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  • richardmitnick 1:03 am on May 13, 2018 Permalink | Reply
    Tags: Black Holes, ,   

    From Michigan State University: “Black holes aren’t totally black, and other insights from Stephen Hawking’s groundbreaking work” 

    Michigan State Bloc

    From Michigan State University

    May 8, 2018
    Chris Adami Microbiology and Molecular Genetics; Physics and Astronomy office
    (517) 884-5068
    adami@msu.edu

    1
    No image caption or credit.

    1
    What goes in doesn’t go out? NASA Goddard, CC BY Christoph Adami, Michigan State University

    Mathematical physicist and cosmologist Stephen Hawking was best known for his work exploring the relationship between black holes and quantum physics. A black hole is the remnant of a dying supermassive star that’s fallen into itself; these remnants contract to such a small size that gravity is so strong even light cannot escape from them. Black holes loom large in the popular imagination – schoolchildren ponder why the whole universe doesn’t collapse into one. But Hawking’s careful theoretical work filled in some of the holes in physicists’ knowledge about black holes.

    Why do black holes exist?

    The short answer is: Because gravity exists, and the speed of light is not infinite.

    Imagine you stand on Earth’s surface, and fire a bullet into the air at an angle. Your standard bullet will come back down, someplace farther away. Suppose you have a very powerful rifle. Then you may be able to shoot the bullet at such a speed that, rather than coming down far away, it will instead “miss” the Earth. Continually falling, and continually missing the surface, the bullet will actually be in an orbit around Earth. If your rifle is even stronger, the bullet may be so fast that it leaves Earth’s gravity altogether. This is essentially what happens when we send rockets to Mars, for example.

    Now imagine that gravity is much, much stronger. No rifle could accelerate bullets enough to leave that planet, so instead you decide to shoot light. While photons (the particles of light) do not have mass, they are still influenced by gravity, bending their path just as a bullet’s trajectory is bent by gravity. Even the heaviest of planets won’t have gravity strong enough to bend the photon’s path enough to prevent it from escaping.

    But black holes are not like planets or stars, they are the remnants of stars, packed into the smallest of spheres, say, just a few kilometers in radius. Imagine you could stand on the surface of a black hole, armed with your ray gun. You shoot upwards at an angle and notice that the light ray instead curves, comes down and misses the surface! Now the ray is in an “orbit” around the black hole, at a distance roughly what cosmologists call the Schwarzschild radius, the “point of no return.”

    Thus, as not even light can escape from where you stand, the object you inhabit (if you could) would look completely black to someone looking at it from far away: a black hole.

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    Hawking worked to popularize his cosmological insights. AP Photo/Keystone, Salvatore Di Nolfi

    But Hawking discovered that black holes aren’t completely black?

    The short answer is: Yes.

    My previous description of black holes used the language of classical physics – basically, Newton’s theory applied to light. But the laws of physics are actually more complicated because the universe is more complicated.

    In classical physics, the word “vacuum” means the total and complete absence of any form of matter or radiation. But in quantum physics, the vacuum is much more interesting, in particular when it is near a black hole. Rather than being empty, the vacuum is teeming with particle-antiparticle pairs that are created fleetingly by the vacuum’s energy, but must annihilate each other shortly thereafter and return their energy to the vacuum.

    You will find all kinds of particle-antiparticle pairs produced, but the heavier ones occur much more rarely. It’s easiest to produce photon pairs because they have no mass. The photons must always be produced in pairs so they’re moving away from each other and don’t violate the law of momentum conservation.

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    No light can be seen coming from a black hole outside the Schwarzschild radius. SubstituteR, CC BY-SA

    Now imagine that a pair is created just at that distance from the center of the black hole where the “last light ray” is circulating: the Schwarzschild radius. This distance could be far from the surface or close, depending on how much mass the black hole has. And imagine that the photon pair is created so that one of the two is pointing inward – toward you, at the center of the black hole, holding your ray gun. The other photon is pointing outward. (By the way, you’d likely be crushed by gravity if you tried this maneuver, but let’s assume you’re superhuman.)

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    A pair of photons that annihilate each other is labeled A. In a second pair of photons, labeled B, one enters the black hole while the other heads outward, setting up an energy debt that is paid by the black hole. Christoph Adami, CC BY-ND

    Now there’s a problem: The one photon that moved inside the black hole cannot come back out, because it’s already moving at the speed of light. The photon pair cannot annihilate each other again and pay back their energy to the vacuum that surrounds the black hole. But somebody must pay the piper and this will have to be the black hole itself. After it has welcomed the photon into its land of no return, the black hole must return some of its mass back to the universe: the exact same amount of mass as the energy the pair of photons “borrowed,” according to Einstein’s famous equality E=mc².

    This is essentially what Hawking showed mathematically. The photon that is leaving the black hole horizon will make it look as if the black hole had a faint glow: the Hawking radiation named after him. At the same time he reasoned that if this happens a lot, for a long time, the black hole might lose so much mass that it could disappear altogether (or more precisely, become visible again).

    Do black holes make information disappear forever?

    Short answer: No, that would be against the law.

    Many physicists began worrying about this question shortly after Hawking’s discovery of the glow. The concern is this: The fundamental laws of physics guarantee that every process that happens “forward in time,” can also happen “backwards in time.”

    This seems counter to our intuition, where a melon that splattered on the floor would never magically reassemble itself. But what happens to big objects like melons is really dictated by the laws of statistics. For the melon to reassemble itself, many gazillions of atomic particles would have to do the same thing backwards, and the likelihood of that is essentially zero. But for a single particle this is no problem at all. So for atomic things, everything you observe forwards could just as likely occur backwards.

    Now imagine that you shoot one of two photons into the black hole. They only differ by a marker that we can measure, but that does not affect the energy of the photon (this is called a “polarization”). Let’s call these “left photons” or “right photons.” After the left or right photon crosses the horizon, the black hole changes (it now has more energy), but it changes in the same way whether the left or right photon was absorbed.

    Two different histories now have become one future, and such a future cannot be reversed: How would the laws of physics know which of the two pasts to choose? Left or right? That is the violation of time-reversal invariance. The law requires that every past must have exactly one future, and every future exactly one past.

    Some physicists thought that maybe the Hawking radiation carries an imprint of left/right so as to give an outside observer a hint at what the past was, but no. The Hawking radiation comes from that flickering vacuum surrounding the black hole, and has nothing to do with what you throw in. All seems lost, but not so fast.

    In 1917, Albert Einstein showed that matter (even the vacuum next to matter) actually does react to incoming stuff, in a very peculiar way. The vacuum next to that matter is “tickled” to produce a particle-antiparticle pair that looks like an exact copy of what just came in. In a very real sense, the incoming particle stimulates the matter to create a pair of copies of itself – actually a copy and an anti-copy. Remember, random pairs of particle and antiparticle are created in the vacuum all the time, but the tickled-pairs are not random at all: They look just like the tickler.

    This copy process is known as the “stimulated emission” effect and is at the origin of all lasers. The Hawking glow of black holes, on the other hand, is just what Einstein called the “spontaneous emission” effect, taking place near a black hole.

    Now imagine that the tickling creates this copy, so that the left photon tickles a left photon pair, and a right photon gives a right photon pair. Since one partner of the tickled pairs must stay outside the black hole (again from momentum conservation), that particle creates the “memory” that is needed so that information is preserved: One past has only one future, time can be reversed, and the laws of physics are safe.

    In a cosmic accident, Hawking died on Einstein’s birthday, whose theory of light – it just so happens – saves Hawking’s theory of black holes.

    See the full article here .

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    Michigan State Campus

    Michigan State University (MSU) is a public research university located in East Lansing, Michigan, United States. MSU was founded in 1855 and became the nation’s first land-grant institution under the Morrill Act of 1862, serving as a model for future land-grant universities.

    MSU pioneered the studies of packaging, hospitality business, plant biology, supply chain management, and telecommunication. U.S. News & World Report ranks several MSU graduate programs in the nation’s top 10, including industrial and organizational psychology, osteopathic medicine, and veterinary medicine, and identifies its graduate programs in elementary education, secondary education, and nuclear physics as the best in the country. MSU has been labeled one of the “Public Ivies,” a publicly funded university considered as providing a quality of education comparable to those of the Ivy League.

    Following the introduction of the Morrill Act, the college became coeducational and expanded its curriculum beyond agriculture. Today, MSU is the seventh-largest university in the United States (in terms of enrollment), with over 49,000 students and 2,950 faculty members. There are approximately 532,000 living MSU alumni worldwide.

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  • richardmitnick 12:50 pm on April 28, 2018 Permalink | Reply
    Tags: , , , Black Holes, , , , , , Thermodynamics   

    From Kavli Institute for the Physics and Mathematics of the Universe: “Study Finds Way to Use Quantum Entanglement to Study Black Holes” 

    KavliFoundation

    The Kavli Foundation

    Kavli IPMU
    Kavli IMPU

    April 23, 2018

    A team of researchers has found a relationship between quantum physics, the study of very tiny phenomena, to thermodynamics, the study of very large phenomena, reports a new study this week in Nature Communications.

    “Our function can describe a variety of systems from quantum states in electrons to, in principle, black holes,” says study author Masataka Watanabe.

    Quantum entanglement is a phenomenon fundamental to quantum mechanics, where two separated regions share the same information. It is invaluable to a variety of applications including being used as a resource in quantum computation, or quantifying the amount of information stored in a black hole.

    Quantum mechanics is known to preserve information, while thermal equilibrium seems to lose some part of it, and so understanding the relationship between these microscopic and macroscopic concepts is important. So a group of graduate students and a researcher at the University of Tokyo, including the Kavli Institute for the Physics and Mathematics of the Universe, investigated the role of the quantum entanglement in thermal equilibrium in an isolated quantum system.

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    Figure 1: Graph showing quantum entanglement and spatial distribution. When separating matter A and B, the vertical axis shows how much quantum entanglement there is, while the horizontal axis shows the length of matter A. (Credit: Nakagawa et al.)

    “A pure quantum state stabilizing into thermal equilibrium can be compared to water being poured into a cup. In a quantum-mechanical system, the colliding water molecules create quantum entanglements, and these quantum entanglements will eventually lead a cup of water to thermal equilibrium. However, it has been a challenge to develop a theory which predicts how much quantum entanglement was inside because lots of quantum entanglements are created in complicated manners at thermal equilibrium,” says Watanabe.

    In their study, the team identified a function predicting the spatial distribution of information stored in an equilibrated system, and they revealed that it was determined by thermodynamic entropy alone. Also, by carrying out computer simulations, they found that the spatial distribution remained the same regardless of what systems were used and regardless of how they reached thermal equilibrium.

    See the full article here .

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    Kavli IPMU (Kavli Institute for the Physics and Mathematics of the Universe) is an international research institute with English as its official language. The goal of the institute is to discover the fundamental laws of nature and to understand the Universe from the synergistic perspectives of mathematics, astronomy, and theoretical and experimental physics. The Institute for the Physics and Mathematics of the Universe (IPMU) was established in October 2007 under the World Premier International Research Center Initiative (WPI) of the Ministry of Education, Sports, Science and Technology in Japan with the University of Tokyo as the host institution. IPMU was designated as the first research institute within the University of Tokyo Institutes for Advanced Study (UTIAS) in January 2011. It received an endowment from The Kavli Foundation and was renamed the “Kavli Institute for the Physics and Mathematics of the Universe” in April 2012. Kavli IPMU is located on the Kashiwa campus of the University of Tokyo, and more than half of its full-time scientific members come from outside Japan. http://www.ipmu.jp/
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    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

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

     
  • richardmitnick 3:24 pm on April 22, 2018 Permalink | Reply
    Tags: , , , Black Holes, , , Is Dark Matter Made of Primordial Black Holes?   

    From Center For Astrophysics: “Is Dark Matter Made of Primordial Black Holes?” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

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    The dwarf irregular galaxy IC1613. Astronomers wondering whether primordial black holes might compose the dark matter in the universe suggest that the shapes of faint dwarf galaxies with dark matter halos might reveal the answer. NASA/JPL-Caltech/SSC

    Astronomers studying the motions of galaxies and the character of the cosmic microwave background radiation came to realize in the last century that most of the matter in the universe was not visible.

