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  • richardmitnick 4:38 pm on December 5, 2014 Permalink | Reply
    Tags: , , , , , , Supermassive Black Holes   

    From Daily Galaxy: “Discovery of a Pulsar and Supermassive Black Hole Pairing Could Help Unlock the Enigma of Gravity” 

    Daily Galaxy
    The Daily Galaxy

    Last year, the very rare presence of a pulsar (named SGR J1745-2900) was also detected in the proximity of a supermassive black hole (Sgr A**, made up of millions of solar masses), but there is a combination that is still yet to be discovered: that of a pulsar orbiting a ‘normal’ black hole; that is, one with a similar mass to that of stars.

    b

    sgr

    Supermassive Black Hole Sagittarius A*

    The center of the Milky Way galaxy, with the supermassive black hole Sagittarius A* (Sgr A*), located in the middle, is revealed in these images. As described in our press release, astronomers have used NASA’s Chandra X-ray Observatory to take a major step in understanding why material around Sgr A* is extraordinarily faint in X-rays.

    NASA Chandra Telescope
    NASA/Chandra

    The large image contains X-rays from Chandra in blue and infrared emission from the Hubble Space Telescope in red and yellow. The inset shows a close-up view of Sgr A* in X-rays only, covering a region half a light year wide. The diffuse X-ray emission is from hot gas captured by the black hole and being pulled inwards. This hot gas originates from winds produced by a disk-shaped distribution of young massive stars observed in infrared observations.

    NASA Hubble Telescope
    NASA/ESA Hubble

    These new findings are the result of one of the biggest observing campaigns ever performed by Chandra. During 2012, Chandra collected about five weeks worth of observations to capture unprecedented X-ray images and energy signatures of multi-million degree gas swirling around Sgr A*, a black hole with about 4 million times the mass of the Sun. At just 26,000 light years from Earth, Sgr A* is one of very few black holes in the universe where we can actually witness the flow of matter nearby.

    The authors infer that less than 1% of the material initially within the black hole’s gravitational influence reaches the event horizon, or point of no return, because much of it is ejected. Consequently, the X-ray emission from material near Sgr A* is remarkably faint, like that of most of the giant black holes in galaxies in the nearby Universe.

    The captured material needs to lose heat and angular momentum before being able to plunge into the black hole. The ejection of matter allows this loss to occur.

    This work should impact efforts using radio telescopes to observe and understand the “shadow” cast by the event horizon of Sgr A* against the background of surrounding, glowing matter. It will also be useful for understanding the impact that orbiting stars and gas clouds might make with the matter flowing towards and away from the black hole.

    The paper is available online and is published in the journal Science. The first author is Q.Daniel Wang from University of Massachusetts at Amherst, MA; and the co-authors are Michael Nowak from Massachusetts Institute of Technology (MIT) in Cambridge, MA; Sera Markoff from University of Amsterdam in The Netherlands, Fred Baganoff from MIT; Sergei Nayakshin from University of Leicester in the UK; Feng Yuan from Shanghai Astronomical Observatory in China; Jorge Cuadra from Pontificia Universidad de Catolica de Chile in Chile; John Davis from MIT; Jason Dexter from University of California, Berkeley, CA; Andrew Fabian from University of Cambridge in the UK; Nicolas Grosso from Universite de Strasbourg in France; Daryl Haggard from Northwestern University in Evanston, IL; John Houck from MIT; Li Ji from Purple Mountain Observatory in Nanjing, China; Zhiyuan Li from Nanjing University in China; Joseph Neilsen from Boston University in Boston, MA; Delphine Porquet from Universite de Strasbourg in France; Frank Ripple from University of Massachusetts at Amherst, MA and Roman Shcherbakov from University of Maryland, in College Park, MD. Image credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI

    k.
    This image was taken with NASA’s Chandra X-Ray Observatory.

    The intermittent light emitted by pulsars, the most precise timekeepers in the universe, allows scientists to verify Einstein’s theory of relativity, especially when these objects are paired up with another neutron star or white dwarf that interferes with their gravity. However, this theory could be analysed much more effectively if a pulsar with a black hole were found, except in two particular cases, according to researchers from Spain and India.

