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  • richardmitnick 9:03 am on January 19, 2021 Permalink | Reply
    Tags: "Missing- One Black Hole With 10 Billion Solar Masses", Advanced Virgo, , , , , , The galaxy A2261-BCG,   

    From The New York Times: “Missing- One Black Hole With 10 Billion Solar Masses” 

    From The New York Times

    Jan. 19, 2021
    Dennis Overbye

    One of the biggest galaxies in the universe seems to lack its dark centerpiece.

    The galaxy cluster Abell 2261, captured by the Hubble Space Telescope. The brightest galaxy, center left, is about one million light-years across and about 10 times the diameter of the Milky Way.Credit: NASA/ESA Hubble, M. Postman (STScI), T. Lauer (NOIRLab/NOAO), and the CLASH team.

    Astronomers are searching the cosmic lost-and-found for one of the biggest, baddest black holes thought to exist. So far they haven’t found it.

    In the past few decades, it has become part of astronomical lore, if not quite a law, that at the center of every luminous city of light, called a galaxy, lurks something like a hungry Beelzebub, a giant black hole into which the equivalent of millions or even billions of suns have disappeared. The bigger the galaxy, the more massive the black hole at its center.

    So it was a surprise a decade ago when Marc Postman, of the Space Telescope Science Institute, using the Hubble Space Telescope to survey clusters of galaxies, found a supergiant galaxy [The Astrophysical Journal] with no sign of a black hole in its center. Normally, the galaxy’s core would have a kink of extra light in its center, a kind of sparkling cloak, produced by stars that had been gathered there by the gravity of a giant black hole.

    On the contrary, at the exact center of the galaxy’s wide core, where a slight bump in starlight should have been, there was a slight dip. Moreover, the entire core, a cloud of stars some 20,000 light years across, was not even centered on the exact middle of the galaxy.

    “Oh, my God, this is really unusual,” Tod Lauer, an expert on galactic nuclei at the NOIRLab National Optical Astronomy Observatory in Tucson, Ariz., and an author on the paper, recalled saying when Dr. Postman showed him the finding.

    Kitt Peak NOIRLab National Observatory of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers 55 mi west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft), annotated.

    That was in 2012. In the years since, the two researchers and their colleagues have been ransacking the galaxy, looking for X-rays or radio waves from the missing black hole.

    The galaxy is the brightest one in a cluster known as Abell 2261. It is about 2.7 billion light-years from here, in the constellation Hercules in the northern sky, not far from the prominent star Vega. Using the standard rule of thumb, the black hole missing from the center of the 2261 galaxy should be 10 billion solar masses or more, comparable to the mightiest of these monsters known to astronomers. The black hole at the center of the Milky Way galaxy is only about four million solar masses.

    SGR A and SGR A* from Penn State and NASA/Chandra.

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

    So where has nature stashed the equivalent of 10 billion suns?

    One possibility is that the black hole is there but has gone silent, having temporarily run out of anything to eat. But another provocative possibility, Dr. Lauer and his colleagues say, is that the black hole was thrown out of the galaxy altogether.

    ‘A pit in every peach’

    Proving the latter could provide insight into some of the most violent and dynamic processes in the evolution of galaxies and the cosmos, about which astronomers have theorized but never seen — a dance of titanic forces and swirling worlds that can fling stars and planets across the void.

    “It’s an intriguing mystery, and we’re on the case,” Dr. Postman said in an email. He added that the upcoming James Webb Space Telescope would have the capability to shed light, so to speak, on the case.

    “What happens when you eject a supermassive black hole from a galaxy?” Dr. Lauer asked.

    “The story of A2261-BCG,” he said, referring to the galaxy’s formal name in literature, “is what happens with the most massive galaxies in the universe, the giant elliptical galaxies, at the end point of galaxy evolution.”

    Dr. Lauer is part of an informal group who call themselves Nukers. The group, whose membership is fluid — “like a band,” he said — first came together under Sandra Faber of the University of California, Santa Cruz, in the early days of the Hubble Space Telescope. Over the past four decades, they have sought to elucidate the nature of galactic nuclei, using the sharp eye of Hubble and other new facilities to peer into the intimate hearts of distant galaxies.

    Radio emissions detected near the center of the galaxy suggested supermassive black hole activity had taken place there 50 million years ago.Credit: NASA/CXC, NASA/STScI, NAOJ/Subaru, NSF/NRAO/VLA.

    NASA Chandra X-ray Space Telescope.

    NASA/ESA Hubble Telescope.

    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level.

    NRAO Karl G Jansky Very Large Array, located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~50 miles (80 km) west of Socorro. The VLA comprises twenty-eight 25-meter radio telescopes.

    Black holes are objects so dense that not even light can escape their gravitational clutches. They are invisible by definition, but the ruckus — X-rays and radio screams — caused by material falling into its grasp can be seen across the universe. The discovery in the 1960s of quasars in the centers of galaxies first led astronomers to consider that supermassive black holes were responsible for such fireworks.

    By the turn of the century, astronomers had come to the conclusion that every galaxy harbored a supermassive black hole, millions to billions of times more massive than the sun, in its bosom. Where they came from — whether they grew from smaller black holes that had formed from the collapse of stars, or formed through some other process early in the universe — nobody is sure. “There is a pit in every peach,” Dr. Lauer said.

    But how do these entities affect their surroundings?

    In 1980, three astronomers, Mitchell Begelman, Martin Rees and Roger Blandford, wrote about how these black holes would alter the evolution of the galaxies they inhabit. When two galaxies collided and merged — an especially common event in the earlier universe — their central black holes would meet and form a binary system, two black holes circling each other.

    Dr. Begelman and his colleagues argued that these two massive black holes, swinging around, would interact with the sea of stars they were immersed in. Every once in a while, one of these stars would have a close encounter with the binary, and gravitational forces would push the star out of the center, leaving the black holes even more tightly bound.

    Over time, more and more stars would be tossed away from the center. Gradually, starlight that was once concentrated at the center would spread out into a broader, diffuse core, with a little kink at the center where the black-hole binary was doing its mating dance. The process is called “scouring.”

    “They were way ahead of the game,” Dr. Lauer said of the three astronomers.

    A knotty problem

    A scoured core was the kind of situation that Dr. Lauer and Dr. Postman thought they had encountered with Abell 2261. But instead of a peak at the center of the core, there was a dip, as if the supermassive black hole and its attendant stars had simply been taken away.

    This raised the even more dramatic possibility that the scenario envisioned by Dr. Begelman and his colleagues had played out all the way to the end: The two black holes had merged into one gigantic mouthful of nothing. The merger would have been accompanied by a cataclysmic burst of gravitational waves, space-time ripples predicted to exist by Einstein in 1916 and finally seen by the LIGO instruments a century later, in 2016.

    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

    If that burst was lopsided, it would have sent the resultant supermassive black hole flying through the galaxy, or even out of it, something astronomers had never observed. So finding the errant black hole was of the utmost importance.

    Further scrutiny of A2261-BCG revealed four little knots of light within the diffuse core. Could one of them be harboring the black hole?

    A team led by Sarah Burke-Spolaor of West Virginia University took to the sky with Hubble [above] and the Very Large Array [above] radio telescope in Socorro, New Mexico. Spectroscopic measurements by the Hubble could tell how fast the stars in the knots were jiggling around, and thus whether some massive object — a black hole — was needed to keep them all together.

    Two of the knots, they concluded, were probably small galaxies with small internal motions being cannibalized by the big galaxy. Measurements of the third knot had such large error bars that it could not yet be ruled in or out as the black hole’s location.

    The fourth, very compact knot near the bottom edge of the core was too faint even for the Hubble, Dr. Burke-Spoloar reported. “Observing this knot would have required an overblown amount of time (hundreds of hours) observing with Hubble Space Telescope,” she said in an email, and so it also remains a candidate for the black-hole hiding spot.

    The galaxy core also emits radio waves, but they didn’t help the search, Dr. Burke-Spolaor said.

    “We were originally hoping the radio emission would be some kind of literal smoking gun, showing an active jet that points directly back to black-hole location,” she said. But the radio relic was at least 50 million years old, according to its spectral characteristics, which meant, she said, that the large black hole would have had ample time to move elsewhere since the jet turned off.

    Next stop was NASA’s orbiting Chandra X-ray Observatory [above]. Kayhan Gultekin of the University of Michigan, another veteran Nuker who was not on the original discovery team, aimed the telescope at the cluster core and those suspicious knots. No dice. The putative black hole would have to be feeding at one-millionth of its potential rate if it were there at all, Dr. Gultekin said.

    “Either any black hole at the center is very faint, or it isn’t there,” he wrote in an email. The same goes for the case of a binary black-hole system, he said; it would need to be eating very little gas to stay hidden.

    In the meantime, Imran Nasim, of the University of Surrey in the U.K., who was not part of Dr. Postman’s team, has published a detailed analysis [MNRAS] of how the merger of two supermassive black holes could reform the galaxy into what the astronomers have found.

    “Simply, gravitational wave recoil ‘kicks’ the supermassive black hole out of the galaxy,” Dr. Nasim explained in an email. Having lost its supermassive anchor, the cloud of stars around the black hole binary spreads out, becoming more diffuse. The density of stars in that region — the densest part of the entire giant galaxy — is only one-tenth the density of stars in our own neighborhood of the Milky Way, resulting in a night sky that would appear anemic compared with our own.

    All this is another reason that astronomers eagerly await the launch of the James Webb Space Telescope, the long-awaited successor to Hubble, which is now scheduled for the end of October. That telescope will be able to examine all four knots at the same time and determine whether any of them are a cloaked, supermassive black hole.

    “Here you see our great sophistication,” Dr. Lauer said. “Hey! Maybe it’s in the knots! — Hey maybe it isn’t! Better search everything!”

    See the full article here .


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  • richardmitnick 11:08 am on September 25, 2020 Permalink | Reply
    Tags: "Physicists Argue That Black Holes From the Big Bang Could Be the Dark Matter", Advanced Virgo, , , , , , , Unseen “primordial” black holes might be the hidden dark matter-a new series of studies has shown how the theory can work.   

    From Quanta Magazine: “Physicists Argue That Black Holes From the Big Bang Could Be the Dark Matter” 

    From Quanta Magazine

    September 23, 2020
    Joshua Sokol

    Primordial black holes would cluster in distinct clumps throughout the universe. Relatively large black holes would be surrounded by much smaller ones. Olena Shmahalo/Quanta Magazine.

    It was an old idea of Stephen Hawking’s: Unseen “primordial” black holes might be the hidden dark matter. It fell out of favor for decades, but a new series of studies has shown how the theory can work.

    Black holes are like sharks. Elegant, simple, scarier in the popular imagination than they deserve, and possibly lurking in deep, dark places all around us.

    Their very blackness makes it hard to estimate how many black holes inhabit the cosmos and how big they are. So it was a genuine surprise when the first gravitational waves thrummed through detectors at the Laser Interferometer Gravitational-Wave Observatory (LIGO) in September 2015.

    MIT /Caltech Advanced aLigo .

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

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    Previously, the largest star-size black holes had topped out at around 20 times the mass of the sun. These new ones were about 30 solar masses each — not inconceivable, but odd. Moreover, once LIGO turned on and immediately started hearing these sorts of objects merge with each other, astrophysicists realized that there must be more black holes lurking out there than they had thought. Maybe a lot more.

    The discovery of these strange specimens breathed new life into an old idea — one that had, in recent years, been relegated to the fringe. We know that dying stars can make black holes. But perhaps black holes were also born during the Big Bang itself. A hidden population of such “primordial” black holes could conceivably constitute dark matter, a hidden thumb on the cosmic scale. After all, no dark matter particle has shown itself, despite decades of searching. What if the ingredients we really needed — black holes — were under our noses the whole time?

    “Yes, it was a crazy idea,” said Marc Kamionkowski, a cosmologist at Johns Hopkins University whose group came out with one of the many eye-catching papers [Physical Review Letters] that explored the possibility in 2016. “But it wasn’t necessarily crazier than anything else.”

    Samuel Velasco/Quanta Magazine; source: LIGO -Virgo/Frank Elavsky, Aaron Geller/Northwestern.

    Alas, the flirtation with primordial black holes soured in 2017, after a paper by Yacine Ali-Haïmoud, an astrophysicist at New York University who had previously been on the optimistic Kamionkowski team, examined how this type of black hole should affect LIGO’s detection rate. He calculated [The merger rate of primordial-black-hole binaries” in Physical Review D] that if the baby universe spawned enough black holes to account for dark matter, then over time, these black holes would settle into binary pairs, orbit each other closer and closer, and merge at rates thousands of times higher than what LIGO observes. He urged other researchers to continue to investigate the idea using alternate approaches. But many lost hope. The argument was so damning that Kamionkowski said it quenched his own interest in the hypothesis.

    Now, however, following a flurry of recent papers, the primordial black hole idea appears to have come back to life. In one of the latest, published last week in the Journal of Cosmology and Astroparticle Physics, Karsten Jedamzik, a cosmologist at the University of Montpellier, showed how a large population of primordial black holes could result in collisions that perfectly match what LIGO observes. “If his results are correct — and it seems to be a careful calculation he’s done — that would put the last nail in the coffin of our own calculation,” said Ali-Haïmoud, who has continued to play with the primordial black hole idea in subsequent papers too. “It would mean that in fact they could be all the dark matter.”

    “It’s exciting,” said Christian Byrnes, a cosmologist at the University of Sussex who helped inspire some of Jedamzik’s arguments. “He’s gone further than anyone has gone before.”