    Cosmic Background Radiation per Planck

    ESA/Planck 2009 to 2013

    About 84% of the matter in the cosmos is dark matter, much of it located in halos around galaxies.

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Dark matter halo. Image credit: Virgo consortium / A. Amblard / ESA

    Milky Way Dark Matter Halo Credit ESO L. Calçada

    It was dubbed dark matter because it does not emit light, but it is also mysterious: it is not composed of atoms or their usual constituents like electrons and protons.

    Meanwhile, astronomers have observed the effects of black holes and recently even detected gravitational waves from a pair of merging black holes.

    Artist’s conception of two merging black holes similar to those detected by LIGO Credit LIGO-Caltech/MIT/Sonoma State /Aurore Simonnet

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Black holes usually are formed in the explosive death of massive stars, a process that can take many hundreds of millions of years as a star coalesces from ambient gas, evolves and finally dies. Some black holes are inferred to exist in the early universe, but there is probably is not enough time in the early universe for the normal formation process to occur. Some alternative methods have been proposed, like the direct collapse of primordial gas or processes associated with cosmic inflation, and many of these primordial black holes could have been made.

    CfA astronomer Qirong Zhu led a group of four scientists investigating the possibility that today’s dark matter is composed of primordial black holes, following up on previously published suggestions. If galaxy halos are made of black holes, they should have a different density distribution than halos made of exotic particles. There are some other differences as well – black hole halos are expected to form earlier in a galaxy’s evolution than do some other kinds of halos. The scientists suggest that looking at the stars in the halos of faint dwarf galaxies can probe these effects because dwarf galaxies are small and faint (they shine with a mere few thousand solar luminosities) where slight effects can be more easily spotted. The team ran a set of computer simulations to test whether dwarf galaxy halos might reveal the presence of primordial black holes, and they find that they could: interactions between stars and primordial halo black holes should slightly alter the sizes of the stellar distributions. The astronomers also conclude that such black holes would need to have masses between about two and fourteen solar masses, right in the expected range for these exotic objects (although smaller than the black holes recently spotted by gravitational wave detectors) and comparable to the conclusions of other studies. The team emphasizes, however, that all the models are still inconclusive and the nature of dark matter remains elusive.

    Science paper:
    Qirong Zhu, Eugene Vasiliev, Yuexing Li, and Yipeng Jing,
    Primordial Black Holes as Dark Matter: Constraints from Compact Ultra-faint Dwarfs
    MNRAS

    See the full article here .

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

     
  • richardmitnick 11:02 am on April 11, 2018 Permalink | Reply
    Tags: , , , Black Holes, , Dense stellar clusters may foster black hole megamergers, ,   

    From Kavli MIT Institute For Astrophysics and Space Research: “Dense stellar clusters may foster black hole megamergers” 

    KavliFoundation

    http://www.kavlifoundation.org/institutes

    Kavli MIT Institute of Astrophysics and Space Research

    Kavli MIT Institute For Astrophysics and Space Research

    April 10, 2018
    Jennifer Chu

    When LIGO’s twin detectors first picked up faint wobbles in their respective, identical mirrors, the signal didn’t just provide first direct detection of gravitational waves — it also confirmed the existence of stellar binary black holes, which gave rise to the signal in the first place.

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    A snapshot of a simulation showing a binary black hole formed in the center of a dense star cluster. Credit: Northwestern Visualization/Carl Rodriguez. https://phys.org

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    A simulation showing an encounter between a binary black hole (in orange) and a single black hole (in blue) with relativistic effects. Eventually two black holes emit a burst of gravitational waves and merge, creating a new black hole (in red). Credit: Massachusetts Institute of Technology. https://phys.org


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    ESA/eLISA the future of gravitational wave research

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

    Stellar binary black holes are formed when two black holes, created out of the remnants of massive stars, begin to orbit each other. Eventually, the black holes merge in a spectacular collision that, according to Einstein’s theory of general relativity, should release a huge amount of energy in the form of gravitational waves.

    Now, an international team led by MIT astrophysicist Carl Rodriguez suggests that black holes may partner up and merge multiple times, producing black holes more massive than those that form from single stars. These “second-generation mergers” should come from globular clusters — small regions of space, usually at the edges of a galaxy, that are packed with hundreds of thousands to millions of stars.

    “We think these clusters formed with hundreds to thousands of black holes that rapidly sank down in the center,” says Carl Rodriguez, a Pappalardo fellow in MIT’s Department of Physics and the Kavli Institute for Astrophysics and Space Research. “These kinds of clusters are essentially factories for black hole binaries, where you’ve got so many black holes hanging out in a small region of space that two black holes could merge and produce a more massive black hole. Then that new black hole can find another companion and merge again.”

    If LIGO detects a binary with a black hole component whose mass is greater than around 50 solar masses, then according to the group’s results, there’s a good chance that object arose not from individual stars, but from a dense stellar cluster.

    “If we wait long enough, then eventually LIGO will see something that could only have come from these star clusters, because it would be bigger than anything you could get from a single star,” Rodriguez says.

    He and his colleagues report their results in a paper appearing in Physical Review Letters.

    Running stars

    For the past several years, Rodriguez has investigated the behavior of black holes within globular clusters and whether their interactions differ from black holes occupying less populated regions in space.

    Globular clusters can be found in most galaxies, and their number scales with a galaxy’s size. Huge, elliptical galaxies, for instance, host tens of thousands of these stellar conglomerations, while our own Milky Way holds about 200, with the closest cluster residing about 7,000 light years from Earth.

    In their new paper, Rodriguez and his colleagues report using a supercomputer called Quest, at Northwestern University, to simulate the complex, dynamical interactions within 24 stellar clusters, ranging in size from 200,000 to 2 million stars, and covering a range of different densities and metallic compositions. The simulations model the evolution of individual stars within these clusters over 12 billion years, following their interactions with other stars and, ultimately, the formation and evolution of the black holes. The simulations also model the trajectories of black holes once they form.

    “The neat thing is, because black holes are the most massive objects in these clusters, they sink to the center, where you get a high enough density of black holes to form binaries,” Rodriguez says. “Binary black holes are basically like giant targets hanging out in the cluster, and as you throw other black holes or stars at them, they undergo these crazy chaotic encounters.”

    It’s all relative

    When running their simulations, the researchers added a key ingredient that was missing in previous efforts to simulate globular clusters.

    “What people had done in the past was to treat this as a purely Newtonian problem,” Rodriguez says. “Newton’s theory of gravity works in 99.9 percent of all cases. The few cases in which it doesn’t work might be when you have two black holes whizzing by each other very closely, which normally doesn’t happen in most galaxies.”

    Newton’s theory of relativity assumes that, if the black holes were unbound to begin with, neither one would affect the other, and they would simply pass each other by, unchanged. This line of reasoning stems from the fact that Newton failed to recognize the existence of gravitational waves — which Einstein much later predicted would arise from massive orbiting objects, such as two black holes in close proximity.

    “In Einstein’s theory of general relativity, where I can emit gravitational waves, then when one black hole passes near another, it can actually emit a tiny pulse of gravitational waves,” Rodriguez explains. “This can subtract enough energy from the system that the two black holes actually become bound, and then they will rapidly merge.”

    The team decided to add Einstein’s relativistic effects into their simulations of globular clusters. After running the simulations, they observed black holes merging with each other to create new black holes, inside the stellar clusters themselves. Without relativistic effects, Newtonian gravity predicts that most binary black holes would be kicked out of the cluster by other black holes before they could merge. But by taking relativistic effects into account, Rodriguez and his colleagues found that nearly half of the binary black holes merged inside their stellar clusters, creating a new generation of black holes more massive than those formed from the stars. What happens to those new black holes inside the cluster is a matter of spin.

    “If the two black holes are spinning when they merge, the black hole they create will emit gravitational waves in a single preferred direction, like a rocket, creating a new black hole that can shoot out as fast as 5,000 kilometers per second — so, insanely fast,” Rodriguez says. “It only takes a kick of maybe a few tens to a hundred kilometers per second to escape one of these clusters.”

    Because of this effect, scientists have largely figured that the product of any black hole merger would get kicked out of the cluster, since it was assumed that most black holes are rapidly spinning.

    This assumption, however, seems to contradict the measurements from LIGO, which has so far only detected binary black holes with low spins. To test the implications of this, Rodriguez dialed down the spins of the black holes in his simulations and found that in this scenario, nearly 20 percent of binary black holes from clusters had at least one black hole that was formed in a previous merger. Because they were formed from other black holes, some of these second-generation black holes can be in the range of 50 to 130 solar masses. Scientists believe black holes of this mass cannot form from a single star.

    Rodriguez says that if gravitational-wave telescopes such as LIGO detect an object with a mass within this range, there is a good chance that it came not from a single collapsing star, but from a dense stellar cluster.

    “My co-authors and I have a bet against a couple people studying binary star formation that within the first 100 LIGO detections, LIGO will detect something within this upper mass gap,” Rodriguez says. “I get a nice bottle of wine if that happens to be true.”

    This research was supported in part by the MIT Pappalardo Fellowship in Physics, NASA, the National Science Foundation, the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) at Northwestern University, the Institute of Space Sciences (ICE, CSIC) and Institut d’Estudis Espacials de Catalunya (IEEC), and the Tata Institute of Fundamental Research in Mumbai, India.

    See the full article here .

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    Mission Statement

    The mission of the MIT Kavli Institute (MKI) for Astrophysics and Space Research is to facilitate and carry out the research programs of faculty and research staff whose interests lie in the broadly defined area of astrophysics and space research. Specifically, the MKI will

    Provide an intellectual home for faculty, research staff, and students engaged in space- and ground-based astrophysics
    Develop and operate space- and ground-based instrumentation for astrophysics
    Engage in technology development
    Maintain an engineering and technical core capability for enabling and supporting innovative research
    Communicate to students, educators, and the public an understanding of and an appreciation for the goals, techniques and results of MKI’s research.

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

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

     
  • richardmitnick 5:02 pm on March 28, 2018 Permalink | Reply
    Tags: , , , Black Holes, , , , UMASSD Professor overturns understanding on black holes   

    From UMass Dartmouth: “Professor overturns understanding on black holes” 

    UMass Dartmouth

    March 28, 2018
    Office of Public Affairs

    Dr. Gaurav Khanna, Ph.D. publishes a paper that sheds new light on space’s most mysterious phenomena.

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    On March 29, 2018, the Physical Review journal [Physical Review D] is set to publish an article by Professors Gaurav Khanna (Physics) of UMass Dartmouth and Lior Burko of Georgia Gwinnett College that demonstrates the existence of extreme black holes that until now were thought to be theoretical and unobservable. “These findings could open the door to new paths of research related to the nature of the universe,” said Khanna.

    Extreme black holes differ from traditional black holes because they have the fastest possible spin allowed by Einstein’s theory of relativity. Khanna and Burko’s research upends conventional wisdom on extreme black holes, which presumed these objects were unstable, and thus did not exist in nature. Through computational research, Khanna and Burko found that extreme black holes are stable and may someday be observed by gravitational-wave observatories.

    Dr. Khanna has a long history of studying these fascinating cosmic objects. In 2015, the universe’s gravitational waves were observed for the very first time by the Laser Interferometer Gravitational-Wave Observatory (LIGO).


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    ESA/eLISA the future of gravitational wave research

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

    This led to a Novel Prize in Physics for the three leaders of the LIGO project. The LIGO project is a collaboration of over 1,000 researchers from more than 20 countries. The UMass Dartmouth Physics Department has had a long relationship with the LIGO project extending over a decade. Physics majors have participated in summer internships at the LIGO laboratory, and others have officially joined the LIGO collaboration later in their careers.

    One of the Nobel winners visited the university in 2016 to discuss his work and Dr. Khanna presented a seminar on this groundbreaking discovery.

    UMass Dartmouth has a strong focus on the cosmos. Recently, astronaut alumnus Scott Tingle (College of Engineering ’87) participated in a satellite downlink event where he answered questions live from the International Space Station. This was preceded by a faculty panel that discussed various perspectives on life in space.

    See the full article here .

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    Mission Statement

    UMass Dartmouth distinguishes itself as a vibrant, public research university dedicated to engaged learning and innovative research resulting in personal and lifelong student success. The University serves as an intellectual catalyst for economic, social, and cultural transformation on a global, national, and regional scale.
    Vision Statement

    UMass Dartmouth will be a globally recognized premier research university committed to inclusion, access, advancement of knowledge, student success, and community engagement.

    The University of Massachusetts Dartmouth (UMass Dartmouth or UMassD) is one of five campuses and operating subdivisions of the University of Massachusetts. It is located in North Dartmouth, Massachusetts, United States, in the center of the South Coast region, between the cities of New Bedford to the east and Fall River to the west. Formerly Southeastern Massachusetts University, it was merged into the University of Massachusetts system in 1991.

    The campus has an overall student body of 8,647 students (school year 2016-2017), including 6,999 undergraduates and 1,648 graduate/law students. As of the 2017 academic year, UMass Dartmouth records 399 full-time faculty on staff. For the fourth consecutive year UMass Dartmouth receives top 20 national rank from President’s Higher Education Community Service Honor Roll for its civic engagement.

    The university also includes the University of Massachusetts School of Law, as the trustees of the state’s university system voted during 2004 to purchase the nearby Southern New England School of Law (SNESL), a private institution that was accredited regionally but not by the American Bar Association (ABA).
    UMass School of Law at Dartmouth opened its doors in September 2010, accepting all current SNESL students with a C or better average as transfer students, and achieved (provisional) ABA accreditation in June 2012. The law school achieved full accreditation in December 2016.

    In 2011, UMass Dartmouth became the first university in the world to have a sustainability report that met the top level of the world’s most comprehensive, credible, and widely used standard (the GRI’s G3.1 standard). In 2013, UMass Dartmouth became the first university in the world whose annual sustainability report achieved an A+ application level according to the Global Reporting Initiative G3.1 standard (by having the sources of data used in its annual sustainability report verified by an independent third party).

     
  • richardmitnick 9:23 pm on March 19, 2018 Permalink | Reply
    Tags: , , , Black Holes, , , Gravastar model, ,   

    From Sky & Telescope: “Physicist Proposes Alternative to Black Holes” 

    SKY&Telescope bloc

    Sky & Telescope

    March 19, 2018
    Ben Skuse

    A physicist has incorporated a quantum mechanical idea with general relativity to arrive at a new alternative to black hole singularities.

    1
    An artist’s rendering of Cygnus X-1, an X-ray-emitting black hole that formed when a large star caved in. (We see its X-rays now as it feeds from its stellar companion.) But are black holes the inevitable next step after neutron stars? NASA / CXC / M.Weiss.

    What do you get when you cross two hypothetical alternatives to black holes? A self-consistent semiclassical relativistic star, according to Raúl Carballo-Rubio (International School for Advanced Studies, Trieste, Italy) whose recently published results in the February 6th Physical Review Letters describe a new mathematical model for the fate of massive stars.

    When a massive star comes to the end of its life, it goes supernova, leaving behind a dense core that — according to conventional thought — continues to collapse to form either a neutron star or black hole. To which fate a particular star is destined comes down to its mass. Neutron stars find a balance between the repulsive force of quantum mechanical degeneracy pressure and the attractive force of gravity, while more massive cores collapse into black holes, unable to fight the overwhelming pull of their own gravity.

    Repulsive Gravity

    Now, Carballo-Rubio adds an extra force into the mix: quantum fluctuations. Quantum mechanics has shown that virtual particles spontaneously pop into and out of existence — the effects can be measured best in a vacuum, but these fluctuations can happen anywhere in spacetime. These particles can be thought of as fluctuations of positive and negative energy that under normal conditions would cancel out. But the extreme gravity of compact objects breaks this balance, effectively generating negative energy. This negative energy creates a repulsive gravitational force.

    “The existence of quantum [fluctuations] due to gravitational fields has been known since the late 1970s,” explains Carballo-Rubio. But physicists didn’t know how to take this effect into account in collapsing stars.

    Carballo-Rubio derived equations that combine general relativity and quantum mechanics in a way that accounts for quantum fluctuations. Moreover, he found solutions that balance attractive and negative gravity for stellar masses that would otherwise have produced black holes. Dubbing them “semiclassical relativistic stars,” these compact objects do not fully collapse under their own weight to form an event horizon, and are therefore not black holes.

    Hybrid Star

    Interestingly, Carballo-Rubio’s semiclassical relativistic stars bear hallmarks of previously proposed black hole alternatives: gravastars and black stars.

    Gravastars and black stars also consist of ordinary matter and quantum fluctuations. But when these ideas were first conceived, equations incorporating quantum flluctuations were not yet known, so theorists Carballo-Rubio’s stars, on the other hand, emerge naturally from a consistent set of equations based on known physics.

    Gravastars and black stars are structured differently: In gravastar cores, large quantum fluctuations push ordinary matter outward to form an ultra-thin shell at the surface. Black stars, on the other hand, balance matter and the quantum fluctuations throughout their structure.

    Carballo-Rubio’s stars are like a hybrid of the two previous ideas. “On the one hand, both matter and the quantum [fluctuations] are present throughout the structure, as in the black star model,” he says. “On the other, the star displays two distinct elements, namely a core and an ultra-thin shell, as in the gravastar model.”

    2
    Artist’s drawing of a neutron star. Casey Reed / Penn State University.

    The Question of Stability

    Whether these hybrid stars exist in the real world is a matter of debate. Carballo-Rubio’s solutions do not incorporate time, so it isn’t clear if a such a star would remain stable or rapidly morph into something else . . . like a black hole.

    “Equilibrium solutions can be found for a pen standing on its tip,” remarks relativistic astrophysicist Luciano Rezzolla (Institute of Theoretical Physics, Germany). “Such a solution is obviously unstable to small perturbations.”

    However, if Carballo-Rubio can show that his semiclassical relativistic stars are indeed dynamically stable — which he will start work on next — the next generation of gravitational wave observatories should offer the level of precision necessary in the coming decades to distinguish unconventional compact bodies from black holes, potentially providing evidence to support the existence of this new type of star.

    See the full article here .

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    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 2:55 pm on February 23, 2018 Permalink | Reply
    Tags: , , , Black Holes, , ,   

    From UCSC: ” Novel search strategy advances the hunt for primordial black holes” 

    UC Santa Cruz

    UC Santa Cruz

    February 21, 2018
    Tim Stephens
    stephens@ucsc.edu

    Some theories of the early universe predict density fluctuations that would have created small “primordial black holes,” some of which could be drifting through our galactic neighborhood today and might even be bright sources of gamma rays.

    Researchers analyzing data from the Fermi Gamma-ray Space Telescope for evidence of nearby primordial black holes have come up empty, but their negative findings still allow them to put an upper limit on the number of these tiny black holes that might be lurking in the vicinity of Earth.

    NASA/Fermi Gamma Ray Space Telescope


    NASA’s Fermi Gamma-ray Space Telescope is a powerful space observatory that opens a wide window on the universe. Primordial black holes are a potential source of gamma rays, the highest-energy form of light. (Illustration credit: NASA)

    “Understanding how many primordial black holes are around today can help us understand the early universe better,” said Christian Johnson, a graduate student in physics at UC Santa Cruz who developed an algorithm to search data from Fermi’s Large Area Telescope (LAT) for the signatures of primordial black holes. Johnson is a corresponding author of a paper on the findings that has been accepted for publication in The Astrophysical Journal.

    Low-mass black holes are expected to emit gamma rays due to Hawking radiation, a theoretical prediction from the work of physicist Stephen Hawking and others. Hawking showed that quantum effects can give rise to particle-antiparticle pairs near the event horizon of a black hole, allowing one of the particles to fall into the black hole and the other to escape. The result is that the black hole emits radiation and loses mass.

    A small black hole that isn’t absorbing enough from its environment to offset the losses from Hawking radiation will steadily lose mass and eventually evaporate entirely. The smaller it gets, the brighter it “burns,” emitting more and more Hawking radiation before exploding in a final cataclysm. Previous searches for primordial black holes using ground-based gamma-ray observatories have looked for these brief explosions, but Fermi should be able to detect the “burn phase” occurring over a period of several years.

    A limitation of the Fermi search was that it could only extend a relatively short distance from Earth (a small fraction of the distance to the nearest star). The advantage of looking nearby, however, is that primordial black holes could be distinguished from other sources of gamma rays by their movement on the sky.

    “It’s like looking at the sky at night and trying to decide if something is an airplane or a star,” Johnson explained. “If it’s an airplane, it will move, and if it’s a star it will stay put.”

    Any primordial black holes still around today would have started out much larger and have been gradually losing mass for billions of years. To detect one with Fermi, it would have to have reached the final burn phase during the roughly four-year observation period of the study. Over a period of a few years, it would go from undetectably dim to extremely bright, and would burn brightly for several years before exploding, Johnson said.

    “Even though we didn’t detect any, the non-detection sets a limit on the rate of explosions and gives us better constraints than previous research,” he said.

    In addition to Johnson, the other corresponding authors of the paper include Steven Ritz, professor of physics and director of the Santa Cruz Institute of Particle Physics at UCSC; and Stefan Funk and Dmitry Malyshev at the Erlangen Centre for Astroparticle Physics in Germany. Other members of the Fermi-LAT Collaboration also contributed to this work and are coauthors of the paper.

    See the full article here .

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    UCO Lick Shane Telescope
    UCO Lick Shane Telescope interior
    Shane Telescope at UCO Lick Observatory, UCSC

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    UC Santa Cruz campus
    The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

    UCSC is the home base for the Lick Observatory.

    Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
    Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

    Search for extraterrestrial intelligence expands at Lick Observatory
    New instrument scans the sky for pulses of infrared light
    March 23, 2015
    By Hilary Lebow
    1
    The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch) UCSC Lick Nickel telescope

    Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

    “Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

    Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

    Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

    5
    UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch)

    Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

    “The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

    The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

    Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

    “We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

    Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

    “This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

    NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

    “Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

    NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

    The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

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    UCSC is the home base for the Lick Observatory.

     
  • richardmitnick 2:44 pm on February 21, 2018 Permalink | Reply
    Tags: , , , Black Holes, , IAC CanariCam on the Gran Telescopio Canarias at Roque de los Muchachos Observatory, MNRAS,   

    From RAS: “Magnetic field traces gas and dust swirling around supermassive black hole” 

    Royal Astronomical Society

    Royal Astronomical Society

    21 February 2018

    Media contacts

    Dr Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7292 3979
    Mob: +44 (0)7802 877699
    rmassey@ras.ac.uk

    Dr Helen Klus
    Royal Astronomical Society
    Tel: +44 (0)20 7292 3976
    hklus@ras.ac.uk

    Science contact

    Professor Pat Roche
    University of Oxford
    pat.roche@physics.ox.ac.uk

    Astronomers reveal a new high resolution map of the magnetic field lines in gas and dust swirling around the supermassive black hole at the centre of our Galaxy, published in a new paper in Monthly Notices of the Royal Astronomical Society.

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

    The team, led by Professor Pat Roche of the University of Oxford, created the map, which is the first of its kind, using the CanariCam infrared camera attached to the Gran Telescopio Canarias sited on the island of La Palma.

    IAC CanariCam on the Gran Telescopio Canarias at Roque de los Muchachos Observatory island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    Black holes are objects with gravitational fields so strong that not even light can escape their grasp. The centre of almost every galaxy appears to host a black hole, and the one we live in, the Milky Way, is no exception. Stars move around the black hole at speeds of up to 30 million kilometres an hour, indicating that it has a mass of more than a million times our Sun.

    2
    The colour scale in the image shows the amount of infrared (heat) radiation coming from warm dust particles in the filaments and luminous stars within a light year of the Galactic centre. The position of the black hole is indicated by an asterisk. The lines trace the magnetic field directions and reveal the complex interactions between the stars and the dusty filaments, and the impact that they and the gravitational force has on them. Credit: E. Lopez-Rodriguez / NASA Ames / University of Texas at San Antonio.

    Visible light from sources in the centre of the Milky Way is blocked by clouds of gas and dust. Infrared light, as well as X-rays and radio waves, passes through this obscuring material, so astronomers use this to see the region more clearly. CanariCam combines infrared imaging with a polarising device, which preferentially filters light with the particular characteristics associated with magnetic fields.

    The new infrared map covers a region about 1 light year on each side of the supermassive black hole. The map shows the intensity of infrared light, and traces magnetic field lines within filaments of warm dust grains and hot gas, which appear as thin lines reminiscent of brush strokes in a painting.

    The filaments, several light years long, appear to meet close to the black hole (at a point below centre in the map), and may indicate where orbits of streams of gas and dust converge. One prominent feature links some of the brightest stars in the centre of the Galaxy. Despite the strong winds flowing from these stars, the filaments remain in place, bound by the magnetic field within them. Elsewhere the magnetic field is less clearly aligned with the filaments. Depending on how the material flows, some of it may eventually be captured and engulfed by the black hole.

    The new observations give astronomers more detailed information on the relationship between the bright stars and the dusty filaments. The origin of the magnetic field in this region is not understood, but it is likely that a smaller magnetic field is stretched out as the filaments are elongated by the gravitational influence of the black hole and stars in the galactic centre.

    Roche praises the new technique and the result: “Big telescopes like GTC, and instruments like CanariCam, deliver real results. We’re now able to watch material race around a black hole 25,000 light years away, and for the first time see magnetic fields there in detail.”

    The team are using CanariCam to probe magnetic fields in dusty regions in our galaxy. They hope to obtain further observations of the Galactic Centre to investigate the larger scale magnetic field and how it links to the clouds of gas and dust orbiting the black hole further out at distances of several light years.

    Science paper:
    The Magnetic Field in the central parsec of the Galaxy

    See the full article here .

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    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

     
  • richardmitnick 4:41 pm on February 15, 2018 Permalink | Reply
    Tags: , , , Black Holes, , Guang Yang,   

    From Chandra: “The Billion-year Race Between Black Holes and Galaxies: Guang Yang” 

    NASA Chandra Banner

    NASA Chandra Telescope

    NASA Chandra

    2018-02-14

    1

    We welcome Guang Yang, a 4th-year Astronomy graduate student at Penn State, as a guest blogger. Guang led one of the two studies reported in our new press release about the evolution of supermassive black holes and galaxies. Before studying at Penn State, he obtained his astronomy B.S. degree at the University of Science and Technology of China.

    Supermassive black holes, with masses over million times that of our sun, sit in the centers of galaxies. The evolution of these black holes and their host galaxies in the past billions of years of cosmic history is still an unsolved mystery. A prevailing idea is that black hole growth is synchronized with host-galaxy growth, i.e., the ratio between black hole and galaxy growth is constant. “What a beautiful theory,” I told my advisor Prof. Niel Brandt, and colleagues Dr. Chien-Ting Chen and Dr. Fabio Vito. “But is it true?” I asked. “Has someone proved it?”

    We searched large amounts of literature but did not find dedicated works proving the idea, although it is widely quoted in published papers. “Then why not prove it with observations?” said my advisor. “It can be a great thesis topic for you.” I was so happy that my thesis topic was settled and I even dreamed about how our data might nicely support the theory.

    We painstakingly analyzed a large amount of data in the Chandra Deep Field-South & North and COSMOS surveys. We successfully tracked the black hole and galaxy growth in the distant universe with NASA’s Chandra, Hubble, Spitzer, and other observatories. The observations are so deep that we can study the evolution of black holes and their host galaxies 12 billion years in the past, when the Universe was less than 15% of its current age.

    “It is like watching a race between black holes and their host galaxies,” I joked with my colleagues, “I’m pretty sure nothing is missed, even though the race lasts for billions of years.” After obtaining the growth rates for black holes and galaxies, we eagerly compared them, thinking that we can finally prove the elegant theory of lockstep evolution.

    The results turned out to be surprisingly different from what we expected. Our data strongly disagree with the synchronization of black hole and galaxy growth. Instead, our work shows that black holes in big galaxies are growing much faster than small galaxies. It would be a little upsetting to kick out such a beautiful theory, but we must accept the results, since the Universe appears to work that way.

    By tracking the growth history of black holes and galaxies, we also predicted the accumulated black-hole mass in the current cosmic epoch, that is, the time we are living now. We found big galaxies have black holes with larger masses than we expected compared to small galaxies. If galaxy A is 10 times bigger than galaxy B, then its black hole is 100 times bigger than galaxy B’s black hole. The story appears to be quite different for big and small galaxies. In big galaxies, the black holes win the race against their hosts. But they lose in small galaxies.

    The progress represented by our discovery is quite dramatic. It teaches me that idealized theories might not be true, no matter how beautiful they are.

    2
    see https://sciencesprings.wordpress.com/2018/02/15/from-chandra-supermassive-black-holes-are-outgrowing-their-galaxies/

    See the full article here .

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

     
  • richardmitnick 4:27 pm on February 15, 2018 Permalink | Reply
    Tags: , , , Black Holes, , Mar Mezcua,   

    The Billion-year Race Between Black Holes and Galaxies: Mar Mezcua 

    NASA Chandra Banner

    NASA Chandra Telescope

    2018-02-14

    NASA Chandra

    1
    Mar Mezcua

    Mar Mezcua is a postdoctoral researcher at the Institute of Space Sciences, in Barcelona (Spain), where she is from. She is a guest blogger today and the leading author of one of the two papers highlighted in our latest press release. She conducted this work last year with Prof. Julie Hlavacek Larrondo while at the University of Montreal (Canada).

    Supermassive black holes (SMBHs) started to fascinate me when I was 13 years old. These monsters reside at the center of massive galaxies and are the most energetic sources in the Universe. When they are actively accreting, the surrounding matter that feeds them (or that the black hole accretes) can radiate over a trillion times as much energy as the Sun, being able even to outshine the galaxy in which they reside. This feeding, or accreted, material emits X-ray radiation that we can detect with X-ray satellites such as Chandra, while the material that is ejected from the SMBH in the form of jets also often emit at radio wavelengths. (Yes, SMBHs do not only swallow but also emit outflows of energetic particles!) It is for all the above that I pursued a career in astrophysics in order to study these powerful behemoths in detail.

    My first close approach took place during my PhD, when I estimated the black holes (BH) masses of a sample of SMBHs whose radio jets had a peculiar morphology. To do this, I used the close relationships that had been recently found between the mass of SMBHs and some of their host galaxy properties, such as how much light was emitted by the central bulge or how quickly and where the stars in the bulge moved.

    The finding of such correlations suggested that SMBHs and their host galaxies grow in tandem — that there is a co-evolution — implying that SMBHs somehow regulate the growth of the galaxy in which they reside. As simple as it might sound, this was an astonishing discovery of the late 90’s. SMBHs typically have masses of between one million and one billion times that of the Sun and sizes similar to that of the Solar System, this is, nearly 10,000 times smaller than the galaxy that hosts them. That’s a huge difference in size! How is it then possible that such a ‘small’ central SMBH controls the whole budget of a galaxy? SMBHs were getting more and more exciting every time, so after my PhD I kept on studying them using all tools I had available: radio, optical, infrared and X-ray observations!

    I started to understand that the SMBH-galaxy synchronized growth can be explained by the effects of the outflows or jets ejected by the SMBH, which penetrate the host galaxy and can hamper (but can also trigger) the formation of stars and thus of stellar mass. The most extreme examples of such SMBH feedback are found in galaxy clusters, which host the brightest and most massive galaxies of the local Universe. So when Prof. Julie Hlavacek Larrondo offered me the possibility to move to Montreal to study SMBHs in galaxy clusters with her, I didn’t hesitate!

    The SMBHs of such brightest cluster galaxies emit radio jets that extend beyond the host galaxies. These jets enter the hot gas that permeates the space between the galaxies in the cluster, opening cavities in this X-ray emitting medium. The brightest cluster galaxies are elliptical galaxies that reside at the intersection of filaments of dark matter — ie material that makes up the bulk of matter in the Universe — in very dense environments, and are thus subject to conditions very different from those of isolated galaxies.

    This raised some pressing questions that intrigued us: Do the brightest cluster galaxies and their SMBHs then follow the same co-evolutionary galaxy/SMBH growth as other galaxies? Is the ratio between the growth rates of SMBHs and their host galaxies the same at the high-mass end, where brightest cluster galaxies are located, as it is at lower masses? In other words, is the BH/galaxy scaling relation the same? To probe this, we investigated the location of the brightest cluster galaxies on the “fundamental plane” of BH accretion, which is an empirical correlation supported by the theoretical expectation that BH accretion is a universal mechanism governing BHs of all masses. This fundamental plane correlates the mass of a BH with its nuclear X-ray luminosity and the radio luminosity of the core of its radio jet, and has been found to be valid both for stellar-mass BHs and SMBHs, thus unifying BHs across all mass scales. It is called a plane because that describes the shape of the relationship in three dimensions.

    Together with other collaborators from the University of Waterloo and Durham University, we took a sample of brightest cluster galaxies that had been observed by Chandra as well as by the major radio telescope arrays in the world. This gave us the SMBHs’ X-ray and radio luminosity, that is the amount of radiation produced. Assuming that the SMBHs followed the correlation between BH mass and bulge luminosity found for massive galaxies, we estimated their BH mass from the luminosity of the host galaxy and then located them on the fundamental plane of BH accretion using this BH mass, the nuclear X-ray luminosity and the core radio luminosity.

    And, surprise!! We found that the brightest cluster galaxies were on average offset from the fundamental plane by about a factor of 10, that is, the masses of their SMBHs were found to be higher than expected if the SMBHs followed the fundamental plane correlation! We investigated several possible explanations of this offset, and found that it did not seem to be caused by cooling of the radio jet. Nor does it appear to be a type of emission process assumed in the derivation of the fundamental plane correlation, among others.

    1
    Black Holes in Chandra Deep Field South
    see https://sciencesprings.wordpress.com/2018/02/15/from-chandra-supermassive-black-holes-are-outgrowing-their-galaxies

    The offset of brightest cluster galaxies from the fundamental plane seemed to be due to the BH mass being underestimated, by the aforementioned factor of about 10, by the correlation between BH mass and bulge luminosity. In other words, the brightest cluster galaxies seem to be more overmassive than expected with respect to the SMBH-galaxy relations. This had been already suggested for a few brightest cluster galaxies for which accurate measurements of their SMBH masses revealed masses larger than predicted from the correlation between BH mass and stellar velocity dispersion, and implies that the BH-galaxy scaling relations do not hold for these extreme objects.

    That was a very exciting discovery for me, as just two years before I had found similar results for another type of elliptical galaxies (of smaller size and not located in galaxy clusters). So all together we seemed to be breaking down the sovereignty of BH-galaxy scaling relations!

    But wait, there’s still more! For the brightest cluster galaxies too, on average, follow the fundamental plane, a large fraction of them should have SMBHs with masses more than 10 billion times that of the Sun. This means they host “ultramassive” BHs. So now you might wonder, (as I did, you should!): how did such beasts form? One possibility is that they underwent a two-phase process in which the BH formed first very rapidly and the galaxy grew later at a slower pace, which defiantly challenges the current paradigm of a synchronized galaxy-BH growth. Alternatively, the SMBHs in the brightest cluster galaxies might be the descendants of the high-redshift, or very distant, seed BHs, invoked to explain the existence of SMBHs when the Universe was only about 0800 million years old. In this scenario, black holes would have grown via mergers following a standard hierarchical process.

    And guess what? As part of a different project in collaboration with the Harvard-Smithsonian Center for Astrophysics, I was (and still am!) precisely studying the presence of such seed BHs in dwarf galaxies also using Chandra data! Two independent projects, two different types of galaxies, but both related somehow to the first BHs formed in the early Universe! Astronomy doesn’t stop surprising me every day, which is what makes doing research so exciting!

    See the full article here .

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

     
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