Tagged: Gravitational waves Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 1:03 pm on September 5, 2018 Permalink | Reply
    Tags: , , , , , , Gravitational waves, ,   

    From Caltech: “Superfast Jet Observed Streaming Away from Stellar Collision” 

    Caltech Logo

    From Caltech

    09/05/2018
    Elise Cutts

    1
    An artist’s impression of the jet (pictured as a ball of fire), produced in the neutron star merger first detected on August 17, 2017 by telescopes around the world, as well as LIGO, which detects gravitational waves (green ripples). Credit: James Josephides (Swinburne University of Technology, Australia)

    Using a collection of National Science Foundation radio telescopes, researchers have confirmed that a narrow jet of material was ejected at near light speeds from a neutron star collision. The collision, which was observed August 17, 2017 and occurred 130 million miles from Earth, initially produced gravitational waves that were observed by the Laser Interferometry Gravitational-wave Observatory (LIGO), alongside a flood of light in the form of gamma rays, X-rays, visible light, and radio waves. It was the first cosmic event to be observed in both gravitational waves and light waves.

    Confirmation that a superfast jet had been produced by the neutron star collision came after radio astronomers discovered that a region of radio emission created by the merger had moved in a seemingly impossible way that only a jet could explain. The radio observations were made using the Very Long Baseline Array (VLBA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Large Array (VLA). The VLA is operated by the National Radio Astronomy Observatory (NRAO), which is closely associated with the other two telescopes involved in the discovery.

    NRAO VLBA



    GBO radio telescope, Green Bank, West Virginia, USA

    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)

    “We measured an apparent motion that is four times faster than light. That illusion, called superluminal motion, results when the jet is pointed nearly toward Earth and the material in the jet is moving close to the speed of light,” says Kunal Mooley, a Caltech postdoctoral scholar with a joint appointment at the NRAO and lead author of a new study about the jet appearing online September 5 in the journal Nature. Mooley and Assistant Professor of Astronomy Gregg Hallinan were part of an international collaboration that observed and interpreted the movement of the radio emission.

    “We were lucky to be able to observe this event, because if the jet had been pointed too much farther away from Earth, the radio emission would have been too faint for us to detect,” says Hallinan.

    Superfast jets are known to give rise to intense, short-duration gamma-ray bursts or sGRBs, predicted by theorists to be associated with neutron star collisions. The observation of a jet associated with this collision is therefore an important confirmation of theoretical expectations.

    Superfast jets are known to give rise to intense, short-duration gamma-ray bursts or sGRBs, predicted by theorists to be associated with neutron star collisions. The observation of a jet associated with this collision is therefore an important confirmation of theoretical expectations.

    The aftermath of the merger is now also better understood: the jet likely interacted with surrounding debris, forming a broad “cocoon” of material that expanded outward and accounted for the majority of the radio signal observed soon after the collision. Later on, the observed radio emission came mainly from the jet.

    Read the full story from NRAO at https://public.nrao.edu/news/superfast-jet-neutron-star-merger/.

    See the full article here .
    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/


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


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

    Advertisements
     
  • richardmitnick 6:19 am on August 24, 2018 Permalink | Reply
    Tags: , , From UCSC "All the Gold in the Unverse", Gravitational waves, , Multimessinger Astonomy,   

    From The Conversation: “We’re going to get a better detector: time for upgrades in the search for gravitational waves” 

    Conversation
    From The Conversation

    August 16, 2018
    Robert Ward

    It’s been a year since ripples in space-time from a colliding pair of dead stars tickled the gravitational wave detectors of the Advanced LIGO and Advanced Virgo facilities.


    Soon after, astronomers around the world began a campaign to observe the afterglow of the collision of a binary neutron star merger in radio waves, microwaves, visible light, x-rays and more.

    See 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/

    This was the dawn of multi-messenger astronomy: a new era in astronomy, where events in the universe are observed with more than just a single type of radiation. In this case, the messengers were gravitational waves and electromagnetic radiation.

    What we’ve learned (so far)

    From this single event, we learned an incredible amount. Last October, on the day the detection was made public, 84 scientific papers were published (or the preprints made available).

    We learned that gravity and light travel at the same speed, neutron star mergers are a source of short gamma-ray bursts, and that kilonovae – the explosion from a neutron star merger – are where our gold comes from.

    This rich science came from the fact that we were able to combine our observatories to witness this single event from multiple astronomical “windows”. The gravitational waves arrived first, followed 1.7 seconds later by gamma-rays. That is a pretty small delay, considering the waves had been travelling for 130 million years.

    Over the next few weeks, visible light and radio waves began to be observed and then slowly faded.

    It seemed like the news about gravitational waves was coming fast and furious, with the first detection announced in 2016, a Nobel prize in 2017, and the announcement of the binary neutron star merger just weeks after the Nobel prize.

    Time for upgrades

    On this first anniversary of the neutron star merger, the gravitational wave detectors are offline for upgrades. They actually went offline shortly after the detection and will come back online some time early in 2019.

    The work of making gravitational wave detectors function requires extraordinary patience and dedication. These are exquisite experiments – it took more than 40 years of technological development by a community of more than a thousand scientists to get to the point of detecting the first signal.

    Naturally, improving on this work is not easy. So what does it actually take?

    We really do listen to gravitational waves, and our detectors act more like microphones than telescopes or cameras.

    Quiet please!

    To detect gravitational waves, we need to do more than just turn off the dishwasher. We need to build the quietest, best-isolated thing on Earth.

    Unfortunately, the laws of quantum mechanics and thermodynamics both prevent us from eliminating the noise entirely. Nonetheless, we strive to do the best that these fundamental limits permit. This involves, among many other extraordinary things, hanging our mirrors on glass threads .

    2
    Before sealing up the chamber and pumping the vacuum system down, a LIGO optics technician inspects one of LIGO’s core optics (mirrors) by illuminating its surface with light at a glancing angle. Matt Heintze/Caltech/MIT/LIGO Lab

    Our mirrors weight 40kg each and are suspended from four of these glass threads, which are less than a half-millimetre in diameter and exquisitely crafted.

    The threads are under enormous stress, and the slightest imperfection (or the slightest touch) can cause them to explode.

    Just such an explosion happened earlier this year while installing a new mirror. Fortunately, the precious mirror fell into a cradle designed for just such a possibility, and was not damaged.

    Nonetheless, the delicate, intricate work of creating the glass threads, attaching them to the mirror, hanging the mirror and then installing it all needed to be redone.

    Improvements to the detector

    This was a heartbreaking setback for the team, but the added delay was not entirely in vain. In parallel with remaking the glass threads and rehanging the new mirror, we made some other improvements to the detector, for which we otherwise would not have had enough time.

    One of the goals of this upgrade period is to install something called a quantum squeezed light source into the gravitational wave detectors.

    As mentioned earlier, quantum mechanics mandates a certain minimum amount of noise in any measurement. We can’t arbitrarily reduce this quantum noise, but we can move it around and change its shape by squeezing it.

    This is a bit like sweeping dust under the rug. It’s not really gone, but it might not bother you so much anymore. The quantum squeezed light source does just this.

    3
    Australian National University scientists Nutsinee Kijbunchoo and Terry McCrae build components for a quantum squeezed light source at LIGO Hanford Observatory in Washington, US. Nutsinee Kijbunchoo

    A gravitational wave detector is already a very complex system, and a squeezed light source is another complex system, so putting them together can be a challenge.

    Despite the complexity of this challenge, when the squeezed light source was activated for the first time at the LIGO detector in Livingston, Louisiana, US, in February this year there was an immediate improvement in the quantum noise: the gravitational wave detector output got just a bit quieter.

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

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Conversation US launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

     
  • richardmitnick 3:05 pm on August 17, 2018 Permalink | Reply
    Tags: , , , , , , Gravitational waves,   

    From Discover Magazine: “Astronomers Find New Way to Supersize Baby Black Holes” 

    DiscoverMag

    From Discover Magazine

    August 16, 2018
    Jake Parks

    1
    This artist’s concept depicts a supermassive black hole surrounded by a dense disk of gas and dust in the center of a galaxy. (Credit: NASA/JPL-Caltech)

    Just last year, three American physicists shared the Nobel Prize in Physics for their role in the historic detection of gravitational waves. The signals came from cosmic ripples in space-time created by some of the most violent events in the universe: colliding black holes.

    Scientists have now detected six gravitational-wave signals — five from merging pairs of stellar-mass black holes, and one from a merging pair of neutron stars. But strangely, most of the stellar-mass black holes involved were more than 20 times as massive as the Sun. The find perplexed astronomers. Stellar-mass black holes, which form when massive stars collapse, typically top out at about 10 to 15 times the mass of the Sun.

    Bulking Up Black Holes

    So, how did these relatively small black holes bulk up before merging?

    In the past, scientists suspected these black holes grew larger because they started their lives as giant stars with very few metals — or elements besides hydrogen and helium. Since low-metallicity stars produce weak solar winds, they keep most of their mass before collapsing into black holes.

    But according to a new study published in The Astrophysical Journal Letters, there may be more than one way to make a black hole balloon in size — and it doesn’t involve a low-metal diet.

    Instead, the authors outline a way that average stellar-mass black hole can grow by gobbling up the material circling a galaxy’s supermassive black hole. Furthermore, this new mechanism also may predict a fresh source of gravitational waves.

    2
    Gravitational waves are produced by the inspiral and eventual merger of two extremely dense objects, such as black holes or neutron stars. This creates ripples in the fabric of space-time that propagate outward at the speed of light. (Credit: R. Hurt/Caltech-JPL)

    Spiraling Disks

    Astronomers know that the majority of large galaxies house supermassive black holes in their cores. Many of these black holes lie dormant for most of their lives, accreting little matter and producing little light.

    However, some supermassive black holes are surrounded by a dense disk of gas and dust that harshly grinds together as it spins inward toward the supermassive black hole itself. This spinning disk generates incredible amounts of friction, which causes the material inside it to glow brightly. If these radiant disks are especially bright, astronomers refer to them as active galactic nuclei, or AGN.

    Just outside these chaotic disks, however, are numerous stars — many of which will eventually evolve into stellar-mass black holes.

    According to the new study, a pair of these nearby stellar-mass black holes can easily become trapped within the AGN’s disk. And when this happens, the black holes feed on the available matter as they spiral ever closer, growing from around seven solar masses to more than 20 solar masses before they eventually merge.

    The gravitational-wave signal generated by such a merger would indicate that the two black holes involved were around 20 solar masses, even though they both initially started much smaller.

    Multi-Messenger Astronomy

    One interesting offshoot of this newly proposed method for forming supersized stellar-mass black holes is that their environment can often cause them to synchronize their spin axes, like two tops spinning in tandem. According to the study, such systems release about 10 percent of their energy as gravitational waves when they do finally merge. That’s as much as three times more gravitational-wave energy than would be released if the black holes were randomly oriented, which means these mergers are likely detectable with current technology, such as the Laser Interferometer Gravitational-wave Observatory (LIGO).


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

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

    The authors also say these black holes would likely emit large amounts of X-rays, gamma rays, or even radio waves. Those wavelengths could provide an electromagnetic counterpart to a gravitational-wave signal, revealing important details that would otherwise remain hidden.

    Last year, astronomers managed to do just this when they observed both gravitational waves and gamma rays from the merger of two neutron stars. At the time, astronomer Josh Simon of Carnegie Observatories said of the neutron star detection, “There are things you can discover with gravitational waves that you could never see with electromagnetic light, and vice versa. Having that combination should provide us with insights into these extreme objects.”

    What’s Next?

    So, is this newly proposed method for forming supersized stellar-mass black holes the explanation for LIGO’s extra-large detections, or are low-metal stars responsible? Or maybe it’s a combination of both. At this point, we just don’t know for sure.

    However, LIGO and its sister detector Virgo are currently undergoing planned upgrades, and should start observing again in early 2019. And when they kick back on, astronomers will no doubt be hunting for gravitational-wave signals that can be paired with electromagnetic observations. Such multi-messenger detections will likely be key to the future of astronomy, so make sure to stay tuned.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 1:39 pm on July 12, 2018 Permalink | Reply
    Tags: CfA/VERITAS a major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy in the GeV - TeV energy range Located at Fred Lawrence Whipple Observatory M, Gravitational waves, , , , VERITAS array has confirmed the detection of gamma rays from the vicinity of a supermassive black hole   

    From CfA: “VERITAS Supplies Critical Piece to Neutrino Discovery Puzzle” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    July 12, 2018
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Peter Edmonds
    Harvard-Smithsonian Center for Astrophysics
    +1 617-571-7279
    pedmonds@cfa.harvard.edu

    CfA/VERITAS, a major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. Located at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m (8,550 ft)

    The VERITAS array has confirmed the detection of gamma rays from the vicinity of a supermassive black hole. While these detections are relatively common for VERITAS, this black hole is potentially the first known astrophysical source of high-energy cosmic neutrinos, a type of ghostly subatomic particle.

    On September 22, 2017 the IceCube Neutrino Observatory, a cubic-kilometer neutrino telescope located at the South Pole, detected a high-energy neutrino of potential astrophysical origin. However, the observation of a single neutrino by itself is not enough for IceCube to claim the detection of a source. For that, scientists needed more information.

    Very quickly after the detection by IceCube was announced, telescopes around the world including VERITAS (which stands for the “Very Energetic Radiation Imaging Telescope Array System”) swung into action to identify the source. The VERITAS, MAGIC and H.E.S.S. gamma-ray observatories all looked at the neutrino position. In addition, two gamma-ray observatories that monitor much of the sky at lower and higher energies also provided coverage.

    These follow-up observations of the rough IceCube neutrino position suggest that the source of the neutrino is a blazar, which is a supermassive black hole with powerful outflowing jets that can change dramatically in brightness over time. This blazar, known as TXS 0506+056, is located at the center of a galaxy about 4 billion light years from Earth.