    The original idea dates back to the 1970s with the work of Stephen Hawking and Bernard Carr. Hawking and Carr reasoned that in the universe’s first fractions of a second, small fluctuations in its density could have endowed lucky — or unlucky — regions with too much mass. Each of these regions would collapse into a black hole. The size of the black hole would be dictated by the region’s horizon — the parcel of space around any point reachable at the speed of light. Any matter within the horizon would feel the black hole’s gravity and fall in. Hawking’s rough calculations showed that if the black holes were bigger than small asteroids, they could plausibly still be lurking in the universe today.

    More progress came in the 1990s. By then, theorists also had the theory of cosmic inflation, which holds that the universe experienced a burst of extreme expansion right after the Big Bang. Inflation could explain where the initial density fluctuations would have come from.


    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes
    Alex Mittelmann, Coldcreation

    Alan Guth’s notes:

    Alan Guth’s original notes on inflation

    On top of those density fluctuations, physicists also considered a key transition that would coax along the collapse.

    When the universe was new, all of its matter and energy seethed in an unthinkably hot plasma. After the first hundred-thousandth of a second or so, the universe cooled a little, and the plasma’s loose quarks and gluons could bind together into heavier particles. With some of the lightning-fast particles now straitjacketed together, the pressure dropped. That might have helped more regions collapse into black holes.

    But back in the 1990s, nobody understood the physics of a fluid of quarks and gluons well enough to make precise predictions about how this transition would affect black hole production. Theorists couldn’t say how massive primordial black holes should be, or how many to expect.

    Moreover, cosmologists didn’t really seem to need primordial black holes. Astronomical surveys scanned patches of sky hoping to find a sea of dense, dark objects like black holes floating on the outskirts of the Milky Way, but they didn’t find many. Instead, most cosmologists came to believe that dark matter was made of ultra-shy particles called WIMPs. And hopes simmered that either purpose-built WIMP detectors or the upcoming Large Hadron Collider would soon find hard evidence of them.

    With the dark matter problem about to wrap itself up with a bow and no observations suggesting otherwise, primordial black holes became an academic backwater. “One senior cosmologist kind of ridiculed me for working on that,” said Jedamzik, who traces his own interest back to the 1990s. “So I stopped that, because I needed to have a permanent position.”

    Of course, no WIMPs have been found in the decades since then, nor any new particles (save the long-predicted Higgs boson). Dark matter remains dark.

    Yet much more is known today about the environment that could have spawned primordial black holes. Physicists can now calculate how pressure and density would have evolved from the quark-gluon plasma at the beginning of the universe. “It took the community really decades to work this out,” said Byrnes. With that information in hand, theorists such as Byrnes and Juan García-Bellido at the Autonomous University of Madrid have spent the last few years publishing studies [Primordial black holes, dark matter and hot-spot electroweak baryogenesis at the quark-hadron epoch] predicting that the early universe could have spawned not just one size of black hole, but a range of them.

    First, the quarks and gluons were glued together into protons and neutrons. That caused a pressure drop and could have spawned one set of primordial black holes. As the universe kept cooling, particles such as pions formed, creating another pressure plunge and possible black hole burst.

    Between these epochs, space itself expanded. The first black holes could suck in about one solar mass of material from the horizon around themselves.

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project.

    The second round could grab perhaps about 30 solar masses’ worth — just like the strange objects first seen by LIGO. “Gravitational waves came to our rescue,” said García-Bellido.

    Within weeks of the first gravitational wave announcement from LIGO in 2016, the primordial black hole hypothesis roared back to life. But the following year, Ali-Haïmoud came out with his argument that primordial black holes would be colliding far too often, which gave proponents a major hurdle to overcome.

    Jedamzik took up the challenge. During a long vacation in Costa Rica, he went after Ali-Haïmoud’s argument. Ali-Haïmoud had done his work analytically, through equations. But when Jedamzik created numerical simulations of the same problem, he found a twist.

    Primordial black holes would indeed form binaries. But Jedamzik concluded that in a universe teeming with black holes, a third black hole would often approach the initial pair and change places with one of them. This process would repeat again and again.

    Over time, this swinging from partner to partner would leave binary black holes with almost circular orbits. These partners would be incredibly slow to collide. Even a huge population of primordial black holes would merge so infrequently that the entire hypothesis would still fit within LIGO’s observed merger rate.

    One arm of the LIGO detector located in Livingston, Louisiana. Credit: William Widmer for Quanta Magazine.

    He posted his work online this June [Primordial Black Hole Dark Matter and the LIGO/Virgo observations], fielding questions from outside experts like Ali-Haïmoud himself. “It was very important to convince the community, as much as you can, that you are not just saying some nonsense,” said Jedamzik, using a more forceful term than “nonsense.”

    He also built on work that predicted that primordial black holes would sit in dark clusters about as large in diameter as the distance between the sun and the nearest star. Each of these clusters might contain around a thousand black holes crammed together. The 30-solar-mass behemoths would sit at the center; the more common littler ones would fill in the rest of the space. These clusters would lurk everywhere astronomers think dark matter is. As with stars in a galaxy or planets circling the sun, each black hole’s orbital motion would keep it from devouring another — except during those uncommon mergers.

    In a second paper [Evidence for primordial black hole dark matter from LIGO/Virgo merger rates], Jedamzik calculated exactly how uncommon these mergers should be. He made the calculations for the big black holes that LIGO has observed, and for the smaller ones, which it has not. (Small black holes would produce faint, high-pitched signals and would have to be close by to be detected.) “I was, of course, stunned to see that one after the other I got the rate right,” he said.

    Advocates of the primordial black hole hypothesis still have a lot of convincing to do. Most physicists still believe that dark matter is made of some kind of elementary particle, one that’s devilishly hard to detect. Moreover, the LIGO black holes aren’t too different from what we would expect if they came from ordinary stars. “It sort of fills a hole in the theory that isn’t actually there,” said Carl Rodriguez, an astrophysicist at Carnegie Mellon University. “There are things that are weird about some of the LIGO sources, but we can explain everything that we’ve seen so far through normal stellar evolutionary process.”

    Selma de Mink, an astrophysicist at Harvard University who has sketched out theories for how stars alone can produce the heavy black hole binaries seen by LIGO, is more blunt: “I think astronomers can laugh a bit about it.”

    Finding just one black hole of sub-solar mass — which should be common, according to the primordial black hole scenario, and which can’t form from stars — would transform this entire debate. And with every subsequent observing run, LIGO has increased its sensitivity, allowing it to eventually either find such small black holes or set strict limits on how many can exist. “This is not one of these stories like string theory, where in a decade or three decades we might still be discussing if it’s correct,” Byrnes said.

    In the meantime, other astrophysicists are probing different aspects of the theory. For example, perhaps the strongest constraints on primordial black holes come from microlensing searches — those same surveys that began in the 1990s. In these efforts, astronomers monitor bright but distant sources, waiting to see if a dark object passes in front of them. These searches have long ruled out an evenly dispersed population of small black holes.

    But if primordial black holes exist at a range of masses, and if they’re packed into dense, massive clusters, those results could be less significant than researchers thought, García-Bellido said.

    Upcoming observations might eventually settle that question, too. The European Space Agency has recently agreed to contribute a key extra feature to NASA’s upcoming Nancy Grace Roman Space Telescope, one that would allow it to do groundbreaking microlensing studies.

    NASA/Nancy Grace Roman Space Telescope.

    The addition came at the behest of Günther Hasinger, ESA’s science director, who made the case that primordial black holes could explain multiple mysteries. To Hasinger, the idea is appealing because it doesn’t invoke new particles or new physics theories. It just repurposes old elements.

    “I believe maybe some of the puzzles which are still out there could actually solve themselves,” he said, “when you look with different eyes.”

    See the full article here .


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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

  • richardmitnick 11:22 am on September 16, 2020 Permalink | Reply
    Tags: "Gaurav Khanna awarded $75K for black hole research", Advanced Virgo, , , ,   

    From UMass Dartmouth: “Gaurav Khanna awarded $75K for black hole research” 

    From UMass Dartmouth

    Dr. Khanna’s research sheds light on many different aspects of black hole physics.

    September 14, 2020
    Adrienne Wartts

    Image of merging black holes Credit Caltech/MIT Advanced aLigo.

    Black holes are perhaps the most mysterious astrophysical objects in the universe. The National Science Foundation (NSF) has awarded Professor Gaurav Khanna of the Physics department a $75,393 grant for his project “Studies of Black Hole Binary Systems Using Time-Domain Perturbation Theory”.

    This newly funded NSF project continues the development of the model that Dr. Khanna has been building for well over a decade on gravitational waves.

    Gravitational waves, predicted by Albert Einstein’s general relativity theory 100 years ago, are “ripples” in the fabric of space-time that travel at the speed of light. LIGO made the first-ever direct detection of a gravitational wave signal from a binary system of two, near 30-solar-mass black holes located over a billion light-years away. In 2016, gravitational waves became directly observable due to the enormous investment in hardware, theory, and data analysis methods, into the National Science Foundation’s LIGO laboratory.

    The founders of LIGO were awarded the 2017 Nobel Prize in Physics. Since then several other detections have been made, more detectors have become operational, and the future space-borne observatory plans may be accelerated.

    MIT /Caltech Advanced aLigo .

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

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    The strongest sources of this radiation are the mergers of highly massive and compact astrophysical objects, such as black holes and neutron stars.

    Dr. Khanna’s research makes use of Einstein’s general relativity theory to estimate properties of the gravitational waves produced by one of their strongest sources — the collision and merger of two black holes. “This is very important to the success of the above-mentioned observatories because theory-based, waveform templates are required to develop a matched-filter for successful detection of these waves,” says Khanna.

    A black hole merger is an extremely complex process, even from the point of view of numerical simulations on the largest supercomputers, therefore Dr. Khanna uses various approximation techniques (black hole perturbation theory) to simplify this problem significantly and make it more tractable. Khanna works closely with collaborators at the Max Planck Institute for Gravitational Physics and MIT, and locally with Dr. Scott Field and Dr. Sigal Gottlieb at UMass Dartmouth and contributes to this major modeling effort.

    “Once this project is completed, it will not only improve signal searches for LIGO data, but also make progress towards the data analysis goals relevant to the upcoming space-borne LISA mission,” he says. Khanna’s black hole research breakthroughs have been noted in The Conversation, The International Business Times, Forbes and The New York Times.

    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 9:51 am on September 5, 2020 Permalink | Reply
    Tags: "History as Told by a Merger Background", , Advanced Virgo, , , , , , , ,   

    From AAS NOVA: “History as Told by a Merger Background” 


    From AAS NOVA

    4 September 2020
    Tarini Konchady

    Artist’s illustration of the merger of two black holes in space. [LIGO/T Pyle.]

    To know the rate of binary black hole mergers over the lifetime of the universe is to know more about the universe’s evolution. For instance, how were binary black holes first created? Did ancient stars in the early universe play a role? And where does chemical composition come into the picture?

    But before all that, we first need to answer this question: how do you even determine the history of binary black hole mergers?

    Have Data, Do Science!

    Discoveries like the one announced this week illustrate how gravitational-wave observatories like the Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo interferometer have pushed the study of binary black hole (BBH) mergers from theory into observation.

    MIT /Caltech Advanced aLigo .

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

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    However, we still haven’t entered an era where BBH mergers are commonplace. This means that it’s hard to do studies that need large ensembles of mergers to make definitive conclusions — like measuring how the rate of BBH mergers changes over the lifetime of the universe.

    Another problem is that gravitational-wave observatories can only probe a relatively small volume of the universe. Models have suggested that historical rates of BBH mergers peak at a distance that’s outside the range of current observatories, so what’s to be done?

    Redshifts and a Gravitational-wave Background

    Two different example models of merger rates versus redshift. Here the peak merger redshift is seen around z ~ 2, and the growth of the low-redshift merger rate is described with a factor called α. [Callister et al 2020.]

    A lot, it turns out! In a new study, a group of researchers led by Tom Callister (Flatiron Institute) used LIGO/Virgo gravitational-wave data to put observational constraints on the evolving rate of BBH mergers. A special feature of their study was that they didn’t just consider directly observed mergers — they also looked at the overall background of gravitational-wave signals that observatories can detect.

    To be specific, Callister and collaborators were attempting to measure how the rate of BBH mergers changes with redshift. LIGO/Virgo can detect individual mergers out to a redshift of z ≲ 1, but models suggest that BBH merger rates peak somewhere between z ~ 2 (about 10 billion years ago) and z ~ 4 (nearly 12 billion years ago). So, Callister and collaborators decided to combine information from individual BBH mergers (“shouts”) with the limits we have on the gravitational-wave background created by more distant, undistinguished mergers (“murmurs”).

    In the Background No More

    Predicted merger rate (in mergers per cubic gigaparsec per year) versus redshift based on ~1 year of simulated Advanced LIGO observations at design sensitivity. The solid line is the “true” merger rate used to generate the simulations; the other lines show the results from different mock detections. The top plot is based solely on directly observed mergers, while the bottom plot includes the gravitational-wave background in the analysis. [Callister et al. 2020.]

    The primary quantities of interest in this study were the redshift at which mergers peak (zp) and how quickly the merger rate grows as we look farther away in the local universe (quantified by the exponent α in the plot shown above).

    By combining direct merger detections with upper limits on the gravitational-wave background for the first time, Callister and collaborators were able to rule out certain combinations of peak merger redshifts and local merger growth rates. In particular, they reject combinations of zp ≳ 1.5 and α ≳ 7, limiting the merger rate to peak more recently than ~9 billion years ago if the local growth rate of BBH mergers is large.

    So what’s next? With the upgraded Advanced LIGO and other gravitational-wave observatories coming online soon, many more mergers will be within reach. The limits the authors have already established are just a start; the authors also show that the upgraded Advanced LIGO may make it possible to pin down the peak merger redshift with certainty. So keep your eyes peeled!


    “Shouts and Murmurs: Combining Individual Gravitational-Wave Sources with the Stochastic Background to Measure the History of Binary Black Hole Mergers,” Tom Callister et al 2020 ApJL 896 L32.

    See the full article here .


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    AAS Mission and Vision Statement

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

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

  • richardmitnick 10:31 am on September 3, 2020 Permalink | Reply
    Tags: "An unexpected origin story for a lopsided black hole merger", Advanced Virgo, , , , ,   

    From MIT News: “An unexpected origin story for a lopsided black hole merger” 

    MIT News

    From MIT News

    September 2, 2020
    Jennifer Chu

    A lopsided merger of two black holes may have unusual origins, based on a reanalysis of LIGO data.
    Credits:Image: MIT News.

    A lopsided merger of two black holes may have an oddball origin story, according to a new study by researchers at MIT and elsewhere.

    The merger was first detected on April 12, 2019 as a gravitational wave that arrived at the detectors of both LIGO (the Laser Interferometer Gravitational-wave Observatory), and its Italian counterpart, Virgo.

    MIT /Caltech Advanced aLigo .

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

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    Scientists labeled the signal as GW190412 and determined that it emanated from a clash between two David-and-Goliath black holes, one three times more massive than the other. The signal marked the first detection of a merger between two black holes of very different sizes.

    Now the new study, published today in the journal Physical Review Letters, shows that this lopsided merger may have originated through a very different process compared to how most mergers, or binaries, are thought to form.

    It’s likely that the more massive of the two black holes was itself a product of a prior merger between two parent black holes. The Goliath that spun out of that first collision may have then ricocheted around a densely packed “nuclear cluster” before merging with the second, smaller black hole — a raucous event that sent gravitational waves rippling across space.

    GW190412 may then be a second generation, or “hierarchical” merger, standing apart from other first-generation mergers that LIGO and Virgo have so far detected.

    “This event is an oddball the universe has thrown at us — it was something we didn’t see coming,” says study coauthor Salvatore Vitale, an assistant professor of physics at MIT and a LIGO member. “But nothing happens just once in the universe. And something like this, though rare, we will see again, and we’ll be able to say more about the universe.”

    Vitale’s coauthors are Davide Gerosa of the University of Birmingham and Emanuele Berti of Johns Hopkins University.

    A struggle to explain

    There are two main ways in which black hole mergers are thought to form. The first is known as a common envelope process, where two neighboring stars, after billions of years, explode to form two neighboring black holes that eventually share a common envelope, or disk of gas. After another few billion years, the black holes spiral in and merge.

    “You can think of this like a couple being together all their lives,” Vitale says. “This process is suspected to happen in the disc of galaxies like our own.”

    The other common path by which black hole mergers form is via dynamical interactions. Imagine, in place of a monogamous environment, a galactic rave, where thousands of black holes are crammed into a small, dense region of the universe. When two black holes start to partner up, a third may knock the couple apart in a dynamical interaction that can repeat many times over, before a pair of black holes finally merges.

    In both the common envelope process and the dynamical interaction scenario, the merging black holes should have roughly the same mass, unlike the lopsided mass ratio of GW190412. They should also have relatively no spin, whereas GW190412 has a surprisingly high spin.

    “The bottom line is, both these scenarios, which people traditionally think are ideal nurseries for black hole binaries in the universe, struggle to explain the mass ratio and spin of this event,” Vitale says.

    Black hole tracker

    In their new paper, the researchers used two models to show that it is very unlikely that GW190412 came from either a common envelope process or a dynamical interaction.

    They first modeled the evolution of a typical galaxy using STAR TRACK, a simulation that tracks galaxies over billions of years, starting with the coalescing of gas and proceeding to the way stars take shape and explode, and then collapse into black holes that eventually merge. The second model simulates random, dynamical encounters in globular clusters — dense concentrations of stars around most galaxies.

    The team ran both simulations multiple times, tuning the parameters and studying the properties of the black hole mergers that emerged. For those mergers that formed through a common envelope process, a merger like GW190412 was very rare, cropping up only after a few million events. Dynamical interactions were slightly more likely to produce such an event, after a few thousand mergers.

    However, GW190412 was detected by LIGO and Virgo after only 50 other detections, suggesting that it likely arose through some other process.

    “No matter what we do, we cannot easily produce this event in these more common formation channels,” Vitale says.

    The process of hierarchical merging may better explain the GW190412’s lopsided mass and its high spin. If one black hole was a product of a previous pairing of two parent black holes of similar mass, it would itself be more massive than either parent, and later significantly overshadow its first-generation partner, creating a high mass ratio in the final merger.

    A hierarchical process could also generate a merger with a high spin: The parent black holes, in their chaotic merging, would spin up the resulting black hole, which would then carry this spin into its own ultimate collision.

    “You do the math, and it turns out the leftover black hole would have a spin which is very close to the total spin of this merger,” Vitale explains.

    No escape

    If GW190412 indeed formed through hierarchical merging, Vitale says the event could also shed light on the environment in which it formed. The team found that if the larger of the two black holes formed from a previous collision, that collision likely generated a huge amount of energy that not only spun out a new black hole, but kicked it across some distance.

    “If it’s kicked too hard, it would just leave the cluster and go into the empty interstellar medium, and not be able to merge again,” Vitale says.

    If the object was able to merge again (in this case, to produce GW190412), it would mean the kick that it received was not enough to escape the stellar cluster in which it formed. If GW190412 indeed is a product of hierarchical merging, the team calculated that it would have occurred in an environment with an escape velocity higher than 150 kilometers per second. For perspective, the escape velocity of most globular clusters is about 50 kilometers per second.

    This means that whatever environment GW190412 arose from had an immense gravitational pull, and the team believes that such an environment could have been either the disk of gas around a supermassive black hole, or a “nuclear cluster” — an incredibly dense region of the universe, packed with tens of millions of stars.

    “This merger must have come from an unusual place,” Vitale says. “As LIGO and Virgo continue to make new detections, we can use these discoveries to learn new things about the universe.”

    This research was funded, in part by the U.S. National Science Foundation and MIT’s Solomon Buchsbaum Research Fund.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    USPS “Forever” postage stamps celebrating Innovation at MIT

    MIT Seal

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

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

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


    From AAS NOVA

    2 September 2020
    Susanna Kohler

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

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

    Masses in the Stellar Graveyard 9-2-20

    The Signal

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

    MIT /Caltech Advanced aLigo.

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

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy.

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

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

    A Decidedly Intermediate Size

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

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

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

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

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

    Polluting the Mass Gap

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

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

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

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

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

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

    Going Forward

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

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


    “Properties and Astrophysical Implications of the 150M☉ Binary Black Hole Merger GW190521,” Abbott et al 2020 ApJL 900 L13.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition


    AAS Mission and Vision Statement

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

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

  • richardmitnick 10:13 am on August 22, 2020 Permalink | Reply
    Tags: "Are we still listening to space?", Advanced Virgo, , , , LIGO suspended its third observing run ahead of schedule. Originally planned to end on April 30 the observing ended on March 27., ,   

    From MIT News: “Are we still listening to space?” 

    MIT News

    From MIT News

    August 19, 2020
    Fernanda Ferreira | School of Science

    Despite the planet’s seeming standstill, graduate students continue to use LIGO to identify astrophysical events.

    In response to Covid-19, LIGO suspended its third observing run ahead of schedule. Originally planned to end on April 30, the observing ended on March 27. Credits: Photo courtesy of the LIGO-Virgo Collaboration.

    MIT /Caltech Advanced aLigo

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

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    When LIGO, the Laser Interferometer Gravitational-Wave Observatory, and its European counterpart, Virgo, detect a gravitational ripple from space, a public alert is sent out. That alert lets researchers know with a decently high confidence that this ripple was probably caused by an exceptional cosmic event, such as the collision of neutron stars or the merging of black holes, somewhere in the universe.

    Then starts the scramble. A pair of researchers is assigned to the incoming event, analyzing the data to get a preliminary location in the sky whence the ripple emanated. Telescopes are pointed in that direction, more data is amassed, and the pair of researchers conducts further followup studies to try to determine what kind of event caused the wave.

    “I often think of it as if we’re in a dark forest and listening to the ground,” says Eva Huang, a third-year Department of Physics graduate student in Assistant Professor Salvatore Vitale’s lab in the MIT Kavli Institute for Astrophysics and Space Research (MKI). “From the footsteps, we’re trying to guess what kind of animal is passing by.”

    The LIGO-Virgo Collaboration keeps a rotation system to determine which researchers get to investigate the latest detection. Sylvia Biscoveanu, a second-year graduate student also in Vitale’s lab, was next on the list when LIGO suspended its third observational run due to Covid-19. If a cosmic event happens in the universe and there’s no one there to detect it, did it even happen?

    Data analysis in isolation

    When MIT similarly scaled back on-campus research in mid-March due to the coronavirus pandemic, the LIGO team at MKI adapted quickly to the new work-from-home normal. “Our work is physically less dependent on being at MIT,” says Vitale, who is also a member of the LIGO Scientific Collaboration. “Still, there are consequences.”

    For Biscoveanu, working from home has entailed being at her computer for at least eight hours a day. “In terms of actually being able to do my research, I haven’t suffered,” she says. What has suffered is her ability to exchange ideas with other members of the LIGO group at MIT. “I had just moved to a bigger office with a bunch of graduate students, and we were really looking forward to being able to talk to each other and ask questions regularly,” says Biscoveanu. “I definitely don’t get as much of that at home.”

    Mentorship also looks different when everyone is at home. Vitale has always had an open-door policy with his graduate students. “I do weekly meetings with my students, but on top of that I had close-to-daily interactions with them,” he says. Unless his door was closed, Vitale says, his students could come in and talk anytime. That immediate connection, he has found, is hard to replicate in the digital world.

    “The thing I tell my students is that we don’t work in a hut where everyone is making their own project and then it’s done,” says Vitale. “Research is more than the sum of its parts.” One advantage of working in a group is the ability to turn to a colleague to discuss a paper you just read, a problem you’re facing, or a crazy idea you had the night before. That’s harder to do when everyone is stuck in their own hut.

    “Now you have to go in the chat room or arrange a telecon if you want to ask a question,” says Ken Ng, a third-year graduate student in the Vitale group. Ng uses gravitational waves to study particle physics, with his work focusing on axions, a proposed elementary particle that is orders of magnitude smaller than the tiniest particle observed. Telecons and Slack, he has found, can be particularly inefficient when you’re trying to quickly sketch out an idea. “I’m actually thinking of buying a white board,” he says.

    Space never stops

    When the third observation run was suspended a month before it was supposed to end, it had collected 56 gravitational wave candidates. In comparison, the first two runs combined amassed a total of 11 candidates. So even though fresh data isn’t arriving in the lab, the work hasn’t ceased, and LIGO scientists are scrutinizing the data from home. “If the pandemic had happened a few months before, we could have missed half the data,” says Ng, looking on the positive side.

    Compared to the other members of the lab, Ng is no pandemic rookie. When the Covid-19 pandemic struck, he thought, “Again?” Ng, who is from Hong Kong, faced the SARS outbreak in 2002 and considers himself the pandemic veteran of the group. That experience has kept him from panicking these days. “I know the importance of social distancing and mask-wearing,” he explains.

    Still, for some in the group, social distancing has led to less productivity and feelings of guilt. “I sometimes feel that, because my work is less impacted, I cannot allow myself to feel frustrated,” says Huang. Her work — analyzing LIGO data to decipher the cosmic events responsible for detected waves — can be done at home, unlike researchers who need to be physically in-lab. Throughout the pandemic, Huang has worked hard to combat the feeling that she needs to earn permission to be self-compassionate. “I can be, and need to be, kind to myself during this time.

    All are looking forward to the day when they can come back to campus. Partly, Ng confesses, for the free food. But mostly to continue studying gravitational waves in the same space. “I miss being able to chat randomly when people are in an office,” he says.

    Vitale acknowledges that there have been some benefits of working from home. “This has obliged everyone to think a bit harder about how to express what we want to say,” he says. Still, like his students, he also can’t wait to leave his hut and get back to campus. “I think for all of us, it will also just be nice to be back at the office and re-establish a clear separation between our living and our working spaces, that right now are collapsed in the same entity.”

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    MIT Seal

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

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  • richardmitnick 5:12 pm on June 25, 2020 Permalink | Reply
    Tags: "Black Hole Collision May Have Exploded with Light", Advanced Virgo, , , , , , ,   

    From Caltech: “Black Hole Collision May Have Exploded with Light” 

    Caltech Logo

    From Caltech

    June 25, 2020
    Whitney Clavin
    (626) 395‑1944

    Artist’s concept of a supermassive black hole and its surrounding disk of gas. Embedded within this disk are two smaller black holes orbiting one another. Using data from the Zwicky Transient Facility (ZTF) at Palomar Observatory, researchers have identified a flare of light suspected to have come from one such binary pair soon after they merged into a larger black hole. The merger of the black holes would have caused them to move in one direction within the disk, plowing through the gas in such a way to create a light flare. The finding, while not confirmed, could amount to the first time that light has been seen from a coalescing pair of black holes. These merging black holes were first spotted on May 21, 2019, by the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector, which picked up gravitational waves generated by the merger.
    Credit: Caltech/R. Hurt (IPAC)

    Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Courtesy Caltech Optical Observatories

    Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, United States, altitude 1,712 m (5,617 ft)

    Possible light flare observed from small black holes within the disk of a massive black hole.

    When two black holes spiral around each other and ultimately collide, they send out ripples in space and time called gravitational waves. Because black holes do not give off light, these events are not expected to shine with any light waves, or electromagnetic radiation. But some theorists have come up with ways in which a black hole merger might explode with light. Now, for the first time, astronomers have seen evidence for one of these light-producing scenarios.

    With the help of Caltech’s Zwicky Transient Facility (ZTF), funded by the National Science Foundation (NSF) and located at Palomar Observatory near San Diego, the scientists have spotted what might be a flare of light from a pair of coalescing black holes. The black hole merger was first witnessed by the NSF’s Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector on May 21, 2019, in an event called S190521g. As the black holes merged, jiggling space and time, they sent out gravitational waves.

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    While this was happening, ZTF was performing its robotic survey of the sky that captured all kinds of objects that flare, erupt, or otherwise vary in the night sky. One flare the survey caught, generated by a distant active supermassive black hole, or quasar, called J1249+3449, was pinpointed to the region of the gravitational-wave event S190521g.

    “This supermassive black hole was burbling along for years before this more abrupt flare,” says Matthew Graham, a research professor of astronomy at Caltech and the project scientist for ZTF. “The flare occurred on the right timescale, and in the right location, to be coincident with the gravitational-wave event. In our study, we conclude that the flare is likely the result of a black hole merger, but we cannot completely rule out other possibilities.” Graham is lead author of the new study, published today, June 25, in the journal Physical Review Letters.

    “ZTF was specifically designed to identify new, rare, and variable types of astronomical activity like this,” says NSF Division of Astronomical Science Director Ralph Gaume. “NSF support of new technology continues to expand how we can track such events.”

    How do two merging black holes erupt with light? In the scenario outlined by Graham and his colleagues, two partner black holes were nestled within a disk surrounding a much larger black hole.

    “At the center of most galaxies lurks a supermassive black hole. It’s surrounded by a swarm of stars and dead stars, including black holes,” says co-author K. E. Saavik Ford of the City University of New York (CUNY) Graduate Center, the Borough of Manhattan Community College (BMCC), and the American Museum of Natural History (AMNH). “These objects swarm like angry bees around the monstrous queen bee at the center. They can briefly find gravitational partners and pair up but usually lose their partners quickly to the mad dance. But in a supermassive black hole’s disk, the flowing gas converts the mosh pit of the swarm to a classical minuet, organizing the black holes so they can pair up,” she says.

    Once the black holes merge, the new, now-larger black hole experiences a kick that sends it off in a random direction, and it plows through the gas in the disk. “It is the reaction of the gas to this speeding bullet that creates a bright flare, visible with telescopes,” says co-author Barry McKernan, also of the CUNY Graduate Center, BMCC, and AMNH.

    Such a flare is predicted to begin days to weeks after the initial splash of gravitational waves produced during the merger. In this case, ZTF did not catch the event right away, but when the scientists went back and looked through archival ZTF images months later, they found a signal that started days after the May 2019 gravitational-wave event. ZTF observed the flare slowly fade over the period of a month.

    The scientists attempted to get a more detailed look at the light of the supermassive black hole, called a spectrum, but by the time they looked, the flare had already faded. A spectrum would have offered more support for the idea that the flare came from merging black holes within the disk of the supermassive black hole. However, the researchers say they were able to largely rule out other possible causes for the observed flare, including a supernova or a tidal disruption event, which occurs when a black hole essentially eats a star.

    What is more, the team says it is not likely that the flare came from the usual rumblings of the supermassive black hole, which regularly feeds off its surrounding disk. Using the Catalina Real-Time Transient Survey, led by Caltech, they were able to assess the behavior of the black hole over the past 15 years, and found that its activity was relatively normal until May of 2019, when it suddenly intensified.

    “Supermassive black holes like this one have flares all the time. They are not quiet objects, but the timing, size, and location of this flare was spectacular,” says co-author Mansi Kasliwal (MS ’07, PhD ’11), an assistant professor of astronomy at Caltech. “The reason looking for flares like this is so important is that it helps enormously with astrophysics and cosmology questions. If we can do this again and detect light from the mergers of other black holes, then we can nail down the homes of these black holes and learn more about their origins.”

    The newly formed black hole should cause another flare in the next few years. The process of merging gave the object a kick that should cause it to enter the supermassive black hole’s disk again, producing another flash of light that ZTF should be able to see.

    The Physical Review Letters paper was funded by the NSF, NASA, the Heising-Simons Foundation, and the GROWTH (Global Relay of Observatories Watching Transients Happen) program. Other co-authors include: K. Burdge, S.G. Djorgovski, A.J. Drake, D. Duev, A.A. Mahabal, J. Belecki, R. Burruss, G. Helou, S.R. Kulkarni, F.J. Masci, T. Prince, D. Reiley, H. Rodriguez, B. Rusholme, R.M. Smith, all from Caltech; N.P. Ross of the University of Edinburgh; Daniel Stern of the Jet Propulsion Laboratory, managed by Caltech for NASA; M. Coughlin of the University of Minnesota; S. van Velzen of University of Maryland, College Park and New York University; E.C. Bellm of the University of Washington; S.B. Cenko of NASA Goddard Space Flight Center; V. Cunningham of University of Maryland, College Park; and M.T. Soumagnac of the Lawrence Berkeley National Laboratory and the Weizmann Institute of Science.

    In addition to the NSF, ZTF is funded by an international collaboration of partners, with additional support from NASA, the Heising-Simons Foundation, members of the Space Innovation Council at Caltech, and Caltech itself.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

    Caltech campus

  • richardmitnick 9:08 am on April 21, 2020 Permalink | Reply
    Tags: Advanced Virgo, , , , , , , , ,   

    From Nature (via SymmetryMag): “This black-hole collision just made gravitational waves even more interesting” 

    From Nature

    20 April 2020
    Davide Castelvecchi

    An unprecedented signal from unevenly sized objects gives astronomers rare insight into how black holes spin.

    A visualization of a collision between two differently sized black holes.Credit: N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

    Gravitational-wave astronomers have for the first time detected a collision between two black holes of substantially different masses — opening up a new vista on astrophysics and on the physics of gravity. The event offers the first unmistakable evidence from these faint space-time ripples that at least one black hole was spinning before merging, giving astronomers rare insight into a key property of these these dark objects.

    “It’s an exceptional event,” said Maya Fishbach, an astrophysicist at the University of Chicago in Illinois. Similar mergers on which data have been published all took place between black holes with roughly equal masses, so this new one dramatically upsets that pattern, she says. The collision was detected last year, and was unveiled on 18 April by Fishbach and her collaborators at a virtual meeting of the American Physical Society, held entirely online because of the coronavirus pandemic.

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) — a pair of twin detectors based in Hanford, Washington, and Livingston, Louisiana — and the Virgo observatory near Pisa, Italy, both detected the event, identified as GW190412, with high confidence on 12 April 2019.

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    The LIGO–Virgo collaboration, which includes Fishbach, posted its findings on the arXiv preprint server [https://arxiv.org/abs/2004.08342].

    LIGO made the first discovery of gravitational waves in September 2015, detecting the space-time ripples from two merging black holes. LIGO, later joined by Virgo, subsequently made ten more detections in two observing runs that ended in 2017: nine more black-hole mergers and one collision of two neutron stars, which helped to explain the origin of the Universe’s heavy chemical elements.

    The third and most recent run started on 1 April 2019 and ended on 27 March 2020, with a month-long break in October. Greatly improved sensitivity enabled the network to accumulate around 50 more ‘candidate events’ at a rate of roughly one per week. Until now, the international collaboration had unveiled only one other event from this observation period — a second merger between two neutron stars, dubbed GW190425, that was revealed in January.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public.

  • richardmitnick 2:12 pm on January 7, 2020 Permalink | Reply
    Tags: "LIGO-Virgo Network Catches Another Neutron Star Collision", Advanced Virgo, , , , , , ,   

    From MIT Caltech Advanced aLIGO and Advanced Virgo: “LIGO-Virgo Network Catches Another Neutron Star Collision” 

    MIT /Caltech Advanced aLigo

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    From MIT Caltech Advanced aLIGO and Advanced Virgo

    January 6, 2020

    Whitney Clavin

    Abigail Abazorius

    Livia Conti

    Josh Chamot

    Artist’s rendition of two colliding neutron stars. Credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet

    On April 25, 2019, the LIGO Livingston Observatory picked up what appeared to be gravitational ripples from a collision of two neutron stars. LIGO Livingston is part of a gravitational-wave network that includes LIGO (the Laser Interferometer Gravitational-wave Observatory), funded by the National Science Foundation (NSF), and the European Virgo detector. Now, a new study confirms that this event was indeed likely the result of a merger of two neutron stars. This would be only the second time this type of event has ever been observed in gravitational waves.

    The first such observation, which took place in August of 2017, made history for being the first time that both gravitational waves and light were detected from the same cosmic event. The April 25 merger, by contrast, did not result in any light being detected. However, through an analysis of the gravitational-wave data alone, researchers have learned that the collision produced an object with an unusually high mass.

    “From conventional observations with light, we already knew of 17 binary neutron star systems in our own galaxy and we have estimated the masses of these stars,” says Ben Farr, a LIGO team member based at the University of Oregon. “What’s surprising is that the combined mass of this binary is much higher than what was expected.”

    “We have detected a second event consistent with a binary neutron star system and this is an important confirmation of the August 2017 event that marked an exciting new beginning for multi-messenger astronomy two years ago,” says Jo van den Brand, Virgo Spokesperson and professor at Maastricht University, and Nikhef and VU University Amsterdam in the Netherlands. Multi-messenger astronomy occurs when different types of signals are witnessed simultaneously, such as those based on gravitational waves and light.

    The study, submitted to The Astrophysical Journal Letters, is authored by an international team comprised of the LIGO Scientific Collaboration and the Virgo Collaboration, the latter of which is associated with the Virgo gravitational-wave detector in Italy. The results were presented at a press briefing today, January 6, at the 235th meeting of the American Astronomical Society in Honolulu, Hawaii.

    One of two science papers:

    On January 6, 2020, the LIGO Scientific Collaboration and the Virgo Collaboration announced the discovery of a second binary neutron star merger, labeled GW190425. This is the first confirmed gravitational-wave detection based on data from a single observatory. No electromagnetic counterpart was found. This system is notable for having a total mass that exceeds that of known galactic neutron star binaries.
    Publications & Documents

    Publication: GW190425: Observation of a compact binary coalescence with total mass ∼3.4 Msun

    The other paper hasn’t been accepted or published yet and may be a while.

    Neutron stars are the remnants of dying stars that undergo catastrophic explosions as they collapse at the end of their lives. When two neutron stars spiral together, they undergo a violent merger that sends gravitational shudders through the fabric of space and time.

    LIGO became the first observatory to directly detect gravitational waves in 2015; in that instance, the waves were generated by the fierce collision of two black holes. Since then, LIGO and Virgo have registered dozens of additional candidate black hole mergers.

    The August 2017 neutron star merger was witnessed by both LIGO detectors, one in Livingston, Louisiana, and one in Hanford, Washington, together with a host of light-based telescopes around the world (neutron star collisions produce light, while black hole collisions are generally thought not to do so). This merger was not clearly visible in the Virgo data, but that fact provided key information that ultimately pinpointed the event’s location in the sky.

    The April 2019 event was first identified in data from the LIGO Livingston detector alone. The LIGO Hanford detector was temporarily offline at the time, and, at a distance of more than 500 million light-years, the event was too faint to be visible in Virgo’s data. Using the Livingston data, combined with information derived from Virgo’s data, the team narrowed the location of the event to a patch of sky more than 8,200 square degrees in size, or about 20 percent of the sky. For comparison, the August 2017 event was narrowed to a region of just 16 square degrees, or 0.04 percent of the sky.

    “This is our first published event for a single-observatory detection,” says Caltech’s Anamaria Effler, a scientist who works at LIGO Livingston. “But Virgo made a valuable contribution. We used information about its non-detection to tell us roughly where the signal must have originated from.”

    The LIGO data reveal that the combined mass of the merged bodies is about 3.4 times the mass of our sun. In our galaxy, known binary neutron star systems have combined masses up to only 2.9 times that of sun. One possibility for the unusually high mass is that the collision took place not between two neutron stars, but a neutron star and a black hole, since black holes are heavier than neutron stars. But if this were the case, the black hole would have to be exceptionally small for its class. Instead, the scientists believe it is much more likely that LIGO witnessed a shattering of two neutron stars.

    “What we know from the data are the masses, and the individual masses most likely correspond to neutron stars. However, as a binary neutron star system, the total mass is much higher than any of the other known galactic neutron star binaries,” says Surabhi Sachdev, a LIGO team member based at Penn State. “And this could have interesting implications for how the pair originally formed.”

    Neutron star pairs are thought to form in two possible ways. They might form from binary systems of massive stars that each end their lives as neutron stars, or they might arise when two separately formed neutron stars come together within a dense stellar environment. The LIGO data for the April 25 event do not indicate which of these scenarios is more likely, but they do suggest that more data and new models are needed to explain the merger’s unexpectedly high mass.


    Please help promote STEM in your local schools.

    Stem Education Coalition

    See the full article here .

    The Collaborations

    LIGO is funded by NSF and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant commitments and contributions to the project. More than 1,200 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. A list of additional partners is available at https://my.ligo.org/census.php.

    The Virgo collaboration consists of more than 300 physicists and engineers belonging to 28 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; 11 from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with IFAE and the Universities of Valencia and Barcelona; two in Belgium with the Universities of Liege and Louvain; Jena University in Germany; and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef. A list of the Virgo Collaboration can be found at http://public.virgo-gw.eu/the-virgo-collaboration/. More information is available on the Virgo website at http://www.virgo-gw.eu.

    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

    ESA/eLISA the future of gravitational wave research

    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)

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