The detection of X-rays demonstrates that neutron star mergers can form powerful jets streaming out at near light speed,” said Goddard’s Eleonora Troja, who led one of the Chandra teams and found the X-ray emission. “We had to wait for nine days to detect it because we viewed it from the side, unlike anything we had seen before.”

    On Aug. 22, NASA’s Hubble Space Telescope began imaging the kilonova and capturing its near-infrared spectrum, which revealed the motion and chemical composition of the expanding debris.

    “The spectrum looked exactly like how theoretical physicists had predicted the outcome of the merger of two neutron stars would appear,” said Andrew Levan at the University of Warwick in Coventry, England, who led one of the proposals for Hubble spectral observations. “It tied this object to the gravitational wave source beyond all reasonable doubt.”

    Astronomers think a kilonova’s visible and infrared light primarily arises through heating from the decay of radioactive elements formed in the neutron-rich debris. Crashing neutron stars may be the universe’s dominant source for many of the heaviest elements, including platinum and gold.

    Because of its Earth-trailing orbit, Spitzer was uniquely situated to observe the kilonova long after the Sun moved too close to the galaxy on the sky for other telescopes to see it. Spitzer’s Sept. 30 observation captured the longest-wavelength infrared light from the kilonova, which unveils the quantity of heavy elements forged.

    “Spitzer was the last to join the party, but it will have the final word on how much gold was forged,” says Mansi Kasliwal, Caltech assistant professor and principal investigator of the Spitzer observing program.

    Numerous scientific papers describing and interpreting these observations have been published in Science, Nature, Physical Review Letters, and The Astrophysical Journal.

    Gravitational waves were directly detected for the first time in 2015 by LIGO, whose architects were awarded the 2017 Nobel Prize in physics for the discovery.

    NASA’s Hubble Studies Source of Gravitational Waves

    On August 17, 2017, weak ripples in the fabric of space-time known as gravitational waves washed over Earth. Unlike previously detected gravitational waves, these were accompanied by light, allowing astronomers to pinpoint the source. NASA’s Hubble Space Telescope turned its powerful gaze onto the new beacon, obtaining both images and spectra. The resulting data will help reveal details of the titanic collision that created the gravitational waves, and its aftermath.

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves at 8:41 a.m. EDT on August 17. Two seconds later, NASA’s Fermi Gamma-ray Space Telescope measured a short pulse of gamma rays known as a gamma-ray burst. Many observatories, including space telescopes, probed the suspected location of the source, and within about 12 hours several spotted their quarry.

    In a distant galaxy called NGC 4993, about 130 million light-years from Earth, a point of light shone where nothing had been before. It was about a thousand times brighter than a variety of stellar flare called a nova, putting it in a class of objects astronomers call “kilonovae.” It also faded noticeably over 6 days of Hubble observations.

    “This appears to be the trifecta for which the astronomical community has been waiting: Gravitational waves, a gamma-ray burst, and a kilonova all happening together,” said Ori Fox of the Space Telescope Science Institute, Baltimore, Maryland.

    The source of all three was the collision of two neutron stars, the aged remains of a binary star system. A neutron star forms when the core of a dying massive star collapses, a process so violent that it crushes protons and electrons together to form subatomic particles called neutrons. The result is like a giant atomic nucleus, cramming several Suns’ worth of material into a ball just a few miles across.

    In NGC 4993, two neutron stars once spiraled around each other at blinding speed. As they drew closer together, they whirled even faster, spinning as fast as a blender near the end. Powerful tidal forces ripped off huge chunks while the remainder collided and merged, forming a larger neutron star or perhaps a black hole. Leftovers spewed out into space. Freed from the crushing pressure, neutrons turned back into protons and electrons, forming a variety of chemical elements heavier than iron.

    “We think neutron star collisions are a source of all kinds of heavy elements, from the gold in our jewelry to the plutonium that powers spacecraft, power plants, and bombs,” said Andy Fruchter of the Space Telescope Science Institute.

    Several teams of scientists are using Hubble’s suite of cameras and spectrographs to study the gravitational wave source. Fruchter, Fox, and their colleagues used Hubble to obtain a spectrum of the object in infrared light. By splitting the light of the source into a rainbow spectrum, astronomers can probe the chemical elements that are present. The spectrum showed several broad bumps and wiggles that signal the formation of some of the heaviest elements in nature.

    “The spectrum looked exactly like how theoretical physicists had predicted the outcome of the merger of two neutron stars would appear. It tied this object to the gravitational wave source beyond all reasonable doubt,” said Andrew Levan at the University of Warwick in Coventry, England, who led one of the proposals for Hubble spectral observations. Additional spectral observations were led by Nial Tanvir of the University of Leicester, England.

    Spectral lines can be used as fingerprints to identify individual elements. However, this spectrum is proving a challenge to interpret.

    “Beyond the fact that two neutron stars flung a lot of matter out into space, we’re not yet sure what else the spectrum is telling us,” explained Fruchter. “Because the material is moving so fast, the spectral lines are smeared out. Also, there are all kinds of unusual isotopes, many of which are short-lived and undergo radioactive decay. The good news is that it’s an exquisite spectrum, so we have a lot of data to work with and analyze.”

    Hubble also picked up visible light from the event that gradually faded over the course of several days. Astronomers believe that this light came from a powerful “wind” of material speeding outward. These observations hint that astronomers viewed the collision from above the orbital plane of the neutron stars. If seen from the side (along the orbital plane), matter ejected during the merger would have obscured the visible light and only infrared light would be visible.

    “What we see from a kilonova might depend on our viewing angle. The same type of event would appear different depending on whether we’re looking at it face-on or edge-on, which came as a total surprise to us,” said Eleonora Troja of the University of Maryland, College Park, Maryland, and NASA’s Goddard Space Flight Center, Greenbelt, Maryland. Troja is also a principal investigator of a team using Hubble observations to study the object.

    The gravitational wave source now is too close to the Sun on the sky for Hubble and other observatories to study. It will come back into view in November. Until then, astronomers will be working diligently to learn all they can about this unique event.

    The launch of NASA’s James Webb Space Telescope also will offer an opportunity to examine the infrared light from the source, should that glow remain detectable in the months and years to come.

    NASA/ESA/CSA Webb Telescope annotated

    Related Links
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    The science paper by N.R. Tanvir et al. (Astrophysical Journal Letters)
    The science paper by A.J. Levan et al. (Astrophysical Journal Letters)
    NASA’s Hubble Portal
    NASA’s Fermi Portal
    NASA’s Swift Portal
    NASA’s Chandra Portal
    NASA’s Spitzer Portal
    LIGO Scientific Collaboration
    European Gravitational Observatory
    Hubble Europe’s Press Release
    The science paper by E. Troja et al (Nature)

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 10:13 am on October 16, 2017 Permalink | Reply
    Tags: , , , , , , Neutron-Star Merger Detected By Many Eyes and Ears, Virgo collaboration, What We Saw (and Didn’t See)   

    From AAS NOVA: “Neutron-Star Merger Detected By Many Eyes and Ears” 

    AASNOVA

    AAS NOVA

    16 October 2017
    Susanna Kohler

    1
    LIGO has officially detected gravitational waves from what appears to be a merger of two neutron stars — and electromagnetic counterparts have been found! [NSF/LIGO/Sonoma State University/A. Simonnet]

    Where were you on Thursday, 17 August 2017? I was in Idaho, getting ready for Monday morning’s solar eclipse. What I didn’t know was that, at the time, around 70 teams around the world were mobilizing to point their ground- and space-based telescopes at a single patch of sky suspected to host the first gravitational-wave-detected merger of two neutron stars.

    Sudden Leaps for Science

    2
    The masses for black holes detected through electromagnetic observations (purple), black holes measured by gravitational-wave observations (blue), neutron stars measured with electromagnetic observations (yellow), and the neutron stars that merged in GW170817 (orange). [LIGO-Virgo/Frank Elavsky/Northwestern University]

    The process of science is long and arduous, generally occurring at a slow plod as theorists make predictions, and observations are then used to chip away at these theories, gradually confirming or disproving them. It is rare that science progresses forward in a giant leap, with years upon years of theories confirmed in one fell swoop.

    14 September 2015 marked the day of one such leap, as the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves for the first time — simultaneously verifying that black holes exist, that black-hole binaries exist, and that they can merge on observable timescales, emitting signals that directly confirm the predictions of general relativity.

    As it turns out, 17 August 2017 was another such day. On this day, LIGO observed a gravitational-wave signal unlike its previous black-hole detections. Instead, this was a signal consistent with the merger of two neutron stars.

    4
    Artist’s illustrations of the stellar-merger model for short gamma-ray bursts. In the model, 1) two neutron stars inspiral, 2) they merge and produce a gamma-ray burst, 3) a small fraction of their mass is flung out and radiates as a kilonova, 4) a massive neutron star or black hole with a disk remains after the event. [NASA, ESA, and A. Feild (STScI)]

    What We Predicted

    Theoretical models describing the merger of two compact objects predict a chirping gravitational-wave signal as the objects spiral closer and closer. Unlike in a black-hole merger, however, the end of the chirp from merging neutron stars should coincide with a phenomenon known as a short gamma-ray burst: a powerful storm of energetic gamma rays produced as the objects finally collide.

    According to the models, these gravitational waves and gamma rays will be followed by a kilonova — a transient source visible in infrared, optical, and ultraviolet — which arises from radioactive decay of heavy elements formed in the collision. This source should gradually decay over a timescale of weeks.

    Lastly, the merger could create a powerful jet of high-energy particles, which could be visible to us in X-ray and radio wavelengths as it is emitted and interacts with its surrounding environment. We could also detect neutrinos from this outflow.

    What We Saw (and Didn’t See)

    3
    The localization of the gravitational-wave, gamma-ray, and optical signals of the neutron-star merger detected on 17 August, 2017. [Abbott et al. 2017]

    So what did we see on 17 August, 2017 and thereafter? Here’s what was found by the army of collaborations searching in gravitational waves, electromagnetic signals across the spectrum, and neutrinos:

    Gravitational Waves
    The gravitational-wave signature of a binary neutron-star merger was observed with all three gravitational-wave detectors currently operating as a part of the LIGO-Virgo collaboration. GW170817’s signal was in the sensitivity band of these detectors for ~100 seconds, arriving first at the Virgo detector in Italy, next at LIGO-Livingston in Louisiana 22 milliseconds later, and finally at LIGO-Hanford in Washington 3 milliseconds after that. These detections localized the source to a region of 31 square degrees at a relatively nearby distance of ~130 million light-years, and they identified the binary components to be neutron stars.

    Gamma-Ray Burst
    The Fermi Gamma-Ray Burst Monitor detected a short (~2-second) gamma-ray burst, GRB170817A, which appears to have occurred 1.7 seconds after the merger indicated by the gravitational-wave signal. This source was later identified by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) spacecraft as well.

    5
    Locations of the many observatories that observed the neutron-star merger first detected on 17 August, 2017. [Abbott et al. 2017]

    Electromagnetic Counterpart and Host Galaxy
    Though they were initially foiled by the signal’s location (the localized region of GW170817 only became visible in Chile 10 hours after its detection), the One-Meter, Two-Hemisphere team used the Swope telescope at Las Campanas Observatory in Chile to discover an optical counterpart to the LIGO and Fermi detection, located in the early-type galaxy NGC 4993. Within an hour, five other teams had independently detected the optical source in NGC 4993, with more following after.

    In the subsequent hours, days, and weeks, observatories across the electromagnetic spectrum monitored the transient. The source soon faded from view in the ultraviolet and gradually reddened in the optical and infrared bands. Delayed X-ray emission was discovered ~9 days after the LIGO signal, and a radio counterpart was discovered a week after that.

    No Neutrinos
    Though several neutrino observatories searched for high-energy neutrinos in the direction of NGC 4993 in the two-week period following the merger, none were detected.

    6
    Summary and timeline of the observations of the neutron-star merger detected on 17 August, 2017 relative to the time tc of the gravitational-wave event. Click for a closer look. [Abbott et al. 2017]

    A Spectacular Confirmation

    So what do these observations tell us? Our model for neutron-star mergers appears to be remarkably successful! The associated detections of gravitational waves and electromagnetic counterparts have confirmed that merging neutron stars produce the expected gravitational-wave signal, that they are the source of gamma-ray bursts, that some of the heaviest elements in the universe are produced during the collision of these stars, and that jets of high-energy particles are created that subsequently interact with their environment.

    As with any interesting scientific discovery, new points of exploration have arisen — we can now wonder why the gamma-ray burst was unusually weak given its close distance, for instance, or why we didn’t detect any neutrinos from the outflow.

    In spite of our new questions, the combination of these recent discoveries provide a resounding verification of our understanding of how compact objects merge. The various signals that began on 17 August, 2017 have simultaneously confirmed a stack of carefully constructed theories that were crafted over decades to explain how seemingly unrelated electromagnetic signals might all tie together. It’s a beautiful thing when science works out this well!

    For more information, check out the ApJL Focus Issue on this result here:
    Focus on The Electromagnetic Counterpart of the Neutron Star Binary Merger GW170817

    Citation

    Abbott, B.P. et al 2017 ApJL 848 L12. doi:10.3847/2041-8213/aa91c9

    See the full article here .

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    STEM Icon

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    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
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