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  • 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

    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.

    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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  • 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

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

    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.


    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 .

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

    Caltech campus

  • richardmitnick 10:48 am on April 7, 2020 Permalink | Reply
    Tags: Black Holes, , ,   

    From Science News: “Quantum mechanics means some black hole orbits are impossible to predict” 

    From Science News

    April 6, 2020
    Emily Conover

    For a trio of orbiting black holes (illustrated), even if their locations are known to the quantum limit, it’s not always possible to predict their future paths. Credit: NASA, CXC, A. Hobart, T. Tibbitts

    Even if you could measure three black holes’ locations as precisely as physically possible, you still might not know where the black holes would go. Such a trio’s complex dance can be so chaotic that the motions are fundamentally unpredictable, new computer simulations show.

    The paths of three black holes orbiting each other can be calculated based on their positions and velocities at one point in time. But in some cases, the orbits depend so sensitively on the black holes’ exact positions that the uncertainty of quantum physics comes into play. Tiny quantum uncertainties in specifying the locations of objects can explode as the black holes’ gyrations continue over tens of millions of years, astrophysicist Tjarda Boekholt and colleagues report in the April Monthly Notices of the Royal Astronomical Society. So the distant future of the black holes’ orbits is impossible to foresee.

    Such extreme sensitivity to initial conditions is known as chaos. The new study suggests, in the case of three black holes, “quantum mechanics imprints into the universe chaos at a fundamental level,” says astrophysicist Nathan Leigh of Universidad de Concepción in Chile, who was not involved with the research.

    In chaotic systems, tiny changes can generate wildly different outcomes. The classic example is a butterfly flapping its wings, thereby altering weather patterns, possibly producing a distant tornado that otherwise wouldn’t have formed (SN: 9/16/13). This chaos also shows up in the orbits of three black holes and other collections of three or more objects, making such orbits difficult to calculate, a conundrum known as the three-body problem.

    To test whether the black holes’ motions were predictable, Boekholt, of the University of Coimbra in Portugal, and colleagues checked if they could run computer simulations of the orbits both forward and backward and achieve the same result. Starting with a given set of locations for three initially stationary black holes, the researchers evolved those orbits forward in time to an end point tens of millions of years in the future. Then, they rewound the simulation, reversing the motions to see if the black holes ended up where they started from.

    Computer simulations have a limited level of accuracy. In this case, for example, the locations of black holes were known only to a certain number of decimal places. That tiny imprecision can balloon over millions of years of the simulation.

    According to quantum mechanics, it is impossible to determine the position of any object better than an utterly tiny distance called the Planck length, about 1.6 times 10-35 meters, or 16 billionths of a trillionth of a trillionth of a millimeter (SN: 4/8/11). Yet even with accuracy the size of the Planck length, the researchers found that about 5 percent of the time the three black holes wouldn’t return to the same spots when the simulation was reversed. That means, even if you measured where the black holes were to the quantum mechanical limit, you couldn’t rewind to find out where they had come from.

    “These systems are fundamentally irreversible,” says Boekholt. “You can’t go forwards and backwards for these 5 percent of systems in nature. And that was quite a surprising result.”

    The result is theoretical and can’t be applied to real black holes, says astrophysicist Nicholas Stone of the Hebrew University of Jerusalem. For example, measurement errors would swamp the importance of quantum physics. But that doesn’t detract from the study’s importance, he says: “It is still quite interesting from a conceptual perspective.”

    See the full article here .


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  • richardmitnick 5:05 pm on March 31, 2020 Permalink | Reply
    Tags: "New method predicts which black holes escape their galaxies", , , , Black Holes, ,   

    From Cornell University: “New method predicts which black holes escape their galaxies” 

    From Cornell University

    March 26, 2020
    Linda B. Glaser

    Shoot a rifle, and the recoil might knock you backward. Merge two black holes in a binary system, and the loss of momentum gives a similar recoil — a “kick” — to the merged black hole.

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    “For some binaries, the kick can reach up to 5000 kilometers a second, which is larger than the escape velocity of most galaxies,” said Vijay Varma, an astrophysicist at the California Institute of Technology and an incoming inaugural Klarman Fellow at Cornell University’s College of Arts & Sciences.

    Varma and his fellow researchers have developed a new method using gravitational wave measurements to predict when a final black hole will remain in its host galaxy and when it will be ejected. Such measurements could provide a crucial missing piece of the puzzle behind the origin of heavy black holes, said Varma, as well as offer insights into galaxy evolution and tests of general relativity. He is lead author of “Extracting the Gravitational Recoil from Black Hole Merger Signals,” published March 13 in Physical Review Letters and co-authored with Maximiliano Isi and Sylvia Biscoveanu of the Massachusetts Institute of Technology.

    This simulation shows the merger of a 35 solar-mass black hole with a 25 solar-mass black hole, followed by the recoil (kick) of the final black hole. The movie is sped-up after the merger to highlight the kick. The arrows indicate the spins (rotation) of the black holes—these interact with the orbital angular momentum (pink arrow), causing the orbital plane to wobble as the binary evolves. The blue and red orbs indicate patterns of gravitational waves generated in the collision. Credit: Vijay Varma

    As black holes orbit in a binary system, their gravitational waves carry away energy and angular momentum, which causes the binary system to shrink as it spirals inward. When a system has asymmetries, such as unequal masses, gravitational waves aren’t emitted equally in all directions, which causes a net loss of linear momentum, resulting in a recoil. Most of that recoil happens right near the merger which can result in a kick great enough to extract the newly merged black hole from its host galaxy.

    The researchers’ models are based on supercomputer simulations that numerically solve Einstein’s equations of general relativity. The simulations were performed as part of a larger research effort under the Simulating eXtreme Spacetimes (SXS) Collaboration that includes research groups from Caltech and Cornell. Saul Teukolsky, Cornell’s Hans A. Bethe Professor of Physics, serves as the group leader.

    “This research shows how gravitational wave signals can be used to learn about astrophysical phenomena in an unexpected way,” said Teukolsky. “It had been believed that we would have to wait more than a decade for detectors sensitive enough to do this kind of work, but this research shows we can in fact do it now – very exciting!”

    While the existing publicly available gravitational wave signals announced by LIGO and Virgo were not strong enough for a good recoil measurement, according to the authors as these detectors improve over the next few years this method will be able to reliably measure the kick.

    The research was made possible by support from the National Science Foundation, the NASA Hubble Fellowship and the Sherman Fairchild Foundation.

    See the full article here .


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

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

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

  • richardmitnick 5:18 pm on January 31, 2020 Permalink | Reply
    Tags: , , , Black Holes, ,   

    From Vanderbilt University: “How many stars eventually collide as black holes? The universe has a budget for that” 

    Vanderbilt U Bloc

    From Vanderbilt University

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

    Jan. 31, 2020
    Spencer Turney

    Since the breakthrough in gravitational wave astronomy back in 2015, scientists have been able to detect more than a dozen pairs of closely located black holes—known as binary black holes—by their collisions into each other, due to gravity. However, scientists still debate how many of these black holes are born from stars, and how they are able to get close enough for a collision within the lifetime of our universe.

    Now, a promising new study developed by one Vanderbilt astrophysicist may give us a method for finding the number of available stars in the history of the universe that collide as binary black holes.

    The research, which appears today in The Astrophysical Journal Letters, will help future scientists interpret the underlying population of stars and test the formation theories of all colliding black holes across cosmic history.

    “Researchers up until now have theorized the formation and existence for pairs of black holes in the universe, but the origins of their predecessors, stars, still remains a mystery,” said Vanderbilt astrophysicist and lead author of the study Karan Jani. “With this study, we did a forensic study of colliding black holes using the astrophysical observations that are currently available. In the process, we developed a fundamental constraint, or budget, which tells us about the fraction of stars since the beginning of the universe that are destined to collide as black holes.”

    Leveraging Einstein’s general theory of relativity, which tells us how black holes interact and eventually collide, Jani and co-author Abraham Loeb at Harvard University used LIGO events on record to take an inventory of the universe’s time and space resources at any given point. They then developed the constraints accounting for each step in the binary black hole process: the number of available stars in the universe, the process of each star transitioning to an individual black hole, and the detection of the eventual collision of those black holes—picked up hundreds of millions of years later by LIGO as gravitational waves emitted by the impact.

    “From the current observations, we find that 14 percent of all the massive stars in the universe are destined to collide as black holes. That’s remarkable efficiency on nature’s part,” added Jani. “These added constraints in our framework should help researchers trace the histories of black holes, answering old questions and undoubtedly opening up more exotic scenarios.”

    The research is funded by the GRAVITY program at Vanderbilt, and supported in part by the Black Hole Initiative at Harvard University, which is funded by grants from the John Templeton Foundation and the Gordon and Betty Moore Foundation.

    See the full article here .


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    Commodore Cornelius Vanderbilt was in his 79th year when he decided to make the gift that founded Vanderbilt University in the spring of 1873.
    The $1 million that he gave to endow and build the university was the commodore’s only major philanthropy. Methodist Bishop Holland N. McTyeire of Nashville, husband of Amelia Townsend who was a cousin of the commodore’s young second wife Frank Crawford, went to New York for medical treatment early in 1873 and spent time recovering in the Vanderbilt mansion. He won the commodore’s admiration and support for the project of building a university in the South that would “contribute to strengthening the ties which should exist between all sections of our common country.”

    McTyeire chose the site for the campus, supervised the construction of buildings and personally planted many of the trees that today make Vanderbilt a national arboretum. At the outset, the university consisted of one Main Building (now Kirkland Hall), an astronomical observatory and houses for professors. Landon C. Garland was Vanderbilt’s first chancellor, serving from 1875 to 1893. He advised McTyeire in selecting the faculty, arranged the curriculum and set the policies of the university.

    For the first 40 years of its existence, Vanderbilt was under the auspices of the Methodist Episcopal Church, South. The Vanderbilt Board of Trust severed its ties with the church in June 1914 as a result of a dispute with the bishops over who would appoint university trustees.

    From the outset, Vanderbilt met two definitions of a university: It offered work in the liberal arts and sciences beyond the baccalaureate degree and it embraced several professional schools in addition to its college. James H. Kirkland, the longest serving chancellor in university history (1893-1937), followed Chancellor Garland. He guided Vanderbilt to rebuild after a fire in 1905 that consumed the main building, which was renamed in Kirkland’s honor, and all its contents. He also navigated the university through the separation from the Methodist Church. Notable advances in graduate studies were made under the third chancellor, Oliver Cromwell Carmichael (1937-46). He also created the Joint University Library, brought about by a coalition of Vanderbilt, Peabody College and Scarritt College.

    Remarkable continuity has characterized the government of Vanderbilt. The original charter, issued in 1872, was amended in 1873 to make the legal name of the corporation “The Vanderbilt University.” The charter has not been altered since.

    The university is self-governing under a Board of Trust that, since the beginning, has elected its own members and officers. The university’s general government is vested in the Board of Trust. The immediate government of the university is committed to the chancellor, who is elected by the Board of Trust.

    The original Vanderbilt campus consisted of 75 acres. By 1960, the campus had spread to about 260 acres of land. When George Peabody College for Teachers merged with Vanderbilt in 1979, about 53 acres were added.

    Vanderbilt’s student enrollment tended to double itself each 25 years during the first century of the university’s history: 307 in the fall of 1875; 754 in 1900; 1,377 in 1925; 3,529 in 1950; 7,034 in 1975. In the fall of 1999 the enrollment was 10,127.

    In the planning of Vanderbilt, the assumption seemed to be that it would be an all-male institution. Yet the board never enacted rules prohibiting women. At least one woman attended Vanderbilt classes every year from 1875 on. Most came to classes by courtesy of professors or as special or irregular (non-degree) students. From 1892 to 1901 women at Vanderbilt gained full legal equality except in one respect — access to dorms. In 1894 the faculty and board allowed women to compete for academic prizes. By 1897, four or five women entered with each freshman class. By 1913 the student body contained 78 women, or just more than 20 percent of the academic enrollment.

    National recognition of the university’s status came in 1949 with election of Vanderbilt to membership in the select Association of American Universities. In the 1950s Vanderbilt began to outgrow its provincial roots and to measure its achievements by national standards under the leadership of Chancellor Harvie Branscomb. By its 90th anniversary in 1963, Vanderbilt for the first time ranked in the top 20 private universities in the United States.

    Vanderbilt continued to excel in research, and the number of university buildings more than doubled under the leadership of Chancellors Alexander Heard (1963-1982) and Joe B. Wyatt (1982-2000), only the fifth and sixth chancellors in Vanderbilt’s long and distinguished history. Heard added three schools (Blair, the Owen Graduate School of Management and Peabody College) to the seven already existing and constructed three dozen buildings. During Wyatt’s tenure, Vanderbilt acquired or built one-third of the campus buildings and made great strides in diversity, volunteerism and technology.

    The university grew and changed significantly under its seventh chancellor, Gordon Gee, who served from 2000 to 2007. Vanderbilt led the country in the rate of growth for academic research funding, which increased to more than $450 million and became one of the most selective undergraduate institutions in the country.

    On March 1, 2008, Nicholas S. Zeppos was named Vanderbilt’s eighth chancellor after serving as interim chancellor beginning Aug. 1, 2007. Prior to that, he spent 2002-2008 as Vanderbilt’s provost, overseeing undergraduate, graduate and professional education programs as well as development, alumni relations and research efforts in liberal arts and sciences, engineering, music, education, business, law and divinity. He first came to Vanderbilt in 1987 as an assistant professor in the law school. In his first five years, Zeppos led the university through the most challenging economic times since the Great Depression, while continuing to attract the best students and faculty from across the country and around the world. Vanderbilt got through the economic crisis notably less scathed than many of its peers and began and remained committed to its much-praised enhanced financial aid policy for all undergraduates during the same timespan. The Martha Rivers Ingram Commons for first-year students opened in 2008 and College Halls, the next phase in the residential education system at Vanderbilt, is on track to open in the fall of 2014. During Zeppos’ first five years, Vanderbilt has drawn robust support from federal funding agencies, and the Medical Center entered into agreements with regional hospitals and health care systems in middle and east Tennessee that will bring Vanderbilt care to patients across the state.

    Today, Vanderbilt University is a private research university of about 6,500 undergraduates and 5,300 graduate and professional students. The university comprises 10 schools, a public policy center and The Freedom Forum First Amendment Center. Vanderbilt offers undergraduate programs in the liberal arts and sciences, engineering, music, education and human development as well as a full range of graduate and professional degrees. The university is consistently ranked as one of the nation’s top 20 universities by publications such as U.S. News & World Report, with several programs and disciplines ranking in the top 10.

    Cutting-edge research and liberal arts, combined with strong ties to a distinguished medical center, creates an invigorating atmosphere where students tailor their education to meet their goals and researchers collaborate to solve complex questions affecting our health, culture and society.

    Vanderbilt, an independent, privately supported university, and the separate, non-profit Vanderbilt University Medical Center share a respected name and enjoy close collaboration through education and research. Together, the number of people employed by these two organizations exceeds that of the largest private employer in the Middle Tennessee region.

  • richardmitnick 9:10 am on December 30, 2019 Permalink | Reply
    Tags: , , , Black Holes, , , , ,   

    From Curiosity: “How Big (or Small) Can a Black Hole Get?” 

    Curiosity Makes You Smarter

    From From Curiosity

    December 21, 2019
    Matthew R. Francis

    The biggest astronomy story of 2019 arguably was the first-ever image of a black hole, captured by a world-spanning observatory, the Event Horizon Telescope.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)

    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope

    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)

    ARO 12m Radio Telescope

    Caltech Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft)

    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.

    One big reason this achievement was so astounding is because black holes are relatively tiny compared to their mass: this black hole is 6.5 billion times the mass of our sun, but in overall size, it’s comparable to the size of the solar system. So what sets the size of a black hole, and how big — or small — can they get? And what does the size of a black hole even mean?

    Beyond the Blue Event Horizon

    Black holes are objects of pure gravity: they don’t have chemical composition or any of the defining characteristics of stars, planets, and other more ordinary inhabitants of the universe. That means they don’t have a surface, atmosphere, or any of the usual things that indicate size.

    Instead, a black hole’s size is defined by its event horizon, which is the boundary past which nothing can escape the gravitational pull, not even light. So even though no material is actually at the horizon, it’s what matters. We literally can’t study what’s inside it.

    Unlike stars, which change size a lot over their lifetimes, a black hole’s size is entirely determined by two factors: its mass and how fast it spins. (Technically it could also carry an electric charge, but realistic black holes probably don’t have enough charge buildup to make a measurable difference.) If it’s not spinning, the diameter of a black hole is approximately 6 kilometers (3.7 miles) for each solar mass — the mass of one sun — it packs in. In other words, a one-solar-mass black hole would be 6 kilometers across, while a 10 solar mass black hole is 60 kilometers (37.3 miles) across. To be very clear, that’s very tiny compared to its mass: the sun is 1.4 million kilometers (865,000 miles) in diameter, while a black hole of equivalent mass has a diameter less than many foot races.

