Tagged: Gravitational wave astronomy Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 5:13 pm on August 3, 2020 Permalink | Reply
    Tags: "Unequal neutron-star mergers create unique 'bang' in simulations", , , , , Gravitational wave astronomy, , ,   

    From Pennsylvania State University: “Unequal neutron-star mergers create unique ‘bang’ in simulations” Updated to include the full list of supercomputers used in this project 

    Penn State Bloc

    From Pennsylvania State University

    8.3.20
    David Radice
    david.radice@psu.edu

    Gail McCormick
    gailmccormick@psu.edu
    Work Phone: 814-863-0901

    1
    Through a series of simulations, an international team of researchers has determined that some mergers of neutron stars produce radiation that should be detectible from Earth. When neutron stars of unequal mass merge, the smaller star is ripped apart by tidal forces from its massive companion (left). Most of the smaller partner’s mass falls onto the massive star, causing it to collapse and to form a black hole (middle). But some of the material is ejected into space; the rest falls back to form a massive accretion disk around the black hole (right). Image: Adapted from Bernuzzi et al. 2020, Monthly Notices of the Royal Astronomical Society.

    When two neutron stars slam together, the result is sometimes a black hole that swallows all but the gravitational evidence of the collision. However, in a series of simulations, an international team of researchers including a Penn State scientist determined that these typically quiet — at least in terms of radiation we can detect on Earth — collisions can sometimes be far noisier.

    “When two incredibly dense collapsed neutron stars combine to form a black hole, strong gravitational waves emerge from the impact,” said David Radice, assistant professor of physics and of astronomy and astrophysics at Penn State and a member of the research team. “We can now pick up these waves using detectors like LIGO in the United States and Virgo in Italy.

    MIT /Caltech Advanced aLigo

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    A black hole typically swallows any other radiation that could have come out of the merger that we would be able to detect on Earth, but through our simulations, we found that this may not always be the case.”

    The research team found that when the masses of the two colliding neutron stars are different enough, the larger companion tears the smaller apart. This causes a slower merger that allows an electromagnetic “bang” to escape. Astronomers should be able to detect this electromagnetic signal, and the simulations provide signatures of these noisy collisions that astronomers could look for from Earth.

    The research team, which includes members of the international collaboration CoRe (Computational Relativity), describe their findings in a paper appearing online in the Monthly Notices of the Royal Astronomical Society.

    “Recently, LIGO announced the discovery of a merger event in which the two stars have possibly very different masses,” said Radice. “The main consequence in this scenario is that we expect this very characteristic electromagnetic counterpart to the gravititational wave signal.”

    After reporting the first detection of a neutron-star merger in 2017, in 2019 the LIGO team reported the second, which they named GW190425. The result of the 2017 collision was about what astronomers expected, with a total mass of about 2.7 times the mass of our sun and each of the two neutron stars about equal in mass. But GW190425 was much heavier, with a combined mass of around 3.5 solar masses and the ratio of the two participants more unequal — possibly as high as 2 to 1.

    “While a 2 to 1 difference in mass may not seem like a large difference, only a small range of masses is possible for neutron stars,” said Radice.

    Neutron stars can exist only in a narrow range of masses between about 1.2 and 3 times the mass of our sun. Lighter stellar remnants don’t collapse to form neutron stars and instead form white dwarfs, while heavier objects collapse directly to form black holes. When the difference between the merging stars gets as large as in GW190425, scientists suspected that the merger could be messier — and louder in electromagnetic radiation. Astronomers had detected no such signal from GW190425’s location, but coverage of that area of the sky by conventional telescopes that day wasn’t good enough to rule it out.

    To understand the phenomenon of unequal neutron stars colliding, and to predict signatures of such collisions that astronomers could look for, the research team ran a series of simulations using Pittsburgh Supercomputing Center’s Bridges platform and the San Diego Supercomputer Center’s Comet platform — both in the National Science Foundation’s XSEDE network of supercomputing centers and computers — and other supercomputers.

    Bridges HPE Apollo 2000 XSEDE-allocated supercomputer at Pittsburgh Supercomputing Center

    SDSC Dell Comet supercomputer at San Diego Supercomputer Center (SDSC)

    4
    The supercomputer Lenovo SuperMUC at at Leibniz Supercomputing Centre, Munich

    MARCONI, CINECA, Lenovo NeXtScale supercomputer Italy

    Dell Poweredge U Texas Austin Stampede Supercomputer. Texas Advanced Computer Center 9.6 PF

    NCSA U Illinois Urbana-Champaign Blue Waters Cray Linux XE/XK hybrid machine supercomputer,
    at the National Center for Supercomputing Applications

    Resources of the National Energy Re-search Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy, used in this workspecific assets not named:

    NERSC at LBNL

    NERSC Cray Cori II supercomputer, named after Gerty Cori, the first American woman to win a Nobel Prize in science

    NERSC Hopper Cray XE6 supercomputer, named after Grace Hopper, One of the first programmers of the Harvard Mark I computer

    NERSC Cray XC30 Edison supercomputer

    NERSC GPFS for Life Sciences


    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

    NERSC PDSF computer cluster in 2003.

    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    Future:

    Cray Shasta Perlmutter SC18 AMD Epyc Nvidia pre-exascale supeercomputer

    NERSC is a DOE Office of Science User Facility.

    The researchers found that as the two simulated neutron stars spiraled in toward each other, the gravity of the larger star tore its partner apart. That meant that the smaller neutron star didn’t hit its more massive companion all at once. The initial dump of the smaller star’s matter turned the larger into a black hole. But the rest of its matter was too far away for the black hole to capture immediately. Instead, the slower rain of matter into the black hole created a flash of electromagnetic radiation.

    The research team hopes that the simulated signature they found can help astronomers using a combination of gravitational-wave detectors and conventional telescopes to detect the paired signals that would herald the breakup of a smaller neutron star merging with a larger.

    The simulations required an unusual combination of computing speed, massive amounts of memory, and flexibility in moving data between memory and computation. The team used about 500 computing cores, running for weeks at a time, over about 20 separate instances. The many physical quantities that had to be accounted for in each calculation required about 100 times as much memory as a typical astrophysical simulation.

    “There is a lot of uncertainty surrounding the properties of neutron stars,” said Radice. “In order to understand them, we have to simulate many possible models to see which ones are compatible with astronomical observations. A single simulation of one model would not tell us much; we need to perform a large number of fairly computationally intensive simulations. We need a combination of high capacity and high capability that only machines like Bridges can offer. This work would not have been possible without access to such national supercomputing resources.”

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Penn State Campus

    About Penn State

    WHAT WE DO BEST

    We teach students that the real measure of success is what you do to improve the lives of others, and they learn to be hard-working leaders with a global perspective. We conduct research to improve lives. We add millions to the economy through projects in our state and beyond. We help communities by sharing our faculty expertise and research.

    Penn State lives close by no matter where you are. Our campuses are located from one side of Pennsylvania to the other. Through Penn State World Campus, students can take courses and work toward degrees online from anywhere on the globe that has Internet service.

    We support students in many ways, including advising and counseling services for school and life; diversity and inclusion services; social media sites; safety services; and emergency assistance.

    Our network of more than a half-million alumni is accessible to students when they want advice and to learn about job networking and mentor opportunities as well as what to expect in the future. Through our alumni, Penn State lives all over the world.

    The best part of Penn State is our people. Our students, faculty, staff, alumni, and friends in communities near our campuses and across the globe are dedicated to education and fostering a diverse and inclusive environment.

     
  • richardmitnick 5:46 pm on July 20, 2020 Permalink | Reply
    Tags: "A High-Energy Take on Black Hole Encounters", Accuracy is necessary for improved LIGO; Virgo; KAGRA and future instruments (LISA; Cosmic Explorer; and the Einstein Telescope), Accurate theoretical models used as templates in the data analysis, Accurate theoretical predictions for the observed waveforms obtained through the notoriously difficult task of solving Einstein’s field equations., , , , Both sophisticated numerical simulations and perturbative analytic calculations are necessary for this purpose., Gravitational wave astronomy, , , Inspired by particle physics where everything is conceptually reduced to scattering processes between point particles., , , , Quantum scattering amplitudes, The binary black hole problem   

    From “Physics”: “A High-Energy Take on Black Hole Encounters” 

    About Physics

    From “Physics”

    July 20, 2020

    A particle physics approach to describing black hole interactions opens up new avenues for understanding gravitational-wave observations.

    1
    APS/Alan Stonebraker.
    Figure 1: Black hole scattering can be treated as a particle-like interaction, in which the black holes exchange gravitons. By calculating the quantum scattering amplitudes, researchers can obtain important information about merging black hole binaries that emit gravitational waves. New work has demonstrated a theoretical shortcut that improves the accuracy of these calculations.

    Gravitational-wave astronomy sounds like science fiction: two massive black holes swirl toward each other at a substantial fraction of the speed of light, radiating a burst of energy that outweighs the Sun in the form of gravitational waves. Millions of light years away, on Earth, we observe these ripples in the geometry of spacetime through the tiny deformations they produce in kilometers-long arms of laser interferometers [1].


    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

    One crucial ingredient in interpreting these gravitational-wave signals is having accurate theoretical predictions for the observed waveforms, obtained through the notoriously difficult task of solving Einstein’s field equations. Future progress depends upon significantly improving these theoretical calculations, as current predictions may not be accurate enough for upgraded detectors coming online in 2022 [2]. Inspired by particle physics, where everything is conceptually reduced to scattering processes between point particles, some theorists have begun to attack the binary black hole problem by studying a related problem in which two black holes fly near each other and are deflected (scattered) by their gravitational interaction. Within this framework, Thibault Damour from the Institute of Advanced Scientific Studies (IHÉS) in France and colleagues have sparked unanticipated progress in theoretical gravitational-wave predictions [3–5]. Their latest work shows that there exists a computational shortcut for the generic scattering problem by considering a special limit where one black hole weighs much less than the other.

    The detection of gravitational waves—as well as the extraction of source information (such as mass, spin, and location) and the testing of fundamental physics—relies heavily on accurate theoretical models used as templates in the data analysis. Both sophisticated numerical simulations and perturbative analytic calculations are necessary for this purpose, and both need to improve in accuracy in order to analyze the data that will come from recently enhanced observatories (LIGO, Virgo, and KAGRA) and future instruments (LISA, Cosmic Explorer, and the Einstein Telescope) [2].


    KAGRA gravitational wave detector, Kamioka mine in Kamioka-cho, Hida-city, Gifu-prefecture, Japan


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Gravity is talking. Lisa will listen. Dialogos of Eide


    ESA/eLISA the future of gravitational wave research

    3
    Cosmic Explorer. Location in USA undetermined or at least unstated anywhere.

    Depiction of the ASPERA Albert Einstein Telescope, Albert Einstein Institute Hannover and Max Planck Institute for Gravitational Physics and Leibniz Universität Hannover

    In perturbation theory, the equations of motion are written as a series of terms that contain some small quantity ϵ taken to increasing powers: first order ϵ, second order ϵ^2, third order ϵ^3, etc. The landscape of perturbative analytic methods can be charted according to the quantity that is small: a weak gravitational field (the post-Minkowskian expansion), a weak field and slow-moving black holes (the post-Newtonian expansion), or a small mass ratio between the black holes (as in the gravitational self-force program). In the past, the post-Minkowskian approximation has received the least attention since it is most useful for the scattering of black holes—an event that would normally produce too little gravitational radiation to be observed. However, theorists recently realized that calculations made for scattering (unbound) black holes can reveal important elements, such as the gravitational potential, for merging (bound) systems. This connection has brought together researchers from the classical and quantum gravity communities, with a continuing interchange of fruitful ideas.

    The basic idea in this scattering approach is to treat black holes as quantum particles that interact through the exchange of gravitons, in the same way that electrons interact through the exchange of photons (Fig. 1). By combining all the different ways that particles interact, researchers can achieve extremely precise predictions—as evidenced by the experimental confirmation of up to 12 digits of the predicted anomalous magnetic dipole moment of the electron [6]. A seminal quantum idea is that scattering amplitudes, which give the probability for particular scattering processes, are strongly constrained from general principles (symmetries, locality, conservation of probability). Several groups are currently applying these and other powerful techniques from quantum field theory to determine gravitational scattering amplitudes between “black hole particles.” The amplitudes are quantum observables, but researchers can extract a classical part, which can be used to construct templates for gravitational-wave analysis [7].

    Damour has discovered a simple yet far-reaching connection between different perturbative approaches to classical black hole scattering calculations [3]. He has shown that the mass dependence of the classical scattering-angle function is such that the function can be completely fixed at a certain order in the post-Minkowskian approximation from lower orders in the self-force (small-mass-ratio) approximation. This finding is powerful since the latter approximation makes full use of the exact (nonlinear) black hole solutions in Einstein’s classical gravity. For instance, according to Damour’s findings, the fourth order in the post-Minkowskian approximation—one order above the state-of-the-art quantum amplitude calculation achieved by Zvi Bern and collaborators [7]—could be determined from only the first-order self-force calculations. This shortcut could accelerate efforts to reach higher-order (more accurate) predictions in the future. Already, Damour and his colleagues have used first-order self-force calculations to determine large parts of the fifth- to sixth-order post-Newtonian conservative dynamics, which are needed to pin down the gravitational potential in bound systems [4, 5, 8]. Some of the terms in these calculations have been fiercely debated and were the subject of a friendly wager between Bern and Damour [9], recently conceded by Damour [5].

    While pushing forward on high-order perturbative predictions is certainly important, Damour has also challenged the community by raising issues over the fundamental aspects of quantum gravitational scattering research [3]. He has posed several subtle questions: Does it make sense to identify a classical part of a scattering amplitude, which is normally a probabilistic quantum observable with no direct classical analog? How precisely does the exchange of gravitons add up to large classical deflection angles? How does classical black hole scattering in the high-energy limit relate to quantum results for scattering of massless particles [10, 11]? Resolving these issues could help researchers map out future avenues to take toward more accurate predictions.

    The study of scattering black holes has become a promising research direction, attracting diverse groups working within a vast range of methodologies. The latest efforts [3–5, 7, 8, 12] demonstrate the potential of this approach for gravitational-wave science: More accurate predictions at high orders in perturbation theory are coming within reach, and further progress in this area can greatly enhance the science capability of near-future gravitational-wave observatories. Furthermore, the confrontation of different communities and their ways of thinking bears unforeseeable opportunities for theoretical discoveries, even beyond gravitational waves. The time has come to pass this horizon.

    This research is published in Physical Review D.

    A High-Energy Take on Black Hole EncountersJuly 20, 2020

    A particle physics approach to describing black hole interactions opens up new avenues for understanding gravitational-wave observations.

    Viewpoint on:
    Donato Bini, Thibault Damour, and Andrea Geralico
    Phys. Rev. D 102, 024061 (2020)

    Thibault Damour
    Phys. Rev. D 102, 024060 (2020)

    Donato Bini, Thibault Damour, and Andrea Geralico
    Phys. Rev. D 102, 024062 (2020)

    References

    B. P. Abbott et al. (LIGO Scientific and Virgo Collaborations), “Observation of gravitational waves from a binary black hole merger,” Phys. Rev. Lett. 116, 061102 (2016).
    M. Pürrer and C.-J. Haster, “Gravitational waveform accuracy requirements for future ground-based detectors,” Phys. Rev. Research 2, 023151 (2020).
    T. Damour, “Classical and quantum scattering in post-Minkowskian gravity,” Phys. Rev. D 102, 024060 (2020).
    D. Bini et al., “Binary dynamics at the fifth and fifth-and-a-half post-Newtonian orders,” Phys. Rev. D 102, 024062 (2020).
    D. Bini et al., “Sixth post-Newtonian local-in-time dynamics of binary systems,” Phys. Rev. D 102, 024061 (2020).
    T. Aoyama et al., “Tenth-order QED contribution to the electron g−2 and an improved value of the fine structure constant,” Phys. Rev. Lett. 109, 111807 (2012).
    Z. Bern et al., “Scattering amplitudes and the conservative Hamiltonian for binary systems at third post-Minkowskian order,” Phys. Rev. Lett. 122, 201603 (2019).
    D. Bini et al., “Novel approach to binary dynamics: Application to the fifth post-Newtonian level,” Phys. Rev. Lett. 123, 231104 (2019).
    Z. Bern, QCD Meets Gravity 2019 conference, introductory slides.
    D. Amati et al., “Higher-order gravitational deflection and soft bremsstrahlung in planckian energy superstring collisions,” Nucl. Phys. B 347, 550 (1990).
    Z. Bern et al., “Universality in the classical limit of massless gravitational scattering,” arXiv:2002.02459.
    A. Antonelli et al., “Gravitational spin-orbit coupling through third-subleading post-Newtonian order: From first-order self-force to arbitrary mass ratios,” Phys. Rev. Lett. 125, 011103 (2020).

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries. Physics provides a much-needed guide to the best in physics, and we welcome your comments (physics@aps.org).

     
  • richardmitnick 12:17 pm on July 14, 2020 Permalink | Reply
    Tags: "Gravitational wave researchers go beyond the quantum limit", , , , , , Gravitational wave astronomy, ,   

    From University of Birmingham UK: “Gravitational wave researchers go beyond the quantum limit” 

    From University of Birmingham UK

    14 Jul 2020

    1
    Scientists working at the LIGO facility in the United States, including a team from the University of Birmingham, have demonstrated how the ultra-fine tuning of the instruments enable it to push the boundaries of fundamental laws of physics.


    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 US-based Laser Interferometer Gravitational-wave Observatory detects gravitational waves produced by catastrophic events in the universe, such as mergers of neutron stars and black holes. These space-time ripples are enabling scientists to observe gravitational effects in extreme conditions and probe fundamental questions about the universe and its history.

    In the core of the LIGO detectors are km-scale laser interferometers that measure the distance between 40 kg suspended mirrors with the best precision ever achieved. Typical LIGO sources – the gravitational waves – modulate the distance between the mirrors by 1/1000 of a nucleus size but are still observed with high fidelity. The unprecedented level of the LIGO sensitivity is achieved by the state-of-the-art engineering required to suppress vibrational and thermal noises in the detectors.

    At these levels of sensitivity, quantum mechanics starts to play an important role. The revolutionary and counter-intuitive theories developed in the 20th century typically describe the microscopic world, such as atoms and molecules, but also puts stringent constraints on the continuous measurement of the giant LIGO mirrors.

    Scientists at the LIGO site have now succeeded in looking below the so-called standard quantum limit – the limit when only natural quantum states are utilised in the measurement. Their results are published in Nature.

    The experiment the LIGO team carried out used non-classical ‘squeezed light’ which reduces quantum fluctuations of the laser field. Denis Martynov, one of the Birmingham scientists who contributed to the research, says: “Just a few years ago, this type of quantum behaviour would have been too weak to be observed. But new measurement techniques are now enabling us to go beyond these limits. Not only that, but the approach taken by LIGO scientists in these experiments means that future improvements and upgrades to the instruments can be made with increased confidence that they will yield the improved sensitivity that we are looking for.”

    The ability to make these measurements, opens up the possibility of reducing the effects of quantum mechanics and improving overall the sensitivity of the instruments. The research marks an important step towards making further improvements in the sensitivity of gravitational wave technologies, enabling instruments in the future to reach even further through space and time to detect the echoes of these massive collisions.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Birmingham has been challenging and developing great minds for more than a century. Characterised by a tradition of innovation, research at the University has broken new ground, pushed forward the boundaries of knowledge and made an impact on people’s lives. We continue this tradition today and have ambitions for a future that will embed our work and recognition of the Birmingham name on the international stage.

     
  • richardmitnick 10:34 am on July 11, 2020 Permalink | Reply
    Tags: "Milky Way neutron star pair illuminates cosmic cataclysms", , , , , , Gravitational wave astronomy, , , , The binary neutron star named PSR J1913+1102, The fast-spinning binary neutron star was discovered in 2012 by the Pulsar Arecibo L-band Feed Array (PALFA) survey at the radio telescope at Arecibo Observatory Puerto Rico.   

    From Cornell Chronicle: “Milky Way neutron star pair illuminates cosmic cataclysms” 

    From Cornell Chronicle

    July 10, 2020
    Blaine Friedlander
    bpf2@cornell.edu

    1
    A pair of binary neutron stars in the Milky Way galaxy in this illustration may give researchers insight into cataclysmic mergers. William Gonzalez/Arecibo Observatory


    NAIC Arecibo Observatory operated by University of Central Florida, Yang Enterprises and UMET, Altitude 497 m (1,631 ft).

    A pair of binary neutron stars in the Milky Way galaxy – discovered eight years ago by a pulsar survey developed at Cornell – is giving researchers a front-row seat at what they believe will be the stars’ eventual cataclysmic merger.

    Two Cornell astronomers with an international team of scientists have found that the masses of the neutron stars orbiting each other are strikingly different – so that when they eventually merge, their two masses will produce more ejecta than otherwise expected.

    The merger will be similar to the famous 2017 neutron star event, named GW170817, that produced the first observed gravitational waves and light – and featured a flurry of electromagnetic phenomena.

    MIT /Caltech Advanced aLigo


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    “The connection is that we’re getting a chance to see this kind of binary in its baby stages,” said James Cordes, the George Feldstein Professor of Astronomy in the College of Arts and Sciences and co-author of a study on the discovery. “Observe locally and understand from afar.”

    The team’s work was published July 8 in Nature.

    In the study, radio astronomers measured the masses of the two neutron stars in the binary neutron star, named PSR J1913+1102, and concluded that they were asymmetric, Cordes said.

    As a result, the astronomers believe that when this binary neutron star merges in about a half-billion years, violent tidal forces will shred the neutron stars and eject a lot of material as it emits gravitational waves.

    They’re basing that hypothesis on the August 2017 event, when the LIGO and Virgo detectors observed gravitational waves visually and by radio telescope that were 130 million light-years away. In the final throes of merging, two neutron stars had emitted copious gravitation waves.

    “That merger event detected in 2017 was a Rosetta stone for ‘multi-messenger’ astronomy, which includes standard observations in the gamma rays, X-rays, and optical and radio bands combined with gravitational waves,” said Cordes. “The cataclysmic event featured more ejecta than expected, allowing the detailed study.”

    For radio astronomers, examining the binary neutron star is a professional treat.

    “We’re watching the whole binary evolution process long before the merger happens,” said co-author Shami Chatterjee, senior research associate in astronomy. “This gives us a front-row seat right in our own Milky Way neighborhood.”

    The fast-spinning binary neutron star was discovered in 2012 by the Pulsar Arecibo L-band Feed Array (PALFA), survey at the radio telescope at Arecibo Observatory, Puerto Rico. Cordes started PALFA in 2004, and Cornell manages the PALFA data through the university’s Center for Advanced Computing.

    The larger neutron star is 1.62 times the mass of our own sun, but all that mass fits tightly into a ball the size of a city, according to the astronomers. The smaller star is about 1.27 times the mass of the sun.

    “Seeing PSR J1913+1102 allows astronomers to calculate what neutron star mergers should look like if the masses are asymmetrical,” Chatterjee said. “We can detect the gravitational waves, spot the neutron stars and know what we’re looking for in other galaxies.”

    The lead authors of the paper, “Asymmetric Mass Ratios for Bright Double Neutron-Star Mergers,” are Robert. D. Ferdman, University of East Anglia, Norwich, England; Paulo Freire, Max Planck Institute for Radio Astronomy, Bonn, Germany; Benetge Perera, Arecibo Observatory; and Nihan Pol from West Virginia University.

    The National Science Foundation funded the Cornell portion of the 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

    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

     
  • richardmitnick 10:01 am on July 8, 2020 Permalink | Reply
    Tags: "Finding NEMO – the future of gravitational-wave astronomy", , , , , , Gravitational wave astronomy, ,   

    From Monash University: “Finding NEMO – the future of gravitational-wave astronomy” 

    Monash Univrsity bloc

    From Monash University

    08 July 2020

    1
    Recent transformational discoveries are only the tip of the iceberg of what the new field of gravitational-wave astronomy could potentially achieve. Credit: Carl Knox (OzGrav/Swinburne)

    A new study released today [ https://arxiv.org/abs/2007.03128 ] makes a compelling case for the development of ‘NEMO’ – a new observatory in Australia that could deliver on some of the most exciting gravitational-wave science next-generation detectors have to offer, but at a fraction of the cost.

    The study, co-authored by the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), coincides with an Astronomy Decadal Plan mid-term review by Australian Academy of Sciences where ‘NEMO’ is identified as a priority goal.

    “Gravitational-wave astronomy is reshaping our understanding of the Universe”, said one of the study’s lead authors ARC Future Fellow, Dr Paul Lasky, from the Monash University School of Physics and Astronomy, and OzGrav.

    “Neutron stars are an end state of stellar evolution,” he said.

    “They consist of the densest observable matter in the Universe, and are believed to consist of a superfluid, superconducting core of matter at supranuclear densities.

    “Such conditions are impossible to produce in the laboratory, and theoretical modelling of the matter requires extrapolation by many orders of magnitude beyond the point where nuclear physics is well understood.”

    The study today presents the design concept and science case for a Neutron Star Extreme Matter Observatory (NEMO): a gravitational-wave interferometer optimised to study nuclear physics with merging neutron stars.

    The concept uses high circulating laser power, quantum squeezing and a detector topology specially designed to achieve the high frequency sensitivity necessary to probe nuclear matter using gravitational waves.

    The study acknowledges that third-generation observatories require substantial, global financial investment and significant technological development over many years.

    According to Monash PhD candidate Francisco Hernandez Vivanco, who also worked on the study, the recent transformational discoveries were only the tip of the iceberg of what the new field of gravitational-wave astronomy could potentially achieve.

    “To reach its full potential, new detectors with greater sensitivity are required,” Francisco said.

    “The global community of gravitational-wave scientists is currently designing the so called ‘third-generation gravitational-wave detectors (we are currently in the second generation of detectors; the first generation were the prototypes that got us where we are today).”

    Third-generation detectors will increase the sensitivity achieved by a factor of 10, detecting every black hole merger throughout the Universe, and most of the neutron star collisions.

    But they have a hefty price tag. At about $1B, they require truly global investment, and are not anticipated to start detecting ripples of gravity until 2035 at the earliest.

    In contrast, NEMO would require a budget of only $50 to $100M, a considerably shorter timescale for development, and it would provide a test-bed facility for technology development for third-generation instruments.

    The paper today concludes that further design studies are required detailing specifics of the instrument, as well as a possible scoping study to find an appropriate location for the observatory, a project known as ‘Finding NEMO’.

    This work was supported by the Australian Research Council (ARC) Centre of Excellence, ARC Future Fellowships, an ARC Discovery Project, and the Direct Grant, Project, from the Research Committee of the Chinese University of Hong Kong.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Monash U campus

    Monash University is an Australian public research university based in Melbourne, Australia. Founded in 1958, it is the second oldest university in the State of Victoria. Monash is a member of Australia’s Group of Eight and the ASAIHL, and is the only Australian member of the influential M8 Alliance of Academic Health Centers, Universities and National Academies. Monash is one of two Australian universities to be ranked in the The École des Mines de Paris (Mines ParisTech) ranking on the basis of the number of alumni listed among CEOs in the 500 largest worldwide companies. Monash is in the top 20% in teaching, top 10% in international outlook, top 20% in industry income and top 10% in research in the world in 2016.

    Monash enrolls approximately 47,000 undergraduate and 20,000 graduate students, It also has more applicants than any university in the state of Victoria.

    Monash is home to major research facilities, including the Australian Synchrotron, the Monash Science Technology Research and Innovation Precinct (STRIP), the Australian Stem Cell Centre, 100 research centres and 17 co-operative research centres. In 2011, its total revenue was over $2.1 billion, with external research income around $282 million.

    The university has a number of centres, five of which are in Victoria (Clayton, Caulfield, Berwick, Peninsula, and Parkville), one in Malaysia. Monash also has a research and teaching centre in Prato, Italy, a graduate research school in Mumbai, India and a graduate school in Jiangsu Province, China. Since December 2011, Monash has had a global alliance with the University of Warwick in the United Kingdom. Monash University courses are also delivered at other locations, including South Africa.

    The Clayton campus contains the Robert Blackwood Hall, named after the university’s founding Chancellor Sir Robert Blackwood and designed by Sir Roy Grounds.

    In 2014, the University ceded its Gippsland campus to Federation University. On 7 March 2016, Monash announced that it would be closing the Berwick campus by 2018.

     
  • richardmitnick 11:33 am on July 7, 2020 Permalink | Reply
    Tags: "Quantum fluctuations can jiggle objects on the human scale", , , Gravitational wave astronomy, ,   

    From MIT News and Caltech: “Quantum fluctuations can jiggle objects on the human scale” 

    Caltech Logo

    From Caltech

    and

    MIT News

    MIT News

    July 1, 2020
    Jennifer Chu

    1
    MIT physicists have observed that LIGO’s 40-kilogram mirrors can move in response to tiny quantum effects. In this photo, a LIGO optics technician inspects one of LIGO’s mirrors. Credit: Matt Heintze/Caltech/MIT/LIGO Lab

    Study shows LIGO’s 40-kilogram mirrors can move in response to tiny quantum effects, revealing the “spooky popcorn of the universe.”

    The universe, as seen through the lens of quantum mechanics, is a noisy, crackling space where particles blink constantly in and out of existence, creating a background of quantum noise whose effects are normally far too subtle to detect in everyday objects.

    Now for the first time, a team led by researchers at MIT LIGO Laboratory has measured the effects of quantum fluctuations on objects at the human scale. In a paper published today in Nature, the researchers report observing that quantum fluctuations, tiny as they may be, can nonetheless “kick” an object as large as the 40-kilogram mirrors of the U.S. National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO), causing them to move by a tiny degree, which the team was able to measure.


    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 turns out the quantum noise in LIGO’s detectors is enough to move the large mirrors by 10^20 meters — a displacement that was predicted by quantum mechanics for an object of this size, but that had never before been measured.

    “A hydrogen atom is 10^10 meters, so this displacement of the mirrors is to a hydrogen atom what a hydrogen atom is to us — and we measured that,” says Lee McCuller, a research scientist at MIT’s Kavli Institute for Astrophysics and Space Research.

    The researchers used a special instrument that they designed, called a quantum squeezer, to “manipulate the detector’s quantum noise and reduce its kicks to the mirrors, in a way that could ultimately improve LIGO’s sensitivity in detecting gravitational waves,” explains Haocun Yu, a physics graduate student at MIT.

    “What’s special about this experiment is we’ve seen quantum effects on something as large as a human,” says Nergis Mavalvala, the Marble Professor and associate head of the physics department at MIT. “We too, every nanosecond of our existence, are being kicked around, buffeted by these quantum fluctuations. It’s just that the jitter of our existence, our thermal energy, is too large for these quantum vacuum fluctuations to affect our motion measurably. With LIGO’s mirrors, we’ve done all this work to isolate them from thermally driven motion and other forces, so that they are now still enough to be kicked around by quantum fluctuations and this spooky popcorn of the universe.”

    Yu, Mavalvala, and McCuller are co-authors of the new paper, along with graduate student Maggie Tse and Principal Research Scientist Lisa Barsotti at MIT, along with other members of the LIGO Scientific Collaboration.

    A quantum kick

    LIGO is designed to detect gravitational waves arriving at the Earth from cataclysmic sources millions to billions of light years away. It comprises twin detectors, one in Hanford, Washington, and the other in Livingston, Louisiana. Each detector is an L-shaped interferometer made up of two 4-kilometer-long tunnels, at the end of which hangs a 40-kilogram mirror.

    To detect a gravitational wave, a laser located at the input of the LIGO interferometer sends a beam of light down each tunnel of the detector, where it reflects off the mirror at the far end, to arrive back at its starting point. In the absence of a gravitational wave, the lasers should return at the same exact time. If a gravitational wave passes through, it would briefly disturb the position of the mirrors, and therefore the arrival times of the lasers.

    Much has been done to shield the interferometers from external noise, so that the detectors have a better chance of picking out the exceedingly subtle disturbances created by an incoming gravitational wave.

    Mavalvala and her colleagues wondered whether LIGO might also be sensitive enough that the instrument might even feel subtler effects, such as quantum fluctuations within the interferometer itself, and specifically, quantum noise generated among the photons in LIGO’s laser.

    “This quantum fluctuation in the laser light can cause a radiation pressure that can actually kick an object,” McCuller adds. “The object in our case is a 40-kilogram mirror, which is a billion times heavier than the nanoscale objects that other groups have measured this quantum effect in.”

    Noise squeezer

    To see whether they could measure the motion of LIGO’s massive mirrors in response to tiny quantum fluctuations, the team used an instrument they recently built as an add-on to the interferometers, which they call a quantum squeezer. With the squeezer, scientists can tune the properties of the quantum noise within LIGO’s interferometer.

    The team first measured the total noise within LIGO’s interferometers, including the background quantum noise, as well as “classical” noise, or disturbances generated from normal, everyday vibrations. They then turned the squeezer on and set it to a specific state that altered the properties of quantum noise specifically. They were able to then subtract the classical noise during data analysis, to isolate the purely quantum noise in the interferometer. As the detector constantly monitors the displacement of the mirrors to any incoming noise, the researchers were able to observe that the quantum noise alone was enough to displace the mirrors, by 10^20 meter.

    Mavalvala notes that the measurement lines up exactly with what quantum mechanics predicts. “But still it’s remarkable to see it be confirmed in something so big,” she says.

    Going a step further, the team wondered whether they could manipulate the quantum squeezer to reduce the quantum noise within the interferometer. The squeezer is designed such that when it set to a particular state, it “squeezes” certain properties of the quantum noise, in this case, phase and amplitude. Phase fluctuations can be thought of as arising from the quantum uncertainty in the light’s travel time, while amplitude fluctuations impart quantum kicks to the mirror surface.

    “We think of the quantum noise as distributed along different axes, and we try to reduce the noise in some specific aspect,” Yu says.

    When the squeezer is set to a certain state, it can for example squeeze, or narrow the uncertainty in phase, while simultaneously distending, or increasing the uncertainty in amplitude. Squeezing the quantum noise at different angles would produce different ratios of phase and amplitude noise within LIGO’s detectors.

    The group wondered whether changing the angle of this squeezing would create quantum correlations between LIGO’s lasers and its mirrors, in a way that they could also measure. Testing their idea, the team set the squeezer to 12 different angles and found that, indeed, they could measure correlations between the various distributions of quantum noise in the laser and the motion of the mirrors.

    Through these quantum correlations, the team was able to squeeze the quantum noise, and the resulting mirror displacement, down to 70 percent its normal level. This measurement, incidentally, is below what’s called the standard quantum limit, which, in quantum mechanics, states that a given number of photons, or, in LIGO’s case, a certain level of laser power, is expected to generate a certain minimum of quantum fluctuations that would generate a specific “kick” to any object in their path.

    By using squeezed light to reduce the quantum noise in the LIGO measurement, the team has made a measurement more precise than the standard quantum limit, reducing that noise in a way that will ultimately help LIGO to detect fainter, more distant sources of gravitational waves.

    This research was funded, in part, by the National Science Foundation.

    See the full article here .


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


    Stem Education Coalition

    MIT Seal

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    MIT Campus

    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 9:40 am on July 6, 2020 Permalink | Reply
    Tags: "The supersizing of quantum physics", , , , Gravitational wave astronomy, , Squeezer table   

    From Australian National University via COSMOS: “The supersizing of quantum physics” 

    ANU Australian National University Bloc

    From Australian National University

    via

    Cosmos Magazine bloc

    COSMOS

    3 July 2020
    Phil Dooley

    Quantum physics is the realm of tiny particles no longer. Scientists at the giant gravitational wave detector LIGO in the US are now measuring the quantum effects of 40-kilogram mirrors used to detect 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

    While physicists routinely observe quantum effects in nanometre-scale experiments, LIGO team member Robert Ward says this new level of sensitivity was unmatched in other experiments.

    1
    ANU’s Nutsinee Kijbunchoo (left) and Terry McRae building a squeezer table at LIGO Hanford. Credit: ANU.

    “There’s nowhere else close, nothing like it. That’s as big as my kids!” says Ward, who is part of the OzGrav Research Centre based at the Australian National University (ANU).

    “The reality that we can measure to this level of precision on an instrument that is so large is incredible,” adds his ANU colleague Terry McRae, who recently spent a year installing new componentry at the Livingston site in Louisiana, US.

    Livingston is one of two linked gravitational wave detectors run by the LIGO organisation. Each detector is made of two high-powered laser beams at right angles, bouncing between mirrors four kilometres apart. The second is in Washington State, 3000 kilometres to the northwest.

    The LIGO team has published results in the journal Nature that accurately show quantum correlations between the 40-kilogram mirrors and the laser beam, which at 200 kilowatts is about 2000 times more powerful than a laser cutter.

    For the purpose of detecting gravitational waves, it has used the correlations and manipulated the quantum properties of the system, to reduce noise and make it more sensitive, a technique called quantum squeezing.

    The sensitivity of LIGO is crucial. Although black hole collisions are the most violent events known to humans, the gravitational waves from them reach earth as tiny flickers in space and time. In the triumphant first detections of gravitational waves, LIGO’s mirrors moved about a billionth of the diameter of the atoms making up the mirrors.

    The two-decade story of LIGO is one of tirelessly removing one noise source after another, says ANU’s Nutsinee Kijbunchoo.

    “We’re always trying to do better: sensitivity less than the width of a hair? Not good enough, we have to keep improving,” she says.

    Kijbunchoo worked with McRae on the recent upgrade at Livingston and was amazed to see people banging on parts of the apparatus to try to induce noise, characterise it precisely and work out how to cut it out.

    A recent paper [Physics]announced the new sensitivity levels reached, thanks to the new quantum squeezing system that Kijbunchoo and McRae were involved in installing. The paper estimated that the improvement would lead to a 50% jump in the rate of gravitational wave detections.

    This new paper takes a step back, however, and discusses the significance of the LIGO’s sensitivity, saying in its conclusions that “the measurements presented here represent long-awaited milestones in verifying the role of quantum mechanics in limiting the measurement of small displacements…”.

    Rob Ward says this moment has been a long time coming, citing Russian scientist Braginsky as one of the first to begin thinking [Reviews of Modern Physics] about the quantum limits of measurement in 1996.

    “Now we’ve crossed that threshold, and now we have to start thinking about the quantum mechanics of our test masses (mirrors). We’re being forced to grapple with the quantum mechanics of a human-sized objects,” Ward says.

    The quantum noise has been revealed after an intricate system of suspension wires, feedback systems, laser stabiliser and cooling systems have stabilised the experiment – removing the so-called classical noise.

    3
    Credit: Nutsinee Kijbunchoo ANU.

    You would think all of these vibrations and wobbles could be cut out completely, but quantum noise is a fundamental property of a system, first expressed by Heisenberg in the famous Uncertainty Principle, which lays out that measurements have limits to their precision, beyond which you cannot pass, no matter how cold, stable or isolated your experiment is.

    But there is a loophole: these measurements come in pairs, and the uncertainty is distributed between the pairs, and can be shifted from one quantity to the other.

    Imagine cleaning the house, which you could measure by how fast it was done, or how clean the house ends up. The quicker the clean-up, the lower the final standard of cleanliness. Or, an exhaustive spring clean could take well past tea time.

    It’s this kind of trade-off that the squeezing system uses – in this case playing off the radiation pressure against the randomness in the arrival time of the photons. The trick is the photons need to be paired – correlated – which enables the quantum link to be leveraged.

    These play into the overall noise differently for different signals, so the LIGO scientists constrain the value of one that will make the experiment most sensitive, say to a neutron star merger, and let the other be a little less certain.

    This is how the LIGO detector achieves sensitivity that is better than non-quantum physics could have imagined – a limit known as the standard quantum limit (SQL).

    These quantum tricks can only be used if the overall noise is infinitesimal, otherwise the pairings become smeared out, and quantum effects can’t be seen.

    This is the case in our everyday world. But now, says Ward, with this exquisite instrument we’re in a realm we’ve never seen before.

    “We never normally see quantum effects of big objects, and we don’t exactly know why, but now we’re getting to that level of precision,” he says. “We’re exploring fundamental questions about reality.”

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    ANU Campus

    ANU is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

    Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.

     
  • richardmitnick 9:46 am on July 1, 2020 Permalink | Reply
    Tags: "Excess neutrinos and missing gamma rays?", , , , , , Gravitational wave astronomy, , ,   

    From Pennsylvania State University: “Excess neutrinos and missing gamma rays?” 

    Penn State Bloc

    From Pennsylvania State University

    June 30, 2020
    Sam Sholtis

    Coronae of supermassive black holes may be the hidden sources of mysterious cosmic neutrinos seen on Earth.

    1
    NASA Hubble Space Telescope image of Galaxy NGC 1068 with its active black hole shown as an illustration in the zoomed-in inset. A new model suggests that the corona around such supermassive black holes could be the source of high-energy cosmic neutrinos observed by the IceCube Neutrino Observatory. Image: NASA/JPL-Caltech

    The origin of high-energy cosmic neutrinos observed by the IceCube Neutrino Observatory, whose detector is buried deep in the Antarctic ice, is an enigma that has perplexed physicists and astronomers.

    U Wisconsin ICECUBE neutrino detector at the South Pole

    A new model could help explain the unexpectedly large flux of some of these neutrinos inferred by recent neutrino and gamma-ray data. A paper by Penn State researchers describing the model, which points to the supermassive black holes found at the cores of active galaxies as the sources of these mysterious neutrinos, appears June 30 in the journal Physical Review Letters.

    “Neutrinos are subatomic particles so tiny that their mass is nearly zero and they rarely interact with other matter,” said Kohta Murase, assistant professor of physics and of astronomy and astrophysics at Penn State and a member of Center for Multimessenger Astrophysics in the Institute for Gravitation and the Cosmos (IGC), who led the research. “High-energy cosmic neutrinos are created by energetic cosmic-ray accelerators in the universe, which may be extreme astrophysical objects such as black holes and neutron stars. They must be accompanied by gamma rays or electromagnetic waves at lower energies, and even sometimes gravitational waves. So, we expect the levels of these various ‘cosmic messengers’ that we observe to be related. Interestingly, the IceCube data have indicated an excess emission of neutrinos with energies below 100 teraelectron volt (TeV), compared to the level of corresponding high-energy gamma rays seen by the Fermi Gamma-ray Space Telescope.”

    NASA/Fermi Gamma Ray Space Telescope

    Scientists combine information from all of these cosmic messengers to learn about events in the universe and to reconstruct its evolution in the burgeoning field of “multimessenger astrophysics.” For extreme cosmic events, like massive stellar explosions and jets from supermassive black holes, that create neutrinos, this approach has helped astronomers pinpoint the distant sources and each additional messenger provides additional clues about the details of the phenomena.

    For cosmic neutrinos above 100 TeV, previous research by the Penn State group [Nature Physics] showed that it is possible to have concordance with high-energy gamma rays and ultra-high-energy cosmic rays which fits with a multimessenger picture. However, there is growing evidence for an excess of neutrinos below 100 TeV, which cannot simply be explained. Very recently, the IceCube Neutrino Observatory reported another excess of high-energy neutrinos in the direction of one of the brightest active galaxies, known as NGC 1068, in the northern sky.

    “We know that the sources of high-energy neutrinos must also create gamma rays, so the question is: Where are these missing gamma rays?” said Murase. “The sources are somehow hidden from our view in high-energy gamma rays, and the energy budget of neutrinos released into the universe is surprisingly large. The best candidates for this type of source have dense environments, where gamma rays would be blocked by their interactions with radiation and matter but neutrinos can readily escape. Our new model shows that supermassive black hole systems are promising sites and the model can explain the neutrinos below 100 TeV with modest energetics requirements.”

    The new model suggests that the corona — the aura of superhot plasma that surrounds stars and other celestial bodies — around supermassive black holes found at the core of galaxies, could be such a source. Analogous to the corona seen in a picture of the Sun during a solar eclipse, astrophysicists believe that black holes have a corona above the rotating disk of material, known as an accretion disk, that forms around the black hole through its gravitational influence. This corona is extremely hot (with a temperature of about one billion degrees kelvin), magnetized, and turbulent. In this environment, particles can be accelerated, which leads to particle collisions that would create neutrinos and gamma rays, but the environment is dense enough to prevent the escape of high-energy gamma rays.

    “The model also predicts electromagnetic counterparts of the neutrino sources in ‘soft’ gamma-rays instead of high-energy gamma rays,” said Murase. “High-energy gamma rays would be blocked but this is not the end of the story. They would eventually be cascaded down to lower energies and released as ‘soft’ gamma rays in the megaelectron volt range, but most of the existing gamma-ray detectors, like the Fermi Gamma-ray Space Telescope, are not tuned to detect them.”

    There are projects under development that are designed specifically to explore such soft gamma-ray emission from space. Furthermore, upcoming and next-generation neutrino detectors, KM3Net in the Mediterranean Sea and IceCube-Gen2 in Antarctica will be more sensitive to the sources.

    Artist’s expression of the KM3NeT neutrino telescope

    IceCube Gen-2 DeepCore anotated

    The promising targets include NGC 1068 in the northern sky, for which the excess neutrino emission was reported, and several of the brightest active galaxies in the southern sky.

    “These new gamma-ray and neutrino detectors will enable deeper searches for multimessenger emission from supermassive black hole coronae,” said Murase. “This will make it possible to critically examine if these sources are responsible for the large flux of mid-energy level neutrinos observed by IceCube as our model predicts.”

    In addition to Murase, the research team at Penn State includes the former IGC fellow Shigeo S. Kimura and Eberly Chair Professor Emeritus Peter Mészáros.

    The Alfred P. Sloan Foundation, the U.S. National Science Foundation, the Japanese Society for the Promotion of Science, NASA, the Penn State Institute for Gravitation and the Cosmos, and the Eberly Foundation funded this work.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Penn State Campus

    About Penn State

    WHAT WE DO BEST

    We teach students that the real measure of success is what you do to improve the lives of others, and they learn to be hard-working leaders with a global perspective. We conduct research to improve lives. We add millions to the economy through projects in our state and beyond. We help communities by sharing our faculty expertise and research.

    Penn State lives close by no matter where you are. Our campuses are located from one side of Pennsylvania to the other. Through Penn State World Campus, students can take courses and work toward degrees online from anywhere on the globe that has Internet service.

    We support students in many ways, including advising and counseling services for school and life; diversity and inclusion services; social media sites; safety services; and emergency assistance.

    Our network of more than a half-million alumni is accessible to students when they want advice and to learn about job networking and mentor opportunities as well as what to expect in the future. Through our alumni, Penn State lives all over the world.

    The best part of Penn State is our people. Our students, faculty, staff, alumni, and friends in communities near our campuses and across the globe are dedicated to education and fostering a diverse and inclusive environment.

     
  • richardmitnick 10:45 am on June 23, 2020 Permalink | Reply
    Tags: "A black hole with a puzzling companion", , , , , Gravitational wave astronomy, ,   

    From Max Planck Gesellschaft and Northwestern University: “A black hole with a puzzling companion” 

    From Max Planck Gesellschaft

    and

    Northwestern U bloc
    Northwestern University

    June 23, 2020

    Media contacts

    Dr. Benjamin Knispel
    Press and Public Relations Officer
    +49 511 762-19104
    benjamin.knispel@aei.mpg.de
    Albert-Einstein-Institut , Hannover

    Dr. Elke Müller
    Press Officer Max Planck Institute for Gravitational Physics, Potsdam-Golm
    +49 331 567-7303
    elke.mueller@aei.mpg.de

    Scientific contacts
    Prof. Dr. Alessandra Buonanno
    Max Planck Institute for Gravitational Physics, Potsdam-Golm
    +49 331 567-7220
    alessandra.buonanno@aei.mpg.de

    Prof. Dr. Karsten Danzmann
    Max Planck Institute for Gravitational Physics (Hannover), Hannover
    +49 511 762-2356
    karsten.danzmann@aei.mpg.de

    Dr. Frank Ohme
    Max Planck Institute for Gravitational Physics (Hannover), Hannover
    +49 511 762-17171
    frank.ohme@aei.mpg.de

    Dr. Jonathan Gair
    Max Planck Institute for Gravitational Physics, Potsdam-Golm
    +49 331 567-7305
    jonathan.gair@aei.mpg.de

    LIGO and Virgo find another surprising binary system.

    MIT /Caltech Advanced aLigo


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    The harvest of exceptional gravitational-wave events from LIGO’s and Virgo’s third observing run (O3) grows. A new signal published today [ The Astrophysical Letters ] comes from the merger of a 23-solar-mass black hole with an object 9 times lighter. The second object is mysterious: its measured mass puts it in the so-called “mass gap” between the heaviest known neutron stars and the lightest known black holes. While the researchers cannot be sure about its true nature, one thing is clear: the observation of this unusual pair challenges the current understanding of how such systems are born and evolve.

    1
    Visualization of the coalescence of two black holes that inspiral and merge, emitting gravitational waves. One black hole is 9.2 times more massive than the other and both objects are non-spinning.
    © N. Fischer, S. Ossokine, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

    “GW190814 is an unexpected and a really exciting discovery,” says Abhirup Ghosh, a post-doctoral researcher in the “Astrophysical and Cosmological Relativity” division at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Potsdam. “It is unique because of two outstanding features. Never before have we witnessed a gravitational-wave signal from a system in which the individual masses are this different: a black hole 23 times the mass of our Sun merging with an object just 2.6 times the mass of the Sun. But what adds to the mystery is that we are not sure about the nature of the lighter object. If it’s indeed a black hole, it’s the lightest, and if it’s a neutron star it’s the most massive we have ever observed in a binary system of two compact objects.”

    Because of the unequal masses, the telltale fingerprints of the neutron star’s tidal deformation that would give away its presence are hard to detect – and were not seen – in GW190814. Therefore, it remains unclear whether the lighter object is a black hole or a neutron star. If it actually is a neutron star, it would be exceptionally massive and would challenge our understanding of how neutron-star matter behaves and how massive these objects can be.

    “Because the objects’ masses are so different, we clearly identified the gravitational-wave hum of a higher harmonic, which is similar to overtones of musical instruments,” says Jonathan Gair, group leader in the “Astrophysical and Cosmological Relativity” division at the AEI in Potsdam. “These harmonics – seen in GW190814 only for the second time ever – allow us to more precisely measure some astrophysical properties of the binary system and enable new tests of Einstein’s theory of general relativity.”

    GW190814 was observed by both LIGO detectors and the Virgo detector on 14th of August 2019, during the detectors’ third observing run O3 – to the day two years after GW170814, the first signal observed by all three instruments.

    “Due to the favourable circumstance of having observed such a loud signal with quite different component masses and for about 10 seconds, we achieved the most precise gravitational-wave measurement of a black hole spin to date,” explains Alessandra Buonanno, director of the “Astrophysical and Cosmological Relativity” division at the AEI in Potsdam. “This is important, because the spin of a black hole carries information about its birth and evolution. We find that this 23-solar-mass black hole spins rather slowly: less than 7% of the maximum spin allowed by general relativity.”

    “Knowing in which environment this unusual binary system was born and how it evolved is really hard. It’s unlike most of the systems we know from simulations of the binary merger population,” says Frank Ohme, leader of an independent Max Planck Research Group at AEI Hannover. “GW190814 and similar future signals could help us to better understand this unexpected new kind of binary system and the processes which give birth to massive neutron stars or light-weight black holes,” he adds.

    The astronomers’ best guess is that the system formed either in young, dense star clusters or the surroundings of active galactic nuclei. Based on their estimates of how many such systems exist in the Universe and how often they merge, they expect to observe more such systems in future LIGO/Virgo observing runs.

    2
    Each of these four images shows a different mode (or overtone) of the gravitational-wave signal in a different color. From left to right and top to bottom, the panels show the quadrupolar (orange), octupolar (magenta), hexadecupolar (purple) and 32-polar (blue) modes.
    © N. Fischer, S. Ossokine, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

    The unequal masses imprint themselves on the emitted gravitational-wave signal, which in turn allows scientists to more precisely determine some of its astrophysical properties, such as the distance to the system.

    Detailed analyses of the LIGO and Virgo data show that the merger happened at a distance of about 780 million light-years from Earth. Its sky position could be determined to an area equivalent to approximately 90 full moons towards the southern-sky constellation “Sculptor”.

    AEI researchers contributed to detecting and analyzing GW190814. They have provided accurate models of the gravitational waves from coalescing black holes that included, for the first time, the precession of the black-holes’ spins, multipole moments beyond the dominant quadrupole, as well as tidal effects introduced by the potential neutron-star companion. Those features imprinted in the waveform are crucial to extract unique information about the source’s properties and carry out tests of general relativity. The high-performance computer clusters “Minerva” and “Hypatia” at AEI Potsdam were employed to develop the waveform models used for the analyses.

    With the distance and the sky position precisely determined, LIGO and Virgo scientists also used GW190814 (and their earlier observation of a binary neutron star merger) to obtain a new gravitational-wave measurement of the Hubble constant, the rate at which the Universe expands. The result improves on previous such gravitational wave determinations; it is less precise than but in agreement with other Hubble constant measurements.

    LIGO and Virgo scientists also used GW190814 to look for deviations of the signal from predictions of Einstein’s general theory of relativity. Even this unusual signal that represents a new type of binary merger follows the theory’s predictions.

    This discovery is the third reported from the third observing run (O3) of the international gravitational-wave detector network. Scientists at the three large detectors have made several technological upgrades to the instruments.

    “In O3 we used squeezed light to enhance the sensitivity of LIGO and Virgo by 40%. We pioneered this technique of carefully tuning the quantum-mechanical properties of the laser light at the German-British detector GEO600,” explains Karsten Danzmann, director at the AEI Hannover and director of the Institute for Gravitational Physics at Leibniz University Hannover. “The AEI is leading the world-wide efforts to maximize the degree of squeezing and our advances in this technology will benefit all future gravitational-wave detectors.”

    The LIGO and Virgo researchers have issued alerts for 56 possible gravitational-wave events (candidates) in O3, which lasted from 1 April 2019 to 27 March 2020. So far, three candidates have been confirmed and made public. LIGO and Virgo scientists are examining all remaining 53 candidates and will publish all those for which detailed follow-up analyses confirm their astrophysical origin.

    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 Max Planck Society is Germany’s most successful research organization. Since its establishment in 1948, no fewer than 18 Nobel laureates have emerged from the ranks of its scientists, putting it on a par with the best and most prestigious research institutions worldwide. The more than 15,000 publications each year in internationally renowned scientific journals are proof of the outstanding research work conducted at Max Planck Institutes – and many of those articles are among the most-cited publications in the relevant field.

    What is the basis of this success? The scientific attractiveness of the Max Planck Society is based on its understanding of research: Max Planck Institutes are built up solely around the world’s leading researchers. They themselves define their research subjects and are given the best working conditions, as well as free reign in selecting their staff. This is the core of the Harnack principle, which dates back to Adolph von Harnack, the first president of the Kaiser Wilhelm Society, which was established in 1911. This principle has been successfully applied for nearly one hundred years. The Max Planck Society continues the tradition of its predecessor institution with this structural principle of the person-centered research organization.

    The currently 83 Max Planck Institutes and facilities conduct basic research in the service of the general public in the natural sciences, life sciences, social sciences, and the humanities. Max Planck Institutes focus on research fields that are particularly innovative, or that are especially demanding in terms of funding or time requirements. And their research spectrum is continually evolving: new institutes are established to find answers to seminal, forward-looking scientific questions, while others are closed when, for example, their research field has been widely established at universities. This continuous renewal preserves the scope the Max Planck Society needs to react quickly to pioneering scientific developments.

    Northwestern South Campus
    South Campus

    On May 31, 1850, nine men gathered to begin planning a university that would serve the Northwest Territory.

    Given that they had little money, no land and limited higher education experience, their vision was ambitious. But through a combination of creative financing, shrewd politicking, religious inspiration and an abundance of hard work, the founders of Northwestern University were able to make that dream a reality.

    In 1853, the founders purchased a 379-acre tract of land on the shore of Lake Michigan 12 miles north of Chicago. They established a campus and developed the land near it, naming the surrounding town Evanston in honor of one of the University’s founders, John Evans. After completing its first building in 1855, Northwestern began classes that fall with two faculty members and 10 students.
    Twenty-one presidents have presided over Northwestern in the years since. The University has grown to include 12 schools and colleges, with additional campuses in Chicago and Doha, Qatar.

    Northwestern is recognized nationally and internationally for its educational programs.

     
  • richardmitnick 1:59 pm on May 21, 2020 Permalink | Reply
    Tags: "New gravitational-wave model can bring neutron stars into even sharper focus", , Gravitational wave astronomy, , ,   

    From University of Birmingham UK via phys.org: “New gravitational-wave model can bring neutron stars into even sharper focus” 

    From University of Birmingham UK

    via


    phys.org

    May 21, 2020

    1
    The results from a numerical relativity simulation of two merging neutron stars similar to GW170817. Credit: University of Birmingham

    Gravitational-wave researchers at the University of Birmingham have developed a new model that promises to yield fresh insights into the structure and composition of neutron stars.

    The model shows that vibrations, or oscillations, inside the stars can be directly measured from the gravitational-wave signal alone. This is because neutron stars will become deformed under the influence of tidal forces, causing them to oscillate at characteristic frequencies, and these encode unique information about the star in the gravitational-wave signal.

    This makes asteroseismology—the study of stellar oscillations—with gravitational waves from colliding neutron stars a promising new tool to probe the elusive nature of extremely dense nuclear matter.

    Neutron stars are the ultradense remnants of collapsed massive stars. They have been observed in the thousands in the electromagnetic spectrum and yet little is known about their nature. Unique information can be gleaned through measuring the gravitational waves emitted when two neutron stars meet and form a binary system. First predicted by Albert Einstein, these ripples in spacetime were first detected by the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) in 2015.

    By utilising the gravitational wave signal to measure the oscillations of the neutron stars, researchers will be able to discover new insights into the interior of these stars. The study is published in Nature Communications.

    Dr. Geraint Pratten, of the University of Birmingham’s Gravitational Wave Institute, is lead author of the study. He explained: “As the two stars spiral around each other, their shapes become distorted by the gravitational force exerted by their companion. This becomes more and more pronounced and leaves a unique imprint in the gravitational wave signal.

    “The tidal forces acting on the neutron stars excite oscillations inside the star giving us insight into their internal structure. By measuring these oscillations from the gravitational-wave signal, we can extract information about the fundamental nature and composition of these mysterious objects that would otherwise be inaccessible.”

    The model developed by the team enables the frequency of these oscillations to be determined directly from gravitational-wave measurements for the first time. The researchers used their model on the first observed gravitational-wave signal from a binary neutron star merger—GW170817.

    Co-lead author, Dr. Patricia Schmidt, added: “Almost three years after the first gravitational-waves from a binary neutron star were observed, we are still finding new ways to extract more information about them from the signals. The more information we can gather by developing ever more sophisticated theoretical models, the closer we will get to revealing the true nature of neutron stars.”

    Next generation gravitational wave observatories planned for the 2030s, will be capable of detecting far more binary neutron stars and observing them in much greater detail than is currently possible. The model produced by the Birmingham team will make a significant contribution to this science.

    “The information from this initial event was limited as there was quite a lot of background noise that made the signal difficult to isolate,” says Dr. Pratten. “With more sophisticated instruments we can measure the frequencies of these oscillations much more precisely and this should start to yield some really interesting insights.”

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Birmingham has been challenging and developing great minds for more than a century. Characterised by a tradition of innovation, research at the University has broken new ground, pushed forward the boundaries of knowledge and made an impact on people’s lives. We continue this tradition today and have ambitions for a future that will embed our work and recognition of the Birmingham name on the international stage.

     
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: