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  • richardmitnick 2:59 pm on December 3, 2018 Permalink | Reply
    Tags: Caltech/MIT Advanced aLigo, , LIGO and Virgo Announce Four New Detections,   

    From MIT Caltech Advanced aLIGO: “LIGO and Virgo Announce Four New Detections” 

    From MIT Caltech Advanced aLIGO

    Valerio Boschi
    
Virgo-EGO Communication Office
    valerio.boschi@ego-gw.it;
    +39 050 752 463

    Antonella Varaschin
    
INFN Communications Office
    antonella.varaschin@presid.infn.it;
    +39 06 68400360

    Kimberly Allen

    Director of Media Relations and Deputy Director, MIT News Office
    allenkc@mit.edu;
    +1 617-253-2702

    Whitney Clavin

    Senior Content and Media Strategist
    Caltech Communications
    wclavin@caltech.edu;
    +1 626-395-1856

    John Toon

    Institute Research and Economic Development Communications
    Georgia Institute of Technology

    john.toon@comm.gatech.edu;
    +1 404-894-6986

    Amanda Hallberg Greenwell
    
Head, Office of Legislative and Public Affairs
    National Science Foundation
    agreenwe@nsf.gov;
    +1 703-292-8070

    1
    LIGO-Virgo/Frank Elavsky/Northwestern

    The observatories are also releasing their first catalog of gravitational-wave events.

    On Saturday, December 1, scientists attending the Gravitational Wave Physics and Astronomy Workshop in College Park, Maryland, presented new results from the National Science Foundation’s LIGO (Laser Interferometer Gravitational-Wave Observatory) and the European- based VIRGO gravitational-wave detector regarding their searches for coalescing cosmic objects, such as pairs of black holes and pairs of neutron stars. The LIGO and Virgo collaborations have now confidently detected gravitational waves from a total of 10 stellar-mass binary black hole mergers and one merger of neutron stars, which are the dense, spherical remains of stellar explosions. Six of the black hole merger events had been reported before, while four are newly announced.

    From September 12, 2015, to January 19, 2016, during the first LIGO observing run since undergoing upgrades in a program called Advanced LIGO, gravitational waves from three binary black hole mergers were detected. The second observing run, which lasted from November 30, 2016, to August 25, 2017, yielded one binary neutron star merger and seven additional binary black hole mergers, including the four new gravitational-wave events being reported now. The new events are known as GW170729, GW170809, GW170818, and GW170823, in reference to the dates they were detected.

    All of the events are included in a new catalog, also released Saturday, with some of the events breaking records. For instance, the new event GW170729, detected in the second observing run on July 29, 2017, is the most massive and distant gravitational-wave source ever observed. In this coalescence, which happened roughly 5 billion years ago, an equivalent energy of almost five solar masses was converted into gravitational radiation.

    GW170814 was the first binary black hole merger measured by the three-detector network, and allowed for the first tests of gravitational-wave polarization (analogous to light polarization).

    The event GW170817, detected three days after GW170814, represented the first time that gravitational waves were ever observed from the merger of a binary neutron star system. What’s more, this collision was seen in gravitational waves and light, marking an exciting new chapter in multi-messenger astronomy, in which cosmic objects are observed simultaneously in different forms of radiation.

    One of the new events, GW170818, which was detected by the global network formed by the LIGO and Virgo observatories, was very precisely pinpointed in the sky. The position of the binary black holes, located 2.5 billion light-years from Earth, was identified in the sky with a precision of 39 square degrees. That makes it the next best localized gravitational-wave source after the GW170817 neutron star merger.

    Caltech’s Albert Lazzarini, Deputy Director of the LIGO Laboratory, says “The release of four additional binary black hole mergers further informs us of the nature of the population of these binary systems in the universe and better constrains the event rate for these types of events.”

    “In just one year, LIGO and VIRGO working together have dramatically advanced gravitational- wave science, and the rate of discovery suggests the most spectacular findings are yet to come,” says Denise Caldwell, Director of NSF’s Division of Physics. “The accomplishments of NSF’s LIGO and its international partners are a source of pride for the agency, and we expect even greater advances as LIGO’s sensitivity becomes better and better in the coming year.”

    “The next observing run, starting in Spring 2019, should yield many more gravitational-wave candidates, and the science the community can accomplish will grow accordingly,” says David Shoemaker, spokesperson for the LIGO Scientific Collaboration and senior research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “It’s an incredibly exciting time.”

    “It is gratifying to see the new capabilities that become available through the addition of Advanced Virgo to the global network,” says Jo van den Brand of Nikhef (the Dutch National Institute for Subatomic Physics) and VU University Amsterdam, who is the spokesperson for the Virgo Collaboration. “Our greatly improved pointing precision will allow astronomers to rapidly find any other cosmic messengers emitted by the gravitational-wave sources.” The enhanced pointing capability of the LIGO-Virgo network is made possible by exploiting the time delays of the signal arrival at the different sites and the so-called antenna patterns of the interferometers.

    “The new catalog is another proof of the exemplary international collaboration of the gravitational wave community and an asset for the forthcoming runs and upgrades”, adds EGO Director Stavros Katsanevas.

    The scientific papers describing these new findings, which are being initially published on the arXiv repository of electronic preprints, present detailed information in the form of a catalog of all the gravitational wave detections and candidate events of the two observing runs as well as describing the characteristics of the merging black hole population. Most notably, we find that almost all black holes formed from stars are lighter than 45 times the mass of the Sun. Thanks to more advanced data processing and better calibration of the instruments, the accuracy of the astrophysical parameters of the previously announced events increased considerably.

    Laura Cadonati, Deputy Spokesperson for the LIGO Scientific Collaboration, says “These new discoveries were only made possible through the tireless and carefully coordinated work of the detector commissioners at all three observatories, and the scientists around the world responsible for data quality and cleaning, searching for buried signals, and parameter estimation for each candidate — each a scientific specialty requiring enormous expertise and experience.”

    Related Links

    Paper: “GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs

    Paper: “Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo

    The Collaborations

    LIGO is funded by NSF and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant commitments and contributions to the project. More than 1,200 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. A list of additional partners is available at https://my.ligo.org/census.php.

    The Virgo collaboration consists of more than 300 physicists and engineers belonging to 28 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; 11 from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with IFAE and the Universities of Valencia and Barcelona; two in Belgium with the Universities of Liege and Louvain; Jena University in Germany; and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef. A list of the Virgo Collaboration can be found at http://public.virgo-gw.eu/the-virgo-collaboration/. More information is available on the Virgo website at http://www.virgo-gw.eu.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition


    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

    ESA/eLISA the future of gravitational wave research

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

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  • richardmitnick 1:44 pm on November 10, 2018 Permalink | Reply
    Tags: A pair of inspiraling neutron stars, A possible scenario would be a neutrino created in the relativistic outflows of a merger of binary neutron stars or black holes or the core-collapse of a supernova all cataclysmic cosmic environments , , , , , Caltech/MIT Advanced aLigo, , , , , , The detection of gravitational waves and neutrinos from a single source would set a new milestone in multimessenger astronomy, The scrutiny of an astrophysical source with three different messengers would not only be the next breakthrough in the field but would also confirm that multimessenger astronomy is the only path to a ,   

    From U Wisconsin IceCube Collaboration: “Multimessenger searches for sources of gravitational waves and neutrinos” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    From From U Wisconsin IceCube Collaboration

    09 Nov 2018
    Sílvia Bravo

    1
    Artist’s now iconic illustration of two merging neutron stars. The rippling space-time grid represents gravitational waves that travel out from the collision, while the narrow beams show the bursts of gamma rays and neutrinos that are shot out just seconds after the gravitational waves. Image: NSF/LIGO/Sonoma State University/A. Simonnet

    Last year was an extraordinary year for multimessenger astrophysics. In August 2017, a gravitational wave and its electromagnetic counterpart emission were detected from a pair of inspiraling neutron stars. Only a month later, a high-energy neutrino was detected at the South Pole and electromagnetic follow-up observations helped identify the first likely source of very high energy neutrinos and cosmic rays.

    Since then, the dream of astrophysicists has been to join neutrinos and gravitational waves in the detection of a multimessenger source. According to our understanding of the extreme universe, a possible scenario would be a neutrino created in the relativistic outflows of a merger of binary neutron stars or black holes or the core-collapse of a supernova, all cataclysmic cosmic environments that should also produce gravitational waves.

    The IceCube, LIGO, Virgo, and ANTARES collaborations have used data from the first observing period of Advanced LIGO and from the two neutrino detectors to search for coincident neutrino and gravitational wave emission from transient sources.

    The goal was to explore the discovery potential of a multimessenger observation, i.e., of a source detection that needs both messengers to confirm its astrophysical origin. Scientists did not find any significant coincidence. The results, recently submitted to The Astrophysical Journal, set a constraint on the density of these sources.

    The detection of gravitational waves and neutrinos from a single source would set a new milestone in multimessenger astronomy, allowing the simultaneous study of the inner and outer processes powering high-energy emission from astrophysical objects.

    A joint detection would also significantly improve the localization of the source and enable faster and more precise electromagnetic follow-up observations. The scrutiny of an astrophysical source with three different messengers would not only be the next breakthrough in the field but would also confirm that multimessenger astronomy is the only path to a profound understanding of the extreme universe.

    Even though the current search was very limited in time, researchers have set a strong constraint for joint emission from core-collapse supernovas, while binary mergers remain secure as potential multimessenger sources of gravitational waves and high-energy neutrinos.

    This study used datasets, spanning less than 2.5 months, that are also limited by LIGO’s sensitivity, which will soon improve by a factor of 2. The addition of new LIGO and Virgo data as well as from IceCube and ANTARES will greatly increase the sensitivity of joint searches. In the longer term, future next-generation neutrino and gravitational wave detectors will boost the potential of discovery for these searches.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 3:46 pm on October 30, 2018 Permalink | Reply
    Tags: , Caltech/MIT Advanced aLigo, Dame Susan Jocelyn Bell Burnell and pulsars, , , , , , Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics, S0-2, , , Vera Rubin and Dark Matter   

    From The New York Times: “Trolling the Monster in the Heart of the Milky Way” 

    New York Times

    From The New York Times

    Oct. 30, 2018
    Dennis Overbye

    In a dark, dusty patch of sky in the constellation Sagittarius, a small star, known as S2 or, sometimes, S0-2, cruises on the edge of eternity. Every 16 years, it passes within a cosmic whisker of a mysterious dark object that weighs some 4 million suns, and that occupies the exact center of the Milky Way galaxy.

    Star S0-2 Keck/UCLA Galactic Center Group

    For the last two decades, two rival teams of astronomers, looking to test some of Albert Einstein’s weirdest predictions about the universe, have aimed their telescopes at the star, which lies 26,000 light-years away. In the process, they hope to confirm the existence of what astronomers strongly suspect lies just beyond: a monstrous black hole, an eater of stars and shaper of galaxies.

    For several months this year, the star streaked through its closest approach to the galactic center, producing new insights into the behavior of gravity in extreme environments, and offering clues to the nature of the invisible beast in the Milky Way’s basement.

    One of those teams, an international collaboration based in Germany and Chile, and led by Reinhard Genzel, of the Max Planck Institute for Extraterrestrial Physics, say they have found the strongest evidence yet that the dark entity is a supermassive black hole, the bottomless grave of 4.14 million suns.

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo

    ESO VLT 4 lasers on Yepun

    The evidence comes in the form of knots of gas that appear to orbit the galactic center. Dr. Genzel’s team found that the gas clouds circle every 45 minutes or so, completing a circuit of 150 million miles at roughly 30 percent of the speed of light. They are so close to the alleged black hole that if they were any closer they would fall in, according to classical Einsteinian physics.

    Astrophysicists can’t imagine anything but a black hole that could be so massive, yet fit within such a tiny orbit.

    The results provide “strong support” that the dark thing in Sagittarius “is indeed a massive black hole,” Dr. Genzel’s group writes in a paper that will be published on Wednesday under the name of Gravity Collaboration, in the European journal Astronomy & Astrophysics.

    “This is the closest yet we have come to see the immediate zone around a supermassive black hole with direct, spatially resolved techniques,” Dr. Genzel said in an email.

    1
    Reinhard Genzel runs the Max Planck Institute for Extraterrestrial Physics in Munich. He has been watching S2, in the constellation Sagittarius, hoping it will help confirm the existence of a supermassive black hole.Credit Ksenia Kuleshova for The New York Times.

    The work goes a long way toward demonstrating what astronomers have long believed, but are still at pains to prove rigorously: that a supermassive black hole lurks in the heart not only of the Milky Way, but of many observable galaxies. The hub of the stellar carousel is a place where space and time end, and into which stars can disappear forever.

    The new data also help to explain how such black holes can wreak havoc of a kind that is visible from across the universe. Astronomers have long observed spectacular quasars and violent jets of energy, thousands of light-years long, erupting from the centers of galaxies.

    Roger Blandford, the director of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, said that there is now overwhelming evidence that supermassive black holes are powering such phenomena.

    “There is now a large burden of proof on claims to the contrary,” he wrote in an email. “The big questions involve figuring out how they work, including disk and jets. It’s a bit like knowing that the sun is a hot, gaseous sphere and trying to understand how the nuclear reactions work.”

    2
    Images of different galaxies — some of which have evocative names like the Black Eye Galaxy, bottom left, or the Sombrero Galaxy, second left — adorn a wall at the Max Planck Institute.Credit Ksenia Kuleshova for The New York Times.

    Sheperd Doeleman, a radio astronomer at the Harvard-Smithsonian Center for Astrophysics, called the work “a tour de force.” Dr. Doeleman studies the galactic center and hopes to produce an actual image of the black hole, using a planet-size instrument called the Event Horizon Telescope.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Hawaii SAO
    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    NSF CfA Greenland telescope

    Greenland Telescope

    Future Array/Telescopes

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    The study is also a major triumph for the European Southern Observatory, a multinational consortium with headquarters in Munich and observatories in Chile, which had made the study of S2 and the galactic black hole a major priority. The organization’s facilities include the Very Large Telescope [shown above], an array of four giant telescopes in Chile’s Atacama Desert (a futuristic setting featured in the James Bond film “Quantum of Solace”), and the world’s largest telescope, the Extremely Large Telescope, now under construction on a mountain nearby.

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

    Einstein’s bad dream

    Black holes — objects so dense that not even light can escape them — are a surprise consequence of Einstein’s general theory of relativity, which ascribes the phenomenon we call gravity to a warping of the geometry of space and time. When too much matter or energy are concentrated in one place, according to the theory, space-time can jiggle, time can slow and matter can shrink and vanish into those cosmic sinkholes.

    Einstein didn’t like the idea of black holes, but the consensus today is that the universe is speckled with them. Many are the remains of dead stars; others are gigantic, with the masses of millions to billions of suns. Such massive objects seem to anchor the centers of virtually every galaxy, including our own. Presumably they are black holes, but astronomers are eager to know whether these entities fit the prescription given by Einstein’s theory.

    Andrea Ghez, astrophysicist and professor at the University of California, Los Angeles, who leads a team of scientists observing S2 for evidence of a supermassive black hole UCLA Galactic Center Group

    Although general relativity has been the law of the cosmos ever since Einstein devised it, most theorists think it eventually will have to be modified to explain various mysteries, such as what happens at the center of a black hole or at the beginning of time; why galaxies clump together, thanks to unidentified stuff called dark matter; and how, simultaneously, a force called dark energy is pushing these clumps of galaxies apart.

    Women in STEM – Vera Rubin

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin

    Fritz Zwicky from http:// palomarskies.blogspot.com


    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    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 existence of smaller black holes was affirmed two years ago, when the Laser Interferometer Gravitational-Wave Observatory, or LIGO, detected ripples in space-time caused by the collision of a pair of black holes located a billion light-years away.


    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

    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)

    But those black holes were only 20 and 30 times the mass of the sun; how supermassive black holes behave is the subject of much curiosity among astronomers.

    “We already know Einstein’s theory of gravity is fraying around the edges,” said Andrea Ghez, a professor at the University of California, Los Angeles. “What better places to look for discrepancies in it than a supermassive black hole?” Dr. Ghez is the leader of a separate team that, like Dr. Genzel’s, is probing the galactic center. “What I like about the galactic center is that you get to see extreme astrophysics,” she said.

    Despite their name, supermassive black holes are among the most luminous objects in the universe. As matter crashes down into them, stupendous amounts of energy should be released, enough to produce quasars, the faint radio beacons from distant space that have dazzled and baffled astronomers since the early 1960s.

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

    Astronomers have long suspected that something similar could be happening at the center of the Milky Way, which is marked by a dim source of radio noise called Sagittarius A* (pronounced Sagittarius A-star).

    Sgr A* from ESO VLT


    SgrA* NASA/Chandra


    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    But the galactic center is veiled by dust, making it all but invisible to traditional astronomical ways of seeing.

    Seeing in the dark

    Reinhard Genzel grew up in Freiburg, Germany, a small city in the Black Forest. As a young man, he was one of the best javelin throwers in Germany, even training with the national team for the 1972 Munich Olympics. Now he is throwing deeper.

    He became interested in the dark doings of the galactic center back in the 1980s, as a postdoctoral fellow at the University of California, Berkeley, under physicist Charles Townes, a Nobel laureate and an inventor of lasers. “I think of myself as a younger son of his,” Dr. Genzel said in a recent phone conversation.

    In a series of pioneering observations in the early 1980s, using detectors that can see infrared radiation, or heat, through galactic dust, Dr. Townes, Dr. Genzel and their colleagues found that gas clouds were zipping around the center of the Milky Way so fast that the gravitational pull of about 4 million suns would be needed to keep it in orbit. But whatever was there, it emitted no starlight. Even the best telescopes, from 26,000 light years away, could make out no more than a blur.

    3
    An image of the central Milky Way, which contains Sagittarius A*, taken by the VISTA telescope at the E.S.O.’s Paranal Observatory, mounted on a peak just next to the Very Large Telescope.CreditEuropean Southern Observatory/VVV Survey/D. Minniti/Ignacio Toledo, Martin Kornmesser


    Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light.
    Credit: ESO/Y. Beletsky, with an elevation of 2,635 metres (8,645 ft) above sea level

    Two advances since then have helped shed some figurative light on whatever is going on in our galaxy’s core. One was the growing availability in the 1990s of infrared detectors, originally developed for military use. Another was the development of optical techniques that could drastically increase the ability of telescopes to see small details by compensating for atmospheric turbulence. (It’s this turbulence that blurs stars and makes them twinkle.)

    Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT.

    These keen eyes revealed hundreds of stars in the galaxy’s blurry core, all buzzing around in a circle about a tenth of a light year across. One of the stars, which Dr. Genzel calls S2 and Dr. Ghez calls S-02, is a young blue star that follows a very elongated orbit and passes within just 11 billion miles of the mouth of the putative black hole every 16 years.

    During these fraught passages, the star, yanked around an egg-shaped orbit at speeds of up to 5,000 miles per second, should experience the full strangeness of the universe according to Einstein. Intense gravity on the star’s surface should slow the vibration of light waves, stretching them and making the star appear redder than normal from Earth.

    This gravitational redshift, as it is known, was one of the first predictions of Einstein’s theory. The discovery of S2 offered astronomers a chance to observe the phenomenon in the wild — within the grip of gravity gone mad, near a supermassive black hole.

    4
    Left, calculations left out at the Max Planck Institute, viewed from above, right.Credit Ksenia Kuleshova for The New York Times

    In the wheelhouse of the galaxy

    To conduct that experiment, astronomers needed to know the star’s orbit to a high precision, which in turn required two decades of observations with the most powerful telescopes on Earth. “You need twenty years of data just to get a seat at this table,” said Dr. Ghez, who joined the fray in 1995.

    And so, the race into the dark was joined on two different continents. Dr. Ghez worked with the 10-meter Keck telescopes, located on Mauna Kea, on Hawaii’s Big Island.


    Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level, showing also NASA’s IRTF and NAOJ Subaru


    UCO Keck Laser Guide Star Adaptive Optics

    Dr. Genzel’s group benefited from the completion of the European Southern Observatory’s brand new Very Large Telescope [above] array in Chile.

    The European team was aided further by a new device, an interferometer named Gravity, that combined the light from the array’s four telescopes.

    ESO GRAVITY insrument on The VLTI, interferometric instrument operating in the K band, between 2.0 and 2.4 μm. It combines 4 telescope beams and is designed to peform both interferometric imaging and astrometry by phase referencing. Credit: MPE/GRAVITY team

    Designed by a large consortium led by Frank Eisenhauer of the Max Planck Institute, the instrument enabled the telescope array to achieve the resolution of a single mirror 130 meters in diameter. (The name originally was an acronym for a long phrase that included words such as “general,” “relativity,” and “interferometry,” Dr. Eisenhauer explained in an email.)

    “All of the sudden, we can see 1,000 times fainter than before,” said Dr. Genzel in 2016, when the instrument went into operation. In addition, they could track the movements of the star S2 from day to day.

    Meanwhile, Dr. Ghez was analyzing the changing spectra of light from the star, to determine changes in the star’s velocity. The two teams leapfrogged each other, enlisting bigger and more sophisticated telescopes, and nailing down the characteristics of S2. In 2012 Dr. Genzel and Dr. Ghez shared the Crafoord Prize in astronomy, an award nearly as prestigious as the Nobel. Events came to head this spring and summer, during a six-month period when S2 made its closest approach to the black hole.

    “It was exciting in the middle of April when a signal emerged and we started getting information,” Dr. Ghez said.

    On July 26, Dr. Genzel and Dr. Eisenhauer held a news conference in Munich to announce that they had measured the long-sought gravitational redshift. As Dr. Eisenhauer marked off their measurements, which matched a curve of expected results, the room burst into applause.

    “The road is wide open to black hole physics,” Dr. Eisenhauer proclaimed.

    In an email a month later, Dr. Genzel explained that detecting the gravitational redshift was only the first step: “I am usually a fairly sober, and sometimes pessimistic person. But you may sense my excitement as I write these sentences, because of these wonderful results. As a scientist (and I am 66 years old) one rarely if ever has phases this productive. Carpe Diem!”

    In early October, Dr. Ghez, who had waited to observe one more phase of the star’s trip, said her team soon would publish their own results.

    A monster in the basement

    In the meantime, Dr. Genzel was continuing to harvest what he called “this gift from nature.”

    The big break came when his team detected evidence of hot spots, or “flares,” in the tiny blur of heat marking the location of the suspected black hole. A black hole with the mass of 4 million suns should have a mouth, or event horizon, about 16 million miles across — too small for even the Gravity instrument to resolve from Earth.

    The hot spots were also too small to make out. But they rendered the central blur lopsided, with more heat on one side of the blur than the other. As a result, Dr. Genzel’s team saw the center of that blur of energy shift, or wobble, relative to the position of S2, as the hot spot went around it.

    As a result, said Dr. Genzel, “We see a little loop on the sky.” Later he added, “This is the first time we can study these important magnetic structures in a spatially resolved manner just like in a physics laboratory.”

    He speculated that the hot spots might be produced by shock waves in magnetic fields, much as solar flares erupt from the sun. But this might be an overly simplistic model, the authors cautioned in their paper. The effects of relativity turn the neighborhood around the black hole into a hall of mirrors, Dr. Genzel said: “Our statements currently are still fuzzy. We will have to learn better to reconstruct reality once we better understand exactly these mirages.”

    The star has finished its show for this year. Dr. Genzel hopes to gather more data from the star next year, as it orbits more distantly from the black hole. Additional observations in the coming years may clarify the star’s orbit, and perhaps answer other questions, such as whether the black hole was spinning, dragging space-time with it like dough in a mixer.

    But it may be hard for Dr. Genzel to beat what he has already accomplished, he said by email. For now, shrink-wrapping 4 million suns worth of mass into a volume just 45 minutes around was a pretty good feat “for a small boy from the countryside.”

    See the full article here .

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  • richardmitnick 5:44 pm on October 29, 2018 Permalink | Reply
    Tags: , , , Caltech/MIT Advanced aLigo, , ,   

    From COSMOS Magazine: “Signs of mergers may help us prove supermassive black holes exist” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    28 October 2018
    Martin Krause

    Black holes with masses billions of times that of the sun have long been theorised. Now, research takes astronomy closer to proving the contention.

    1
    Visible light image of the radio galaxy Hercules A obtained by the Hubble Space Telescope superposed with a radio image taken by the Very Large Array of radio telescopes in New Mexico, USA. NASA

    NASA/ESA Hubble Telescope

    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)

    Observations of nature tend to throw up unexpected results and new mysteries – whether you’re investigating the rain forest or outer space. When radio astronomy took off in the 1950s, we had no idea that it would lead to the discovery that galaxies including our own seem to have terrifyingly large black holes at their centre – millions to billions of times the mass of the sun.

    A few decades later, we still haven’t been able to prove that these beasts – dubbed supermassive black holes – actually exist. But our new research, published in the Monthly Notices of the Royal Astronomical Society, could one day help us do so.

    Early radio astronomers discovered that some galaxies emit radio waves (a type of electromagnetic radiation). They knew that galaxies sometimes collide and merge, and naturally wondered whether this could have something to do with the radio emission. Better observations, however, refuted this idea over the years.

    They also discovered that the radio waves were emitted as narrow jets, meaning that the power came from a tiny region in the nucleus. The radio power was indeed huge – often surpassing the luminosity of all the stars in the galaxy taken together. Various suggestions were made as to how such a huge amount of energy could be produced, and it was in the 1970s that scientists finally proposed [Astronomy and Astrophysics] that a supermassive black hole could be the culprit. The objects are nowadays known as quasars.

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

    Theoretical models estimated that these objects would have a mass of an entire small galaxy concentrated in a space comparable to Earth’s orbit around the sun. But because only some galaxies produce energetic outbursts, it was unclear how common supermassive black holes would be. With the advent of the Hubble Space Telescope in 1990, the centres of nearby galaxies that did not emit radio bursts could finally be investigated. Did they contain supermassive black holes too?

    It turned out that many did – astronomers saw signs of gravitating masses influencing the matter around it without emitting any light. Even the Milky Way showed evidence of having a supermassive black hole at the centre, now known as Sgr A*.

    Sgr A* from ESO VLT


    SgrA* NASA/Chandra


    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    At this point, astronomers became increasingly convinced that supermassive black holes were a reality and could plausibly explain the extreme energetic outbursts from some galaxies.

    However, there is no definitive proof yet. That is despite the fact that some supermassive black holes emit jets – these come from the surroundings of the black hole rather than the black hole itself. So how do you prove the existence of something completely dark? A black hole as defined by Einstein’s theory of general relativity is a region of space bounded by a horizon – a surface from inside of which no light or material object can ever escape. So, it’s a pretty difficult task for astronomers: they need to see something that emits nothing.

    For smaller black holes the size of a stellar mass, a proof was indeed found: when two such objects merge, they emit gravitational waves, a tiny wobbling of space that was for the first time registered in 2015. The detection proved that black holes exist, that they sometimes form pairs and that they indeed merge. This was a tremendous success, honoured with the Nobel prize in 2017.

    We also have a good understanding of where normal sized black holes come from – they are what is left after a star much more massive than the sun has arrived at the end of its lifetime. But both the existence and the origin of supermassive black holes are shrouded in mystery.

    Spinning black holes

    We have now found indications that many of the radio jets produced by supermassive black holes may in fact be the result of these objects forming pairs, orbiting each other. We did this by comparing the observed radio maps of their regions with our computer models.

    The presence of a second black hole would make the jets produced by the first one change direction in a periodic way over hundreds of thousands of years. We realised that the cyclic change in jet direction would cause a very specific appearance in radio maps of the galaxy centre.

    2
    Lobes are created by the jets depositing energy to surrounding particles. Author provided.

    We found evidence of such a pattern in about 75% of our sample of “radio galaxies” (galaxies that emit radio waves), suggesting that supermassive black hole pairs are the rule, not the exception. Such pairs are actually expected to form after galaxies merge. Each galaxy contains a supermassive black hole, and since they are heavier than all the individual stars, they sink to the centre of the newly formed galaxy where they first form a close pair and then merge under emission of gravitational waves.

    While our observation provides an important piece of evidence for the existence of pairs of supermassive black holes, it’s not a proof either. What we observe are still the effects that the black holes somehow cause indirectly. Just like with normal black holes, a full proof of the existence of supermassive black hole pairs requires detection of gravitational waves emitted by them.

    Current gravitational wave telescopes can only detect gravitational waves from stellar mass black holes.


    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

    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)

    The reason is that they orbit around one another much faster, which leads to the production of higher frequency gravitational waves that we can detect. The next generation of instruments will however be able to register low frequency gravitational waves as well – potentially from supermassive black hole pairs.

    ESA/eLISA the future of gravitational wave research

    This would finally prove their existence – half a century after they were first proposed. It’s an exciting time to be a scientist.

    See the full article here .


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    Please help promote STEM in your local schools.

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  • richardmitnick 3:29 pm on October 26, 2018 Permalink | Reply
    Tags: , , , Caltech/MIT Advanced aLigo, , Gravitational waves could soon provide measure of universe’s expansion, , ,   

    From University of Chicago: “Gravitational waves could soon provide measure of universe’s expansion” 

    U Chicago bloc

    From University of Chicago

    Oct 22, 2018
    Louise Lerner

    1
    Image by Robin Dienel/The Carnegie Institution for Science

    UChicago scientists estimate, based on LIGO’s quick first detection of a first neutron star collision, that they could have an extremely precise measurement of the universe’s rate of expansion within five to ten years. [Too bad for me, I’ll be long gone.]

    Twenty years ago, scientists were shocked to realize that our universe is not only expanding, but that it’s expanding faster over time.

    Pinning down the exact rate of expansion, called the Hubble constant after famed astronomer and UChicago alumnus Edwin Hubble, has been surprisingly difficult. Since then scientists have used two methods to calculate the value, and they spit out distressingly different results. But last year’s surprising capture of gravitational waves radiating from a neutron star collision offered a third way to calculate the Hubble constant.

    Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope, (credit: Emilio Segre Visual Archives/AIP/SPL)

    That was only a single data point from one collision, but in a new paper published Oct. 17 in Nature, three University of Chicago scientists estimate that given how quickly researchers saw the first neutron star collision, they could have a very accurate measurement of the Hubble constant within five to ten years.

    “The Hubble constant tells you the size and the age of the universe; it’s been a holy grail since the birth of cosmology. Calculating this with gravitational waves could give us an entirely new perspective on the universe,” said study author Daniel Holz, a UChicago professor in physics who co-authored the first such calculation from the 2017 discovery. “The question is: When does it become game-changing for cosmology?”

    In 1929, Edwin Hubble announced that based on his observations of galaxies beyond the Milky Way, they seemed to be moving away from us—and the farther away the galaxy, the faster it was receding. This is a cornerstone of the Big Bang theory, and it kicked off a nearly century-long search for the exact rate at which this is occurring.

    To calculate the rate at which the universe is expanding, scientists need two numbers. One is the distance to a faraway object; the other is how fast the object is moving away from us because of the expansion of the universe. If you can see it with a telescope, the second quantity is relatively easy to determine, because the light you see when you look at a distant star gets shifted into the red as it recedes. Astronomers have been using that trick to see how fast an object is moving for more than a century—it’s like the Doppler effect, in which a siren changes pitch as an ambulance passes.

    Major questions in calculations

    But getting an exact measure of the distance is much harder. Traditionally, astrophysicists have used a technique called the cosmic distance ladder, in which the brightness of certain variable stars and supernovae can be used to build a series of comparisons that reach out to the object in question.

    Cosmic Distance Ladder, skynetblogs

    “The problem is, if you scratch beneath the surface, there are a lot of steps with a lot of assumptions along the way,” Holz said.

    Perhaps the supernovae used as markers aren’t as consistent as thought. Maybe we’re mistaking some kinds of supernovae for others, or there’s some unknown error in our measurement of distances to nearby stars. “There’s a lot of complicated astrophysics there that could throw off readings in a number of ways,” he said.

    The other major way to calculate the Hubble constant is to look at the cosmic microwave background [CMB]—the pulse of light created at the very beginning of the universe, which is still faintly detectable.

    CMB per ESA/Planck

    While also useful, this method also relies on assumptions about how the universe works.

    The surprising thing is that even though scientists doing each calculation are confident about their results, they don’t match. One says the universe is expanding almost 10 percent faster than the other. “This is a major question in cosmology right now,” said the study’s first author, Hsin-Yu Chen, then a graduate student at UChicago and now a fellow with Harvard University’s Black Hole Initiative.

    Then the LIGO detectors picked up their first ripple in the fabric of space-time from the collision of two stars last year.


    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

    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 not only shook the observatory, but the field of astronomy itself: Being able to both feel the gravitational wave and see the light of the collision’s aftermath with a telescope gave scientists a powerful new tool. “It was kind of an embarrassment of riches,” Holz said.

    Gravitational waves offer a completely different way to calculate the Hubble constant. When two massive stars crash into each other, they send out ripples in the fabric of space-time that can be detected on Earth. By measuring that signal, scientists can get a signature of the mass and energy of the colliding stars. When they compare this reading with the strength of the gravitational waves, they can infer how far away it is.

    This measurement is cleaner and holds fewer assumptions about the universe, which should make it more precise, Holz said. Along with Scott Hughes at MIT, he suggested the idea of making this measurement with gravitational waves paired with telescope readings in 2005. The only question is how often scientists could catch these events, and how good the data from them would be.

    4
    Illustration by A. Simon
    Unlike previous LIGO detections of black holes merging, the two neutron stars that collided sent out a bright flash of light—making it visible to telescopes on Earth.

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

    ‘It’s only going to get more interesting’

    The paper predicts that once scientists have detected 25 readings from neutron star collisions, they’ll measure the expansion of the universe within an accuracy of 3 percent. With 200 readings, that number narrows to 1 percent.

    “It was quite a surprise for me when we got into the simulations,” Chen said. “It was clear we could reach precision, and we could reach it fast.”

    A precise new number for the Hubble constant would be fascinating no matter the answer, the scientists said. For example, one possible reason for the mismatch in the other two methods is that the nature of gravity itself might have changed over time. The reading also might shed light on dark energy, a mysterious force responsible for the expansion of the universe.

    “With the collision we saw last year, we got lucky—it was close to us, so it was relatively easy to find and analyze,” said Maya Fishbach, a UChicago graduate student and the other author on the paper. “Future detections will be much farther away, but once we get the next generation of telescopes, we should be able to find counterparts for these distant detections as well.”

    The LIGO detectors are planned to begin a new observing run in February 2019, joined by their Italian counterparts at VIRGO. Thanks to an upgrade, the detectors’ sensitivities will be much higher—expanding the number and distance of astronomical events they can pick up.

    “It’s only going to get more interesting from here,” Holz said.

    The authors ran calculations at the University of Chicago Research Computing Center.

    Funding: Kavli Foundation, John Templeton Foundation, National Science Foundation.

    See the full article here .

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    U Chicago Campus

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

    University of Chicago

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

    The University of Chicago is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

    We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with UChicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

    UChicago research has led to such breakthroughs as discovering the link between cancer and genetics, establishing revolutionary theories of economics, and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations with our national and affiliated laboratories: Argonne National Laboratory, Fermi National Accelerator Laboratory, and the Marine Biological Laboratory in Woods Hole, Massachusetts.

    The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

    In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.

     
  • richardmitnick 9:21 pm on October 16, 2018 Permalink | Reply
    Tags: "We have a case of cosmic look-alikes " said co-author Geoffrey Ryan of UMCP-so the simplest explanation is that they are from the same family of objects.", , , , , Caltech/MIT Advanced aLigo, , GW170817 and GRB 150101B, ,   

    From NASA Chandra: All in the Family: Kin of Gravitational-Wave Source Discovered 

    NASA Chandra Banner

    NASA/Chandra Telescope

    From NASA Chandra

    October 16, 2018
    Media contacts:
    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    1
    Credit: X-ray: NASA/CXC/GSFC/UMC/E. Troja et al.; Optical and infrared: NASA/STScI

    NASA/ESA Hubble Telescope

    A source with remarkable similarities to GW170817, the first source identified to emit gravitational waves and light, has been discovered.

    This new object, called GRB 150101B, was first seen as a gamma-ray burst in January 2015.

    Follow-up observations with Chandra and several other telescopes at different wavelengths uncovered common traits between the two objects.

    Chandra images showed how GRB 150101B faded with time, a key piece of information.

    About a year ago, astronomers excitedly reported the first detection of electromagnetic waves, or light, from a gravitational wave source. Now, a year later, researchers are announcing the existence of a cosmic relative to that historic event.

    The discovery was made using data from telescopes including NASA’s Chandra X-ray Observatory, Fermi Gamma-ray Space Telescope, Neil Gehrels Swift Observatory, the NASA Hubble Space Telescope (HST), and the Discovery Channel Telescope (DCT).

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    NASA Neil Gehrels Swift Observatory


    Discovery Channel Telescope at Lowell Observatory, Happy Jack AZ, USA, Altitude 2,360 m (7,740 ft)

    The object of the new study, called GRB 150101B, was first reported as a gamma-ray burst detected by Fermi in January 2015. This detection and follow-up observations at other wavelengths show GRB 150101B shares remarkable similarities to the neutron star merger and gravitational wave source discovered by Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) and its European counterpart Virgo in 2017 known as GW170817. The latest study concludes that these two separate objects may, in fact, be related.


    “It’s a big step to go from one detected object to two,” said Eleonora Troja, lead author of the study from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland at College Park (UMCP). “Our discovery tells us that events like GW170817 and GRB 150101B could represent a whole new class of erupting objects that turn on and off in X-rays and might actually be relatively common.”

    Troja and her colleagues think both GRB 150101B and GW170817 were most likely produced by the same type of event: the merger of two neutron stars, a catastrophic coalescence that generated a narrow jet, or beam, of high-energy particles. The jet produced a short, intense burst of gamma rays (known as a short GRB), a high-energy flash that can last only seconds. GW170817 proved that these events may also create ripples in space-time itself called gravitational waves.

    The apparent match between GRB 150101B and GW170817 is striking: both produced an unusually faint and short-lived gamma ray burst, and both were a source of bright, blue optical light lasting a few days, and X-ray emission lasted much longer. The host galaxies are also remarkably similar, based on Hubble Space Telescope and DCT observations. Both are bright elliptical galaxies with a population of stars a few billion years old and displaying no evidence for new stars forming.

    “We have a case of cosmic look-alikes,” said co-author Geoffrey Ryan of UMCP. “They look the same, act the same and come from similar neighborhoods, so the simplest explanation is that they are from the same family of objects.”

    In the cases of both GRB 150101B and GW170817, the slow rise in the X-ray emission compared to most GRBs implies that the explosion was likely viewed “off-axis,” that is, with the jet not pointing directly towards the Earth. The discovery of GRB150101 represents only the second time astronomers have ever detected an off-axis short GRB.

    While there are many commonalities between GRB 150101B and GW170817, there are two very important differences. One is their location. GW170817 is about 130 million light years from Earth, while GRB 150101B lies about 1.7 billion light years away. Even if Advanced LIGO had been operating in early 2015, it would very likely not have detected gravitational waves from GRB 150101B because of its greater distance.

    “The beauty of GW170817 is that it gave us a set of characteristics, kind of like genetic markers, to identify new family members of explosive objects at even greater distances than LIGO can currently reach,” said co-author Luigi Piro of National Institute for Astrophysics in Rome.

    The optical emission from GB150101B is largely in the blue portion of the spectrum, providing an important clue that this event involved a so-called kilonova, as seen in GW170817. A kilonova is an extremely powerful explosion that not only releases a large amount energy, but may also produce important elements like gold, platinum, and uranium that other stellar explosions do not.

    It is possible that a few mergers like the ones seen in GW170817 and GRB 150101B had been detected as short GRBs before but had not been identified with other telescopes. Without detections at longer wavelengths like X-rays or optical light, GRB positions are not accurate enough to determine what galaxy they are located in.

    In the case of GRB 150101B, astronomers thought at first that the counterpart was an X-ray source detected by Swift in the center of the galaxy, likely from material falling into a supermassive black hole. However, follow-up observations with Chandra detected the true counterpart away from the center of the host galaxy.

    The other important difference between GW170817 and GRB 150101B is that without gravitational wave detection, the team does not know the masses of the two objects that merged. It is possible that the merger was between a black hole and a neutron star, rather than two neutron stars.

    “We need more cases like GW170817 that combine gravitational wave and electromagnetic data to find an example between a neutron star and black hole. Such a detection would be the first of its kind,” said co-author Hendrik Van Eerten of the University of Bath in the United Kingdom. “Our results are encouraging for finding more mergers and making such a detection.”

    A paper describing these results appears in the journal Nature Communications today.

    See the full article here .


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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 10:35 pm on October 12, 2018 Permalink | Reply
    Tags: , , , , Caltech/MIT Advanced aLigo, , , GRB 150101B, GRB 170817A, GRB's-Gamma ray bursts,   

    From AAS NOVA: ” Two Explosions with Similar Quirks” 

    AASNOVA

    From AAS NOVA

    12 October 2018
    Susanna Kohler

    1
    Artist’s by now iconic illustration of the merger of two neutron stars, producing a short gamma-ray burst. [NSF/LIGO/Sonoma State University/A. Simonnet]

    High-energy radiation released during the merger of two neutron stars last year has left astronomers puzzled. Could a burst of gamma rays from 2015 help us to piece together a coherent picture of both explosions?

    A Burst Alone?

    When two neutron stars collided last August, forming a distinctive gravitational-wave signal and a burst of radiation detected by telescopes around the world, scientists knew that these observations would change our understanding of short gamma-ray bursts (GRBs).Though we’d previously observed thousands of GRBs, GRB 170817A was the first to have such a broad range of complementary observations — both in gravitational waves and across the electromagnetic spectrum — providing insight into its origin.

    2
    Total isotropic-equivalent energies for Fermi-detected gamma-ray bursts with known redshifts. GRB 170817A (pink star) is a factor of ~1,000 dimmer than typical short GRBs (orange points). GRB 170817A and GRB 150101B (green star) are two of the closest detected short GRBs. [Adapted from Burns et al. 2018]

    But it quickly became evident that GRB 170817A was not your typical GRB. For starters, this burst was unusually weak, appearing 1,000 times less luminous than a typical short GRB. Additionally, the behavior of this burst was unusual: instead of having only a single component, the ~2-second explosion exhibited two distinct components — first a short, hard (higher-energy) spike, and then a longer, soft (lower-energy) tail.

    The peculiarities of GRB 170817A prompted a slew of models explaining its unusual appearance. Ultimately, the question is: can our interpretations of GRB 170817A safely be applied to the general population of gamma-ray bursts? Or must we assume that GRB 170817A is a unique event, not representative of the general population?

    New analysis of a GRB from 2015 — presented in a recent study led by Eric Burns (NASA Goddard SFC) — may help to answer this question.

    A Matter of Angles

    What does a burst from 2015 have to do with the curious case of GRB 170817A? Burns and collaborators have demonstrated that this 2015 burst, GRB 150101B, exhibited the same strange behavior as GRB 170817A: its emission can be broken down into two components consisting of a short, hard spike, followed by a long, soft tail. Unlike GRB 170817A, however, GRB 150101B is not underluminous — and it lasted less than a tenth of the time.

    3
    Fermi count rates in different energy ranges showing the short hard spike and the longer soft tail in GRB 150101B. The short hard spike is visible above 50 keV (top and middle panels). The soft tail is visible in the 10–50 keV channel (bottom panel). [Burns et al. 2018]

    Intriguingly, these similarities and differences can all be explained by a single model. Burns and collaborators propose that GRB 150101B and GRB 170817A exhibit the exact same two-component behavior, and their differences in luminosity and duration can be explained by quirks of special relativity.

    High-speed outflows such as these will have different apparent luminosities and durations depending on whether we view them along their axis or slightly from the side. Burns and collaborators demonstrate that these the two bursts could easily have the same profile — but GRB 150101B was viewed nearly on-axis, whereas GRB 170817A was viewed from an angle.

    If this is true, then perhaps more GRBs have hard spikes and soft tails similar to these two; the tails may just be difficult to detect in more distant bursts. While more work remains to be done, the recognition that GRB 170817A may not be unique is an important one for understanding both its behavior and that of other short GRBs.

    Citation

    “Fermi GBM Observations of GRB 150101B: A Second Nearby Event with a Short Hard Spike and a Soft Tail,” E. Burns et al 2018 ApJL 863 L34.
    http://iopscience.iop.org/article/10.3847/2041-8213/aad813/meta


    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

    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/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    See the full article here .


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    Please help promote STEM in your local schools.

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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

     
  • richardmitnick 8:37 am on October 4, 2018 Permalink | Reply
    Tags: , Blue Waters supercomputer at the University of Illinois at Urbana-Champaign, Caltech/MIT Advanced aLigo, , ,   

    From NASA Goddard Space Flight Center via Manu Garcia of IAC: “New Simulation Sheds Light on Spiraling Supermassive Black Holes” 


    From Manu Garcia, a friend from IAC.

    The universe around us.
    Astronomy, everything you wanted to know about our local universe and never dared to ask.

    NASA Goddard Banner
    From NASA Goddard Space Flight Center

    Oct. 2, 2018
    Jeanette Kazmierczak
    jeanette.a.kazmierczak@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    1
    This animation rotates 360 degrees around a frozen version of the simulation in the plane of the disk. Credit: NASA’s Goddard Space Flight Center

    A new model is bringing scientists a step closer to understanding the kinds of light signals produced when two supermassive black holes, which are millions to billions of times the mass of the Sun, spiral toward a collision. For the first time, a new computer simulation that fully incorporates the physical effects of Einstein’s general theory of relativity shows that gas in such systems will glow predominantly in ultraviolet and X-ray light.

    Just about every galaxy the size of our own Milky Way or larger contains a monster black hole at its center. Observations show galaxy mergers occur frequently in the universe, but so far no one has seen a merger of these giant black holes.

    “We know galaxies with central supermassive black holes combine all the time in the universe, yet we only see a small fraction of galaxies with two of them near their centers,” said Scott Noble, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The pairs we do see aren’t emitting strong gravitational-wave signals because they’re too far away from each other. Our goal is to identify — with light alone — even closer pairs from which gravitational-wave signals may be detected in the future.”

    A paper describing the team’s analysis of the new simulation was published Tuesday, Oct. 2, in The Astrophysical Journal.


    Gas glows brightly in this computer simulation of supermassive black holes only 40 orbits from merging. Models like this may eventually help scientists pinpoint real examples of these powerful binary systems. Credits: NASA’s Goddard Space Flight Center

    Scientists have detected merging stellar-mass black holes — which range from around three to several dozen solar masses — using the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO).

    Gravitational waves are space-time ripples traveling at the speed of light. They are created when massive orbiting objects like black holes and neutron stars spiral together and merge.

    Black holes heading toward a merger. Precise laser interferometry can detect the ripples in space-time generated when two black holes collide. LIGO-Caltech-MIT-Sonoma State Aurore Simonn

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Supermassive mergers will be much more difficult to find than their stellar-mass cousins. One reason ground-based observatories can’t detect gravitational waves from these events is because Earth itself is too noisy, shaking from seismic vibrations and gravitational changes from atmospheric disturbances. The detectors must be in space, like the Laser Interferometer Space Antenna (LISA) led by ESA (the European Space Agency) and planned for launch in the 2030s.


    ESA/NASA eLISA space based, the future of gravitational wave research

    Observatories monitoring sets of rapidly spinning, superdense stars called pulsars may detect gravitational waves from monster mergers. Like lighthouses, pulsars emit regularly timed beams of light that flash in and out of view as they rotate. Gravitational waves could cause slight changes in the timing of those flashes, but so far studies haven’t yielded any detections.

    But supermassive binaries nearing collision may have one thing stellar-mass binaries lack — a gas-rich environment. Scientists suspect the supernova explosion that creates a stellar black hole also blows away most of the surrounding gas. The black hole consumes what little remains so quickly there isn’t much left to glow when the merger happens.

    Supermassive binaries, on the other hand, result from galaxy mergers. Each supersized black hole brings along an entourage of gas and dust clouds, stars and planets. Scientists think a galaxy collision propels much of this material toward the central black holes, which consume it on a time scale similar to that needed for the binary to merge. As the black holes near, magnetic and gravitational forces heat the remaining gas, producing light astronomers should be able to see.

    “It’s very important to proceed on two tracks,” said co-author Manuela Campanelli, director of the Center for Computational Relativity and Gravitation at the Rochester Institute of Technology in New York, who initiated this project nine years ago. “Modeling these events requires sophisticated computational tools that include all the physical effects produced by two supermassive black holes orbiting each other at a fraction of the speed of light. Knowing what light signals to expect from these events will help modern observations identify them. Modeling and observations will then feed into each other, helping us better understand what is happening at the hearts of most galaxies.”

    The new simulation shows three orbits of a pair of supermassive black holes only 40 orbits from merging. The models reveal the light emitted at this stage of the process may be dominated by UV light with some high-energy X-rays, similar to what’s seen in any galaxy with a well-fed supermassive black hole.

    Three regions of light-emitting gas glow as the black holes merge, all connected by streams of hot gas: a large ring encircling the entire system, called the circumbinary disk, and two smaller ones around each black hole, called mini disks. All these objects emit predominantly UV light. When gas flows into a mini disk at a high rate, the disk’s UV light interacts with each black hole’s corona, a region of high-energy subatomic particles above and below the disk. This interaction produces X-rays. When the accretion rate is lower, UV light dims relative to the X-rays.

    Based on the simulation, the researchers expect X-rays emitted by a near-merger will be brighter and more variable than X-rays seen from single supermassive black holes. The pace of the changes links to both the orbital speed of gas located at the inner edge of the circumbinary disk as well as that of the merging black holes.


    This 360-degree video places the viewer in the middle of two circling supermassive black holes around 18.6 million miles (30 million kilometers) apart with an orbital period of 46 minutes. The simulation shows how the black holes distort the starry background and capture light, producing black hole silhouettes. A distinctive feature called a photon ring outlines the black holes. The entire system would have around 1 million times the Sun’s mass. Credits: NASA’s Goddard Space Flight Center; background, ESA/Gaia/DPAC

    “The way both black holes deflect light gives rise to complex lensing effects, as seen in the movie when one black hole passes in front of the other,” said Stéphane d’Ascoli, a doctoral student at École Normale Supérieure in Paris and lead author of the paper. “Some exotic features came as a surprise, such as the eyebrow-shaped shadows one black hole occasionally creates near the horizon of the other.”

    The simulation ran on the National Center for Supercomputing Applications’ Blue Waters supercomputer at the University of Illinois at Urbana-Champaign.

    U Illinois Urbana-Champaign Blue Waters Cray Linux XE/XK hybrid machine supercomputer

    Modeling three orbits of the system took 46 days on 9,600 computing cores. Campanelli said the collaboration was recently awarded additional time on Blue Waters to continue developing their models.

    The original simulation estimated gas temperatures. The team plans to refine their code to model how changing parameters of the system, like temperature, distance, total mass and accretion rate, will affect the emitted light. They’re interested in seeing what happens to gas traveling between the two black holes as well as modeling longer time spans.

    “We need to find signals in the light from supermassive black hole binaries distinctive enough that astronomers can find these rare systems among the throng of bright single supermassive black holes,” said co-author Julian Krolik, an astrophysicist at Johns Hopkins University in Baltimore. “If we can do that, we might be able to discover merging supermassive black holes before they’re seen by a space-based gravitational-wave observatory.”

    See the full article here.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

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


    NASA/Goddard Campus

     
  • richardmitnick 2:02 pm on September 25, 2018 Permalink | Reply
    Tags: , Caltech/MIT Advanced aLigo, , , , , , LSND, , , ,   

    From Symmetry: “How not to be fooled in physics” 

    Symmetry Mag
    From Symmetry

    09/25/18
    Laura Dattaro

    1
    Illustration by Sandbox Studio, Chicago with Ana Kova

    Particle physicists and astrophysicists employ a variety of tools to avoid erroneous results.

    In the 1990s, an experiment conducted in Los Alamos, about 35 miles northwest of the capital of New Mexico, appeared to find something odd.

    Scientists designed the Liquid Scintillator Neutrino Detector experiment at the US Department of Energy’s Los Alamos National Laboratory to count neutrinos, ghostly particles that come in three types and rarely interact with other matter.

    LSND experiment at Los Alamos National Laboratory and Virginia Tech

    LSND was looking for evidence of neutrino oscillation, or neutrinos changing from one type to another.

    Several previous experiments had seen indications of such oscillations, which show that neutrinos have small masses not incorporated into the Standard Model, the ruling theory of particle physics. LSND scientists wanted to double-check these earlier measurements.

    By studying a nearly pure source of one type of neutrinos—muon neutrinos—LSND did find evidence of oscillation to a different type of neutrinos, electron neutrinos. However, they found many more electron neutrinos in their detector than predicted, creating a new puzzle.

    This excess could have been a sign that neutrinos oscillate between not three but four different types, suggesting the existence of a possible new type of neutrino, called a sterile neutrino, which theorists had suggested as a possible way to incorporate tiny neutrino masses into the Standard Model.

    Or there could be another explanation. The question is: What? And how can scientists guard against being fooled in physics?

    Brand new thing

    Many physicists are looking for results that go beyond the Standard Model. They come up with experiments to test its predictions; if what they find doesn’t match up, they have potentially discovered something new.

    “Do we see what we expected from the calculations if all we have there is the Standard Model?” says Paris Sphicas, a researcher at CERN.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.


    Standard Model of Particle Physics from Symmetry Magazine

    “If the answer is yes, then it means we have nothing new. If the answer is no, then you have the next question, which is, ‘Is this within the uncertainties of our estimates? Could this be a result of a mistake in our estimates?’ And so on and so on.”

    A long list of possible factors can trick scientists into thinking they’ve made a discovery. A big part of scientific research is identifying them and finding ways to test what’s really going on.

    “The community standard for discovery is a high bar, and it ought to be,” says Yale University neutrino physicist Bonnie Fleming. “It takes time to really convince ourselves we’ve really found something.”

    In the case of the LSND anomaly, scientists wonder whether unaccounted-for background events tipped the scales or if some sort of mechanical problem caused an error in the measurement.

    Scientists have designed follow-up experiments to see if they can reproduce the result. An experiment called MiniBooNE, hosted by Fermi National Accelerator Laboratory, recently reported seeing signs of a similar excess. Other experiments, such as the MINOS experiment, also at Fermilab, have not seen it, complicating the search.

    FNAL/MiniBooNE

    FNAL Minos map


    FNAL/MINOS


    FNAL MINOS Far Detector in the Soudan Mine in northern Minnesota

    “[LSND and MiniBooNE] are clearly measuring an excess of events over what they expect,” says MINOS co-spokesperson Jenny Thomas, a physicist at University College London. “Are those important signal events, or are they a background they haven’t estimated properly? That’s what they are up against.”

    Managing expectations

    Much of the work in understanding a signal involves preparatory work before one is even seen.

    In designing an experiment, researchers need to understand what physics processes can produce or mimic the signal being sought, events that are often referred to as “background.”

    Physicists can predict backgrounds through simulations of experiments. Some types of detector backgrounds can be identified through “null tests,” such as pointing a telescope at a blank wall. Other backgrounds can be identified through tests with the data itself, such as so-called “jack-knife tests,” which involve splitting data into subsets—say, data from Monday and data from Tuesday—which by design must produce the same results. Any inconsistencies would warn scientists about a signal that appears in just one subset.

    Researchers looking at a specific signal work to develop a deep understanding of what other physics processes could produce the same signature in their detector. MiniBooNE, for example, studies a beam primarily made of muon neutrinos to measure how often those neutrinos oscillate to other flavors. But it will occasionally pick up stray electron neutrinos, which look like muon neutrinos that have transformed. Beyond that, other physics processes can mimic the signal of an electron neutrino event.

    “We know we’re going to be faked by those, so we have to do the best job to estimate how many of them there are,” Fleming says. “Whatever excess we find has to be in addition to those.”

    Even more variable than a particle beam: human beings. While science strives to be an objective measurement of facts, the process itself is conducted by a collection of people whose actions can be colored by biases, personal stories and emotion. A preconceived notion that an experiment will (or won’t) produce a certain result, for example, could influence a researcher’s work in subtle ways.

    “I think there’s a stereotype that scientists are somehow dispassionate, cold, calculating observers of reality,” says Brian Keating, an astrophysicist at University of California San Diego and author of the book Losing the Nobel Prize, which chronicles how the desire to make a prize-winning discovery can steer a scientist away from best practices. “In reality, the truth is we actually participate in it, and there are sociological elements at work that influence a human being. Scientists, despite the stereotypes, are very much human beings.”

    Staying cognizant of this fact and incorporating methods for removing bias are especially important if a particular claim upends long-standing knowledge—such as, for example, our understanding of neutrinos. In these cases, scientists know to adhere to the adage: Extraordinary claims require extraordinary evidence.

    “If you’re walking outside your house and you see a car, you probably think, ‘That’s a car,’” says Jonah Kanner, a research scientist at Caltech. “But if you see a dragon, you might think, ‘Is that really a dragon? Am I sure that’s a dragon?’ You’d want a higher level of evidence.”


    Dragon or discovery?

    Physicists have been burned by dragons before. In 1969, for example, a scientist named Joe Weber announced that he had detected gravitational waves: ripples in the fabric of space-time first predicted by Albert Einstein in 1916. Such a detection, which many had thought was impossible to make, would have proved a key tenet of relativity. Weber rocketed to momentary fame, until other physicists found they could not replicate his results.

    The false discovery rocked the gravitational wave community, which, over the decades, became increasingly cautious about making such announcements.

    So in 2009, as the Laser Interferometer Gravitational Wave Observatory, or LIGO, came online for its next science run, the scientific collaboration came up with a way to make sure collaboration members stayed skeptical of their results. They developed a method of adding a false or simulated signal into the detector data stream without alerting the majority of the 800 or so researchers on the team. They called it a blind injection. The rest of the members knew an injection was possible, but not guaranteed.

    “We’d been not detecting signals for 30 years,” Kanner, a member of the LIGO collaboration, says. “How clear or obvious would the signature have to be for everyone to believe it?… It forced us to push our algorithms and our statistics and our procedures, but also to test the sociology and see if we could get a group of people to agree on this.”

    In late 2010, the team got the alert they had been waiting for: The computers detected a signal. For six months, hundreds of scientists analyzed the results, eventually concluding that the signal looked like gravitational waves. They wrote a paper detailing the evidence, and more than 400 team members voted on its approval. Then a senior member told them it had all been faked.

    Picking out and spending so much time examining such an artificial signal may seem like a waste of time, but the test worked just as intended. The exercise forced the scientists to work through all of the ways they would need to scrutinize a real result before one ever came through. It forced the collaboration to develop new tests and approaches to demonstrating the consistency of a possible signal in advance of a real event.

    “It was designed to keep us honest in a sense,” Kanner says. “Everyone to some extent goes in with some guess or expectation about what’s going to come out of that experiment. Part of the idea of the blind injection was to try and tip the scales on that bias, where our beliefs about whether we thought nature should produce an event would be less important.”

    All of the hard work paid off: In September 2015, when an authentic signal hit the LIGO detectors, scientists knew what to do. In 2016, the collaboration announced the first confirmed direct detection of gravitational waves. One year later, the discovery won the Nobel Prize.


    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

    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)

    No easy answers

    While blind injections worked for the gravitational waves community, each area of physics presents its own unique challenges.

    Neutrino physicists have an extremely small sample size with which to work, because their particles interact so rarely. That’s why experiments such as the NOvA experiment and the upcoming Deep Underground Neutrino experiment use such enormous detectors.

    FNAL/NOvA experiment map


    FNAL NOvA detector in northern Minnesota


    FNAL NOvA Near Detector

    Astronomers have even fewer samples: They have just one universe to study, and no way to conduct controlled experiments. That’s why they conduct decades-long surveys, to collect as much data as possible.

    Researchers working at the Large Hadron Collider have no shortage of interactions to study—an estimated 600 million events are detected every second.

    LHC

    CERN map


    CERN LHC Tunnel

    CERN LHC particles

    But due to the enormous size, cost and complexity of the technology, scientists have built only one LHC. That’s why inside the collider sit multiple different detectors, which can check one another’s work by measuring the same things in a variety of ways with detectors of different designs.

    CERN ATLAS


    CERN/CMS Detector



    CERN ALICE detector


    CERN LHCb chamber, LHC

    While there are many central tenets to checking a result—knowing your experiment and background well, running simulations and checking that they agree with your data, testing alternative explanations of a suspected result—there’s no comprehensive checklist that every physicist performs. Strategies vary from experiment to experiment, among fields and over time.

    Scientists must do everything they can to test a result, because in the end, it will need to stand up to the scrutiny of their peers. Fellow physicists will question the new result, subject it to their own analyses, try out alternative interpretations, and, ultimately, try to repeat the measurement in a different way. Especially if they’re dealing with dragons.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 7:42 pm on September 11, 2018 Permalink | Reply
    Tags: A cool fact about this accelerator? It’s 60 years old and includes a Van de Graaff accelerator that was repurposed for use with CASPAR, , , “We are made of stardust.” Carl Sagan, , Caltech/MIT Advanced aLigo, , , , LUNA at Gran Sasso, Stellar burning and evolutionary phases in stars,   

    From Sanford Underground Research Facility: “CASPAR” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    Constance Walter
    Photos by Matt Kapust

    1
    CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.

    “We are made of stardust.”

    While that statement may sound like a song title from the 1960s, it was actually made by astrophysicist and science fiction author Carl Sagan.

    Carl Sagan NASA/JPL

    And he was right. The nuclear burning inside collapsing stars produces the elements that make up and sustain life on Earth: carbon, nitrogen, iron and calcium, to name a few. Even lead, gold and the rock beneath our feet come from stars.

    The Compact Accelerator System for Performing Astrophysical Research (CASPAR) collaboration uses a low-energy accelerator to better understand how elements are produced in the Universe and at what rate and how much energy is produced during the process.

    “Unlike other underground experiments, we look at many different interactions and are not focused on discovering just one event,” said Dan Robertson, research associate professor at the University of Notre Dame. “All of these details give us a better understanding of the life of a star and what material is kicked out into the Universe during explosive stellar events.”

    2

    Studying the stars from underground

    Although it may seem counter-intuitive, going nearly a mile underground at Sanford Lab gives the CASPAR team a perfect place to study those stellar environments. CASPAR is one of just two underground accelerators in the world studying stellar environments. The other is the Laboratory for Underground Nuclear Astrophysics (LUNA), which is located at Gran Sasso National Laboratory in Italy and has been in existence for 25 years. Frank Strieder, principal investigator for the project and an associate professor of physics at South Dakota School of Mines & Technology (SD Mines), worked on that experiment for 22 years.

    LUNA-Laboratory for Underground Nuclear Astrophysics , which is located at Gran Sasso National Laboratory in Italy

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    “Both experiments are studying stellar burning and evolutionary phases in stars, but the work is different,” Strieder said. “And with our accelerator, we can cover a larger energy range than previous underground experiments.”

    3
    The accelerator

    The most famous particle accelerator in the world is the 17-mile long Large Hadron Collider, located in Switzerland and France, which generates up to 7 trillion volts as it hurls particles toward each other at nearly the speed of light.

    LHC

    CERN map


    CERN LHC Tunnel

    CERN LHC particles

    CASPAR, on the other hand, is a 50-foot long system that includes a Van de Graaff accelerator that uses radio-frequency energy to accelerate a beam of protons or alpha particles toward a target of up to 1.1 million volts.

    Robertson compares the accelerator to a tabletop version of the Van de Graaff used in high school or at a science museum—touch the polished metal dome and your hair stands on end. “Think of the accelerator as generating and storing a large voltage which then repels ionized particles (which we create at its heart) away from it.”

    A cool fact about this accelerator? It’s 60 years old and was repurposed for use with CASPAR.

    4
    The target

    Every reaction the CASPAR team investigates, requires two elements to interact—a projectile and a target. The target material varies according to the interaction they want to study and could include anything from nitrogen and carbon up to magnesium. These elements are usually stored on a heavier backing material for stability, which are kept extremely cold.

    The team bombards the target with either a proton beam or alpha beam generated in the accelerator. The power the beam dissipates in the target is up to 100 watts, “which is the same power as a good light bulb,” Strieder said.

    What’s LIGO got to do with it?

    In late 2017, the Laser-Interferometer Gravitational Wave Observatory (LIGO), recorded a violent collision of two neutron stars—this was on top of two previous observations of black hole mergers that emitted gravitational waves. Observations made after the collision reinforce the need for measurements like those CASPAR hopes to take, explained Strieder.


    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

    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)
    See also https://sciencesprings.wordpress.com/2017/10/16/from-ucsc-a-uc-santa-cruz-special-report-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/

    “The basic point is that from the information we learned from this cataclysmic event, we can calculate the amount of heavy element material produced.” Strieder said. “And then compare it with the heavy elements found in our planetary system.”

    1,100,000
    Volts of energy generated by CASPAR

    7,700,000,000
    Volts of energy generated by LHC

    5
    Collecting data

    In July 2017, CASPAR achieved first beam and began full operations earlier this year. The accelerator runs for several days at a time, collecting data using a germanium detector.

    “We are recording the number of reactions that occur per time period, and in what conditions,” Roberson said. “For example, what energy did the interacting particle have prior to striking the target? The measurement of radiation and particles emitted during the interaction helps us backtrack what happened in the target material and at what rate. This can then be extrapolated to events in a star and scaled up for the star’s massive size.”

    6
    A lofty goal

    The end goal for the field of nuclear astrophysics is to complete the puzzle of how everything is made in the Universe and the locations and processes that govern such production. The experiments studying stellar processes are looking at singular puzzle pieces without knowing what the complete picture is.

    “Only as we understand how these pieces fit can we begin to put the whole puzzle together,” Robertson said. “CASPAR’s unique location deep underground means it is able to more clearly investigate the images previously obscured by cosmic interference.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

     
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