    Realistic black holes spin, though, based on astronomical observations. This rotation shrinks the event horizon diameter by as much as half, making realistic black holes even tinier in comparison to their masses. The rapidly-spinning 6.5 billion solar mass black hole in M87 is the size of a solar system, but 6.5 billion stars are enough for a small galaxy.

    Absolute Units

    Even M87’s black hole isn’t as massive as they get. The record-holder is a 40 billion solar mass giant in the galaxy Holm 15A, and it’s possible even bigger black holes lurk elsewhere. That’s because the only upper limit on a black hole’s size is a practical one.

    In fact, how supermassive black holes get that big is still mysterious. They seem to have formed to be that massive, based on observations of galaxies from early times. However, they can also get bigger by eating matter — though like Cookie Monster, they’re messy eaters — and by merging with other black holes. We haven’t seen that happen for supermassive black holes yet, so between that and the messiness of black hole eating habits, it’s unlikely black holes can get too much bulkier than Holm 15A over the 13.8 billion year history of the universe so far.

    How Low Can You Go?

    Supermassive black holes are outnumbered by their “stellar mass” cousins, which are no bigger than a few dozen solar masses. These are formed from the supernova explosions of very massive stars, which sets a lower limit on stellar-mass black holes: they can’t be any smaller than three solar masses (give or take) because smaller stars leave behind neutron stars or white dwarfs rather than black holes.

    Since stars only grow so large before they’re too unstable, scientists predict the maximum is about 20 solar masses. However, the gravitational wave observatories LIGO and Virgo have identified multiple stellar-mass black holes bigger than that, and astronomers detected what might be a 70-solar-mass black hole in the Milky Way, so we still have some mysteries to solve.

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Milky Way Credits: NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

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

    SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

    Sgr A* from ESO VLT

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the milky way

    Some theories also predict smaller black holes that formed in the very early universe. These primordial black holes could range in size from smaller than atoms to very large, with the smaller variety being more likely. However, we’ve never convincingly seen primordial black holes, and various studies have limited how many of them there might be in the universe. Rare or common, truly tiny black holes weighing in at less than a gram would be very difficult to detect, since the way we find their astronomical relatives is by their influence on nearby stars or gas.

    As a result, the universe could conceivably contain really low-mass black holes and we’d never know it without a lucky break. However, the monsters like that of M87 are the ones that will continue to give us the best shot at seeing the way black holes twist and bend spacetime, as small (relatively) as they are.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Curiosity Makes You Smarter

    Curiosity is on a mission to make learning easier and more fun than it has ever been. Our goal is to ignite curiosity and inspire people to learn. Each day, we create and curate engaging topics for millions of lifelong learners worldwide.

    Experience Curiosity on our website, through our apps and across social media. We designed Curiosity with your busy life in mind. Our editors find interesting and important topics that you’ll want to know more about, and introduce you to the best ways to keep learning.

    We hope you make Curiosity part of your daily digital diet. Never stop learning!

  • richardmitnick 2:21 pm on December 28, 2019 Permalink | Reply
    Tags: , , , Black Holes, , , , Event Horizon, ,   

    From Ethan Siegel: “Ask Ethan: Can Black Holes Ever Spit Anything Back Out?” 

    From Ethan Siegel
    Dec 28, 2019

    A black hole’s event horizon is thought of as the point of no return. But perhaps there are ways back out, after all.

    Black holes just might be the most extreme objects that exist in the entire Universe. While every quantum of matter or energy is affected by the gravitational force, there are other forces capable of overcoming gravity everywhere you go, except inside a black hole. The most important feature of a black hole is the existence of an event horizon; no other class of object has them. Although black holes have this region where gravity is so strong that nothing can escape, not even if they move at the speed of light, perhaps there are loopholes to the inescapability of a black hole’s gravity, after all. That’s the subject of this week’s question, which comes from Noah, who asks,

    Do black holes ever spit things out at any time?

    And if they do, do they ever spit out light?

    The answer must be yes. After all, the most surprising thing about black holes — both predicted theoretically and observed directly — is that they aren’t black at all.

    The second-largest black hole as seen from Earth, the one at the center of the galaxy Messier 87, is shown in three views here. At the top is optical from Hubble, at the lower-left is radio from NRAO, and at the lower-right is X-ray from Chandra. These differing views have different resolutions dependent on the optical sensitivity, wavelength of light used, and size of the telescope mirrors used to observe them. These are all examples of radiation emitted from the regions around black holes, demonstrating that black holes aren’t so black, after all. (TOP, OPTICAL, HUBBLE SPACE TELESCOPE / NASA / WIKISKY; LOWER LEFT, RADIO, NRAO / VERY LARGE ARRAY (VLA); LOWER RIGHT, X-RAY, NASA / CHANDRA X-RAY TELESCOPE)

    NASA/ESA Hubble Telescope

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

    NASA/Chandra X-ray Telescope

    If black holes were entirely dark, there would be no way to detect them at all, save for the gravitational influence that they might have on the other objects around them. If we had a black hole and a star in orbit around one another, we’d be able to infer the existence (and the mass) of the black hole simply by watching how the star appeared to move over time.

    As it wobbled back-and-forth in its orbit, we could determine the parameters of the other object present, including the mass, orbital separation distance, and if our measurements were good enough, even its angle-of-inclination relative to our line of sight. Based on the light that comes from it, we could know whether it was a star, a white dwarf, a neutron star, or — if there were no light at all — even a black hole.

    When a black hole and a companion star orbit one another, the star’s motion will change over time owing to the gravitational influence of the black hole, while matter from the star can accrete onto the black hole, resulting in X-ray and radio emissions. (JINGCHUAN YU/BEIJING PLANETARIUM/2019)

    But in our practical, realistic Universe, the black holes that orbit other stars are actually detectable through radiation.

    “Hang on,” you might object, “if black holes are regions of space from which nothing can escape, not even light, then how are we seeing radiation coming from the black hole itself?”

    That’s a valid point, but what you have to understand is that the space outside of a black hole’s event horizon doesn’t have to be devoid of matter. In fact, if there’s another star nearby, that star can serve as a rich source of matter, capable of being siphoned onto the black hole, particularly if the nearby star is giant and diffuse. This sort of system, in particular, creates what we observe as an X-ray binary, and it’s how the first black hole we ever found was detected.

    Black holes are not isolated objects in space, but exist amidst the matter and energy in the Universe, galaxy, and star systems where they reside. They grow by accreting and devouring matter and energy, and when they actively feed they emit X-rays. Binary black hole systems that emit X-rays are how the majority of our known non-supermassive black holes were discovered. (NASA/ESA HUBBLE SPACE TELESCOPE COLLABORATION)

    Matter, if you break it down to a subatomic level, is made of charged particles. Put this matter in the vicinity of a black hole, and it will:

    move rapidly,
    collide with other matter particles,
    heat up,
    create electric currents and magnetic fields,
    and emit radiation.

    Some of the matter will lose momentum and fall into the black hole, passing through the event horizon and adding to the black hole’s mass. However, the majority of the matter won’t fall in at all, but rather will get funneled into an accretion disk (or more generally, an accretion flow) that experiences the electromagnetic forces from all the accelerating matter. As a result, we see two jets that get expelled in opposite directions emanating from black holes.

    While distant host galaxies for quasars and active galactic nuclei can often be imaged in visible/infrared light, the jets themselves and the surrounding emission is best viewed in both the X-ray and the radio, as illustrated here for the galaxy Hercules A. The gaseous outflows are highlighted in the radio, and if X-ray emissions follow the same path into the gas, they can be responsible for creating hot spots owing to the acceleration of electrons. (NASA, ESA, S. BAUM AND C. O’DEA (RIT), R. PERLEY AND W. COTTON (NRAO/AUI/NSF), AND THE HUBBLE HERITAGE TEAM (STSCI/AURA))

    These relativistic jets are made of particles aAn illustration of an active black hole, one that accretes matter and accelerates a portion of it outwards in two perpendicular jets. The normal matter undergoing an acceleration like this describes how quasars work extremely well, while the accretion flows are ultimately responsible for the emitted particles and radiation we observe. (MARK A. GARLICK)nd emit enormous amounts of light from their dynamical interactions with the particles in the interstellar medium. In fact, the same physics is at play in the supermassive black holes found at the centers of galaxies: matter that falls in towards the black hole largely gets ripped apart, funneled into accretion flows, accelerated, and ejected in jet-like structures.

    If you were a real particle outside of the black hole’s event horizon, but were gravitationally bound to the black hole, you’d be compelled to move in an elliptical orbit around it. At your point of closest approach — the periapsis of your orbit — you’ll be moving at your fastest speed, which gives you the greatest likelihood of interacting with other particles. If they’re present, you’ll experience inelastic collisions, friction, electromagnetic forces, etc. In other words, all the forces that cause charged particles to emit radiation.

    An illustration of an active black hole, one that accretes matter and accelerates a portion of it outwards in two perpendicular jets. The normal matter undergoing an acceleration like this describes how quasars work extremely well, while the accretion flows are ultimately responsible for the emitted particles and radiation we observe. (MARK A. GARLICK)

    Radiation, although it covers the entire electromagnetic spectrum from low-energy radio waves all the way up to X-rays and gamma rays, is just the general term for all forms of light. So long as you have particles that exist outside of the black hole’s event horizon, they will create this form of radiation, and in the cases where relatively nearby black holes are feeding at fast enough rates, we’ll actually observe that characteristic X-ray radiation.

    In fact, we can even look at the supermassive black holes from outside our own galaxy, and find those same features, only scaled up in both power and extent. The same physics is at play — charged object in motion create magnetic fields, and those fields accelerate particles along one particular axis — which is what creates the relativistic jets we observe from a distance. Those jets produce showers of both particles and radiation, and we can catch them even from Earth, sometimes even in visible light.

    The galaxy Centaurus A, shown in a composite of visible light, infrared (submillimeter) light and in the X-ray. This is the nearest active galaxy to the Milky Way, and its bipolar jets are thought to arise from the active, feeding black hole inside. (ESO/WFI (OPTICAL); MPIFR/ESO/APEX/A.WEISS ET AL. (SUBMILLIMETRE); NASA/CXC/CFA/R.KRAFT ET AL. (X-RAY))

    Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla

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

    In some cases, where black holes are active and feeding, we can even observe a spectacular phenomenon known as a photon sphere. Around black holes, the fabric of space is so severely curved that it isn’t just particles that make circular-and-elliptical orbits around that central mass, but even photons: light itself.

    The photon sphere is a little bit larger than the event horizon, and for realistic (rotating) black holes, the physics is more complicated than a simple, non-rotating case. However, the extreme curvature of space means that these photons will create a ring-like structure visible from any faraway perspective. The ring itself is larger than the event horizon, and the curvature of space makes the angular size of the ring appear even larger than that, but this is one of the things we need to calculate in order to understand why our first image of a black hole’s event horizon appears with the famous donut-like shape we observe.

    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.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)

    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope

    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)

    ARO 12m Radio Telescope

    Caltech Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft)

    All of that, however, as interesting and light-emitting as it may be, only arises from material that hasn’t yet fallen through that critical region of space around the black hole: it’s all for things that remain outside the event horizon. Nothing can be seen arising from any material that actually goes inside the event horizon and winds up physically over that critical boundary.

    However, if you could create a black hole that was completely isolated from everything else in the Universe — isolated from particles, radiation, neutrinos, dark matter, other sources of mass, etc. — all you’d have was the curved space resulting from the black hole’s presence itself. Unlike the static picture of curved space that you typically see, any particle at rest would feel as though the space it occupies is being dragged around and into the black hole; it’s as though the space beneath a particle’s proverbial “feet” is in motion, as though it’s fundamentally on a moving walkway.

    In the vicinity of a black hole, space flows like either a moving walkway or a waterfall, depending on how you want to visualize it. At the event horizon, even if you ran (or swam) at the speed of light, there would be no overcoming the flow of spacetime, which drags you into the singularity at the center. Outside the event horizon, though, other forces (like electromagnetism) can frequently overcome the pull of gravity, causing even infalling matter to escape. (ANDREW HAMILTON / JILA / UNIVERSITY OF COLORADO)

    You’d have that curved space, an event horizon, and the laws of physics. And one of the things that the laws of physics teaches us is that the quantum fields that govern the Universe, even in the absence of any particles, are still present, constantly fluctuating as they inevitably must.

    In flat space, this wouldn’t be a big deal. Energy fluctuations occur in the quantum vacuum, and in flat space, the quantum vacuum has equivalent properties everywhere. But when you have curved space — and in particular, space that’s more severely curved in one direction (towards the black hole) than the other (away from the black hole) — observers at different locations will disagree as to what the correct description of the lowest-energy state of the vacuum is.

    Visualization of a quantum field theory calculation showing virtual particles in the quantum vacuum. (Specifically, for the strong interactions.) Even in empty space, this vacuum energy is non-zero, and what appears to be the ‘ground state’ in one region of curved space will look different from the perspective of an observer where the spatial curvature differs. (DEREK LEINWEBER)

    For someone far away from the event horizon, where space appears flat, they’ll observe some low-energy radiation coming from the more severely curved regions of space, even in the absence of any particles. This radiation carries real energy, and is a consequence of how quantum fields behave in curved space. The greater the curvature of space, the greater the rate that this radiation — known as Hawking radiation — gets emitted.

    The energy for the radiation only has one possible source: it has to be stolen from the mass of the black hole. Fortunately, Einstein’s most famous equation, E = mc², describes this balance exactly. The smaller in mass the black hole is, the smaller the event horizon and the greater the curvature is near it. When you put this together, you wind up with a fascinating discovery: the less massive your black hole is, the more quickly it loses mass, emits Hawking radiation, and decays away.

    Cosmic microwave background radiation. Stephen Hawking Center for Theoretical Cosmology U Cambridge

    The event horizon of a black hole is a spherical or spheroidal region from which nothing, not even light, can escape. But outside the event horizon, the black hole is predicted to emit radiation. Hawking’s 1974 work was the first to demonstrate this, and it was arguably his greatest scientific achievement. (NASA; DANA BERRY, SKYWORKS DIGITAL, INC.)

    The rate at which an isolated black hole radiates its mass away, through Hawking radiation, is incredibly slow for any realistic black hole in our Universe. A black hole of our Sun’s mass would take 10⁶⁷ years to evaporate, while the one at the Milky Way’s center needs 10⁸⁷ years and the most massive ones known take up to 10¹⁰⁰ years!

    Still, this is the only case where we can say that some form of energy from inside the black hole’s event horizon affects what we observe outside of it. The things that fall in through a black hole’s event horizon don’t come out again, not under any circumstances. The only things that a black hole can spit out come from outside the event horizon, from particles to conventional photons to even the Hawking radiation that get their energy from the black hole’s mass itself. There may be plenty of light that arises from black holes, but none of it can ever come from inside the event horizon.

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

    SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the milky way

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

  • richardmitnick 9:15 am on December 24, 2019 Permalink | Reply
    Tags: , , , Black hole LB-1 is twice as massive as what we thought possible., Black Holes, ,   

    From Keck Observatory: “Unpredicted Stellar Black Hole Discovered” 

    Keck Observatory, operated by Caltech and the University of California, Maunakea Hawaii USA, 4,207 m (13,802 ft)

    From Keck Observatory

    November 27, 2019
    By: Chinese Academy of Sciences Headquarters
    Media Contact:
    XU Ang, annxu@nao.cas.cn

    Our Milky Way Galaxy is estimated to contain 100 million stellar black holes – cosmic bodies formed by the collapse of massive stars and so dense even light can’t escape.

    Until now, scientists had estimated the mass of an individual stellar black hole in our Galaxy at no more than 20 times that of the Sun. But the discovery of a huge black hole by a Chinese-led team of international scientists has toppled that assumption.

    The team, headed by Prof. LIU Jifeng of the National Astronomical Observatory of China of the Chinese Academy of Sciences (NAOC), spotted a stellar black hole with a mass 70 times greater than the Sun.

    The monster black hole is located 15 thousand light-years from Earth and has been named LB-1 by the researchers. The discovery is reported in today’s issue of Nature.

    The discovery came as a big surprise.

    “Black holes of such mass should not even exist in our Galaxy, according to most of the current models of stellar evolution,” said Prof. LIU. “We thought that very massive stars with the chemical composition typical of our Galaxy must shed most of their gas in powerful stellar winds, as they approach the end of their life. Therefore, they should not leave behind such a massive remnant. LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation.”

    Until just a few years ago, stellar black holes could only be discovered when they gobbled up gas from a companion star. This process creates powerful X-ray emissions, detectable from Earth, that reveal the presence of the collapsed object.

    The vast majority of stellar black holes in our Galaxy are not engaged in a cosmic banquet, though, and thus don’t emit revealing X-rays. As a result, only about two dozen Galactic stellar black holes have been well identified and measured.

    To counter this limitation, Prof. LIU and collaborators surveyed the sky with China’s Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), looking for stars that orbit an invisible object, pulled by its gravity.

    LAMOST telescope located in Xinglong Station, Hebei Province, China

    This observational technique was first proposed by the visionary English scientist John Michell in 1783, but it has only become feasible with recent technological improvements in telescopes and detectors.

    Still, such a search is like looking for the proverbial needle in a haystack: only one star in a thousand may be circling a black hole.

    After the initial discovery, the world’s largest optical telescopes – Spain’s 10.4-m Gran Telescopio Canarias and W. M. Keck Observatory’s 10-m Keck I telescope on Maunakea, Hawaii [above] – were used to determine the system’s physical parameters.

    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

    The results were nothing short of fantastic: a star eight times heavier than the Sun was seen orbiting a 70-solar-mass black hole, every 79 days.

    The discovery of LB-1 fits nicely with another breakthrough in astrophysics. Recently, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo gravitational wave detectors have begun to catch ripples in spacetime caused by collisions of black holes in distant galaxies.

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Intriguingly, the black holes involved in such collisions are also much bigger than what was previously considered typical.

    The direct sighting of LB-1 proves that this population of over-massive stellar black holes exists even in our own backyard. “This discovery forces us to re-examine our models of how stellar-mass black holes form,” said LIGO Director Prof. David Reitze from the University of Florida in the U.S.

    “This remarkable result along with the LIGO-Virgo detections of binary black hole collisions during the past four years really points towards a renaissance in our understanding of black hole astrophysics,” said Reitze.

    This work was made possible by LAMOST (Xinglong, China), the Gran Telescopio Canarias (Canary Islands, Spain), the W. M. Keck Observatory (Hawaii, United States), and the Chandra X-ray Observatory (United States).

    NASA/Chandra X-ray Telescope

    The research team comprised scientists from China, the United States, Spain, Australia, Italy, Poland and the Netherlands.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    To advance the frontiers of astronomy and share our discoveries with the world.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.

    Keck UCal

  • richardmitnick 10:31 am on December 15, 2019 Permalink | Reply
    Tags: "A second black hole at our galaxy’s center?", , , , Black Holes, , , , , ,   

    From UCLA via EarthSky: “A second black hole at our galaxy’s center?” 

    UCLA bloc

    From UCLA




    December 15, 2019
    Smadar Naoz, University of California, Los Angeles

    Artist’s concept of 2 black holes entwined in a gravitational tango. Image via NASA/ JPL-Caltech/ SwRI/ MSSS/ Christopher Go.

    There’s a supermassive black hole – 4 million times our sun’s mass – in the center of our Milky Way galaxy. Astronomers who’ve measured star movements near this central black hole are now saying there might be a 2nd companion black hole near it.

    Do supermassive black holes have friends? The nature of galaxy formation suggests that the answer is yes, and in fact, pairs of supermassive black holes should be common in the universe.

    I am an astrophysicist and am interested in a wide range of theoretical problems in astrophysics, from the formation of the very first galaxies to the gravitational interactions of black holes, stars and even planets. Black holes are intriguing systems, and supermassive black holes and the dense stellar environments that surround them represent one of the most extreme places in our universe.

    The supermassive black hole that lurks at the center of our galaxy, called Sgr A*, has a mass of about 4 million times that of our sun.

    SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

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

    A black hole is a place in space where gravity is so strong that neither particles or light can escape from it. Surrounding Sgr A* is a dense cluster of stars. Precise measurements of the orbits of these stars allowed astronomers to confirm the existence of this supermassive black hole and to measure its mass. For more than 20 years, scientists have been monitoring the orbits of these stars around the supermassive black hole. Based on what we’ve seen, my colleagues and I show that if there is a friend there, it might be a second black hole nearby that is at least 100,000 times the mass of the sun.

    Supermassive black holes and their friends

    Almost every galaxy, including our Milky Way, has a supermassive black hole at its heart, with masses of millions to billions of times the mass of the sun.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

    Astronomers are still studying why the heart of galaxies often hosts a supermassive black hole. One popular idea connects to the possibility that supermassive holes have friends.

    To understand this idea, we need to go back to when the universe was about 100 million years old, to the era of the very first galaxies. They were much smaller than today’s galaxies, about 10,000 or more times less massive than the Milky Way. Within these early galaxies the very first stars that died created black holes, of about tens to thousand the mass of the sun. These black holes sank to the center of gravity, the heart of their host galaxy. Since galaxies evolve by merging and colliding with one another, collisions between galaxies will result in supermassive black hole pairs – the key part of this story.

    Milkdromeda -Andromeda on the left-Earth’s night sky in 3.75 billion years-NASA

    The black holes then collide and grow in size as well. A black hole that is more than a million times the mass of our sun is considered supermassive.

    If indeed the supermassive black hole has a friend revolving around it in close orbit, the center of the galaxy is locked in a complex dance. The partners’ gravitational tugs will also exert its own pull on the nearby stars disturbing their orbits. The two supermassive black holes are orbiting each other, and at the same time, each is exerting its own pull on the stars around it.

    The gravitational forces from the black holes pull on these stars and make them change their orbit; in other words, after one revolution around the supermassive black hole pair, a star will not go exactly back to the point at which it began.

    Using our understanding of the gravitational interaction between the possible supermassive black hole pair and the surrounding stars, astronomers can predict what will happen to stars. Astrophysicists like my colleagues and me can compare our predictions to observations, and then can determine the possible orbits of stars and figure out whether the supermassive black hole has a companion that is exerting gravitational influence.

    Using a well-studied star, called S0-2, which orbits the supermassive black hole that lies at the center of the galaxy every 16 years, we can already rule out the idea that there is a second supermassive black hole with mass above 100,000 times the mass of the sun and farther than about 200 times the distance between the sun and the Earth.

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the milky way

    If there was such a companion, then I and my colleagues would have detected its effects on the orbit of SO-2.

    But that doesn’t mean that a smaller companion black hole cannot still hide there. Such an object may not alter the orbit of SO-2 in a way we can easily measure.

    The physics of supermassive black holes

    Supermassive black holes have gotten a lot of attention lately. In particular, the recent image of such a giant at the center of the galaxy Messier 87 opened a new window to understanding the physics behind black holes.