    Initially, NASA’s Fermi Gamma-ray Space Telescope observed that TXS 0506+056 was several times brighter than usually seen in its all-sky monitoring. Eventually, the MAGIC observatory made a detection of much higher-energy gamma rays within two weeks of the neutrino detection, while VERITAS, H.E.S.S. and HAWC did not see the blazar in any of their observations during the two weeks following the alert.

    MAGIC Cherenkov gamma ray telescope on the Canary island of La Palma, Spain, Altitude 2,200 m (7,200 ft)

    Given the importance of higher-energy gamma-ray detections in identifying the possible source of the neutrino, VERITAS continued to observe TXS 0506+056 over the following months, through February 2018, and revealed the source but at a dimmer state than what was detected by MAGIC.

    “The VERITAS detection shows us that the gamma-ray brightness of the source changes, which is a signature of a blazar,” said Wystan Benbow of the Smithsonian Astrophysical Observatory (SAO) that operates and manages VERITAS, and the Principal Investigator of VERITAS operations. “Finding a link between an astrophysical source and a neutrino event could open yet another window of exploration to the extreme Universe.”

    The detection of gamma rays coincident with neutrinos is tantalizing, since both particles must be produced in the generation of cosmic rays. Since they were first detected over one hundred years ago, cosmic rays — highly energetic particles that continuously rain down on Earth from space — have posed an enduring mystery. What creates and launches these particles across such vast distances? Where do they come from?

    “The potential connection between the neutrino event and TXS 0506+056 would shed new light on the acceleration mechanisms that take place at the core of these galaxies, and provide clues on the century-old question of the origin of cosmic rays,” said co-author and spokesperson of VERITAS Reshmi Mukherjee of Barnard College, Columbia University in New York, New York.

    “The era of multi-messenger astrophysics is here,” said NSF Director France Córdova. “Each messenger – from electromagnetic radiation, gravitational waves and now neutrinos – gives us a more complete understanding of the universe, and important new insights into the most powerful objects and events in the sky. Such breakthroughs are only possible through a long-term commitment to fundamental research and investment in superb research facilities.”

    “The detection of very-high-energy gamma-rays from TXS 0506+056 with VERITAS provides vital information to understand the powerful processes taking place in this and other potential neutrino sources,” said co-author Marcos Santander of the University of Alabama in Tuscaloosa, who led the study. “The deep interconnection between neutrinos and gamma-rays is allowing us, for the first time, to study astrophysical objects using multimessenger observations in a way that would be impossible using single messengers.”

    A paper describing the deep VERITAS observations of TXS 0506+056 (“VERITAS Observations of the BL Lac Object TXS 0506+056”) is accepted for publication in The Astrophysical Journal Letters and appears online on July 12, 2018 (the accepted version is available here). A paper on the IceCube and initial gamma-ray observations, including VERITAS’s, appears in the latest issue of the journal Science.

    VERITAS is a ground-based facility located at the SAO’s Fred Lawrence Whipple Observatory in southern Arizona. It consists of an array of four 12-meter optical telescopes that can detect gamma rays via the extremely brief flashes of blue “Cherenkov” light created when gamma rays are absorbed in the Earth’s atmosphere. The VERITAS Collaboration consists of about 80 scientists from 20 institutions in the United States, Canada, Germany and Ireland.

    See the full article here .
    See also From Astronomy Magazine: “A cosmic particle spewed from a distant galaxy strikes Earth


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

    Stem Education Coalition

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

     
  • richardmitnick 10:32 am on February 16, 2018 Permalink | Reply
    Tags: , , , , Gravitational waves, ,   

    From Science Magazine: “Gravitational waves help reveal the weight limit for neutron stars, the densest objects in the cosmos” 

    AAAS
    Science Magazine

    Feb. 15, 2018
    Adrian Cho

    1
    To derive the new mass limit, astrophysicists teased out the evolution of the famed merger of two neutron stars, spotted on 17 August 2017 and shown in this artist’s conception. University of Warwick/Mark Garlick/Wikimedia Commons (CC BY 4.0)

    How heavy can neutron stars get? Astrophysicists have long wondered how massive these stellar corpses could be without collapsing under their own gravity to form a black hole. Last year’s blockbuster observations of two neutron stars merging revealed a collapse as it happened, enabling four different groups to converge on the maximum mass—about 2.2 times that of the sun.


    “I’m encouraged that they all agree,” says James Lattimer, a nuclear astrophysicist at the State University of New York in Stony Brook. A solid mass limit for neutron stars will help theorists understand these mysterious objects. “Of all the characteristics of a neutron star, the two most important are the maximum mass and the radius,” Lattimer says.

    A dying star can have one of three afterlives. A lightweight star shrinks into a white dwarf, an Earth-size sphere of carbon. A heavy star explodes when its massive core collapses to an infinitesimal point: a black hole. A star in the middle range—8 to 25 solar masses—also explodes, but leaves behind a fantastically dense sphere of nearly pure neutrons measuring a couple of dozen kilometers across: a neutron star.

    As the neutron stars spiraled into each other, gravitational-wave detectors in the United States and Italy sensed ripples in space generated by the whirling bodies. The waves allowed physicists to peg their combined mass at 2.73 solar masses. Two seconds after the gravitational waves, orbiting telescopes detected a powerful, short gamma ray burst. Telescopes on Earth spotted the event’s afterglow, which faded over several days from bright blue to dimmer red.

    Together, the clues suggest the merger first produced a spinning, overweight neutron star momentarily propped up by centrifugal force. The afterglow shows that the merger spewed between 0.1 and 0.2 solar masses of newly formed radioactive elements into space, more than could have escaped from a black hole. The ejected material’s initial blue tint shows that at first, it lacked heavy elements called lanthanides. A flux of particles called neutrinos presumably slowed those elements’ formation, and a neutron star radiates copious neutrinos. The short gamma ray burst, the supposed birth cry of a black hole, indicates that the merged neutron star collapsed in seconds.

    To derive their mass limits, the teams dove into the details of the spinning neutron star. They generally argue that at first the outer layers of the merged neutron star likely spun faster than its center. Then it flung off material and slowed to form a rigid spinning body whose mass researchers could calculate from the masses of the original neutron stars minus the ejected material. The fact that this spinning neutron star survived only momentarily suggests that its mass was close to the limit for such a spinner.

    That last inference is essential, Rezzolla says. Theory suggests that the mass of a rigidly spinning neutron star can exceed that of a stationary one by up to 18%, he says. That scaling allows researchers to infer the maximum mass of a stationary, stable neutron star. The whole argument works because the initial neutron stars weren’t so massive that they immediately produced a black hole or so light that they produced a spinning neutron star that lingered longer, Shibata says. “This was a very lucky event,” he says.

    The analyses are persuasive, Lattimer says, although he quibbles with the precision implied in numbers such as 2.17 solar masses. “If you say 2.2 plus or minus a 10th, I would think it gets the same message across.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 2:51 pm on February 6, 2018 Permalink | Reply
    Tags: , , , BurstCube, , , , , Gravitational waves,   

    From Goddard: “NASA Technology to Help Locate Electromagnetic Counterparts of Gravitational Waves” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    Feb. 6, 2018
    By Lori Keesey
    NASA’s Goddard Space Flight Center

    1
    Principal Investigator Jeremy Perkins and his co-investigator, Georgia de Nolfo, recently won funding to build a new CubeSat mission, called BurstCube. Respectively, Perkins and de Nolfo hold a crystal, or scintillator, and silicon photomultiplier array technology that will be used to detect and localize gamma-ray bursts for gravitational-wave science. The photomultiplier array shown here specifically was developed for another CubeSat mission called TRYAD, which will investigate gamma-ray bursts in high-altitude lightning clouds.
    Credits: NASA/W. Hrybyk

    A compact detector technology applicable to all types of cross-disciplinary scientific investigations has found a home on a new CubeSat mission designed to find the electromagnetic counterparts of events that generate gravitational waves.

    NASA scientist Georgia de Nolfo and her collaborator, astrophysicist Jeremy Perkins, recently received funding from the agency’s Astrophysics Research and Analysis Program to develop a CubeSat mission called BurstCube. This mission, which will carry the compact sensor technology that de Nolfo developed, will detect and localize gamma-ray bursts caused by the collapse of massive stars and mergers of orbiting neutron stars. It also will detect solar flares and other high-energy transients once it’s deployed into low-Earth orbit in the early 2020s.

    The cataclysmic deaths of massive stars and mergers of neutron stars are of special interest to scientists because they produce gravitational waves — literally, ripples in the fabric of space-time that radiate out in all directions, much like what happens when a stone is thrown into a pond.

    Since the Laser Interferometer Gravitational Wave Observatory, or LIGO, confirmed their existence a couple years ago, LIGO and the European Virgo detectors have detected other events, including the first-ever detection of gravitational waves from the merger of two neutron stars announced in October 2017.

    Less than two seconds after LIGO detected the waves washing over Earth’s space-time, NASA’s Fermi Gamma-ray Space Telescope detected a weak burst of high-energy light — the first burst to be unambiguously connected to a gravitational-wave source.

    These detections have opened a new window on the universe, giving scientists a more complete view of these events that complements knowledge obtained through traditional observational techniques, which rely on detecting electromagnetic radiation — light — in all its forms.

    Complementary Capability

    Perkins and de Nolfo, both scientists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, see BurstCube as a companion to Fermi in this search for gravitational-wave sources. Though not as capable as the much larger Gamma-ray Burst Monitor, or GBM, on Fermi, BurstCube will increase coverage of the sky. Fermi-GBM observes the entire sky not blocked by the Earth. “But what happens if an event occurs and Fermi is on the other side of Earth, which is blocking its view,” Perkins said. “Fermi won’t see the burst.”

    BurstCube, which is expected to launch around the time additional ground-based LIGO-type observatories begin operations, will assist in detecting these fleeting, hard-to-capture high-energy photons and help determine where they originated. In addition to quickly reporting their locations to the ground so that other telescopes can find the event in other wavelengths and home in on its host galaxy, BurstCube’s other job is to study the sources themselves.

    Miniaturized Technology

    BurstCube will use the same detector technology as Fermi’s GBM; however, with important differences.

    Under the concept de Nolfo has advanced through Goddard’s Internal Research and Development program funding, the team will position four blocks of cesium-iodide crystals, operating as scintillators, in different orientations within the spacecraft. When an incoming gamma ray strikes one of the crystals, it will absorb the energy and luminesce, converting that energy into optical light.

    Four arrays of silicon photomultipliers and their associated read-out devices each sit behind the four crystals. The photomultipliers convert the light into an electrical pulse and then amplify this signal by creating an avalanche of electrons. This multiplying effect makes the detector far more sensitive to this faint and fleeting gamma rays.

    Unlike the photomultipliers on Fermi’s GBM, which are bulky and resemble old-fashioned television tubes, de Nolfo’s devices are made of silicon, a semiconductor material. “Compared with more conventional photomultiplier tubes, silicon photomultipliers significantly reduce mass, volume, power and cost,” Perkins said. “The combination of the crystals and new readout devices makes it possible to consider a compact, low-power instrument that is readily deployable on a CubeSat platform.”

    In another success for Goddard technology, the BurstCube team also has baselined the Dellingr 6U CubeSat bus that a small team of center scientists and engineers developed to show that CubeSat platforms could be more reliable and capable of gathering highly robust scientific data.

    “This is high-demand technology,” de Nolfo said. “There are applications everywhere.”

    For other Goddard technology news, go to https://www.nasa.gov/sites/default/files/atoms/files/winter_2018_final_lowrez.pdf

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    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 4:00 pm on December 20, 2017 Permalink | Reply
    Tags: , , , Gravitational waves, Update on Neutron Star Smash-Up: Jet Hits a Roadblock   

    From Caltech: “Update on Neutron Star Smash-Up: Jet Hits a Roadblock” 

    Caltech Logo

    Caltech

    12/20/2017

    Whitney Clavin
    (626) 395-1856
    wclavin@caltech.edu

    1
    On August 17, 2017, observatories around the world witnessed the collision of two neutron stars. At first, many scientists thought a narrow high-speed jet, directed away from our line of sight, or off-axis, was produced (diagram at left). But observations made at radio wavelengths now indicate the jet hit surrounding material, producing a slower-moving, wide-angle outflow, dubbed a cocoon (pink structure at right). Credit: NRAO/AUI/NSF/D. Berry

    Radio observations are illuminating what happened during recent gravitational-wave event.

    Millions of years ago, a pair of extremely dense stars, called neutron stars, collided in a violent smash-up that shook space and time. On August 17, 2017, both gravitational waves—ripples in space and time—and light waves emitted during that neutron star merger finally reached Earth. The gravitational waves came first and were detected by the twin detectors of the National Science Foundation (NSF)-funded Laser Interferometry Gravitational-wave Observatory (LIGO), aided by the European Virgo observatory.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    The light waves were observed seconds, days, and months later by dozens of telescopes on the ground and in space.

    Now, scientists from Caltech and several other institutions are reporting that light with radio wavelengths continues to brighten more than 100 days after the August 17 event. These radio observations indicate that a jet, launched from the two neutron stars as they collided, is slamming into surrounding material and creating a slower-moving, billowy cocoon.

    “We think the jet is dumping its energy into the cocoon,” says Gregg Hallinan, an assistant professor of astronomy at Caltech. “At first, people thought the material from the collision was coming out in a jet like a firehose, but we are finding that that the flow of material is slower and wider, expanding outward like a bubble.”

    The findings, made with the Karl G. Jansky Very Large Array in New Mexico, the Australia Telescope Compact Array, and the Giant Metrewave Radio Telescope in India, are reported in a new paper in the December 20 online issue of the journal Nature. The lead author is Kunal Mooley (PhD ’15), formerly of the University of Oxford and now a Jansky Fellow at Caltech.

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

    CSIRO ATCA at the Paul Wild Observatory, about 25 km west of the town of Narrabri in rural NSW about 500 km north-west of Sydney, AU

    GMRT Radio Telescope, located near Pune, India

    The new data argue against a popular theory describing the aftermath of the neutron star merger—a theory that proposes the event created a fast-moving and beam-like jet thought to be associated with extreme blasts of energy called gamma-ray bursts, and in particular with short gamma-ray bursts, or sGRBs. Scientists think that sGRBs, which pop up every few weeks in our skies, arise from the merger of a pair of neutron stars or the merger of a neutron star with a black hole (an event that has yet to be detected by LIGO). An sGRB is seen when the jet points exactly in the direction of Earth.


    A hydrodynamical simulation shows a cocoon breaking out of the neutron star merger. This model explains the gamma-ray, X-ray, ultraviolet, optical, infrared, and radio data gathered by the GROWTH team from 18 telescopes around the world. Credit: Ehud Nakar (Tel Aviv), Ore Gottlieb (Tel Aviv), Leo Singer (NASA), Mansi Kasliwal (Caltech), and the GROWTH collaboration.

    On August 17, NASA’s Fermi Gamma-ray Space Telescope and the European INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) missions detected gamma rays just seconds after the neutron stars merged.

    NASA/Fermi LAT


    NASA/Fermi Telescope

    ESA/Integral

    The gamma rays were much weaker than what is expected for sGRBS, so the researchers reasoned that a fast and narrowly focused jet was produced but must have been pointed slightly askew from the direction of Earth, or off-axis.

    The radio emission—originally detected 16 days after the August 17 event and still measurable and increasing in strength as of December 2—tells a different story. If the jet had been fast and beam-like, the radio light would have weakened with time as the jet lost energy. The fact that the brightness of the radio light is increasing instead suggests the presence of a cocoon that is choking the jet. The reason for this is complex, but it has to do with the fact that the slower-moving, wider-angle material of the cocoon gives off more radio light than the faster-moving, sharply focused jet material.

    “It’s like the jet was fogged out,” says Mooley. “The jet may be off-axis, but it is not a simple pointed beam or as fast as some people thought. It may be blocked off by material thrown off during the merger, giving rise to a cocoon and emitting light in many different directions.”

    This means that the August 17 event was not a typical sGRB as originally proposed.

    “Standard sGRBs are 10,000 times brighter than we saw for this event,” says Hallinan. “Many people thought this was because the gamma-ray emission was off-axis and thus much weaker. But it turns out that the gamma rays are coming from the cocoon rather than the jet. It is possible that the jet managed to eventually break out through the cocoon, but we haven’t seen any evidence for this yet. It is more likely that it got trapped and snuffed out by the cocoon.”

    The possibility that a cocoon was involved in the August 17 event was originally proposed in a study led by Caltech’s Mansi Kasliwal (MS ’07, PhD ’11), assistant professor of astronomy, and colleagues. She and her team from the NSF-funded Global Relay of Observatories Watching Transients Happen (GROWTH) project observed the event at multiple wavelengths using many different telescopes.

    “The cocoon model explains puzzling features we have observed in the neutron star merger,” says Kasliwal. “It fits observations across the electromagnetic spectrum, from the early blue light we witnessed to the radio waves and X-rays that turned on later. The cocoon model had predicted that the radio emission would continue to increase in brightness, and that’s exactly what we see.”

    The researchers say that future observations with LIGO, Virgo, and other telescopes will help further clarify the origins and mechanisms of these extreme events. The observatories should be able to detect additional neutron star mergers—and perhaps eventually, mergers of neutron stars and black holes.

    Work at Caltech on this study was funded by the NSF, the Sloan Research Foundation, and Research Corporation for Science Advancement. Other Caltech authors are Kishalay De, a graduate student, and Shri Kulkarni, George Ellery Hale Professor of Astronomy and Planetary Science.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 1:51 pm on December 11, 2017 Permalink | Reply
    Tags: , , , Binary neutron stars, , , Gravitational waves, ,   

    From DES: “What the galaxy that hosted the gravitational wave event GW170817 can teach us about binary neutron stars” 

    Dark Energy Icon

    The Dark Energy Survey

    November 22, 2017 [Just now in social media.]
    Antonella Palmese
    Sunayana Bhargava

    Astronomers know many facts about galaxies. For example, we know that their colours tell us about the stars inside them and how old they are. We also know that their shapes can tell us about how they formed. Past and current large-scale surveys such as the Dark Energy Survey (DES) observe millions of galaxies at different distances, and therefore at different stages of their evolution. These galaxies can be catalogued and characterized in a number of different ways. However, one type of star system we know little about are binary neutron stars (BNS). The handful of confirmed binary neutron stars found have all been within our own galaxy.

    The optical counterpart to GW170817 was observed by the Dark Energy Camera (DECam) and other instruments to have come from a galaxy named NGC 4993, which is 130 million light years away from us. This event was likely produced by a binary neutron star merger. Antonella Palmese, together with other galaxy evolution and gravitational wave experts (Will Hartley, Marcelle Soares-Santos, Jim Annis, Huan Lin, Christopher Conselice, Federica Tarsitano and more) asked the question: what can we learn about the stars in NGC 4993? How did this binary system emerge in the overall history of the galaxy? Although we only have one snapshot of this galaxy, which is precisely 130 million years old, we can make use of other properties to infer how this galaxy evolved over cosmic time.

    At first glance, NGC 4993 looks like a normal, old massive elliptical galaxy (left panel in Figure 1), known by astronomers as an “early type galaxy”. But if we examine it more closely, we see that it contains shell structures: arcs of brighter stellar densities around the center of the galaxy. If we consider the profile of a typical, early type galaxy (see middle panel in Figure 1) and subtract it from the profile of NGC 4993, we notice key differences that help us characterize the kind of environment needed for binary neutron stars to form.

    1
    Figure 1. Left panel: DECam image of NCG 4993. Shell structures indicative of a recent galaxy merger are clearly visible. Middle panel: r-band residuals after subtraction of a Sérsic light profile. Right panel: F606W-band HST ACS image with a 3 component galaxy model subtracted. Dust lanes crossing the centre of the galaxy are evident after this subtraction. The green lines show the position of the transient.

    A number of papers starting from the 1980s have supported, with simulations and observations, the idea that these kind of shell structures are the debris of a recent merger between two galaxies (see a simulation example: http://hubblesite.org/video/558/news/4-galaxies ). During the merger, the stars from the smaller galaxy that passed close to NGC4993 millions of years ago were stripped away. As a result, many stars are concentrated in these arc-like regions. From the innermost shell position and the velocity of stars, we estimate that the shells in this galaxy should be visible for ~200 million years before dispersing. This means, if we still see them, the galaxy merger must have happened up to 200 million years before the BNS coalescence (see Figure 2 for a timeline). Could the dynamics of this galaxy merger be involved in the formation of the GW progenitor?

    3
    Figure 2. Timeline of NGC 4993

    DES only observes in optical photometric bands so we added information from infrared and spectroscopic surveys to study this galaxy in greater detail. We find more evidence for a recent galaxy merger (e.g. dust lanes, right panel of Figure 1, and two different stellar populations). We also find that the age of most of the stars in this galaxy is ~11 billion years old – only a few billion years younger than the Universe! This means that during its ‘recent’ stages, this galaxy has not been forming stars.

    Most of the current models for the formation of BNS suggest that they begin as a binary of two massive stars from a star formation event. During the evolution of the massive star binary, both stars will become supernova. If the gravitational force between the stars is strong enough to keep them bound against the force of the supernovae explosions, they become neutron stars in orbit until they coalesce. Simulations show us that neutron stars usually orbit around each other for ~500 million years before they merge, but it can take up to some billion years. Their lifetime before becoming neutron stars is much shorter than that.

    So if there was no recent star formation in NGC 4993, where did these massive stars, which go on to become neutron stars, come from? If they formed 11 billion years ago with other stars in the galaxy, why did they only merge now? Our work shows that it is unlikely that the BNS was formed ordinarily. We do not expect this BNS to be so old given the current knowledge of their expected lifetime from simulations. We instead suggest that the formation of the BNS was not through traditional channels. Instead, dynamical interactions between stars due to the galaxy merger might have caused the two neutron stars to form a binary or to coalesce. The plan for the future is to discover many more of these BNS systems inside their galactic hosts. With more data, it will be possible to determine how galaxies are able to produce the right conditions for this energetic dance of dense bodies to occur, creating ripples of energy (gravitational waves) that teach us about the Universe.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 3:11 pm on November 14, 2017 Permalink | Reply
    Tags: , , , Gravitational waves,   

    From Symmetry: “Q&A with Nobel laureate Barry Barish” 

    Symmetry Mag
    Symmetry

    11/14/17
    Leah Hesla

    1
    Illustration by Ana Kova

    These days the LIGO experiment seems almost unstoppable.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    In September 2015, LIGO detected gravitational waves directly for the first time in history. Afterward, they spotted them three times more, definitively blowing open the doors on the new field of gravitational-wave astronomy.

    On October 3, the Nobel Committee awarded their 2017 prize in physics to some of the main engines behind the experiment. Just two weeks after that, LIGO scientists revealed that they’d seen, for the first time, gravitational waves from the collision of neutron stars, an event confirmed by optical telescopes—yet another first.

    These recent achievements weren’t inevitable. It took LIGO scientists decades to get to this point.

    LIGO leader Barry Barish, one of the three recipients of the 2017 Nobel, recently sat down with Symmetry writer Leah Hesla to give a behind-the-scenes look at his 22 years on the experiment.

    2
    Barry Barish, who obtained his B.S. and Ph.D from UC Berkeley in 1957 and 1962, respectively, shared the 2017 Nobel Prize in Physics for the discovery of gravitational waves. Barish is the Ronald and Maxine Linde Professor of Physics, Emeritus, at Caltech. (Caltech photo)

    What has been your role at LIGO?

    I started in 1994 and came on board at a time when we didn’t have the money. I had to get the money and have a strategy that [the National Science Foundation] would buy into, and I had to have a plan that they would keep supporting for 22 years. My main mission was to build this instrument—which we didn’t know how to make—well enough to do what it did.

    So we had to build enough trust and success without discovering gravitational waves so that NSF would keep supporting us. And we had to have the flexibility to evolve LIGO’s design, without costing an arm and a leg, to make the improvements that would eventually make it sensitive enough to succeed.

    We started running in about 2000 and took data and improved the experiment over 10 years. But we just weren’t sensitive enough. We managed to get a major improvement program to what’s called Advanced LIGO from the National Science Foundation. After a year and a half or so of making it work, we turned on the device in September of 2015 and, within days, we’d made the detection.

    What steps did LIGO take to be as sensitive as possible?

    We were limited very much by the shaking of the Earth—at the low frequencies, the Earth just shakes too much. We also couldn’t get rid of the background noise at high frequencies—we can’t sample fast enough.

    In the initial LIGO, we reduced the shaking by something like 100 million. We had the fanciest set of shock absorbers possible. The shock absorbers in your car take a bump that you go over, which is high-frequency, and transfer it softly to low-frequency. You get just a little up and down; you don’t feel very much when you go over a bump. You can’t get rid of the bump—that’s energy—but you can transfer it out of the frequencies where it bothers you.

    So we do the same thing. We have a set of springs that are fancier but are basically like shock absorbers in your car. That gave us a factor of 100 million reduction in the shaking of the Earth.

    But that wasn’t good enough [for initial LIGO].

    What did you do to increase sensitivity for Advanced LIGO?

    After 15 years of not being able to detect gravitational waves, we implemented what we call active seismic isolation, in addition to passive springs. It’s very much equivalent to what happens when you get on an airplane and you put those [noise cancellation] earphones on. All of a sudden the airplane is less noisy. That works by detecting the ambient noise—not the noise by the attendant dropping a glass or something. That’s a sharp noise, and you’d still hear that, or somebody talking to you, which is a loud independent noise. But the ambient noise of the motors and the shaking of the airplane itself are more or less the same now as they were a second ago, so if you measure the frequency of the ambient noise, you can cancel it.

    In Advanced LIGO, we do the same thing. We measure the shaking of the Earth, and then we cancel it with active sensors. The only difference is that our problem is much harder. We have to do this directionally. The Earth shakes in a particular direction—it might be up and down, it might be sideways or at an angle. It took us years to develop this active seismic isolation.

    The idea was there 15 years ago, but we had to do a lot of work to develop very, very sensitive active seismic isolation. The technology didn’t exist—we developed all that technology. It reduced the shaking of the Earth by another factor of 100 [over LIGO’s initial 100 million], so we reduced it by a factor of 10 billion.

    So we could see a factor of 100 further out in the universe than we could have otherwise. And each factor of 10 gets cubed because we’re looking at stars and galaxies [in three dimensions]. So when we improved [initial LIGO’s sensitivity] by a factor of 100 beyond this already phenomenal number of 100 million, it improved our sensitivity immediately, and our rate of seeing these kinds of events, by a factor of a hundred cubed—by a million.

    That’s why, after a few days of running, we saw something. We couldn’t have seen this in all the years that we ran at lower sensitivity.

    What key steps did you take when you came on board in 1994?

    First we had to build a kind of technical group that had the experience and abilities to take on a $100 million project. So I hired a lot of people. It was a good time to do that because it was soon after the closure of the Superconducting Super Collider in Texas. I knew some of the most talented people who were involved in that, so I brought them into LIGO, including the person who would be the project manager.

    Second, I made sure the infrastructure was scaled to a stage where we were doing it not the cheapest we could, but rather the most flexible.

    The third thing was to convince NSF that doing this construction project wasn’t the end of what we had to do in terms of development. So we put together a vigorous R&D program, which NSF supported, to develop the technology that would follow similar ones that we used.

    And then there were some technical changes—to become as forward-looking as possible in terms of what we might need later.

    What were the technical changes?

    The first was to change from what was the most popularly used laser in the 1990s, which was a gas laser, to a solid-state laser, which was new at that time. The solid-state laser had the difficulty that the light was no longer in the visible range. It was in the infrared, and people weren’t used to interferometers like that. They like to have light bouncing around that they can see, but you can’t see the solid-state laser light with your naked eye. That’s like particle physics. You can’t see the particles in the accelerator either. We use sensors to do that. So we made that kind of change, going from analog controls to digital controls, which are computer-based.

    We also inherited the kind of control programs that had been developed for accelerators and used at the Superconducting Super Collider, and we brought the SSC controls people into LIGO. These changes didn’t pay off immediately, but paved the road toward making a device that could be modern and not outdated as we moved through the 20 years. It wasn’t so much fixing things as making LIGO much more forward-looking—to make it more and more sensitive, which is the key thing for us.

    Did you draw on past experience?

    I think my history in particle physics was crucial in many ways, for example, in technical ways—things like digital controls, how we monitored beam. We don’t use the same technology, but the idea that you don’t have to see it physically to monitor it—those kinds of things carried over.

    The organization, how we have scientific collaborations, was again something that I created here at LIGO, which was modeled after high-energy physics collaborations. Some of it has to be modified for this different kind of project—this is not an accelerator—but it has a lot of similarities because of the way you approach a large scientific project.

    Were you concerned the experiment wouldn’t happen? If not, what did concern you?

    As long as we kept making technical progress, I didn’t have that concern. My only real concern was nature. Would we be fortunate enough to see gravitational waves at the sensitivities we could get to? It wasn’t predicted totally. There were optimistic predictions—that we could have detected things earlier — but there are also predictions we haven’t gotten to. So my main concern was nature.

    When did you hear about the first detection of gravitational waves?

    If you see gravitational waves from some spectacular thing, you’d also like to be able to see something in telescopes and electromagnetic astronomy that’s correlated. So because of that, LIGO has an early alarm system that alerts you that there might be a gravitational wave event. We more or less have the ability to see spectacular things early. But if you want people to turn their telescopes or other devices to point at something in the sky, you have to tell them something in time scales of minutes or hours, not weeks or months.

    The day we saw this, which we saw early in its running, it happened at 4:50 in the morning in Louisiana, 2:50 in the morning in California, so I found out about it at breakfast time for me, which was about four hours later. When we alert the astronomers, we alert key people from LIGO as well. We get things like that all the time, but this looked a little more serious than others. After a few more hours that day, it became clear that this was nothing like anything we’d seen before, and in fact looked a lot like what we were looking for, and so I would say some people became convinced within hours.

    I wasn’t, but that’s my own conservatism: What’s either fooling us or how are we fooling ourselves? There were two main issues. One is the possibility that maybe somebody was inserting a rogue event in our data, some malicious way to try to fool us. We had to make sure we could trace the history of the events from the apparatus itself and make sure there was no possibility that somebody could do this. That took about a month of work. The second was that LIGO was a brand new, upgraded version, so I wasn’t sure that there weren’t new ways to generate things that would fool us. Although we had a lot of experience over a lot of years, it wasn’t really with this version of LIGO. This version was only a few days old. So it took us another month or so to convince us that it was real. It was obvious that there was going to be a classic discovery if it held up.

    What does it feel like to win the Nobel Prize?

    It happened at 3 in the morning here [in California]. [The night before], I had a nice dinner with my wife, and we went to bed early. I set the alarm for 2:40. They were supposed to announce the result at 2:45. I don’t know why I set it for 2:40, but I did. I moved the house phone into our bedroom.

    The alarm did go off at 2:40. There was no call, obviously—I hadn’t been awakened, so I assumed, kind of in my groggy state, that we must have been passed over. I started going to my laptop to see who was going to get it. Then my cell phone started ringing. My wife heard it. My cell phone number is not given out, generally. There are tens of people who have it, but how [the Nobel Foundation] got it, I’m not sure. Some colleague, I suppose. It was a surprise to me that it came on the cell phone.

    The president of the Nobel Foundation told me who he was, said he had good news and told me I won. And then we chatted for a few minutes, and he asked me how I felt. And I spontaneously said that I felt “thrilled and humbled at the same time.” There’s no word for that, exactly, but that mixture of feeling is what I had and still have.

    Do you have advice for others organizing big science projects?

    We have an opportunity. As I grew into this and as science grew big, we always had to push and push and push on technology, and we’ve certainly done that on LIGO. We do that in particle physics, we do that in accelerators.

    I think the table has turned somewhat and that the technology has grown so fast in the recent decades that there’s incredible opportunities to do new science. The development of new technologies gives us so much ability to ask difficult scientific questions. We’re in an era that I think is going to propagate fantastically into the future.

    Just in the new millennium, maybe the three most important discoveries in physics have all been done with, I would say, high-tech, modern, large-scale devices: the neutrino experiments at SNO and Kamiokande doing the neutrino oscillations, which won a Nobel Prize in 2013; the Higgs boson—no device is more complicated or bigger or more technically advanced than the CERN LHC experiments; and then ours, which is not quite the scale of the LHC, but it’s the same scale as these experiments—the billion dollar scale—and it’s very high-tech.

    Einstein thought that gravitational waves could never be detected, but he didn’t know about lasers, digital controls and active seismic isolation and all things that we developed, all the high-tech things that are coming from industry and our pushing them a little bit harder.

    The fact is, technology is changing so fast. Most of us can’t live without GPS, and 10 or 15 years ago, we didn’t have GPS. GPS exists because of general relativity, which is what I do. The inner silicon microstrip detectors in the CERN experiment were developed originally for particle physics. They developed rapidly. But now, they’re way behind what’s being done in industry in the same area. Our challenge is to learn how to grab what is being developed, because technology is becoming great.

    I think we need to become really aware and understand the developments of technology and how to apply those to the most basic physics questions that we have and do it in a forward-looking way.

    What are your hopes for the future of LIGO?

    It’s fantastic. For LIGO itself, we’re not limited by anything in nature. We’re limited by ourselves in terms of improving it over the next 15 years, just like we improved in going from initial LIGO to Advanced LIGO. We’re not at the limit.

    So we can look forward to certainly a factor of 2 to 3 improvement, which we’ve already been funded for and are ready for, and that will happen over the next few years. And that factor of 2 or 3 gets cubed in our case.

    This represents a completely new way to look at the universe. Everything we look at was with electromagnetic radiation, and a little bit with neutrinos, until we came along. We know that only a few percent of what’s out there is luminous, and so we are opening a new age of astronomy, really. At the same time, we’re able to test Einstein’s theories of general relativity in its most important way, which is by looking where the fields are the strongest, around black holes.

    That’s the opportunity that exists over a long time scale with gravitational waves. The fact that they’re a totally different way of looking at the sky means that in the long term it will develop into an important part of how we understand our universe and where we came from. Gravitational waves are the best way possible, in theory—we can’t do it now—of going back to the very beginning, the Big Bang, because they weren’t absorbed. What we know now comes from photons, but they can go back to only 300,000 years from the Big Bang because they’re absorbed.

    We can go back to the beginning. We don’t know how to do it yet, but that is the potential.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 3:16 pm on November 13, 2017 Permalink | Reply
    Tags: , , , , , Gravitational waves, , Observing low-frequency gravitational waves would be akin to being able to hear bass singers not just sopranos. To explore this uncharted area of gravitational wave science researchers look not to hum, The new Nature Astronomy study concerns supermassive black hole binaries   

    From JPL-Caltech: “Listening for Gravitational Waves Using Pulsars” 

    NASA JPL Banner

    JPL-Caltech

    November 13, 2017
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    (818) 354-6425
    Elizabeth.Landau@jpl.nasa.gov

    1
    This computer simulation shows the collision of two black holes, which produces gravitational waves. Credit: Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project.

    One of the most spectacular achievements in physics so far this century has been the observation of gravitational waves, ripples in space-time that result from masses accelerating in space. So far, there have been five detections of gravitational waves, thanks to the Laser Interferometer Gravitational-Wave Observatory (LIGO) and, more recently, the European Virgo gravitational-wave detector.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    Using these facilities, scientists have been able to pin down the extremely subtle signals from relatively small black holes and, as of October, neutron stars.

    UC Santa Cruz

    UC Santa Cruz

    14

    A UC Santa Cruz special report

    Tim Stephens

    Astronomer Ryan Foley says “observing the explosion of two colliding neutron stars” [see https://sciencesprings.wordpress.com/2017/10/17/from-ucsc-first-observations-of-merging-neutron-stars-mark-a-new-era-in-astronomy ]–the first visible event ever linked to gravitational waves–is probably the biggest discovery he’ll make in his lifetime. That’s saying a lot for a young assistant professor who presumably has a long career still ahead of him.

    2
    The first optical image of a gravitational wave source was taken by a team led by Ryan Foley of UC Santa Cruz using the Swope Telescope at the Carnegie Institution’s Las Campanas Observatory in Chile. This image of Swope Supernova Survey 2017a (SSS17a, indicated by arrow) shows the light emitted from the cataclysmic merger of two neutron stars. (Image credit: 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley)

    Carnegie Institution Swope telescope at Las Campanas, Chile, 100 kilometres (62 mi) northeast of the city of La Serena. near the north end of a 7 km (4.3 mi) long mountain ridge. Cerro Las Campanas, near the southern end and over 2,500 m (8,200 ft) high, at Las Campanas, Chile

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

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

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

    THE MERGER

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

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

    But there are merging objects far larger whose gravitational wave signals have not yet been detected: supermassive black holes, more than 100 million times more massive than our Sun. Most large galaxies have a central supermassive black hole. When galaxies collide, their central black holes tend to spiral toward each other, releasing gravitational waves in their cosmic dance. Much as a large animal like a lion produces a deeper roar than a tiny mouse’s squeak, merging supermassive black holes create lower-frequency gravitational waves than the relatively small black holes LIGO and similar ground-based experiments can detect.

    “Observing low-frequency gravitational waves would be akin to being able to hear bass singers, not just sopranos,” said Joseph Lazio, chief scientist for NASA’s Deep Space Network, based at NASA’s Jet Propulsion Laboratory, Pasadena, California, and co-author of a new study in Nature Astronomy.

    To explore this uncharted area of gravitational wave science, researchers look not to human-made machines, but to a natural experiment in the sky called a pulsar timing array. Pulsars are dense remnants of dead stars that regularly emit beams of radio waves, which is why some call them “cosmic lighthouses.” Because their rapid pulse of radio emission is so predictable, a large array of well-understood pulsars can be used to measure extremely subtle abnormalities, such as gravitational waves. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav), a Physics Frontier Center of the National Science Foundation, is one of the leading groups of researchers using pulsars to search for gravitational waves.

    The new Nature Astronomy study concerns supermassive black hole binaries — systems of two of these cosmic monsters. For the first time, researchers surveyed the local universe for galaxies likely to host these binaries, then predicted which black hole pairs are the likeliest to merge and be detected while doing so. The study also estimates how long it will take to detect one of these mergers.

    “By expanding our pulsar timing array over the next 10 years or so, there is a high likelihood of detecting gravitational waves from at least one supermassive black hole binary,” said Chiara Mingarelli, lead study author, who worked on this research as a Marie Curie postdoctoral fellow at Caltech and JPL, and is now at the Flatiron Institute in New York.

    Mingarelli and colleagues used data from the 2 Micron All-Sky Survey (2MASS), which surveyed the sky from 1997 to 2001, and galaxy merger rates from the Illustris simulation project, an endeavor to make large-scale cosmological simulations. In their sample of about 5,000 galaxies, scientists found that about 90 would have supermassive black holes most likely to merge with another black hole.

    While LIGO and similar experiments detect objects in the final seconds before they merge, pulsar timing arrays are sensitive to gravitational wave signals from supermassive black holes that are spiraling toward each other and will not combine for millions of years. That’s because galaxies merge hundreds of millions of years before the central black holes they host combine to make one giant supermassive black hole.

    Researchers also found that while bigger galaxies have bigger black holes and produce stronger gravitational waves when they combine, these mergers also happen fast, shortening the time period for detection. For example, black holes merging in the large galaxy M87 would have a 4-million-year window of detection. By contrast, in the smaller Sombrero Galaxy, black holes mergers typically take about 160 million years, offering more opportunities for pulsar timing arrays to detect gravitational waves from them.

    Black hole mergers generate gravitational waves because, as they orbit each other, their gravity distorts the fabric of space-time, sending ripples outward in all directions at the speed of light. These distortions actually shift the position of Earth and the pulsars ever so slightly, resulting in a characteristic and detectable signal from the array of celestial lighthouses.

    “A difference between when the pulsar signals should arrive, and when they do arrive, can signal a gravitational wave,”Mingarelli said. “And since the pulsars we study are about 3,000 light-years away, they act as a galactic-scale gravitational-wave detector.”

    Because all supermassive black holes are so distant, gravitational waves, which travel at the speed of light, take a long time to arrive at Earth. This study looked at supermassive black holes within about 700 million light-years, meaning waves from a merger between any two of them would take up to that long to be detected here by scientists. By comparison, about 650 million years ago, algae flourished and spread rapidly in Earth’s oceans — an event important to the evolution of more complex life.

    Many open questions remain about how galaxies merge and what will happen when the Milky Way approaches Andromeda, the nearby galaxy that will collide with ours in about 4 billion years.

    “Detecting gravitational waves from billion-solar-mass black hole mergers will help unlock some of the most persistent puzzles in galaxy formation,” said Leonidas Moustakas, a JPL research scientist who wrote an accompanying “News and Views” article in the journal.

    2MASS was funded by NASA’s Office of Space Science, the National Science Foundation, the U.S. Naval Observatory and the University of Massachusetts. JPL managed the program for NASA’s Office of Space Science, Washington. Data was processed at IPAC at Caltech in Pasadena, California.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo

    NASA image

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: