Tagged: Caltech/MIT aLIGO Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 3:06 pm on July 18, 2017 Permalink | Reply
    Tags: Caltech/MIT aLIGO, , ,   

    From COSMOS: “How giant atoms may help catch gravitational waves from the Big Bang” 

    Cosmos Magazine bloc

    COSMOS

    7.18.17
    Diego A. Quiñones, U Leeds

    Huge, highly excited atoms may give off flashes of light when hit by a gravitational wave.

    1
    Some of the earliest known galaxies in the universe, seen by the Hubble Space Telescope. NASA/ESA

    NASA/ESA Hubble Telescope

    There was a lot of excitement last year when the LIGO collaboration detected gravitational waves, which are ripples in the fabric of space itself.


    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

    And it’s no wonder – it was one of the most important discoveries of the century. By measuring gravitational waves from intense astrophysical processes like merging black holes, the experiment opens up a completely new way of observing and understanding the universe.

    But there are limits to what LIGO can do. While gravitational waves exist with a big variety of frequencies, LIGO can only detect those within a certain range. In particular, there’s no way of measuring the type of high frequency gravitational waves that were generated in the Big Bang itself. Catching such waves would revolutionise cosmology, giving us crucial information about how the universe came to be. Our research presents a model that may one day enable this.

    In the theory of general relativity developed by Einstein, the mass of an object curves space and time – the more mass, the more curvature. This is similar to how a person stretches the fabric of a trampoline when stepping on it. If the person starts moving up and down, this would generate undulations in the fabric that will move outwards from the position of the person. The speed at which the person is jumping will determine the frequency of the generated ripples in the fabric.

    An important trace of the Big Bang is the Cosmic Microwave Background.

    CMB per ESA/Planck

    ESA/Planck

    This is the radiation left over from the birth of the universe, created about 300,000 years after the Big Bang. But the birth of our universe also created gravitational waves – and these would have originated just a fraction of a second after the event. Because these gravitational waves contain invaluable information about the origin of the universe, there is a lot of interest in detecting them. The waves with the highest frequencies may have originated during phase transitions of the primitive universe or by vibrations and snapping of cosmic strings.

    An instant flash of brightness

    Our research team, from the universities of Aberdeen and Leeds, think that atoms may have an edge in detecting elusive, high-frequency gravitational waves. We have calculated that a group of “highly excited” atoms (called Rydberg atoms – in which the electrons have been pushed out far away from the atom’s nucleus, making it huge – will emit a bright pulse of light when hit by a gravitational wave.

    To make the atoms excited, we shine a light on them. Each of these enlarged atoms is usually very fragile and the slightest perturbation will make them collapse, releasing the absorbed light. However, the interaction with a gravitational wave may be too weak, and its effect will be masked by the many interactions such as collisions with other atoms or particles.

    Rather than analysing the interaction with individual atoms, we model the collective behaviour of a big group of atoms packed together. If the group of atoms is exposed to a common field, like our oscillating gravitational field, this will induce the excited atoms to decay all at the same time. The atoms will then release a large number of photons (light particles), generating an intense pulse of light, dubbed “superradiance”.

    As Rydberg atoms subjected to a gravitational wave will superradiate as a result of the interaction, we can guess that a gravitational wave has passed through the atomic ensemble whenever we see a light pulse.

    By changing the size of the atoms, we can make them radiate to different frequencies of the gravitational wave. This can be this useful for detection in different ranges. Using the proper kind of atoms, and under ideal conditions, it could be possible to use this technique to measure relic gravitational waves from the birth of the universe. By analysing the signal of the atoms it is possible to determine the properties, and therefore the origin, of the gravitational waves.

    There may be some challenges for this experimental technique: the main one is getting the atoms in an highly excited state. Another one is to have enough atoms, as they are so big that they become very hard to contain.

    A theory of everything?

    Beyond the possibility of studying gravitational waves from the birth of the universe, the ultimate goal of the research is to detect gravitational fluctuations of empty space itself – the vacuum. These are extremely faint gravitational variations that occur spontaneously at the smallest scale, popping up out of

    Discovering such waves could lead to the unification of general relativity and quantum mechanics, one of the greatest challenges in modern physics. General relativity is unparalleled when it comes to describing the world on a large scale, such as planets and galaxies, while quantum mechanics perfectly describes physics on the smallest scale, such as the atom or even parts of the atom. But working out the gravitational impact of the tiniest of particles will therefore help bridge this divide.

    But discovering the waves associated with such quantum fluctuations would require a great number of atoms prepared with an enormous amount of energy, which may not be possible to do in the laboratory. Rather than doing this, it might be possible to use Rydberg atoms in outer space. Enormous clouds of these atoms exist around white dwarfs – stars which have run out of fuel – and inside nebulas with sizes more than four times larger than anything that can be created on Earth. Radiation coming from these sources could contain the signature of the vacuum gravitational fluctuations, waiting to be unveiled.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 5:58 pm on June 28, 2017 Permalink | Reply
    Tags: , , , Caltech/MIT aLIGO, , , NRAO VLBA, ,   

    From Stanford and Kavli: “Stanford Research Reveals Extremely Fine Measurements of Motion in Orbiting Supermassive Black Holes” 

    Stanford University Name
    Stanford University

    KavliFoundation

    The Kavli Foundation

    1
    Observations from radio telescopes like this one appear to indicate that two black holes are orbiting each other, 750 million light years from Earth. (Credit: National Radio Astronomy Observatory)

    Approximately 750 million light years from Earth lies a gigantic, bulging galaxy with two supermassive black holes at its center. These are among the largest black holes ever found, with a combined mass 15 billion times that of the sun. New research from Stanford University, published today (June 27) in Astrophysical Journal, has used long-term observation to show that one of the black holes seems to be orbiting around the other.

    If confirmed, this is the first duo of black holes ever shown to be moving in relation to each other. It is also, potentially, the smallest ever recorded movement of an object across the sky, also known as angular motion.

    “If you imagine a snail on the recently discovered Earth-like planet orbiting Proxima Centauri – a bit over four light years away – moving at one centimeter a second, that’s the angular motion we’re resolving here,” said co-author of the paper, Roger W. Romani, professor of physics at Stanford and a member of the Kavli Insititute for Particle Astrophysics and Cosmology. The team also included researchers from the University of New Mexico, the National Radio Observatory and the United States Naval Observatory.

    The technical achievements of this measurement alone are reason for celebration. But the researchers also hope this impressive finding will offer insight into how black holes merge, how these mergers affect the evolution of the galaxies around them and ways to find other binary black-hole systems.

    Miniscule movement

    Over the past 12 years, scientists, led by Greg Taylor, a professor of physics and astronomy at the University of New Mexico, have taken snapshots of the galaxy containing these black holes – called radio galaxy 0402+379 – with a system of ten radio telescopes that stretch from the U.S. Virgin Islands to Hawaii and New Mexico to Alaska.

    NRAO VLBA


    NRAO VLBA

    The galaxy was officially discovered back in 1995. In 2006, scientists confirmed it as a supermassive black-hole binary system with an unusual configuration.

    “The black holes are at a separation of about seven parsecs, which is the closest together that two supermassive black holes have ever been seen before,” said Karishma Bansal, a graduate student in Taylor’s lab and lead author of the paper.

    With this most recent paper, the team reports that one of the black holes moved at a rate of just over one micro-arcsecond per year, an angle about 1 billion times smaller than the smallest thing visible with the naked eye. Based on this movement, the researchers hypothesize that one black hole may be orbiting around the other over a period of 30,000 years.
    Two holes in ancient galaxy

    Although directly measuring the black hole’s orbital motion may be a first, this is not the only supermassive black-hole binary ever found. Still, the researchers believe that 0402+379 likely has a special history.

    “We’ve argued it’s a fossil cluster,” Romani said. “It’s as though several galaxies coalesced to become one giant elliptical galaxy with an enormous halo of X-rays around it.”

    Researchers believe that large galaxies often have large black holes at their centers and, if large galaxies combine, their black holes eventually follow suit. It’s possible that the apparent orbit of the black hole in 0402+379 is an intermediary stage in this process.

    “For a long time, we’ve been looking into space to try and find a pair of these supermassive black holes orbiting as a result of two galaxies merging,” Taylor said. “Even though we’ve theorized that this should be happening, nobody had ever seen it, until now.”

    A combination of the two black holes in 0402+379 would create a burst of gravitational radiation, like the famous bursts recently discovered by the Laser Interferometer Gravitational-Wave Observatory, but scaled up by a factor of a billion.


    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

    It would be the most powerful gravitational burst in the universe, Romani said. This kind of radiation burst happens to be what he wrote his first-ever paper on when he was an undergraduate.

    Very slow dance

    This theorized convergence between the black holes of 0402+379, however, may never occur. Given how slowly the pair is orbiting, the scientists think the black holes are too far apart to come together within the estimated remaining age of the universe, unless there is an added source of friction. By studying what makes this stalled pair unique, the scientists said they may be able to better understand the conditions under which black holes normally merge.

    Romani hopes this work could be just the beginning of heightening interest in unusual black-hole systems.

    “My personal hope is that this discovery inspires people to go out and find other systems that are even closer together and, hence, maybe do their motion on a more human timescale,” Romani said. “I would sure be happy if we could find a system that completed orbit within a few decades so you could really see the details of the black holes’ trajectories.”

    Additional co-authors on this paper are A.B. Peck, Gemini Observatory (formerly of the National Radio Astronomy Observatory); and R.T. Zavala, U.S. Naval Observatory.

    This work was funded by NASA and the National Radio Astronomical Observatory.

    See the full Stanford article here .
    See the Full Kavli Foundation article here.

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition

    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 4:39 pm on June 23, 2017 Permalink | Reply
    Tags: Caltech/MIT aLIGO, , , , NASA/DLR Grace   

    From Goddard: “ESA to Develop Gravitational Wave Space Mission with NASA Support” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    June 22, 2017
    Francis Reddy
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    ESA (the European Space Agency) has selected the Laser Interferometer Space Antenna (LISA) for its third large-class mission in the agency’s Cosmic Vision science program. The three-spacecraft constellation is designed to study gravitational waves in space and is a concept long studied by both ESA and NASA.

    ESA’s Science Program Committee announced the selection at a meeting on June 20. The mission will now be designed, budgeted and proposed for adoption before construction begins. LISA is expected to launch in 2034. NASA will be a partner with ESA in the design, development, operations and data analysis of the mission.

    ESA/eLISA the future of gravitational wave research

    Gravitational radiation was predicted a century ago by Albert Einstein’s general theory of relativity. Massive accelerating objects such as merging black holes produce waves of energy that ripple through the fabric of space and time. Indirect proof of the existence of these waves came in 1978, when subtle changes observed in the motion of a pair of orbiting neutron stars showed energy was leaving the system in an amount matching predictions of energy carried away by gravitational waves.

    In September 2015, these waves were first directly detected by the National Science Foundation’s ground-based Laser Interferometer Gravitational-Wave Observatory (LIGO).


    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

    The signal arose from the merger of two stellar-mass black holes located some 1.3 billion light-years away. Similar signals from other black hole mergers have since been detected.

    Seismic, thermal and other noise sources limit LIGO to higher-frequency gravitational waves around 100 cycles per second (hertz). But finding signals from more powerful events, such as mergers of supermassive black holes in colliding galaxies, requires the ability to detect frequencies much lower than 1 hertz, a sensitivity level only possible from space.

    LISA consists of three spacecraft separated by 1.6 million miles (2.5 million kilometers) in a triangular formation that follows Earth in its orbit around the sun. Each spacecraft carries test masses that are shielded in such a way that the only force they respond to is gravity. Lasers measure the distances to test masses in all three spacecraft. Tiny changes in the lengths of each two-spacecraft arm signals the passage of gravitational waves through the formation.

    For example, LISA will be sensitive to gravitational waves produced by mergers of supermassive black holes, each with millions or more times the mass of the sun. It will also be able to detect gravitational waves emanating from binary systems containing neutron stars or black holes, causing their orbits to shrink. And LISA may detect a background of gravitational waves produced during the universe’s earliest moments.

    For decades, NASA has worked to develop many technologies needed for LISA, including measurement, micropropulsion and control systems, as well as support for the development of data analysis techniques.

    For instance, the GRACE Follow-On mission, a U.S. and German collaboration to replace the aging GRACE satellites scheduled for launch late this year, will carry a laser measuring system that inherits some of the technologies originally developed for LISA.

    NASA/DLR Grace

    The mission’s Laser Ranging Interferometer will track distance changes between the two satellites with unprecedented precision, providing the first demonstration of the technology in space.

    In 2016, ESA’s LISA Pathfinder successfully demonstrated key technologies needed to build LISA.

    ESA/LISA Pathfinder

    Each of LISA’s three spacecraft must gently fly around its test masses without disturbing them, a process called drag-free flight. In its first two months of operations, LISA Pathfinder demonstrated this process with a precision some five times better than its mission requirements and later reached the sensitivity needed for the full multi-spacecraft observatory. U.S. researchers collaborated on aspects of LISA Pathfinder for years, and the mission carries a NASA-supplied experiment called the ST7 Disturbance Reduction System, which is managed by NASA’s Jet Propulsion Laboratory in Pasadena, California.

    For more information about the LISA project, visit:

    https://lisa.nasa.gov

    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 4:13 pm on June 15, 2017 Permalink | Reply
    Tags: Barry Barish, , Caltech/MIT aLIGO, Kip S. Thorne, LIGO Team Wins Princess of Asturias Award, The late Caltech professor of physics Ronald W. P. Drever   

    From Caltech: “LIGO Team Wins Princess of Asturias Award” 

    Caltech Logo

    Caltech

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

    1
    Barry Barish and Kip Thorne of Caltech

    2
    Rainer Weiss of MIT

    Caltech scientists Barry Barish, the Ronald and Maxine Linde Professor of Physics, Emeritus, and Kip S. Thorne (BS ’62), the Richard P. Feynman Professor of Theoretical Physics, Emeritus, have been awarded the 2017 Princess of Asturias Award for Technical and Scientific Research, along with Rainer Weiss of MIT and the entire LIGO Scientific Collaboration (LSC), a body of more than 1,000 international scientists who perform LIGO research. Past winners of the award in this category include Peter Higgs, François Englert and CERN (the European Organization for Nuclear Research), and Stephen Hawking. The prize consists a Joan Miró sculpture symbolizing the award and a cash prize of 50,000 euros (about 56,000 U.S. dollars).

    Thorne and Weiss, together with the late Caltech professor of physics Ronald W. P. Drever,

    4
    Ronald W. P. Drever

    are the founders of LIGO, the Laser Interferometer Gravitational-wave Observatory, which made history in 2016 when the LIGO team announced the first direct observation of gravitational waves—ripples in space and time predicted by Einstein 100 years earlier.

    Barish was the principal investigator for LIGO from 1994 to 2005, and director of the LIGO Laboratory from 1997 until 2006. He led LIGO through its final design stages and, under his leadership, the project was funded by the National Science Foundation and construction of the interferometers was completed. In 1997, he established the LSC, which continues to detect gravitational waves with LIGO.


    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

    The Princess of Asturias Awards have been presented every year since 1981 by H. M. King Felipe of Spain. They come in eight different categories, from arts to international cooperation. Past recipients in all categories include Nelson Mandela, Arthur Miller, Susan Sontag, Doris Lessing, David Attenborough, Francis Ford Coppola, the Gates Foundation, and many more.

    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 12:07 pm on June 1, 2017 Permalink | Reply
    Tags: , , , Caltech/MIT aLIGO, , , LIGO snags another set of gravitational waves   

    From ScienceNews: “LIGO snags another set of gravitational waves” 

    ScienceNews bloc

    ScienceNews

    June 1, 2017
    Emily Conover

    Spacetime vibrations arrive from black hole collision 3 billion light-years away.

    1
    THREE OF A KIND Scientists have made a third detection of gravitational waves. A pair of black holes, shown above, fused into one, in a powerful collision about 3 billion light-years from Earth. That smashup churned up ripples in spacetime that were detected by the LIGO experiment.

    For a third time, scientists have detected the infinitesimal reverberations of spacetime: gravitational waves.

    Two black holes stirred up the spacetime wiggles, orbiting one another and spiraling inward until they fused into one jumbo black hole with a mass about 49 times that of the sun. Ripples from that union, which took place about 3 billion light-years from Earth, zoomed across the cosmos at the speed of light, eventually reaching the Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, which detected them on January 4.

    “These are the most powerful astronomical events witnessed by human beings,” Michael Landry, head of LIGO’s Hanford, Wash., observatory, said during a news conference May 31 announcing the discovery. As the black holes merged, they converted about two suns’ worth of mass into energy, radiated as gravitational waves.

    ________________________________________________________________________________
    Place in space

    Based on the time that signals arrived at each of LIGO’s two detectors, scientists were able to determine regions on the sky from which the gravitational waves came. LIGO’s three detections are shown, plus a fourth possible detection that was not strong enough to confirm. Lines indicate probabilities that the signal originated within each region. Outermost curves indicate 90 percent, while inner curves indicate 10 percent.

    2
    Leo Singer/LIGO, Caltech, MIT; Axel Mellinger (Milky Way image)

    ________________________________________________________________________________

    LIGO’s two detectors, located in Hanford and Livingston, La., each consist of a pair of 4-kilometer-long arms. They act as outrageously oversized rulers to measure the stretching of spacetime caused by gravitational waves.


    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

    According to Einstein’s theory of gravity, the general theory of relativity, massive objects bend the fabric of space and create ripples when they accelerate — for example, when two objects orbit one another. Gravitational ripples are tiny: LIGO is tuned to detect waves that stretch and squeeze the arms by a thousandth of the diameter of a proton. Black hole collisions are one of the few events in the universe that are catastrophic enough to produce spacetime gyrations big enough to detect.

    The two black holes that spawned the latest waves were particularly hefty [Physical Review Letters], with masses about 31 and 19 times that of the sun, scientists report June 1 in Physical Review Letters. LIGO’s first detection, announced in February 2016, came from an even bigger duo: 36 and 29 times the mass of the sun (SN: 3/5/16, p. 6). Astrophysicists don’t fully understand how such big black holes could have formed. But now, “it seems that these are not so uncommon, so clearly there’s a way to produce these massive black holes,” says physicist Clifford Will of the University of Florida in Gainesville. LIGO’s second detection featured two smaller black holes, 14 and eight times the mass of the sun (SN: 7/9/16, p. 8).

    _________________________________________________________________________________

    Sizing up gravitational waves

    LIGO’s three gravitational wave sightings all came from merging black holes. But those mergers varied in mass, distance and the amount of energy radiated in gravitational waves.
    First detection

    Date: September 14, 2015
    Mass of first black hole: 36.2 solar masses
    Mass of second black hole: 29.1 solar masses
    Merged mass: 62.3 solar masses
    Energy radiated as gravitational waves: 3 solar masses
    Distance from Earth: 1.4 billion light-years
    Second detection

    Date: December 26, 2015
    Mass of first black hole: 14.2 solar masses
    Mass of second black hole: 7.5 solar masses
    Merged mass: 20.8 solar masses
    Energy radiated as gravitational waves: 1 solar mass
    Distance from Earth: 1.4 billion light-years
    Third detection

    Date: January 4, 2017
    Mass of first black hole: 31.2 solar masses
    Mass of second black hole: 19.4 solar masses
    Merged mass: 48.7 solar masses
    Energy radiated as gravitational waves: 2 solar masses
    Distance from Earth: 2.9 billion light-years

    _________________________________________________________________________________

    Weighty black holes are difficult to explain, because the stars that collapsed to form them must have been even more massive. Typically, stellar winds steadily blow away mass as a star ages, leading to a smaller black hole. But under certain conditions, those winds might be weak — for example, if the stars contain few elements heavier than helium or have intense magnetic fields (SN Online: 12/12/16). The large masses of LIGO’s black holes suggest that they formed in such environments.

    Scientists also disagree about how black holes partner up. One theory is that two neighboring stars each explode and produce two black holes, which then spiral inward. Another is that black holes find one another within a dense cluster of stars, as massive black holes sink to the center of the clump (SN Online: 6/19/16).

    The new detection provides some support for the star cluster theory: The pattern of gravitational waves LIGO observed hints that one of the black holes might be spinning in the opposite direction from its orbit. Like a cosmic do-si-do, each black hole in a pair twirls on its own axis as it spirals inward. Black holes that pair up as stars are likely to have their spins aligned with their orbits. But if the black holes instead find one another in the chaos of a star cluster, they could spin any which way. The potentially misaligned black hole LIGO observed somewhat favors the star cluster scenario. The measurement is “suggestive, but it’s not definite,” says astrophysicist Avi Loeb of Harvard University.

    Scientists will need more data to sort out how the black hole duos form, says physicist Emanuele Berti of the University of Mississippi in Oxford. “Probably the truth is somewhere in between.” Various processes could contribute to the formation of black hole pairs, Berti says.

    As with previous detections of gravitational waves, the scientists used their measurements to test general relativity. For example, while general relativity predicts that gravitational waves travel at the speed of light, some alternative theories of gravity predict that gravitational waves of different energies travel at different speeds. LIGO scientists found no evidence of such an effect, vindicating Einstein once again.

    Now, with three black hole mergers under their belts, scientists are looking forward to a future in which gravitational wave detections become routine. The more gravitational waves scientists detect, the better they can test their theories. “There are already surprises that make people stop and revisit some old ideas,” Will says. “To me that’s very exciting.”

    See the full article here .

    Science News offers readers a concise, current and comprehensive overview of the latest scientific research in all fields and applications of science and technology.

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 1:00 pm on May 12, 2017 Permalink | Reply
    Tags: , Are LIGO’s Black Holes Made From Smaller Black Holes?, , , , Caltech/MIT aLIGO,   

    From AAS NOVA: “Are LIGO’s Black Holes Made From Smaller Black Holes?” 

    AASNOVA

    American Astronomical Society

    1
    A still image from a simulation that shows a black-hole binary inside a globular cluster. A new study examines how we can tell whether the black holes detected by LIGO were formed hierarchically from mergers of smaller black holes. [Northwestern Visualization/Carl Rodriguez]

    The recent successes of the Laser Interferometer Gravitational-Wave Observatory (LIGO) has raised hopes that several long-standing questions in black-hole physics will soon be answerable. Besides revealing how the black-hole binary pairs are built, could detections with LIGO also reveal how the black holes themselves form?


    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

    Isolation or Hierarchy

    The first detection of gravitational waves, GW150914, was surprising for a number of reasons. One unexpected result was the mass of the two black holes that LIGO saw merging: they were a whopping 29 and 36 solar masses.

    2
    On the left of this schematic, two first-generation (direct-collapse) black holes form a merging binary. The right illustrates a second-generation hierarchical merger: each black hole in the final merging binary was formed by the merger of two smaller black holes. [Adapted from Gerosa et al., a simultaneously published paper that also explores the problem of hierarchical mergers and reaches similar conclusions]

    How do black holes of this size form? One possibility is that they form in isolation from the collapse of a single massive star. In an alternative model, they are created through the hierarchical merger of smaller black holes, gradually building up to the size we observed.

    A team of scientists led by Maya Fishbach (University of Chicago) suggests that we may soon be able to tell whether or not black holes observed by LIGO formed hierarchically. Fishbach and collaborators argue that hierarchical formation leaves a distinctive signature on the spins of the final black holes — and that as soon as we have enough merger detections from LIGO, we can use spin measurements to statistically determine if LIGO black holes were formed hierarchically.

    Spins from Major Mergers

    When two black holes merge, both their original spins and the angular momentum of the pair contribute to the spin of the final black hole that results. Fishbach and collaborators calculate the expected distribution of these final spins assuming that all the hierarchical mergers are so-called “major mergers” — i.e., the smaller black hole of the pair is at least 70% of the mass of the larger one.

    3
    Distribution of spins for 4th-generation mergers, with two different mass ratios (q = 0.7 and q = 1) and initial first-generation spins (non-spinning and maximally spinning). [Fishbach et al. 2017]

    The authors find that hierarchical major mergers result in a distribution of spins with a distinctive shape, peaking at a spin of a ~ 0.7 with relatively low contribution from spins below a ~ 0.5. Intriguingly, this distribution is universal — if you include several generations of mergers, the resulting spin distribution converges to the same shape every time. This is true regardless of the details of the hierarchical merger scenario, like the exact black hole mass ratio (as long as only major mergers occur) or the initial spin distributions.

    Testing the Model

    What does this tell us? Since the hierarchical merger model predicts a very specific distribution of spins for the black holes detected by LIGO, we can compare future LIGO detections to see if they’re consistent with this model.

    The authors calculate the statistics to show that after order ~100 LIGO detections, we should be able to tell whether these black holes are consistent with a hierarchical merger formation model or not. With luck, this could mean that we will have solved this mystery within a few years of advanced LIGO operations!

    Citation

    Maya Fishbach et al 2017 ApJL 840 L24. doi:10.3847/2041-8213/aa7045

    Related Journal Articles
    See the full article for more articles and papers, complete with links

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 8:43 am on May 2, 2017 Permalink | Reply
    Tags: , , , , Caltech/MIT aLIGO, , Counterparts to Gravitational Wave Events: Very Important Needles in a Very Large Haystack,   

    From astrobites: “Counterparts to Gravitational Wave Events: Very Important Needles in a Very Large Haystack” 

    Astrobites bloc

    Astrobites

    May 2, 2017
    Thankful Cromartie

    Title: Where and when: optimal scheduling of the electromagnetic follow-up of gravitational-wave events based on counterpart lightcurve models
    Authors: Om Sharan Salafia, Monica Colpi, Marica Branchesi, Eric Chassande-Mottin, Giancarlo Ghirlanda, Gabriele Ghisellini, & Susanna Vergani
    First Author’s Institutions: Universita degli Studi di Milano-Bicocca, Milano, Italy; INAF – Osservatorio Astronomico di Brera Merate, Merate, Italy; INFN – Sezione di Milano-Bicocca, Milano, Italy
    1
    2
    3
    Status: Submitted to ApJ [open access]

    The LIGO Scientific Collaboration’s historic direct detection of gravitational waves (GWs) brought with it the promise of answers to long-standing astrophysical puzzles that were unsolvable with traditional electromagnetic (EM) observations. In previous astrobites, we’ve mentioned that an observational approach that involves both the EM and GW windows into the Universe can help shed light on mysteries such as the neutron star (NS) equation of state, and can serve as a unique test of general relativity. Today’s paper highlights the biggest hinderance to EM follow-up of GW events: the detection process doesn’t localize the black hole (BH) and NS mergers well enough to inform a targeted observing campaign with radio, optical, and higher-frequency observatories. While EM counterparts to GW-producing mergers are a needle that’s likely worth searching an entire haystack for, the reality is that telescope time is precious, and everyone needs a chance to use these instruments for widely varying scientific endeavors.

    The first GW detection by LIGO, GW150914, was followed up by many observatories that agreed ahead of time to look for EM counterparts to LIGO triggers.


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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


    The authors of this study propose to improve upon the near-aimless searches in swaths of hundreds of degrees that have been necessary following the first few GW candidate events (see Figure 1). Luckily, there are two key pieces of information we have a priori (in advance): information about the source of the GW signal that can be pulled out of the LIGO data, and an understanding of the EM signal that will be emitted during significant GW-producing events

    4
    Figure 1: Simplified skymaps for the two likely and one candidate (LVT151012) GW detections as 3-D projections onto the Milky Way. The largest contours are 90-percent confidence intervals, while the innermost are 10-percent contours. From the LIGO Scientific Collaboration.

    What are we even looking for?

    Mergers that produce strong GW signals include BH-BH, BH-NS, and NS-NS binary inspirals. GW150914 was a BH-BH merger, which is less likely to produce a strong EM counterpart due to a lack of circumbinary material. The authors of this work therefore focus on the two most likely signals following a BH-NS or NS-NS merger. The first is a short gamma-ray burst (sGRB), which would produce an immediate (“prompt”) gamma-ray signal and a longer-lived “afterglow” in a large range of frequencies. Due to relativistic beaming, it’s rare that prompt sGRB emission is detected, as jets must be pointing in our direction to be seen. GRB afterglows are more easily caught, however. The second is “macronova” emission from material ejected during the merger, which contains heavy nuclei that decay and produce a signal in the optical and infrared shortly after coalescence. One advantage to macronova events is that they’re thought to be isotropic (observable in all directions), so they’ll be more easily detected than the beamed, single-direction sGRBs.

    (Efficiently) searching through the haystack

    LIGO’s direct GW detection method yields a map showing the probability of the merger’s location on the sky (more technically, the posterior probability density for sky position, or “skymap”). The uncertainty in source position is partly so large because many parameters gleaned from the received GW signal, like distance, inclination, and merger mass, are degenerate. In other words, many different combinations of various parameters can produce the same received signal.

    An important dimension that’s missing from the LIGO skymap is time. No information can be provided about the most intelligent time to start looking for the EM counterpart after receiving the GW signal unless the search is informed by information about the progenitor system. In order to produce a so-called “detectability map” showing not only where the merger is possibly located but also when we’re most likely to observe the resulting EM signal at a given frequency, the authors follow an (albeit simplified) procedure to inform their searches.

    The first available pieces of information are the probability that the EM event, at some frequency, will be detectable by a certain telescope, and the time evolution of the signal strength. This information is available a priori given a model of the sGRB or macronova. Then, LIGO will detect a GW signal, from which information about the binary inspiral will arise. These parameters are combined with the aforementioned progenitor information to create a map that helps inform not only where the source will most likely be, but also when various observatories should look during the EM follow-up period. Such event-based, time-dependent detection maps will be created after each GW event, allowing for a much more responsive search for EM counterparts.

    6
    Figure 2: The suggested radio telescope campaign for injection 28840, the LIGO signal used to exemplify a more refined observing strategy. Instead of blindly searching this entire swath of sky, observations are prioritized by signal detectability as a function of time (see color gradient for the scheduled observation times). Figure 8 in the paper.

    Using these detectability maps to schedule follow-up observations with various telescopes (and therefore at different frequencies) is complicated to say the least. The authors present a potential strategy for follow-up using a real LIGO injection (a fake signal fed into data to test their detection pipelines) of a NS-NS merger with an associated afterglow. Detectability maps are constructed and observing strategies are presented for an optical, radio, and infrared follow-up search (see Figure 2 as an example). Optimizing the search for an EM counterpart greatly increased the efficiency of follow-up searches for the chosen injection event; for example, the example radio search would have found the progenitor in 4.7 hours, whereas an unprioritized search could have taken up to 47 hours.

    Conclusions

    The process of refining an efficient method for EM follow-up is distressingly complicated. Myriad unknowns, like EM signal strength, LIGO instrumental noise, observatory availability, and progenitor visibility on the sky all present a strategic puzzle that needs to be solved in the new era of multimessenger astronomy. This work proves that improvements in efficiency are readily available, and that follow-up searches for EM counterparts to GW events will likely be more fruitful as the process is refined.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 7:18 pm on February 24, 2017 Permalink | Reply
    Tags: , Caltech/MIT aLIGO,   

    From Science: “Spinning black holes could fling off clouds of dark matter particles” 

    ScienceMag
    Science Magazine

    Feb. 22, 2017
    Adrian Cho

    1

    A spinning black hole (white) should produce huge clouds of particles called axions (blue), which would then produce detectable gravitational waves, a new calculation predicts. Masha Baryakhtar

    Few things are more mind bending than black holes, gravitational waves, and the nearly massless hypothetical particles called axions, which could be the mysterious dark matter whose gravity holds galaxies together. Now, a team of theoretical physicists has tied all three together in a surprising way. If the axion exists and has the right mass, they argue, then a spinning black hole should produce a vast cloud of the particles, which should, in turn, produce gravitational waves akin to those discovered a year ago by the Laser Interferometer Gravitational-Wave Observatory (LIGO). If the idea is correct, LIGO might be able to detect axions, albeit indirectly.

    “It’s an awesome idea,” says Tracy Slatyer, a particle astrophysicist at the Massachusetts Institute of Technology (MIT) in Cambridge, who was not involved in the work. “The [LIGO] data is going to be there, and it would be amazing if we saw something.” Benjamin Safdi, a theoretical particle physicist at MIT, is also enthusiastic. “This is really the best idea we have to look for particles in this mass range,” he says.

    A black hole is the intense gravitational field left behind when a massive star burns out and collapses to a point. Within a certain distance of that point—which defines the black hole’s “event horizon”—gravity grows so strong that not even light can escape. In September 2015, LIGO detected a burst of ripples in space called gravitational waves that emanated from the merging of two black holes.

    The axion—if it exists—is an uncharged particle perhaps a billionth as massive as the electron or lighter. Dreamed up in the 1970s, it helps explain a curious mathematical symmetry in the theory of particles called quarks and gluons that make up protons and neutrons. Axions floating around might also be the dark matter that’s thought to make up 85% of all matter in the universe. Particle physicists are searching for axions in experiments that try to convert them into photons using magnetic fields.

    But it may be possible to detect axions by studying black holes with LIGO and its twin detectors in Louisiana and Washington states, argue Asimina Arvanitaki and Masha Baryakhtar, theorists at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, and their colleagues.

    If its mass is in the right range, then an axion stuck in orbit around a black hole should be subject to a process called superradiance that occurs in many situations and causes photons to multiply in a certain type of laser. If an axion strays near, but doesn’t cross, a black hole’s event horizon, then the black hole’s spin will give the axion a boost in energy. And because the axion is a quantum particle with some properties like those of the photon, that boost will create more axions, which will, in turn, interact with the black hole in the same way. The runaway process should thus generate vast numbers of the particles.

    But for this to take place, a key condition has to be met. A quantum particle like the axion can also act like a wave, with lighter particles having longer wavelengths. For superradiance to kick in, the axion’s wavelength must be as long as the black hole is wide. So the axion’s mass must be extremely light: between 1/10,000,000 and 1/10,000 the range probed in current laboratory experiments. The axions wouldn’t just emerge willy-nilly, either, but would crowd into huge quantum waves like the orbitals of the electrons in an atom. As fantastical as that sounds, the basic physics of superradiance is well established, Safdi says.

    The axion cloud might reveal itself in multiple ways, Baryakhtar says. Most promising, axions colliding in the cloud should annihilate one another to produce gravitons, the particles thought to make up gravitational waves just as photons make up light. Emerging from orderly quantum clouds, the gravitons would form continuous waves with a frequency set by the axion’s mass. LIGO would be able to spot thousands of such sources per year [Physical Review D], Baryakhtar and colleagues estimate in a paper published 8 February in Physical Review D—although tracking those continuous signals may be harder than detecting bursts from colliding black holes. Spotting multiple same-frequency sources would be a “smoking gun” for axions, Slatyer says.

    The axion clouds could produce indirect signals, too. In principle, a black hole can spin at near light speed. However, generating axions would sap a black hole’s angular momentum and slow it. As a result, LIGO should observe that the spins of colliding black holes never reach that ultimate speed, but top out well below it, Baryakhtar says. Detecting that limit on spin would be challenging, as LIGO can measure a colliding black hole’s spin with only 25% precision.

    Safdi cautions that the analysis assumes that LIGO will see lots of black-hole mergers and will perform as expected. And if LIGO doesn’t see the signals, it won’t rule out the axion, he says. Still, he says, “This is probably the most promising paper I’ve seen so far on the new physics we might probe with gravitational waves.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 1:11 pm on October 12, 2016 Permalink | Reply
    Tags: Caltech/MIT aLIGO, , , ,   

    From Symmetry: “Citizen scientists join search for gravitational waves” 

    Symmetry Mag
    Symmetry

    10/12/16
    Amanda Solliday

    1
    Artwork by Sandbox Studio, Chicago with Ana Kova

    A new project pairs volunteers and machine learning to sort through data from LIGO.

    Barbara Téglás was looking to try something different while on a break from her biotechnology work.

    So she joined Zooniverse, a website dedicated to citizen science projects, and began to hunt pulsars and classify cyclones from her home computer.

    “It’s a great thing that scientists share data and others can analyze it and participate,” Téglás says. “The project helps me stay connected with science in other fields, from anywhere.”

    In April, at her home in the Caribbean Islands, Téglás saw a request for volunteers to help with a new gravitational-wave project called Gravity Spy. Inspired by the discovery of gravitational waves by the Laser Interferometer Gravitational-wave Observatory, or LIGO, she signed up the same day.

    LSC LIGO Scientific Collaboration
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    “To be a complete outsider and have the opportunity to contribute to an astrophysics project such as LIGO, it’s extraordinary,” Téglás says.

    Tuning out the noise

    It took a century after Albert Einstein predicted the existence of gravitational waves—or ripples in space-time—for scientists to build an instrument sophisticated enough to see them. LIGO observed these ripples for the first (and second) time, using two L-shaped detectors called interferometers designed to measure infinitesimal changes in distance. These changes were generated by two black holes that collided a billion years in the past, giving off gravitational waves that eventually passed through Earth. As they traveled through our planet, these gravitational waves stretched and shrank the 4-kilometer arms of the detectors.

    The LIGO detectors can measure a change in distance about 10,000 times smaller than the diameter of a proton. Because the instruments are so sensitive, this also makes them prone to capturing other vibrations, such as earthquakes or heavy vehicles driving near the detectors. Equipment fluctuations can also create noise.

    The noise, also called a glitch, can move the arms of the detector and potentially mimic an astrophysical signal.

    The two detectors are located nearly 2000 miles apart, one in Louisiana and the other in Washington state. Gravitational waves from astrophysical events will hit both detectors at nearly the same time, since gravitational waves travel straight through Earth at the speed of light. However, the distance between the two makes it unlikely that other types of vibrations will be felt simultaneously.

    “But that’s really not enough,” says Mike Zevin, a physics and astronomy graduate student at Northwestern University and a member of the Gravity Spy science team. “Glitches happen often enough that similar vibrations can appear in both detectors at nearly the same time. The glitches can tarnish the data and make it unusable.”

    Gravity Spy enlists the help of volunteers to analyze noise that appears in LIGO detectors.

    This information is converted to an image called spectrogram, and the patterns show the time and frequencies of the noise. Shifts in blue, green and yellow indicate the loudness of the glitch, or how much the noise moved the arms of the detector. The glitches show up frequently in the large amount of information generated by the detectors.

    “Some of these glitches in the spectrograms are easily identified by computers, while others aren’t,” Zevin says. “Humans are actually better at spotting new patterns in the images.”

    The Gravity Spy volunteers are tasked with labeling these hard-to-identify categories of glitches. In addition, the information is used to create training sets for computer algorithms.

    As the training sets grow larger, the computers become better at classifying glitches. That can help scientists eliminate the noise from the detectors or find ways to account for glitches as they look at the data.

    “One of our goals is to create a new way of doing citizen science that scales with the big-data era we live in now,” Zevin says.

    Gravity Spy is a collaboration between Adler Planetarium, California State University-Fullerton, Northwestern University, Syracuse University, University of Alabama at Huntsville, and Zooniverse. The project is supported by an interdisciplinary grant from the National Science Foundation.

    About 1400 people volunteered for initial tests of Gravity Spy. Once the beta testing of Gravity Spy is complete, the volunteers will look at new images created when LIGO begins to collect data during its second observing run.

    2
    Artwork by Sandbox Studio, Chicago with Ana Kova

    A human endeavor

    The project also provides an avenue for human-computer interaction research.

    Another goal for Gravity Spy is to learn the best ways to keep citizen scientists motivated while looking at immense data sets, says Carsten Oesterlund, information studies professor at Syracuse University and member of the Gravity Spy research team.

    “What is really exciting from our perspective is that we can look at how human learning and machine learning can go hand-in-hand,” Oesterlund says. “While the humans are training the machines, how can we organize the task to also facilitate human learning? We don’t want them simply looking at image after image. We want developmental opportunities for the volunteers.”

    The researchers are examining how to encourage the citizen scientists to collaborate as a team. They also want to support new discoveries, or make it easier for people to find unique sets of glitches.

    One test involves incentives—in an earlier study, the computing researchers found if a volunteer knows that they are the first to classify an image, they go on to classify more images.

    “We’ve found that the sense of novelty is actually quite motivating,” says Kevin Crowston, a member of the Gravity Spy science team and associate dean for research at Syracuse University’s School of Information Studies.

    Almost every day, Téglás works on the Gravity Spy project. When she has spare time, she sits down at her computer and looks at glitches. Since April, she’s classified nearly 15,000 glitches and assisted other volunteers with hundreds of additional images through talk forums on Zooniverse.

    She’s pleased that her professional skills developed while inspecting genetics data can also help many citizen science projects.

    On her first day with Gravity Spy, Téglás helped identify a new type of glitch. Later, she classified another unique glitch called “paired doves” after its repeating, chirp-like patterns, which closely mimic the signal created by binary black holes. She’s also found several new variations of known glitches. Her work is recognized in LIGO’s log, and the newly found glitches are now part of the official workflow for the experiment.

    Different experiences, backgrounds and ways of thinking can make citizen science projects stronger, she says.

    “For this project, you’re not only using your eyes,” Téglás says. “It’s also an opportunity to understand an important experiment in modern science.”

    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 11:51 am on July 20, 2016 Permalink | Reply
    Tags: , Caltech/MIT aLIGO, ,   

    From SLAC: “Stanford, SLAC X-ray Studies Could Help Make LIGO Gravitational Wave Detector 10 Times More Sensitive” 


    SLAC Lab

    July 19, 2016

    Scientists from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory are using powerful X-rays to study high-performance mirror coatings that could help make the LIGO gravitational wave observatory 10 times more sensitive to cosmic events that ripple space-time.

    LSC LIGO Scientific Collaboration

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

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

    The current version of the Laser Interferometer Gravitational-Wave Observatory, called Advanced LIGO, was the first experiment to directly observe gravitational waves, which were predicted by Albert Einstein 100 years ago. In September 2015, it detected a signal coming from two black holes, each about 30 times heavier than the sun, which merged into a single black hole 1.3 billion years ago. The experiment picked up a similar second event in December 2015.

    “The detection of gravitational waves will fundamentally change our understanding of the universe in years to come,” says Riccardo Bassiri, a physical science research associate at Stanford’s interdisciplinary Ginzton Laboratory. ”Extremely precise mirrors are the heart of LIGO, and their coatings determine the experiment’s sensitivity, or ability to measure gravitational waves. So improving those coatings will make future generations of the experiment even more powerful.”

    Bassiri has teamed up with Apurva Mehta, a staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), to study the atomic structure of coating materials and develop ideas for better ones. SSRL is a DOE Office of Science User Facility.

    SLAC SSRL Tunnel
    SLAC SSRL

    Since LIGO consists of two nearly identical instruments, located 1,900 miles apart in Hanford, Washington, and Livingston, Louisiana, it can also roughly determine a gravitational wave’s cosmic origin.

    “The effects of gravitational waves on the LIGO detectors are incredibly small, with relative changes in arm length on the order of one thousandth of the diameter of an atomic nucleus,” Bassiri says. “On this scale, random atomic motions in the mirror coatings, known as thermal noise, can obscure signals from gravitational waves.”

    1
    An experimental setup at SSRL used to study mirror coating materials with the grazing-incidence X-ray pair distribution function (GI-XPDF) technique.

    Understanding Thermal Noise

    All materials exhibit thermal noise to some degree, but some are less noisy than others. LIGO’s mirrors, which are among the least noisy in the world, are coated with thin layers of silica and tantala, oxides of the chemical elements silicon and tantalum.

    Previous research has shown that heating tantala to hundreds of degrees Fahrenheit and adding titanium oxide, or titania, to its layers in a process called doping can lower the thermal noise. However, scientists do not know exactly why.

    “At the moment, we’re only beginning to understand how these treatments affect the atomic structure,” Mehta says. “If we were able to get a better grasp of how a material’s properties are linked to its structure, we might be able to design better materials in a more efficient, controlled way instead of searching for them with a trial-and-error approach.”


    In this video, Stanford’s Riccardo Bassiri explains his work at SSRL, which aims to better understand thermal noise in mirror coatings.

    Applications Beyond LIGO

    The researchers are in the process of testing a number of materials to see how various doping percentages and manufacturing procedures change the medium-range order. Their hope is that this will lead to detailed models of the atomic structures and to theories that can predict how tweaking these structures can yield better material properties.

    “Advanced LIGO and the desire to understand the fundamental physics of gravitational waves are the main drivers for this type of research,” Bassiri says. “But it also has the potential for influencing a whole industry that uses amorphous coating materials for a wide range of applications, from precise atomic clocks to high-performance electronics and computing to corrosion-resistant coatings.”

    The research team includes Stanford Professors Robert Byer and Martin Fejer as well as SLAC scientists Badri Shyam, Kevin Stone and Michael Toney. Other institutions involved in this research are the California Institute of Technology; the University of Glasgow, UK; the University of Oxford, UK; and members of the LIGO scientific collaboration. Funding sources include the National Science Foundation and the Science and Technology Facilities Council, UK.

    3
    SLAC’s Apurva Mehta (left) and Stanford’s Riccardo Bassiri discuss their X-ray experiments at SSRL.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
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: