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  • richardmitnick 2:54 pm on September 24, 2020 Permalink | Reply
    Tags: "A new spin on supermassive black holes", , , , Black Holes, ,   

    From Yale University: “A new spin on supermassive black holes” 

    From Yale University

    September 23, 2020
    Fred Mamoun:
    fred.mamoun@yale.edu
    203-436-2643

    Written by
    Jim Shelton

    1
    This Hubble Ultra Deep Field image reveals a random sample of nearly 10,000 galaxies, including some of the most distant ever found. It was combined from 800 separate exposures with the Hubble Space Telescope Advanced Camera for Surveys over the course of 400 Hubble orbits around Earth, in the period Sept. 24, 2003 and Jan. 16, 2004. (Credit: NASA, ESA, and S. Beckwith [STScI] and the HUDF Team)

    NASA Hubble Advanced Camera for Surveys.

    NASA/ESA Hubble Telescope.

    New observational research suggests that supermassive black holes — the mysterious, light-swallowing objects at the heart of nearly all large galaxies — are spinning like crazy.

    It’s a finding that has sweeping implications for how black holes form, how they grow, and how the shape of the universe as we know it came into being. The research appears in a new study accepted for publication in The Astrophysical Journal.

    “This isn’t the final word on black hole growth, but it’s a big step forward,” said the study’s first author, Tonima Ananna, a former Yale graduate student who is now a postdoctoral researcher at Dartmouth College. Her doctoral adviser was Meg Urry, Yale’s Israel Munson Professor of Physics and Astronomy and senior author of the study.

    A black hole is a point in space where matter is compacted so tightly that it creates intense gravity. This gravity is strong enough that even light can’t escape its pull. A black hole can be as small as a single atom or as large as billions of miles in diameter.

    Black holes have two critical properties: their mass and their spin rate. Yet not much is known about this spin. In recent years spins have been estimated for a few individual black holes, but this is the first time that scientists have been able to assess spin for the entire population of supermassive black holes (SMBHs), based on a representative sample.

    A spinning black hole is slightly squashed compared to a black hole that doesn’t spin, the researchers explained. This allows the infalling gas to get closer to the black hole before it disappears inside, converting more of its energy into radiation.

    Urry, Ananna, and their colleagues looked at the accreting efficiency of rapidly growing SMBHs using four space X-ray satellites: Chandra, XMM-Newton, NuSTAR, and Swift-BAT. They compared the X-ray light to the total mass in SMBHs today and found that matter drawn into SMBHs converted to radiation with high efficiency. This implied that most SMBHs must be rotating rapidly, the researchers said.

    NASA/Chandra X-ray Telescope

    ESA/XMM Newton X-ray telescope.

    NASA/DTU/ASI NuSTAR X-ray telescope.

    NASA Neil Gehrels Swift Observatory.

    “Rapid spin suggests that supermassive black holes grow mainly by the accretion of gas they pull in, rather than by merging with other black holes,” Urry said. “Current theories assume both mergers and accretion add to black hole mass but there are almost no constraints on how much of either. Now we have observational evidence.”

    The new study offers major insights into a key phase of the early universe, as well.

    Astronomers know that for hundreds of thousands of years after the Big Bang, diffuse gas distributed throughout the universe was electrically charged, or ionized. But as this gas — mostly hydrogen — cooled, the atoms lost their ionization. For nearly a billion years after this cooling, the universe remained neutral, meaning its atoms were balanced between positive and negative electrical charges.

    “Because light is easily absorbed by neutral atoms, we cannot peer back into that time. Only after the universe is nearly fully ionized can we see light from early stars, galaxies, and growing black holes,” Urry said.

    “Among other things, this prevents us from observing much from that time because any early light from the first stars or galaxies is absorbed by the neutral hydrogen,” Urry added. “It’s like a curtain we can’t see behind. But once there were enough stars, the hydrogen became ionized and the nearer parts of the universe became visible.”

    The new study found that young stars, and not accreting black holes, were primarily responsible for re-ionizing the universe.

    The researchers added up all of the light created by accreting black holes, as tracked by the X-ray data. It totaled less than 10% of the light needed for re-ionization. “Our work rules out black holes as a larger contributor,” Urry said.

    Urry and Ananna said their team’s work will help theorists build new cosmological models that trace the evolution of galaxies across the past 13 billion years. Those models rely on understanding how much energy accreting black holes deposit into their host galaxies.

    “Our work gives a precise prescription for that profile of energy injection, all validated by experimental data,” Ananna said. “It’s no longer an assumption.”


    Seeing Black Holes

    The National Science Foundation and NASA helped to fund the group’s research.

    See the full article here .

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    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

     
  • richardmitnick 8:46 am on September 24, 2020 Permalink | Reply
    Tags: "The wobbling shadow of the Messier 87* black hole", , , , Black Holes, ,   

    From MIT News: “The wobbling shadow of the Messier 87* black hole” 

    MIT News

    From MIT News

    September 23, 2020
    Nancy Wolfe Kotary | MIT Haystack Observatory

    MIT Haystack Observatory, Westford, Massachusetts, USA, Altitude 131 m (430 ft).

    Analysis of Event Horizon Telescope observations from 2009 to 2017 reveals turbulent evolution of the M87* black hole image.

    1
    Snapshots of the Messier 87* black hole obtained through imaging/geometric modeling, and the EHT array of telescopes from 2009 to 2017. The diameter of all rings is similar, but the location of the bright side varies. Credits: Image courtesy of M. Wielgus, D. Pesce, and the EHT Collaboration.

    In 2019, the Event Horizon Telescope (EHT) Collaboration, including a team of MIT Haystack Observatory scientists, delivered the first image of a black hole, revealing M87* — the supermassive object in the center of the M87 galaxy. The EHT team has used the lessons learned last year to analyze the archival data sets from 2009 to 2013, some of which were not published before. The analysis reveals the behavior of the black hole image across multiple years, indicating persistence of the crescent-like shadow feature, but also variation of its orientation — the crescent appears to be wobbling. The full results appear today in The Astrophysical Journal in an article titled, Monitoring the Morphology of M87* in 2009–2017 with the Event Horizon Telescope.

    The EHT is a global array of telescopes, performing synchronized observations using the technique of very long baseline interferometry.

    EHT map.

    Together they form a virtual Earth-sized radio dish, providing a uniquely high image resolution. In 2009–13, Messier 87* was observed by early-EHT prototype arrays, with telescopes located at three geographical sites from 2009 to 2012 and four sites in 2013. In 2017, the EHT reached maturity with telescopes located at five distinct geographical sites across the globe.

    Datasets for this research were fully correlated at MIT Haystack Observatory. The 2009–2013 observations consist of less data than the ones performed in 2017, making it impossible to create an image. But the EHT team was able to use statistical modeling to look at changes in the appearance of Messier 87* over time. In the modeling approach, the data are compared to a family of geometric templates, in this case rings of non-uniform brightness. A statistical framework is then employed to determine if the data are consistent with such models and to find the best-fitting model parameters.

    “This is a beautiful example of creative data analysis. Extracting important new astrophysical understanding and squeezing new insight out of previous observations is an imaginative example of how scientists can maximally use the information content of such painstakingly collected data,” says Colin Lonsdale, director of MIT Haystack Observatory and chair of the EHT Collaboration Board. “The behavior of this event horizon scale structure over a period of years allows important additional constraints to be placed on the properties of this fascinating object.”

    Expanding the analysis to the 2009–2017 observations, EHT scientists have shown that Messier 87* adheres to theoretical expectations. The black hole’s shadow diameter has remained consistent with the prediction of Einstein’s theory of general relativity for a black hole of 6.5 billion solar masses.

    “In this study, we show that the general morphology, or presence of an asymmetric ring, most likely persists on timescales of several years,” says Kazu Akiyama, research scientist at MIT Haystack Observatory and a participant in the project. “The consistency throughout multiple observational epochs gives us more confidence than ever about the nature of Messier 87* and the origin of the shadow.”

    Although the crescent diameter remained consistent, the EHT team found that the data were hiding a surprise: The ring is wobbling, and that means big news for scientists. For the first time, they can get a glimpse of the dynamical structure of the accretion flow so close to the black hole’s event horizon, in extreme gravity conditions. Studying this region holds the key to understanding phenomena such as relativistic jet launching, and will allow scientists to formulate new tests of the theory of general relativity.

    The gas falling onto a black hole heats up to billions of degrees, ionizes, and becomes turbulent in the presence of magnetic fields. “Because the flow of matter is turbulent, the crescent appears to wobble with time,” says Maciek Wielgus of the Harvard and Smithsonian Center for Astrophysics, who is a Black Hole Initiative fellow, and lead author of the paper. “Actually, we see quite a lot of variation there, and not all theoretical models of accretion allow for so much wobbling. What it means is that we can start ruling out some of the models based on the observed source dynamics.”

    “MIT Haystack Observatory was instrumental in organizing these early observations, correlating the massive amounts of data returned on large numbers of hard drives, and reducing the data,” says Vincent Fish, research scientist at Haystack Observatory. “While we were able to place important constraints on the size and nature of the emission in M87* at the time, the images made from the much better 2017 array data provided critical context for fully understanding what the earlier data were trying to tell us.”

    Haystack scientist Geoff Crew adds, “After working on EHT technology for a decade, I’m gratified that M87* has been making equally good use of its time.”


    The Wobbling Shadow of the Messier 87* Black Hole.

    See the full article here.
    See also the full article from Max Planck Institute for Radio Astronomy here.


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  • richardmitnick 4:16 pm on September 2, 2020 Permalink | Reply
    Tags: "LIGO/Virgo’s Newest Merger Defies Mass Expectations", , , , , , Black Holes, , , , GW190521 black hole merger,   

    From AAS NOVA: “LIGO/Virgo’s Newest Merger Defies Mass Expectations” 

    AASNOVA

    From AAS NOVA

    2 September 2020
    Susanna Kohler

    1
    Numerical simulation of two black holes that inspiral and merge, emitting gravitational waves. [N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration.]

    Been waiting for new signals to be parsed from LIGO/Virgo’s third observing run data? Wait no longer! The latest detection announced in Physical Review Letters and The Astrophysical Journal Letters is big news — both figuratively and literally. The two black holes that merged in GW190521 are the most massive we’ve observed yet, and this has major astrophysical implications.

    Masses in the Stellar Graveyard 9-2-20

    The Signal

    On May 21, 2019, the LIGO/Virgo gravitational-wave observatories detected a strong signal in all three of their detectors.

    MIT /Caltech Advanced aLigo.

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

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    After the conclusion of the observing run and careful analysis of the waves, the collaboration is now announcing GW190521 as an official detection of the inspiral and merger of two extremely massive black holes.

    This signal is unique, record-breaking, and extremely intriguing for two reasons. First, the final product of the merger is ~142 times the mass of the Sun, which places it firmly in the category of elusive intermediate-mass black holes. And second, the two merging black holes had masses of ~85 and ~66 solar masses, which virtually guarantees that at least one of them falls into the so-called pair-instability mass gap.

    A Decidedly Intermediate Size

    Let’s unpack these things, starting with the final product.

    The black holes astronomers have thus far observed in the universe fall into two primary categories: stellar-mass black holes (on the order of ~10 solar masses), and supermassive black holes (millions to tens of billions of solar masses).

    Intermediate-mass black holes (IMBHs) should exist as a bridge between the two, spanning the range of 100–100,000 solar masses. Until now, however, evidence for these bodies has been slim: only a few candidates, all with masses at the upper end of the IMBH mass range, have been identified.

    The detection of GW190521’s 142-solar-mass final product therefore marks a major discovery in a black-hole-mass desert. It confirms not only that IMBHs do exist, but also that they can be formed by the merger of two smaller black holes.

    3
    Illustration of the steps of a hierarchical merger, in which four stellar-mass black holes combine in pairs to eventually form a single, large black hole. [LIGO/Caltech/MIT/R. Hurt (IPAC).]

    Polluting the Mass Gap

    Stellar-mass black holes form when a massive star evolves and collapses at the end of its lifetime. But there’s an instability that’s thought to get in the way for some stars, expelling mass and preventing black holes of a certain range of masses from forming.

    This forbidden pair-instability mass gap lies roughly between 65 and 120 solar masses — and yet the masses of the merging black holes in GW190521 fall squarely within that range!

    How can this be? The LIGO/Virgo collaboration outlines a few possible ways to defy the mass gap:

    1.Second-generation black holes.
    Black holes that formed from the merger of two smaller black holes (instead of from the collapse of a star) can lie within the mass gap. GW190521 might be the result of four stellar-mass black holes undergoing progressive hierarchical mergers to eventually form an intermediate-mass black hole.
    2.Stellar mergers in young star clusters.
    In some scenarios, the merger of an evolved star with a main-sequence companion can create a giant star with an oversized envelope. This type of star could collapse directly into a black hole that lies in the mass gap.

    4
    Artist’s illustration of two merging black holes embedded in the gas disk surrounding a supermassive black hole. [Caltech/R. Hurt (IPAC).]

    3.Black-hole mergers in the disks of active galactic nuclei
    The disk of material that feeds the supermassive black hole at the center of an active galaxy may host tens of thousands of stellar-mass black holes. Trapped in the disk, these smaller black holes can more efficiently accrete material and merge, providing an avenue for rapid growth into mass-gap sizes.

    Going Forward

    We can’t yet be sure whether GW190521 represents a new kind of black hole binary, or if it’s simply the upper-mass end of the population we’ve already observed. But this will soon change, as upgrades to the LIGO/Virgo network’s sensitivity should allow for the detection of several hundreds of mergers per year, reaching ever higher redshifts. And next-generation ground- and space-based detectors will soon provide an additional perspective.

    With the surprising discoveries of GW190521, one thing is clear: the paradigm shifts from gravitational-wave astronomy are only just beginning.

    Citation

    “Properties and Astrophysical Implications of the 150M☉ Binary Black Hole Merger GW190521,” Abbott et al 2020 ApJL 900 L13.
    https://iopscience.iop.org/article/10.3847/2041-8213/aba493

    See the full article here .


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    AAS Mission and Vision Statement

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

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
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  • 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., , , Black Holes, Both sophisticated numerical simulations and perturbative analytic calculations are necessary for this purpose., , , , 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 .

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    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 10:06 am on July 11, 2020 Permalink | Reply
    Tags: "The behemoth behind the brightness", , , , Black Holes, Christopher Onken, , , Fuyan Bian   

    From ESOblog: “The behemoth behind the brightness” 

    ESO 50 Large

    From ESOblog

    1
    Christopher Onken

    2
    Fuyan Bian

    3
    Finding one of the biggest black holes in the Universe powering the brightest quasar ever detected.

    10 July 2020
    Science@ESO

    Two years ago a team of astronomers used Australian telescopes to accurately image a distant quasar that was subsequently revealed to be the most luminous ever detected. A quasar is a bright object at the centre of a galaxy, in which a supermassive black hole is feeding on matter falling into it from a surrounding disk of gas. Revisiting the colossal quasar with ESO’s Very Large Telescope, the team has revealed another staggering feat: it is powered by the most massive black hole ever found in the early Universe. We speak to team members Christopher Onken and Fuyan Bian to find out more.

    Q. Your team expanded on research from nearly two years ago when you discovered the brightest quasar ever. What did you find this time?

    Fuyan Bian (FB): What we found two years ago was the most luminous quasar astronomers have discovered so far at over 10^14 (100 000 000 000 000!) times brighter than the Sun. For this follow-up research, we carried out extensive observations of the object using the VLT and Keck Observatory.

    This quasar lies at the centre of a galaxy, and hot gas from its host galaxy is actively falling onto this central supermassive black hole, forming a brightly shining accretion disc around the black hole that astronomers call a quasar. The purpose of our follow-up observations was to view this hot gas in much higher detail to measure the mass of the supermassive black hole.

    Christopher Onken (CO): We knew from our initial study that this quasar has a very high redshift, meaning it is very distant, and therefore the light left it long ago when the Universe was very young. In the latest research, we found that the quasar is powered by a black hole 34 billion times the mass of the Sun, making it the most massive black hole found in the early Universe and one of the biggest ever detected. This object has a mass of about half of all the stars in the Milky Way condensed into the space that doesn’t even stretch 1% of the distance between the Sun and the nearest star.


    Artist’s impression of the Black Hole at the heart of Messier 87. Credit: ESO/M. Kornmesser

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Q. So what exactly is a supermassive black hole, and how is this one different from others found in the past?

    FB: There are many types of black holes with quite different evolutionary histories. Primordial black holes are very small and are still only predicted by theory; they’ve never been observed. Stellar black holes form from the last phase of a massive star exploding as a supernova.

    CO: Higher in mass still we see supermassive black holes. With around 20 years of experience studying these objects we have found that every reasonably large galaxy has a black hole at its centre, ranging from a hundred thousand to a few billion times the mass of the Sun. What’s interesting is that the black hole we found looks in all other aspects just like an ordinary black hole powering a quasar; it’s really only its extraordinary mass that sets it apart.

    Q. Do you know how something this big formed?

    CO: The basic answer is that we just don’t know definitively how these objects form.The growth of a black hole is a self-limiting process. They grow as surrounding matter in the accretion disc falls into them. However, the more they grow, the more light and radiation pressure the quasar produces, pushing away the feeding gas from around the black hole, slowing the progression of falling matter. So there is a limit to how fast black holes can grow.

    In the case of particularly massive black holes, we are unsure if they started off being large when they initially formed or if they grew in some other way that the unusual conditions of the early Universe could have allowed for. There are various theories and ideas but this is something that we just don’t have a good enough understanding of yet.

    FB: We tend to find these types of black holes at the early epoch of the Universe when the first galaxies were still forming. One theory for how they formed suggests that they started small, forming from black hole “seeds”’ during this early period, growing larger and larger to the point at which they are observable. The size of this black hole suggests the “seed” needed to be quite massive to let this black hole become so large in such a short period of time.

    Q: How did you both feel when you realised the extraordinary mass of this black hole?

    FB: I remember it really well. I remember putting the numbers from my measurements into my computer code and clicking the button and thinking, “oh wow this is actually very massive!” We had predicted that this black hole would be large, but we didn’t know exactly how large. We realised only later that it was one of the largest ever found when checking with one of our collaborators. It definitely felt as if all the hard work paid off.

    CO: Initially I was mostly worried about how reliable our estimate was. Once we had convinced ourselves that we did everything right and there weren’t any other strange explanations for our measurement it was quite amazing to think about.

    Q. Why do you think it is important to study bright quasars and massive black holes?

    FB: The largest black holes likely started to form around 100 million years after the Big Bang. The new data helps us understand the formation process for black holes as big as this one during this very early time period, and discover what the environment must have been like for something this big to have formed. It also tells us about how the first generation of stars formed in such an extreme environment, which is certainly very different from our Milky Way.

    CO: Most supermassive black holes we find are in the nearby Universe. This is one of just a few we have identified that is located far away, at a time where the Universe is only around 1.25 billion years old. In the nearby Universe we find that the mass of a quasar is mainly proportionate to the mass of its host galaxy, but we don’t have nearly enough data to conclude this relation in the early Universe.

    The hope is that by looking at these extreme early cases, even if our measurements have a bit of uncertainty in them, we can construct a clear enough picture to see if this relationship still holds true, that the galaxy is indeed also incredibly massive, growing at the same pace as the black hole.

    2
    SkyMapper Southern Sky Survey image of the brightest quasar ever detected (the faint red dot in the middle). This image is about five arcminutes on each side.

    In future research we plan to use ALMA [below] to measure the cold gas within quasar host galaxies to find their mass as well. Hopefully we can uncover some clues about the relationship and physical processes that link quasars with host galaxies, revealing the properties of early galaxies themselves.

    Q. You originally used data from survey telescopes to look at this object, then used spectroscopic instruments including X-shooter on the VLT [below]. Why were further observations with spectroscopic instruments needed?

    ESO X-shooter on VLT on UT2 at Cerro Paranal, Chile

    FB: The survey telescopes we used measure only the amount of total amount og light emitted by an object, so we used them to pick quasar candidates to observe in more detail, but their results are not actually very useful for detailed studies. For this, we have to use large, precise spectroscopic telescopes like the VLT.

    CO: Indeed; the data from the Australian survey telescopes that we used only allow us to distinguish the quasars from stars in our own galaxy. In order to conduct “spectroscopic analysis” and really nail down the mass of these objects, we needed specialised equipment like the X-shooter spectrograph that splits light up into a spectrum of wavelengths.

    Q. Can you explain in more detail how you used X-shooter to find the black hole’s mass?

    CO: There are two key things you need to measure to estimate a black hole’s mass in this way. You need to figure out how fast the gas orbiting the black hole is moving and how far away from the black hole the gas is sitting. We measured the velocity of the gas by analysing a specific emission line on the spectrum of light coming from the quasar — the MgII doublet emission line. This singled out the light emitted by ionised magnesium near the black hole. The width of this line on a spectrum directly tells us how fast the gas is spinning around the central black hole.

    FB: The X-shooter instrument has a wide enough coverage and resolution to give us an accurate measurement of both of these values — the velocity of the gas and its distance from the black hole — allowing us to weigh a black hole from billions of light years away.

    Q. Why did you choose to use the VLT for your extra research? What benefit did this bring over other spectroscopic telescopes in Australia?

    CO: Two main reasons. The first is that the VLT is much larger than any telescope in Australia. Secondly, the VLT’s X-shooter instrument is really unique in the world, and certainly unique in the facilities that Australia has access to. It is the best in the world for this particular kind of work, with very high wavelength coverage and high spectral resolution, making it perfect for our specific research where we wanted to clearly distinguish the magnesium lines we were after.

    Q. How was the strategic partnership between ESO and Australia beneficial to your research?

    FB: I moved to ESO in 2018, the same year that Australia became a strategic partner with ESO. Teaming up with researchers from Australia was an opportunity for my research where I can contribute my expertise, observation experience and project design with the Australian team. A good combination and opportunity for us both.

    CO: It’s great because it lets us do the science that we want to do. There’s really nothing local in Australia that can make the precise measurements that we wanted for this research. As a partner of ESO, we can use these world-leading instruments and facilities that also cover the southern sky. ESO instruments give us an opportunity to make fantastically detailed observations, including follow-ups to what we can observe using local telescopes. It’s more than what we could have asked for having access to these extra facilities.

    See the full article here .


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    Visit ESO in Social Media-

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

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

    Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system


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

    ESO VLT 4 lasers on Yepun


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

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

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

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

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


    ESO APEXESO/MPIfR APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft)at the Llano de Chajnantor Observatory in the Atacama desert.

    A novel gamma ray telescope under construction on Mount Hopkins, Arizona. a large project known as the Cherenkov Telescope Array, composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile. The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the University of Wisconsin–Madison, and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev

     
  • richardmitnick 3:01 pm on July 2, 2020 Permalink | Reply
    Tags: "The twisted jet and the weakly polarised nucleus in Messier 87", , , , Black Holes, ,   

    From Max Planck Institute for Extraterrestrial Physics: “The twisted jet and the weakly polarised nucleus in Messier 87” 

    From Max Planck Institute for Extraterrestrial Physics

    July 02, 2020
    Fresco, Alejandra
    diploma student
    +49 (0)89 30000-1
    +49 (0)89 30000
    No email address made available

    A study led by Alejandra Yrupe Fresco (Max Planck Institute for Extraterrestrial Physics) during her stay at the Instituto de Astrofísica de Canarias (IAC) has revealed the dim core and the jet structure in the nuclear region of M87, the brightest galaxy in the Virgo cluster. The observations were acquired in early April 2017, almost simultaneously with the Event Horizon Telescope campaign that delivered the world famous first image of the event horizon in a black hole in the nucleus of the galaxy Messier 87.

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professor. On the committee for the next iteration of the EHT .

    Massive black holes are complex environments involving high-energy physics, where accelerated particles are collimated along the system axis. These processes lead to the formation of prominent jets that extend for several kiloparsecs beyond the boundaries of their host galaxies. The polarisation of the light encodes valuable information on the physical conditions and the magnetic field configuration in the vicinity of the black hole, where this radiation was emitted. When observed in polarised light, the nucleus of M87 looks much fainter and less polarised than the extended jet, which reaches a remarkable polarisation degree above 20%. This difference reflects the complexity of the nuclear region, where the jet structure shrinks down to the smallest physical scales.

    “By mapping the orientation angle of the polarised light, we can trace the helical structure of the magnetic field distribution in the jet,” explains Alejandra Fresco, who is currently working on her PhD at Andrea Merloni (MPE) and Celine Peroux (ESO). “This structure is usually formed in jets due to the angular momentum carried by the ejected material, which twists the magnetic field lines along the jet direction.” This is revealed by a characteristic pattern where neighbouring sections in the jet emit polarised light with perpendicular orientations.

    2
    Detailed observations of the core of M87 reveal that the nucleus looks much fainter and less polarised than the extended jet, which reaches a remarkable polarisation degree above 20%. The zoomed image shows the knots of the jet (A, B, C and G) with their correspondent linear polarisation in the I-band; the black lines on top are the polarisation angle for each knot respectively. Credit: A. Fresco/MPE; IAC

    An additional result of the study is the low level of activity in the vicinity of the nucleus during the observations. HST-1, a famous recollimation region that became even brighter than the nucleus during a period of flaring activity during 2005-2007, is barely detected in the ALFOCS images from April 2017. X-ray observations with the Chandra Telescope during the same epoch confirm these observations.

    This project was carried out in collaboration with the IAC researchers Juan Antonio Fernández Ontiveros, Almudena Prieto, and Jose Antonio Acosta Pulido, and was possible due to the unique polarimetric capabilities of the ALFOSC instrument mounted on the Nordic Optical Telescope (NOT), at the Roque de los Muchachos Observatory in La Palma.

    Science paper:
    “Low optical polarization at the core of the optically thin jet of M87”
    MNRAS

    See the full article here .

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    For their astrophysical research, the MPE scientists measure the radiation of far away objects in different wavelenths areas: from millimetere/sub-millimetre and infared all the way to X-ray and gamma-ray wavelengths. These methods span more than twelve decades of the electromagnetic spectrum.

    The research topics pursued at MPE range from the physics of cosmic plasmas and of stars to the physics and chemistry of interstellar matter, from star formation and nucleosynthesis to extragalactic astrophysics and cosmology. The interaction with observers and experimentalists in the institute not only leads to better consolidated efforts but also helps to identify new, promising research areas early on.

    The structural development of the institute mainly has been directed by the desire to work on cutting-edge experimental, astrophysical topics using instruments developed in-house. This includes individual detectors, spectrometers and cameras but also telescopes and integrated, complete payloads. Therefore the engineering and workshop areas are especially important for the close interlink between scientific and technical aspects.

    The scientific work is done in four major research areas that are supervised by one of the directors:

    Center for Astrochemical Studies (CAS)
    Director: P. Caselli

    High-Energy Astrophysics
    Director: P. Nandra

    Infrared/Submillimeter Astronomy
    Director: R. Genzel

    Optical & Interpretative Astronomy
    Director: R. Bender

    Within these areas scientists lead individual experiments and research projects organised in about 25 project teams.

    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.

     
  • richardmitnick 2:35 pm on June 30, 2020 Permalink | Reply
    Tags: , , , , Black Holes, , , The giant black hole-known as J2157-was discovered in 2018.   

    From Australian National University via phys.org: “Hungriest of black holes among the most massive in the universe” 

    ANU Australian National University Bloc

    From Australian National University

    via


    phys.org

    June 30, 2020

    1
    Credit: NASA/JPL-Caltech

    We now know just how massive the fastest-growing black hole in the Universe actually is, as well as how much it eats, thanks to new research led by The Australian National University (ANU).

    It is 34 billion times the mass of our sun and gorges on nearly the equivalent of one sun every day, according to Dr. Christopher Onken and his colleagues.

    “The black hole’s mass is also about 8,000 times bigger than the black hole in the centre of the Milky Way,” Dr. Onken said.

    “If the Milky Way’s black hole wanted to grow that fat, it would have to swallow two thirds of all the stars in our Galaxy.”

    This giant black hole—known as J2157—was discovered by the same research team in 2018.

    “We’re seeing it at a time when the universe was only 1.2 billion years old, less than 10 percent of its current age,” Dr. Onken said.

    “It’s the biggest black hole that’s been weighed in this early period of the Universe.”

    Exactly how black holes grew so big so early in the life-span of the Universe is still a mystery, but the team is now searching for more black holes in the hope they might provide some clues.

    “We knew we were onto a very massive black hole when we realised its fast growth rate,” said team member Dr. Fuyan Bian, a staff astronomer at the European Southern Observatory (ESO).

    “How much black holes can swallow depends on how much mass they already have.

    “So, for this one to be devouring matter at such a high rate, we thought it could become a new record holder. And now we know.”

    The team, including researchers from the University of Arizona, used ESO’s Very Large Telescope in Chile to accurately measure the black hole’s mass.

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

    “With such an enormous black hole, we’re also excited to see what we can learn about the galaxy in which it’s growing,” Dr. Onken said.

    “Is this galaxy one of the behemoths of the early Universe, or did the black hole just swallow up an extraordinary amount of its surroundings? We’ll have to keep digging to figure that out.”

    The research is being published in Monthly Notices of the Royal Astronomical Society.

    See the full article here .

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    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 10:34 am on June 25, 2020 Permalink | Reply
    Tags: "‘Twisted’ sound experiment helps confirm 50-year-old science theory", A 50-year-old theory that began as speculation about how an alien civilisation could use a black hole to generate energy has been experimentally verified for the first time in a Glasgow research lab., , , Black Holes, , Roger Penrose and Yakov Zel’dovich, They built a system which uses small ring of speakers to create a twist in the sound waves analogous to the twist in the light waves proposed by Zel’dovich., University of Glasgow’s School of Physics and Astronomy   

    From University of Glasgow: “‘Twisted’ sound experiment helps confirm 50-year-old science theory” 

    U Glasgow bloc

    From University of Glasgow

    22 Jun 2020

    A 50-year-old theory that began as speculation about how an alien civilisation could use a black hole to generate energy has been experimentally verified for the first time in a Glasgow research lab.

    In 1969, British physicist Roger Penrose suggested that energy could be generated by lowering an object into the black hole’s ergosphere – the outer layer of the black hole’s event horizon, where an object would have to move faster than the speed of light in order to remain still.

    Penrose predicted that the object would acquire a negative energy in this unusual area of space. By dropping the object and splitting it in two so that one half falls into the black hole while the other is recovered, the recoil action would measure a loss of negative energy – effectively, the recovered half would gain energy extracted from the black hole’s rotation. The scale of the engineering challenge the process would require is so great, however, that Penrose suggested only a very advanced, perhaps alien, civilisation would be equal to the task.

    Two years later, another physicist named Yakov Zel’dovich suggested the theory could be tested with a more practical, earthbound experiment. He proposed that ’twisted’ light waves, hitting the surface of a rotating metal cylinder turning at just the right speed, would end up being reflected with additional energy extracted from the cylinder’s rotation thanks to a quirk of the rotational doppler effect.

    But Zel’dovich’s idea has remained solely in the realm of theory since 1971 because, for the experiment to work, his proposed metal cylinder would need to rotate at least a billion times a second – another insurmountable challenge for the current limits of human engineering.

    Now, researchers from the University of Glasgow’s School of Physics and Astronomy have finally found a way to experimentally demonstrate the effect that Penrose and Zel’dovich proposed by twisting sound instead of light – a much lower frequency source, and thus much more practical to demonstrate in the lab.

    In a new paper published today in Nature Physics, the team describe how they built a system which uses small ring of speakers to create a twist in the sound waves analogous to the twist in the light waves proposed by Zel’dovich.

    1

    2
    The experiment. (Cromb et al., Nature Physics, 2020)

    Those twisted sound waves were directed towards a rotating sound absorber made from a foam disc. A set of microphones behind the disc picked up the sound from the speakers as it passed through the disc, which steadily increased the speed of its spin.

    What the team were looking to hear in order to know that Penrose and Zel’dovich’s theories were correct was a distinctive change in the frequency and amplitude of the sound waves as they travelled through the disc, caused by that quirk of the doppler effect.

    Marion Cromb, a PhD student in the University’s School of Physics and Astronomy, is the paper’s lead author. Marion said: “The linear version of the doppler effect is familiar to most people as the phenomenon that occurs as the pitch of an ambulance siren appears to rise as it approaches the listener but drops as it heads away. It appears to rise because the sound waves are reaching the listener more frequently as the ambulance nears, then less frequently as it passes.

    “The rotational doppler effect is similar, but the effect is confined to a circular space. The twisted sound waves change their pitch when measured from the point of view of the rotating surface. If the surface rotates fast enough then the sound frequency can do something very strange – it can go from a positive frequency to a negative one, and in doing so steal some energy from the rotation of the surface.”

    As the speed of the spinning disc increases during the researchers’ experiment, the pitch of the sound from the speakers drops until it becomes too low to hear. Then, the pitch rises back up again until it reaches its previous pitch – but louder, with amplitude of up to 30% greater than the original sound coming from the speakers.

    Marion added: “What we heard during our experiment was extraordinary. What’s happening is that the frequency of the sound waves is being doppler-shifted to zero as the spin speed increases. When the sound starts back up again, it’s because the waves have been shifted from a positive frequency to a negative frequency. Those negative-frequency waves are capable of taking some of the energy from the spinning foam disc, becoming louder in the process – just as Zel’dovich proposed in 1971.”

    Professor Daniele Faccio, also of the University of Glasgow’s School of Physics and Astronomy, is a co-author on the paper. Prof Faccio added: “We’re thrilled to have been able to experimentally verify some extremely odd physics a half-century after the theory was first proposed. It’s strange to think that we’ve been able to confirm a half-century-old theory with cosmic origins here in our lab in the west of Scotland, but we think it will open up a lot of new avenues of scientific exploration. We’re keen to see how we can investigate the effect on different sources such as electromagnetic waves in the near future.”

    The research team’s paper, titled ‘Amplification of waves from a rotating body’, is published in Nature Physics. The research was supported by funding from the Engineering and Physical Sciences Research Council (EPSRC) and the European Union’s Horizon 2020 programme.

    See the full article here .

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    U Glasgow campus

    The University of Glasgow (Scottish Gaelic: Oilthigh Ghlaschu, Latin: Universitas Glasguensis) is the fourth oldest university in the English-speaking world and one of Scotland’s four ancient universities. It was founded in 1451. Along with the University of Edinburgh, the University was part of the Scottish Enlightenment during the 18th century. It is currently a member of Universitas 21, the international network of research universities, and the Russell Group.

    In common with universities of the pre-modern era, Glasgow originally educated students primarily from wealthy backgrounds, however it became a pioneer[citation needed] in British higher education in the 19th century by also providing for the needs of students from the growing urban and commercial middle class. Glasgow University served all of these students by preparing them for professions: the law, medicine, civil service, teaching, and the church. It also trained smaller but growing numbers for careers in science and engineering.[4]

    Originally located in the city’s High Street, since 1870 the main University campus has been located at Gilmorehill in the West End of the city.[5] Additionally, a number of university buildings are located elsewhere, such as the University Marine Biological Station Millport on the Island of Cumbrae in the Firth of Clyde and the Crichton Campus in Dumfries.

    Alumni or former staff of the University include philosopher Francis Hutcheson, engineer James Watt, philosopher and economist Adam Smith, physicist Lord Kelvin, surgeon Joseph Lister, 1st Baron Lister, seven Nobel laureates, and two British Prime Ministers.

     
  • richardmitnick 9:53 am on May 6, 2020 Permalink | Reply
    Tags: , , , Black Holes, , , The new source named 3XMM J215022.4-055108   

    From The New York Times: “Deep in the Cosmic Forest, a Black Hole Goldilocks Might Like” 

    From The New York Times

    May 6, 2020
    Dennis Overbye

    1
    A Hubble Space Telescope image showing the location of an intermediate-mass black hole, named 3XMM J215022.4-055108, indicated by the white circle. Credit: NASA, ESA and D. Lin/University of New Hampshire

    Seven hundred and forty million years ago, a star disappeared in a shriek of X-rays.

    In 2006 a pair of satellites, NASA’s Chandra X-ray Observatory and the European Space Agency’s X-ray Multi-Mission (XMM-Newton, for short), detected that shriek as a faint spot of radiation coming from a far-off corner of the Milky Way.

    NASA/Chandra X-ray Telescope

    ESA/XMM Newton

    To Ducheng Lin, an astronomer at the University of New Hampshire who hunts black holes, those signals were the trademark remains of a star that had been swallowed by a black hole: an arc of leftover fire, like drool on the lips of the ultimate cosmic maw.

    Such events tend to be perpetrated by supermassive black holes like the one that occupies the center of our own Milky Way. But this X-ray signal was not coming from the center of our or any other galaxy.

    Rather the X-rays, the fading Cheshire smile of a black hole, perhaps were coming from the edge of a disk-shaped galaxy about 740 million light years from Earth, in the direction of Aquarius but far beyond the stars that make up that constellation.

    That meant that Dr. Lin had every reason to suspect that he had hooked one of the rarest and most-sought creatures in the cosmic bestiary — an intermediate-mass black hole.

    The word “intermediate” might be a misnomer. If Dr. Lin was right, he (or, more to the point, that unlucky star) had stumbled upon an invisible sinkhole with the gravitational suction of 50,000 suns. He is the lead author of a paper, published in March in Astronomy and Astrophysics, that describes a cosmic ambulance chase.

    [related: The Astrophysical Journal Letters]

    Black holes are the unwelcome consequence of Albert Einstein’s general theory of relativity, which explains gravity as the warping of space-time by mass and energy, much as a heavy sleeper sags a mattress. Too much mass in one place causes space-time to sag beyond its limit, trapping even light on a one-way tunnel to eternity.

    Einstein disliked the idea, but astronomers have discovered that the universe is littered with black holes. Many are the remains of massive stars that collapsed after burning through their thermonuclear trust funds. Sometimes they collide, rippling space-time and rattling antennas like the LIGO gravitational wave detectors.


    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

    These holes — the stellar survivors — tend to tip the scales at a few times the mass of the sun. At the other extreme of cosmic extremities are supermassive black holes — weighing in at millions of billions of solar masses — squatting in the centers of galaxies. Their belches produce the fireworks we call quasars.

    Nobody knows where these holes came from or how they get so big. Two years ago Australian astronomers discovered a black hole that was 20 billion times more massive than the sun, gorging itself back when the universe was only a couple billion years old.

    Astronomers for years have sought the “missing link” in this line of mythological-sounding monsters: black holes “only” thousands or hundreds of thousands of times more massive than the sun.

    “Intermediate mass black holes are indeed fascinating, and in some sense these are becoming the frontier of black hole studies,” Daniel Holz, a University of Chicago astrophysicist who was not part of Dr. Lin’s team, said in an email.

    “Why would the universe only make big and little black holes, and not ones in between? Goldilocks would not be pleased. What makes this particularly troubling for astronomers has to do with our origin stories.”

    There is a suggestive correlation between the mass of a galaxy and the mass of the black hole in its center: The bigger the galaxy, the bigger its hole. This has led astronomers to a rough theory of how the universe gets built in the dark: Small galaxies with their “small” holes accrete into bigger and bigger assemblages of stars, with ever-bigger black holes at the center of it all.

    Intermediate-mass black holes, weighing hundreds or tens of thousands of solar masses, could be expected to anchor the centers of smaller dwarf galaxies. But as such they would be hard to find.

    We only notice black holes when they feed. Stellar-size black holes call attention to themselves as they cannibalize their companions in double star systems. Their supergiant cousins feed at troughs at the centers of big galaxies. But intermediate black holes living in dwarf galaxies would normally find little to eat.

    “We could only find them when gas and dust fall onto them,” said Natalie Webb, an astronomer at the Institut de Recherche en Astrophysique et Planetologie in Toulouse, France, a member of the XMM team and a co-author of the paper. “When this happens, they shine less brightly than the supermassive black holes, but they are usually just as far away (if not further), so they are usually too faint for our observatories.”

    In effect they are only visible when they swallow a star, an event that occurs only once every 10,000 years in any particular galaxy, Dr. Webb said.

    So Dr. Lin may have been lucky indeed. The new source, which his team named 3XMM J215022.4-055108, would be only the second good candidate known.

    2
    The Hubble image around the field of J2150-0551. The green box of 1farcs2 × 1farcs2, with the zoomed inset, is centered around the source. Gal1 is the main host galaxy of the source, and near the source is a possible satellite galaxy Gal2, which might be connected with Gal1 by a tidal stream.Credit…Lin et al., Astronomy and Astrophysics, 2020.

    But there was a possibility that he had been unlucky, and merely detected an outburst on a dense neutron star left over from a supernova explosion in our own galaxy.

    Using the Hubble Space Telescope and the XMM for more observations, Dr. Lin and his team traced the X-ray emanations to a dense knot of stars about 80 light-years wide that was far past the Milky Way. It was on the outskirts of a faraway galaxy named Gal1.

    By coincidence, astronomers using the Canada-France-Hawaii Telescope on Mauna Kea had recorded an outburst of light from that same spot in 2005. That was perhaps the first fatal bite.


    CFHT Telescope, Maunakea, Hawaii, USA, at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    Moreover, the knot of stars resembled precisely what astronomers thought the core of a small galaxy would look like if it had been swallowed by bigger one. It fit the notion that galaxies are assembled by mergers.

    “This is good news, as it was thought that it is likely that intermediate-mass black holes are found in dwarf galaxies,” Dr. Webb said.

    Back in the day, the black hole had been the center of its own little dwarf galaxy. Now it was an empty-nester, most of its stars gone. And it was on the way to an eventual marriage with the bigger black hole at the center of Gal1.

    “Therefore, the new observations confirm the source as one of the best intermediate-mass black hole candidates,” Dr. Lin wrote in the recent paper.

    This is only one of a few good candidates for the missing link black holes. Another one, HLX-1, was discovered in 2009 — by many of the same astronomers — on the edge of a distant galaxy called ESO 243-49. It, too, is in a small cluster of stars that looks like the remains of a dwarf core, and weighs in at about 20,000 solar masses.

    In the case of HLX-1, however, the X-rays seem to be coming from an accretion disk, the doughnut of hot, doomed material swirling outside the edge of a black hole — material that is periodically ripped from a star orbiting the black hole.

    Dr. Webb, who was the lead discoverer of HLX-1, said, “The star keeps coming back to a similar position and a bit more mass is ripped off and falls onto the black hole,” she said. “We have now seen eight X-ray flares from HLX-1 and have observed it with many different types of telescope.”

    The main difference with the new missing link candidate, “is that our object is tearing a star apart, providing strong evidence that it is a massive black hole,” Dr. Lin said in a statement released by the Space Telescope Science Institute.

    Left unanswered is where such gigantic vortices of hungry nothing come from. The universe seems to come with some assembly required, and black holes are key, but astronomers are still struggling to put the parts list together.

    Astronomers have a pretty good sense of how “ordinary” black holes, three to 100 times more massive than the sun, result from the collapse and explosions of massive stars. But there has not been enough time in the history of the universe for such black holes to grow millions or billions of times bigger into the supermassive black holes we see today.

    “They must have formed from something else,” Dr. Webb said, namely, intermediate mass black holes. Such holes would be dragged together as their home galaxies coalesced into ever bigger galaxies.

    Dr. Lin agreed that it was “popular“ to believe that supermassive black holes can form from intermediate mass black holes, dragged together as their home galaxies collide and merge.

    Less certain is where these medium-class black holes — too massive to result from the collapse of stars as we know them today — came from. One possibility, Dr. Lin said, was that they were created by runaway mergers of massive stars in star clusters.

    Another idea, Dr. Webb said, is that they are left over from the first generation of stars in the universe. Astronomers have calculated that such stars, composed only of primordial hydrogen and helium fresh from the ovens of the Big Bang, could have grown much more massive than stars today and produced giant black holes capable of growing into the missing-link intermediate-mass black holes.

    Indeed, some astronomers theorize, hugely dense clouds of primordial gas or dark matter could have collapsed directly into black holes, bypassing the star stage altogether.

    Regardless, intermediate-mass black holes “are the missing link between stellar and supermassive black holes,” Dr. Holtz of Chicago said. “If we confidently detect this population, it will provide insights into how the universe makes all of its black holes.”

    If not, he added, “theorists will need to work even harder to explain how a baby universe makes monster black holes.”

    See the full article here .

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    Please help promote STEM in your local schools.

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  • richardmitnick 9:59 am on April 9, 2020 Permalink | Reply
    Tags: "Black Hole Bends Light Back on Itself", A black hole that is orbited by a sun-like star; together the pair is called XTE J1550-564., , , , Black Holes, ,   

    From Caltech : “Black Hole Bends Light Back on Itself” 

    Caltech Logo

    From Caltech

    April 08, 2020

    Whitney Clavin
    (626) 395‑1944
    wclavin@caltech.edu

    New study proves a theory first predicted more than 40 years ago.

    1
    This illustration shows how some of the light coming from a disk around a black hole is bent back onto the disk itself due to the gravity of the hefty black hole. The light is then reflected back off the disk. Astronomers using data from NASA’s now-defunct Rossi X-ray Timing Explorer (RXTE) mission were able to distinguish between light that came straight from the disk and light that was reflected. The bluish material coming off the black hole is an outflowing jet of energetic particles. Credit: NASA/JPL-Caltech/R. Hurt (IPAC)/R. Connors (Caltech)

    You may have heard that nothing escapes the gravitational grasp of a black hole, not even light. This is true in the immediate vicinity of a black hole, but a bit farther out—in disks of material that swirl around some black holes—light can escape. In fact, this is the reason actively growing black holes shine with brilliant X-rays.

    Now, a new study accepted for publication in The Astrophysical Journal offers evidence that, in fact, not all of the light streaming from a black hole’s surrounding disk easily escapes. Some of it gives in to the monstrous pull of the black hole, turns back, and then ultimately bounces off the disk and escapes.

    “We observed light coming from very close to the black hole that is trying to escape, but instead is pulled right back by the black hole like a boomerang,” says Riley Connors, lead author of the new study and a postdoctoral scholar at Caltech. “This is something that was predicted in the 1970s, but hadn’t been shown until now.”

    The new findings were made possible by combing through archival observations from NASA’s now-defunct Rossi X-ray Timing Explorer (RXTE) mission, which came to an end in 2012.

    NASA/ROSSI

    The researchers specifically looked at a black hole that is orbited by a sun-like star; together, the pair is called XTE J1550-564. The black hole “feeds” off this star, pulling material onto a flat structure around it called an accretion disk. By looking closely at the X-ray light coming from the disk as the light spirals toward the black hole, the team found imprints indicating that the light had been bent back toward the disk and reflected off.

    “The disk is essentially illuminating itself,” says co-author Javier Garcia, a research assistant professor of physics at Caltech. “Theorists had predicted what fraction of the light would bend back on the disk, and now, for the first time, we have confirmed those predictions.”

    The scientists say that the new results offer another indirect confirmation of Albert Einstein’s general theory of relativity, and also will help in future measurements of the spin rates of black holes, something that is still poorly understood.

    “Since black holes can potentially spin very fast, they not only bend the light but twist it,” says Connors. “These recent observations are another piece in the puzzle of trying to figure out how fast black holes spin.”

    The new study, titled, “Evidence for Returning Disk Radiation in the Black Hole X-ray Binary XTEJ1550-564,” was funded by NASA, the Alexander von Humboldt Foundation, and the Margarete von Wrangell Fellowship. Other co-authors are Thomas Dauser, Stefan Licklederer, and Jörn Wilms of The University of Erlangen-Nüremberg in Germany; Victoria Grinberg of the Universität Tübingen in Germany; James Steiner of the MIT Kavli Institute for Astrophysics and Space Research and Harvard University; Navin Sridhar of Columbia University; John Tomsick of UC Berkeley; and Fiona Harrison, the Harold A. Rosen Professor of Physics at Caltech and the Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy.

    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 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

     
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