    Pulsars are very dense neutron stars that are the size of a city (their radius approaches ten kilometres), which, like lighthouses for the universe, emit gamma radiation beams or X-rays when they rotate up to hundreds of times per second. These characteristics make them ideal for testing the validity of the theory of general relativity, published by Einstein between 1915 and 1916.

    “Pulsars act as very precise timekeepers, such that any deviation in their pulses can be detected,” Diego F. Torres, ICREA researcher from the Institute of Space Sciences (IEEC-CSIC), explains to SINC. “If we compare the actual measurements with the corrections to the model that we have to use in order for the predictions to be correct, we can set limits or directly detect the deviation from the base theory.”

    These deviations can occur if there is a massive object close to the pulsar, such as another neutron star or a white dwarf. A white dwarf can be defined as the stellar remnant left when stars such as our Sun use up all of their nuclear fuel. The binary systems, comprised of a pulsar and a neutron star (including double pulsar systems) or a white dwarf, have been very successfully used to verify the theory of gravity.

    Until now scientists had considered the strange pulsar/black hole pairing to be an authentic ‘holy grail’ for examining gravity, but there exist at least two cases where other pairings can be more effective. This is what is stated in the study that Torres and the physicist Manjari Bagchi, from the International Centre of Theoretical Sciences (India) and now postdoc at the IEEC-CSIC, have published in the Journal of Cosmology and Astroparticle Physics. The work also received an Honourable Mention in the 2014 Essays of Gravitation prize.

    The first case occurs when the so-called principle of strong equivalence is violated. This principle of the theory of relativity indicates that the gravitational movement of a body that we test only depends on its position in space-time and not on what it is made up of, which means that the result of any experiment in a free fall laboratory is independent of the speed of the laboratory and where it is found in space and time.

    The other possibility is if one considers a potential variation in the gravitational constant that determines the intensity of the gravitational pull between bodies. Its value is G = 6.67384(80) x 10-11 N m2/kg2. Despite it being a constant, it is one of those that is known with the least accuracy, with a precision of only one in 10,000.

    In these two specific cases, the pulsar-black hole combination would not be the perfect ‘holy grail’, but in any case scientists are anxious to find this pair, because it could be used to analyse the majority of deviations. In fact, it is one of the desired objectives of X-ray and gamma ray space telescopes (such as Chandra, NuStar or Swift), as well as that of large radio telescopes that are currently being built, such as the enormous ‘Square Kilometre Array’ (SKA) in Australia and South Africa.

    NASA NuSTAR
    NASA/Nu-STAR

    NASA SWIFT Telescope
    NASA/Swift

    SKA Square Kilometer Array

    The image at the top of the page shows dynamic rings, wisps and jets of matter and antimatter around the pulsar in the Crab Nebula as observed in X-ray light by Chandra Space Observatory in 2001.

    Manjari Bagchi y Diego F. Torres. “In what sense a neutron star−black hole binary is the holy grail for testing gravity?”. Journal of Cosmology and Astroparticle Physics, 2014. Doi:10.1088/1475-7516/2014/08/055.

    See the full article here.

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  • richardmitnick 4:04 pm on December 5, 2014 Permalink | Reply
    Tags: Andrea Ghez, , , , , , Supermassive Black Holes, UCLA   

    From NSF: “After the Lecture…Andrea Ghez” 

    nsf
    National Science Foundation

    December 5, 2014

    NSF-funded UCLA astrophysicist Andrea Ghez on probing our galaxy’s supermassive black hole

    Andrea Ghez
    Dr.Andrea Ghez is an astrophysicist at UCLA who has been recognized many times for her research in galactic astronomy, including receiving a MacArthur Fellowship, a Packard Fellowship award, and several other awards early on in her career. Credit: Courtesy of the John D. and Catherine T. MacArthur Foundation via Wikimedia Commons

    Andrea's Favorite SO-2
    Andrea’s Favorite SO-2
    December 5, 2014

    We sat down with UCLA’s Andrea Ghez after her recent talk on Unveiling the Heart of the Galaxy as part of the NSF Distinguished Lectures in Mathematical and Physical Sciences. A few minutes later, we were probing the connection between ballet and astrophysics and why sometimes being outside of mainstream science can offer a scientist creative license that seeds transformational research.

    I was not a science fiction buff. I was always a puzzle buff, and I absolutely loved math. I still think of my job as puzzle solving. As a child, I also was fascinated by stories of women explorers–my favorite was Amelia Earhart.

    At some point in high school, I got fascinated by the concepts of black holes and the beginning of time.

    It’s asking the biggest questions we can possibly ask. It’s understanding our position in the universe. It’s what makes us uniquely human–to try and understand our context in the biggest possible terms. It’s what inspires us.

    Adaptive optics has transformed what we can do. When we started with speckle imaging, it was this bizarre little technique only a few people knew how to do. It was a niche-like a boutique technique. Adaptive optics has opened up the world of science so we can ask a much richer set of questions. It’s made it a technique for every astronomer.

    I used to be tremendously afraid of public speaking. I would shake if you asked me to introduce myself. I chose grad school for places where I would not have to teach because I was so deathly afraid of getting in front of an audience. But my adviser made me give a lunchtime talk, and every bone in my body shook. He was sweet but said I needed to teach. I’ve always been strongly committed to encouraging young girls to go into science, so I figured if I was going to teach, I would do it in a meaningful way for me. You just can’t get nervous every day, and I learned how to translate nervousness into excitement. That becomes your style. You are no longer nervous.

    I haven’t seen Interstellar. It’s on the top of my why-haven’t-I-seen-it list.

    You’re basically an idiot until you prove you’re smart. That’s what it’s like to be in science.

    My approach has always been to give myself the highest credentials possible. So when I thought about where to go to school, I really did think about the school that would give me the best “coat of armor” for dealing with any doubt. At every stage of my career, I think there’s been someone who pipes up with “you’ve only done this because you’re a woman” comment. And it’s not like everyone says this. It’s just that that’s the one comment you listen to.

    It’s really important to pick a good mentor. I think this is true, independent of gender.

    I almost increasingly think that there is an advantage to being outside mainstream because a lot of progress in science comes from the ability to think differently and to not necessarily accept what everyone has put out there. If you propose something different from what people are doing, how comfortable are you with being outside the group?

    To do science, it’s so important to take risks and accept failure. How do you train your students to do that? It’s a very important characteristic.

    I was really interested in dancing when I was young; I wanted to be a ballerina. At one point I got more interested in choreography. For some reason, I now think of my work as this combination of puzzle solving and choreography. I would never have made the connection between that kind of thinking and what I do today, yet it’s totally there.

    There have definitely been moments where I felt like I’m not playing on the right playground because I’m not seeing anyone I can relate to. Meeting people you can relate to is remarkably powerful and sometimes you find those people who inspire you to go onto the next step in very unexpected places.

    I think if I were not a physicist, I’d be some other sort of scientist or mathematician who is focused on solving problems.

    Ivy F. Kupec, (703) 292-8796 ikupec@nsf.gov

    Investigators
    Andrea Ghez

    Related Institutions/Organizations
    California Institute of Technology
    University of California-Los Angeles

    Locations
    Los Angeles , California

    Related Awards
    #0909218 A Laser Guide Star Adaptive Optics Study of Stellar Dynamics at the Galactic Center: A Laboratory for Understanding Interactions with a Central Supermassive Black Holes
    #1412615 New Probes of the Galactic Black Hole and its Environs

    See the full article http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=133541&WT.mc_id=USNSF_1
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  • richardmitnick 9:38 am on November 20, 2014 Permalink | Reply
    Tags: , , , , , , Supermassive Black Holes   

    From AAAS: “What powers a black hole’s mighty jets?” 

    AAAS

    AAAS

    19 November 2014
    Daniel Clery

    Black holes have a reputation for devouring everything in their path. But some of them like to give as well as receive. A small fraction of supermassive black holes—the ginormous ones that lurk at the centers of galaxies—fire off light-speed jets of particles as they snack. A new survey of more than 200 of these cosmic beasts finds that the jets are much more powerful than scientists thought. Astronomers don’t know what powers jets, but this new result, the team says, supports one proposed explanation: The jets are tapping into the rotational energy of the black hole itself.

    bh
    A black hole’s gravity can heat up the disk around it to shine brightly, but what powers the jets some of them produce remains a mystery. (NASA/JPL-Caltech)

    “It’s very exciting,” says Andrew Fabian, director of the Institute of Astronomy at the University of Cambridge in the United Kingdom, who was not involved in the research. “It’s long been debated whether this is possible.”

    About 1% of supermassive black holes have an “accretion disk” of gas and dust swirling around them. When material from this disk falls toward the black hole, the plunging debris gets so hot that it shines more brightly than the whole rest of its galaxy. One in 10 of these active black holes also produces jets that fire out particles at 99.995% of the speed of light. Astrophysicists suspect that accretion disks produce the jets, but they don’t know how.

    To get a better idea, a team led by astrophysicist Gabriele Ghisellini of the National Institute for Astrophysics in Merate, Italy, surveyed archival data and picked out a sample of 217 bright supermassive black holes for which they could find gamma ray observations (which reveal the brightness of the jets) and optical observations (to get the luminosity of the accretion disks). Key to the survey were data from NASA’s Fermi Gamma-ray Space Telescope, launched in 2008. “It took time to build up a collection of samples with the required information,” Ghisellini says.

    NASA Fermi Telescope
    NASA/Fermi

    Plotting the luminosity of the accretion disks against the gamma ray power of their jets, the team reports online today in Nature that there is a clear linear relationship between the two. The brighter the disk, the more powerful the jets—cementing the idea that accretion disks and jets are linked. But in terms of total power being beamed out into space, Ghisellini says, most of the jets were producing 10 times that of their accretion disks. “There must be another engine, not just the gravitational energy [of accreting matter falling toward the black hole].”

    The most popular explanation of how jets form is that the fast-spinning accretion disk, which contains charged particles, will produce a powerful magnetic field that is in contact with the black hole. If the black hole is spinning, it drags on the field, winding it into a tight cone at the rotational poles of the black hole. It is this twisted field that accelerates particles away from the black hole as jets and, in the process, extracts energy from the rotation of the black hole. Ghisellini says the group’s finding that jets are so much more powerful than accretion disks shows that disks alone can’t power the jets; the black hole’s spin must also be involved.

    Fabian says he still has a “slight reservation” about the assertion that the results prove the role of black hole spin. It’s also possible, he says, that the magnetic field is sucking power out of the accretion disk, making it appear less bright.

    “The next step for science is to measure the spin of a black hole,” Ghisellini says, to see whether spin rate is related to jet power. “But it is very hard to measure.” Fabian says researchers using NASA’s NuSTAR x-ray telescope have measured the spin rate of stellar-sized black holes formed from just one or a few stars. Confusingly, some of these small spinning black holes have jets and some don’t. “There must be some other parameter [defining whether a black hole has jets], but we don’t know what that is,” Fabian says.

    NASA NuSTAR
    NASA/Nu-STAR

    So although evidence is mounting that black hole spin is powering jets, astrophysicists may have to wait until they can measure the spin of a supermassive black hole before they can nail it. Ghisellini thinks Europe’s Athena x-ray observatory will be able to do the job, but he’s got a long wait ahead: Athena’s launch is slated for 2028.

    ESA Athena spacecraft
    Athena

    See the full article here.

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  • richardmitnick 11:04 am on October 24, 2014 Permalink | Reply
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    From CfA: “Accreting Supermassive Black Holes in the Early Universe” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    October 24, 2014
    No Writer Credit

    Supermassive black holes containing millions or even billions of solar-masses of material are found at the nuclei of galaxies. Our Milky Way, for example, has a nucleus with a black hole with about four million solar masses of material. Around the black hole, according to theories, is a torus of dust and gas, and when material falls toward the black hole (a process called accretion) the inner edge of the disk can be heated to millions of degrees. Such accretion heating can power dramatic phenomena like bipolar jets of rapidly moving charged particles. Such actively accreting supermassive black holes in galaxies are called active galactic nuclei (AGN).

    torus
    Torus

    The evolution of AGN in cosmic time provides a picture of their role in the formation and co-evolution of galaxies. Recently, for example, there has been some evidence that AGN with more modest luminosities and accretion rates (compared to the most dramatic cases) developed later in cosmic history (dubbed “downsizing”), although the reasons for and implications of this effect are debated. CfA astronomers Eleni Kalfontzou, Francesca Civano, Martin Elvis and Paul Green and a colleague have just published the largest study of X-ray selected AGN in the universe from the time when it was only 2.5 billion years old, with the most distant AGN in their sample dating from when the universe was about 1.2 billion years old.

    The astronomers studied 209 AGN detected with the Chandra X-ray Observatory.

    NASA Chandra Telescope
    NASA/Chandra

    image
    A multicolor image of galaxies in the field of the Chandra Cosmic Evolution Survey. A large, new study of 209 galaxies in the early universe with X-ray bright supermassive black holes finds that more modest AGN tend to peak later in cosmic history, and that obscured and unobscured AGN evolve in similar ways.
    X-ray: NASA/CXC/SAO/F.Civano et al. Optical: NASA/STScI

    They note that the X-ray observations are less contaminated by host galaxy emission than optical surveys, and consequently that they span a wider, more representative range of physical conditions. The team’s analysis confirms the proposed trend towards downsizing, while it also can effectively rule out some alternative proposals. The scientists also find, among other things, that this sample of AGN represents nuclei with a wide range of molecular gas and dust extinction. Combined with the range of AGN dates, this result enables them to conclude that obscured and unobscured phases of AGN evolve in similar ways.

    See the full article here.

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

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  • richardmitnick 10:54 am on August 19, 2014 Permalink | Reply
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    From SPACE.com: “Supermassive Death: 3 Stars Eaten by Black Holes” 

    space-dot-com logo

    SPACE.com

    August 19, 2014
    Ian O’Neill

    Astrophysicists have analyzed two decades-worth of X-ray data and discovered three events inside galactic cores that can be interpreted in only one way: stellar destruction.

    ANALYSIS: Supermassive Black Hole Jet Mystery Solved

    For any given galaxy, it is estimated that a star will be destroyed by the central supermassive black hole approximately once every 10,000 years. The vast majority of known galaxies are thought to contain at least one supermassive black hole in their cores, having a dramatic effect on galactic and stellar evolution. [Images: Black Holes of the Universe]

    As a star drifts too close to a supermassive black hole, intense tidal stresses rip the star to shreds. As this happens, the shredded material will be dragged into the black hole’s accretion disk — a hot disk of gas that is gradually pulled into the black hole’s event horizon, bulking up the black hole’s mass, or blasted as energetic jets from its poles.

    Should there be a rapid injection of material — i.e. a star becoming blended and ingested into the accretion disk — powerful X-rays of a specific signature will be generated.

    NEWS: Supermassive Black Holes are Not Doughnuts!

    In a new study by the Moscow Institute of Physics and Technology and Space Research Institute of the Russian Academy of Sciences, astrophysicists trawled through observations from two space observatories to discover three likely occasions where stars have been eaten by supermassive black holes. Their work has been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.

    Using data from the German ROSAT and European XMM-Newton space observatories, X-ray data from 1990 (to today) could be accessed and three events in different galaxies were positively identified — designated 1RXS J114727.1 + 494302, 1RXS J130547.2 + 641252 and 1RXS J235424.5-102053. Invaluable to this study was the long-duration observations by ROSAT (which operated from 1990 to 1999) and XMM-Newton (launched in 1999) that could detect the moment of stellar death, keeping track of the X-ray emissions over the years as the star’s material was gradually ingested.

    ROSAT Spacecraft
    ROSAT

    ESA XMM Newton
    ESA/XMM-Newton

    NEWS: Intermediate Black Hole Implicated in Star’s Death

    No more than two dozen other stellar death event candidates were seen in the observations, but positive identifications probably won’t be available until the launch of the multi-instrument Spectrum-X-Gamma space observatory in 2016.

    Spectrum GammaX
    Spectrum-X-Gamma space observatory

    This work has added some much needed detail to these rare events, indicating that (on average) one star every 30,000 years in any given galaxy will be destroyed by the central supermassive black hole, though the researchers caution that more observations of stars being eaten by supermassive black holes are needed.

    See the full article here.

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  • richardmitnick 10:24 am on August 18, 2014 Permalink | Reply
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    From SPACE.com: ” It’s Confirmed! Black Holes Do Come in Medium Sizes” 

    space-dot-com logo

    SPACE.com

    August 18, 2014
    Mike Wall

    Black holes do indeed come in three sizes: small, medium and extra large, a new study suggests.

    Astronomers have studied many black holes at either size extreme — “stellar-mass” black holes, which are a few dozen times as weighty as the sun, and supermassive black holes, which can contain millions or billions of times the mass of the sun and lurk at the heart of most, if not all, galaxies.

    Researchers have spotted hints of much rarer medium-size black holes, which harbor between 100 and several hundred thousand solar masses. But it’s tough to weigh these objects definitively — so tough that their existence has been a matter of debate.

    But that debate can now be put to rest, says a research team that has measured an intermediate black hole’s mass with unprecedented precision. A black hole in the nearby galaxy M82 weighs in at 428 solar masses, give or take a hundred suns or so, they report today (Aug. 17) in the journal Nature.

    “Objects in this range are the least expected of all black holes,” study co-author Richard Mushotzky, an astronomy professor at the University of Maryland, said in a statement. “Astronomers have been asking, ‘Do these objects exist, or do they not exist? What are their properties?’ Until now, we have not had the data to answer these questions.”

    Patterns in the light

    Black holes famously gobble up anything that gets too close, including light. But that doesn’t mean astronomers can’t see them; bright X-ray light streams from the superhot disk of material spiraling into a black hole’s mouth.

    About 15 years ago, NASA’s Chandra X-ray Observatory spacecraft spotted such emissions coming from a source in the galaxy M82, which lies about 12 million light-years away from Earth. For a long time, Mushotzky and some other scientists suspected that the object, called M82 X-1, was a medium-size black hole. But those suspicions were tough to confirm.

    NASA Chandra Telescope
    NASA/Chandra

    “For reasons that are very hard to understand, these objects have resisted standard measurement techniques,” Mushotzky said.

    In the new study, a team led by University of Maryland doctoral student Dheeraj Pasham took a closer look at M82 X-1. They studied observations made from 2004 to 2010 by NASA’s Rossi X-ray Timing Explorer (RXTE) satellite, which ceased operations in 2012.

    rxte
    NASA/ RXTE

    The RXTE data revealed a pair of repeating oscillations in M82 X-1’s X-ray emissions. These oscillations occurred 5.1 times per second and 3.3 times per second, respectively — a ratio of three to two. This fact allowed the team to determine the black hole’s mass.

    “In essence, [the] frequency of these 3:2 ratio oscillations scales inverse[ly] with black hole mass,” Pasham told Space.com via email. “Simply put, if the black hole is small, the orbital periods at the innermost circular orbit are shorter, but if the black hole is big, the orbital periods are longer (smaller frequencies).”

    The researchers calculated M82 X-1’s mass at 428 suns, plus or minus 105 solar masses.

    “In our opinion, and as the paper’s referees seem to agree, this is the most accurate mass measurement of an intermediate-mass black hole to date,” Pasham said.

    Learning about black-hole growth

    Confirming the existence of intermediate black holes could help researchers better understand the supermassive monsters at the cores of galaxies.

    Such behemoths apparently first formed in the universe’s very early days, just a few hundred million years after the Big Bang. They could not have grown so big so fast if their “seeds” were small stellar-mass black holes (which result from the collapse of giant stars), Pasham said.

    “Many theories, therefore, have suggested that these initial seed black holes had to have been a few 100 -1,000 times our sun,” he said. “But we did not have firm evidence for such intermediate-mass black holes.”

    Stellar-mass black holes also often feature paired X-ray oscillations that occur in a 3:2 frequency ratio. Therefore, the new observations suggest that medium-size black holes may behave like scaled-up versions of stellar-mass black hole systems, Pasham added.

    The research is detailed in the Aug. 17 edition of the journal Nature.

    See the full article here.

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  • richardmitnick 6:14 pm on August 12, 2014 Permalink | Reply
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    From The Royal Astronomical Society: “NASA’s NuSTAR sees rare blurring of black hole light” 

    Royal Astronomical Society

    Royal Astronomical Society

    12 August 2014
    J.D. Harrington
    Headquarters, Washington
    202-358-5241
    j.d.harrington@nasa.gov

    Whitney Clavin
    Jet Propulsion Laboratory
    Pasadena
    California
    United States
    Tel: +1 818 354 4673
    whitney.clavin@jpl.nasa.gov

    Science contact

    Prof Michael Parker
    Institute of Astronomy
    Cambridge
    United Kingdom
    Tel: +44 (0)1223 337 511
    mlparker@ast.cam.ac.uk

    Scientists have used NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), an orbiting X-ray telescope, to capture an extreme and rare event in the regions immediately surrounding a supermassive black hole. A compact source of X-rays that sits near the black hole, called the corona, has moved closer to the black hole over a period of just days. The researchers publish their results in Monthly Notices of the Royal Astronomical Society.

    NASA NuSTAR
    NASA/NuSTAR

    smbh
    An artist’s impression of a supermassive black hole and its surroundings. The regions around supermassive black holes shine brightly in X-rays. Some of this radiation comes from a surrounding disk, and most comes from the corona, pictured here as the white light at the base of a jet. This is one possible configuration for the Mrk 335 corona, as its actual shape is unclear. Credit: NASA-JPL / Caltech.

    “The corona recently collapsed in towards the black hole, with the result that the black hole’s intense gravity pulled all the light down onto its surrounding disk, where material is spiralling inward,” said Michael Parker of the Institute of Astronomy in Cambridge, lead author of the new paper.

    As the corona shifted closer to the black hole, the black hole’s gravitational field exerted a stronger tug on the x-rays emitted by the corona. The result was an extreme blurring and stretching of the X-ray light. Such events had been observed previously, but never to this degree and in such detail.

    Supermassive black holes are thought to reside in the centres of all galaxies. Some are more massive and rotate faster than others. The black hole in this new study, referred to as Markarian 335, or Mrk 335, is about 324 million light-years from Earth in the direction of the Pegasus constellation. It is one of the most extreme systems of which the mass and spin rate have ever been measured. The black hole squeezes about 10 million times the mass of our Sun into a region only 30 times as wide as the Sun’s diameter, and it spins so rapidly that space and time are dragged around with it.

    Even though some light falls into a supermassive black hole never to be seen again, other high-energy light emanates from both the corona and the surrounding accretion disk of superheated material. Though astronomers are uncertain of the shape and temperature of coronas, they know that they contain particles that move close to the speed of light.

    NASA’s Swift satellite has monitored Mrk 335 for years, and recently noted a dramatic change in its X-ray brightness. In what is called a ‘target-of-opportunity’ observation, NuSTAR was redirected to take a look at high-energy X-rays from this source in the range of 3 to 79 kiloelectron volts. This particular energy range offers astronomers a detailed look at what is happening near the event horizon, the region around a black hole from which light can no longer escape gravity’s grasp.

    NASA SWIFT Telescope
    NASA/SWIFT

    Follow-up observations indicate that the corona still is in this close configuration, months after it moved. Researchers don’t know whether and when the corona will shift back. What is more, the NuSTAR observations reveal that the grip of the black hole’s gravity pulled the corona’s light onto the inner portion of its superheated disk, better illuminating it. The shifting corona lit up the precise region they wanted to study, almost as if somebody had shone a flashlight for the astronomers.

    The new data could ultimately help determine more about the mysterious nature of black hole coronas. In addition, the observations have provided better measurements of Mrk 335’s furious relativistic spin rate. Relativistic speeds are those approaching the speed of light, as described by Albert Einstein’s theory of relativity.

    “We still don’t understand exactly how the corona is produced or why it changes its shape, but we see it lighting up material around the black hole, enabling us to study the regions so close in that effects described by Einstein’s theory of general relativity become prominent,” said NuSTAR Principal Investigator Fiona Harrison of the California Institute of Technology (Caltech) in Pasadena. “NuSTAR’s unprecedented capability for observing this and similar events allows us to study the most extreme light-bending effects of general relativity.”

    See the full article here.

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

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  • richardmitnick 2:13 pm on August 7, 2014 Permalink | Reply
    Tags: , , , , , Supermassive Black Holes   

    From SPACE.com: “How Did Supermassive Black Holes Get So Big So Fast?” 

    space-dot-com logo

    SPACE.com

    August 07, 2014
    Charles Q. Choi

    Black holes may have grown incredibly rapidly in the newborn universe, perhaps helping explain why they appear so early in cosmic history, researchers say.

    Black holes possess gravitational pulls so powerful that not even light can escape their clutches. They are generally believed to form after massive stars die in gargantuan explosions known as supernovas, which crush the remaining cores into incredibly dense objects.

    smbh
    visualiztion of a supermassive black hole

    Supermassive black holes millions to billions of times the mass of the sun occur at the center of most, if not all, galaxies. Such monstrously large black holes have existed since the infancy of the universe, some 800 million years or so after the Big Bang. However, it remains a mystery how these giants could have grown so big in the relatively short amount of time they had to form.

    In modern black holes, features called accretion disks limit the speed of growth. These disks of gas and dust that swirl into black holes can prevent black holes from growing rapidly in two different ways, researchers say. First, as matter in an accretion disk gets close to a black hole, traffic jams occur that slow down any other infalling material. Second, as matter collides within these traffic jams, it heats up, generating energetic radiation that drives gas and dust away from the black hole.

    “Black holes don’t actively suck in matter — they are not like vacuum cleaners,” said lead study author Tal Alexander, an astrophysicist at the Weizmann Institute of Science in Rehovot, Israel.

    “A star or a gas stream can be on a stable orbit around a black hole, exactly as the Earth revolves around the sun, without falling into it,” Alexander told Space.com. “It is actually quite a challenge to think of efficient ways to drive gas into the black hole at a high enough rate that can lead to rapid growth.”

    Alexander and his colleague Priyamvada Natarajan may have found a way in which early black holes could have grown to supermassive proportions — in part, by operating without the restrictions of accretion disks. The pair detailed their findings online today (Aug. 7) in the journal Science.

    The scientists began with a model of a black hole 10 times the mass of the sun embedded in a cluster of thousands of stars. They fed the simulated black hole continuous flows of dense, cold, opaque gas.

    “The early universe was much smaller and hence denser on average than it is today,” Alexander said.

    This cold, dense gas would have obscured a substantial amount of the energetic radiation given off by matter falling into the black hole. In addition, the gravitational pull of the many stars around the black hole “causes it to zigzag randomly, and this erratic motion prevents the formation of a slowly draining accretion disk,” Alexander said. This means that matter falls into the black hole from all sides instead of getting forced into a disk around the black hole, from which it would swirl in far more slowly.

    The “supra-exponential growth” observed in the model black hole suggests that a black hole 10 times the mass of the sun could have grown to more than 10 billion times the mass of the sun by just 1 billion years after the Big Bang, researchers said.

    “This theoretical result shows a plausible route to the formation of supermassive black holes very soon after the Big Bang,” Alexander said.

    Future research could examine whether supra-exponential growth of black holes could occur in modern times as well. The high-density and high-mass cold flows seen in the ancient universe may exist “for short times in unstable, dense, star-forming clusters, or in dense accretion disks around already-existing supermassive black holes,” Alexander said.

    You can read the abstract of the new study here.

    See the full article here.

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