    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.

    The proximity of the Milky Way’s galactic center – a mere 24,000 light-years away – provides a unique laboratory for addressing issues in the fundamental physics of supermassive black holes. For example, astrophysicists like myself would like to understand their impact on the central regions of galaxies and their role in galaxy formation and evolution. The detection of a pair of supermassive black holes in the galactic center would indicate that the Milky Way merged with another, possibly small, galaxy at some time in the past.

    That’s not all that monitoring the surrounding stars can tell us. Measurements of the star S0-2 allowed scientists to carry out a unique test of Einstein’s general theory of relativity. In May 2018, S0-2 zoomed past the supermassive black hole at a distance of only about 130 times the Earth’s distance from the sun. According to Einstein’s theory, the wavelength of light emitted by the star should stretch as it climbs from the deep gravitational well of the supermassive black hole.

    The stretching wavelength that Einstein predicted – which makes the star appear redder – was detected and proves that the theory of general relativity accurately describes the physics in this extreme gravitational zone. I am eagerly awaiting the second closest approach of S0-2, which will occur in about 16 years, because astrophysicists like myself will be able to test more of Einstein’s predictions about general relativity, including the change of the orientation of the stars’ elongated orbit. But if the supermassive black hole has a partner, this could alter the expected result.

    This NASA/ESA Hubble Space Telescope image show’s the result of a galactic collision between two good-sized galaxies. This new jumble of stars is slowly evolving to become a giant elliptical galaxy. Image via ESA/ Hubble/ NASA/ Judy Schmidt

    NASA/ESA Hubble Telescope

    Finally, if there are two massive black holes orbiting each other at the galactic center, as my team suggests is possible, they will emit gravitational waves.

    Gravitational waves. Credit: MPI for Gravitational Physics/Werner Benger

    Since 2015, the LIGO-Virgo observatories have been detecting gravitational wave radiation from merging stellar-mass black holes and neutron stars.

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    These groundbreaking detections have opened a new way for scientists to sense the universe.

    Any waves emitted by our hypothetical black hole pair will be at low frequencies, too low for the LIGO-Virgo detectors to sense. But a planned space-based detector known as LISA may be able to detect these waves, which will help astrophysicists figure out whether our galactic center black hole is alone or has a partner.


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

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    UC LA Campus

    For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

    We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

    This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

  • richardmitnick 3:57 pm on December 3, 2019 Permalink | Reply
    Tags: , , , , Black Holes, , , ,   

    From Sky&Telescope: “The Appearance of a Black Hole’s Shadow” 

    SKY&Telescope bloc

    From Sky & Telescope

    In April of this year, the Event Horizon Telescope captured the first detailed images of the shadow of a black hole. In a new study, a team of scientists has now explored what determines the size and shape of black hole shadows like this one.

    Simulation of accreting gas swirling around a supermassive black hole. How do the details of this gas affect the observed appearance of the black hole’s shadow?
    Jordy Davelaar et al. / Radboud University / BlackHoleCam

    Messier 87 supermassive black hole from the EHT

    The stunning new radio images of the supermassive black hole in nearby galaxy Messier 87, released this spring by the Event Horizon Telescope team, revealed a bright ring of emission surrounding a dark, circular region.

    This distinct structure is a result of the warped spacetime around massive objects like black holes. The ring of light is comprised of photons from the hot, radiating gas that surrounds the black hole, whose paths have been bent around the black hole before arriving at our telescopes. The dark region in the center is termed the black hole’s “shadow”; this is the collection of paths of photons that did not escape, but were instead captured by the black hole.

    Comparison of conceptions of a black hole surrounded by a thin accretion disk vs. a thick accretion disk.
    Top: NASA ; bottom: Nicolle R. Fuller / NSF

    The Shape of Accretion

    While some previous studies have explored what a black hole shadow looks like when the black hole is surrounded by a very thin disk of accreting gas (think the black hole + disk from the movie Interstellar), most supermassive black holes — like Messier 87, or our own supermassive black hole, Sagittarius A* — are more likely to be surrounded by hot, accreting gas that is more broadly distributed, forming a thick or quasi-spherical disk.

    ,SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

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

    Does the geometry and motion of the accreting gas affect the size and shape of a black hole’s shadow?

    Models of Monsters

    In a new study, three scientists — Ramesh Narayan and Michael Johnson (Harvard-Smithsonian Center for Astrophysics) and Charles Gammie (University of Illinois at Urbana–Champaign) — have teamed up to explore how a black hole’s shadow changes based on the behavior of the hot gas around it.

    The image of the black hole shadow for three of the authors’ models: non-relativistic spacetime (top), relativistic spacetime with static surrounding gas (center), and relativistic spacetime with accreting gas flowing radially inwards (bottom).
    Adapted from Narayan et al. 2019

    Narayan, Johnson, and Gammie built analytical models of a black hole surrounded by hot, optically thin gas (which means that the radiation escapes the gas and is observable). They then analyzed how the shadow would appear using different spacetimes, with different gas motions, and with different behaviors of the gas close to the black hole.

    Reducing Complications

    Intriguingly, the authors found that the appearance of the black hole’s shadow doesn’t depend on the details of the gas accretion close to the black hole. The size of the shadow was primarily determined by the spacetime itself (which is impacted by the mass of the black hole). But how the gas is distributed around the black hole, and whether that gas is stationary or accreting, doesn’t hugely affect the appearance of the shadow.

    Real life is a little messier than this simple, spherically symmetric model; black hole spin and the presence of jets or outflows will cause asymmetries in the shadow. But the authors’ results generally tell us that the close-in details of accretion flows aren’t complicating what we’re seeing. And that’s valuable information we can use as we interpret future observations of black hole shadows!

    Science paper
    The Astrophysical Letters

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    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.”

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