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  • richardmitnick 3:04 pm on May 20, 2017 Permalink | Reply
    Tags: , , , Black Holes, , , What Happens When A Black Hole's Singularity Evaporates?   

    From Ethan Siegel: “Ask Ethan: What Happens When A Black Hole’s Singularity Evaporates?” 

    Ethan Siegel
    May 20, 2017

    1
    The event horizon of a black hole is a spherical or spheroidal region from which nothing, not even light, can escape. But outside the event horizon, the black hole is predicted to emit radiation. NASA; Jörn Wilms (Tübingen) et al.; ESA

    It’s hard to imagine, given the full diversity of forms that matter takes in this Universe, that for millions of years, there were only neutral atoms of hydrogen and helium gas. It’s perhaps equally hard to imagine that someday, quadrillions of years from now, all the stars will have gone dark. Only the remnants of our now-vibrant Universe will be left, including some of the most spectacular objects of all: black holes. But even they won’t last forever. David Weber wants to know how that happens for this week’s Ask Ethan, inquiring:

    What happens when a black hole has lost enough energy due to hawking radiation that its energy density no longer supports a singularity with an event horizon? Put another way, what happens when a black hole ceases to be a black hole due to hawking radiation?

    In order to answer this question, it’s important to understand what a black hole actually is.

    2
    The anatomy of a very massive star throughout its life, culminating in a Type II Supernova when the core runs out of nuclear fuel. Nicole Rager Fuller/NSF

    Black holes generally form during the collapse of a massive star’s core, where the spent nuclear fuel ceases to fuse into heavier elements. As fusion slows and ceases, the core experiences a severe drop in radiation pressure, which was the only thing holding the star up against gravitational collapse. While the outer layers often experience a runaway fusion reaction, blowing the progenitor star apart in a supernova, the core first collapses into a single atomic nucleus — a neutron star — but if the mass is too great, the neutrons themselves compress and collapse to such a dense state that a black hole forms. (A black hole can also form if a neutron star accretes enough mass from a companion star, crossing the threshold necessary to become a black hole.)

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    When a neutron star accretes enough matter, it can collapse to a black hole. When a black hole accretes matter, it grows an accretion disk and will increase its mass as matter gets funneled into the event horizon. NASA/ESA Hubble Space Telescope collaboration

    NASA/ESA Hubble Telescope

    From a gravitational point of view, all it takes to become a black hole is to gather enough mass in a small enough volume of space that light cannot escape from within a certain region. Every mass, including planet Earth, has an escape velocity: the speed you’d need to achieve to completely escape from the gravitational pull at a given distance (e.g., the distance from Earth’s center to its surface) from its center-of-mass. But if there’s enough mass so that the speed you’d need to achieve at a certain distance from the center of mass is the speed of light or greater, then nothing can escape from it, since nothing can exceed the speed of light.

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    Cornell SXS team; Bohn et al 2015

    That distance from the center of mass where the escape velocity equals the speed of light — let’s call it R — defines the size of the black hole’s event horizon. But the fact that there’s matter inside under these conditions has another consequence that’s less-well appreciated: this matter must collapse down to a singularity. You might think there could be a state of matter that’s stable and has a finite volume within the event horizon, but that’s not physically possible.

    In order to exert an outward force, an interior particle would have to send a force-carrying particle away from the center-of-mass and closer to the event horizon. But that force-carrying particle is also limited by the speed of light, and no matter where you are inside the event horizon, all light-like curves wind up at the center. The situation is even worse for slower, massive particles. Once you form a black hole with an event horizon, all the matter inside gets crunched into a singularity.

    5
    http://www.speed-light.info/miracles_of_quran/singularity.htm

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    The exterior spacetime to a Schwarzschild black hole, known as Flamm’s Paraboloid, is easily calculable. But inside an event horizons, all geodesics lead to the central singularity. Wikimedia Commons user AllenMcC

    And since nothing can escape, you might think a black hole would remain a black hole forever. If it weren’t for quantum physics, this would be exactly what happens. But in quantum physics, there’s a non-zero amount of energy inherent to space itself: the quantum vacuum. In curved space, the quantum vacuum takes on slightly different properties than in flat space, and there are no regions where the curvature is greater than near the singularity of a black hole. Combining these two laws of nature — quantum physics and the General Relativistic spacetime around a black hole — gives us the phenomenon of Hawking radiation.

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    Ethan Siegel

    8
    A visualization of QCD illustrates how particle/antiparticle pairs pop out of the quantum vacuum for very small amounts of time as a consequence of Heisenberg uncertainty. Derek B. Leinweber

    Performing the quantum field theory calculation in curved space yields a surprising solution: that thermal, blackbody radiation is emitted in the space surrounding a black hole’s event horizon. And the smaller the event horizon is, the greater the curvature of space near the event horizon is, and thus the greater the rate of Hawking radiation. If our Sun were a black hole, the temperature of the Hawking radiation would be about 62 nanokelvin; if you took the black hole at the center of our galaxy, 4,000,000 times as massive, the temperature would be about 15 femtokelvin, or just 0.000025% the temperature of the less massive one.

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    An X-ray / Infrared composite image of the black hole at the center of our galaxy: Sagittarius A*. It has a mass of about four million Suns, and is found surrounded by hot, X-ray emitting gas. However, it also emits (undetectable) Hawking radiation, at much, much lower temperatures. X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI

    NASA/Chandra Telescope

    NASA Infrared Telescope facility Mauna Kea, Hawaii, USA

    This means the smallest black holes decay the fastest, and the largest ones live the longest. Doing the math, a solar mass black hole would live for about 10^67 years before evaporating, but the black hole at the center of our galaxy would live for 10^20 times as long before decaying. The crazy thing about it all is that right up until the final fraction-of-a-second, the black hole still has an event horizon. Once you form a singularity, you remain a singularity — and you retain an event horizon — right up until the moment your mass goes to zero.

    That final second of a black hole’s life, however, will result in a very specific and very large release of energy. When the mass drops down to 228 metric tonnes, that’s the signal that exactly one second remains. The event horizon size at the time will be 340 yoctometers, or 3.4 × 10^-22 meters: the size of one wavelength of a photon with an energy greater than any particle the LHC has ever produced. But in that final second, a total of 2.05 × 10^22 Joules of energy, the equivalent of five million megatons of TNT, will be released. It’s as though a million nuclear fusion bombs went off all at once in a tiny region of space; that’s the final stage of black hole evaporation.

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    As a black hole shrinks in mass and radius, the Hawking radiation emanating from it becomes greater and greater in temperature and power. NASA

    What’s left? Just outgoing radiation. Whereas previously, there was a singularity in space where mass, and possibly charge and angular momentum existed in an infinitesimally small volume, now there is none. Space has been restored to its previously non-singular state, after what must have seemed like an eternity: enough time for the Universe to have done all it’s done to date trillions upon trillions of times over. There will be no other stars or sources of light left when this occurs for the first time in our Universe; there will be no one to witness this spectacular explosion. But there’s no “threshold” where this occurs. Rather, the black hole needs to evaporate completely. When it does, to the best of our knowledge, there will be nothing left behind at all but outgoing radiation.

    11
    Against a seemingly eternal backdrop of everlasting darkness, a single flash of light will emerge: the evaporation of the final black hole in the Universe. ortega-pictures / pixabay

    In other words, if you were to watch the last black hole in our Universe evaporate, you would see an empty void of space, that displayed no light or signs of activity for perhaps 10^100 years or more. All of a sudden, a tremendous outrush of radiation of a very particular spectrum and magnitude would appear, leaving a single point in space at 300,000 km/s. For the last time in our observable Universe, an event would have occurred to bathe the Universe in radiation. The last black hole evaporation of all would, in a poetic way, be the final time that the Universe would ever say, “Let there be light!”

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

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

     
  • richardmitnick 1:59 pm on April 29, 2017 Permalink | Reply
    Tags: Ask Ethan: What should a black hole’s event horizon look like?, Black Holes, , , , ,   

    From Ethan Siegel: “Ask Ethan: What should a black hole’s event horizon look like?” 

    Ethan Siegel
    Apr 29, 2017

    1
    An illustration of a black hole. Despite how dark it is, all black holes are thought to have formed from normal matter alone, but illustrations like these are only partially accurate. Image credit: NASA / JPL-Caltech.

    You might think that it should be all black, but then how would we see it?

    “It is conceptually interesting, if not astrophysically very important, to calculate the precise apparent shape of the black hole… Unfortunately, there seems to be no hope of observing this effect.” -Jim Bardeen

    Earlier this month, telescopes from all around the world took data, simultaneously, of the Milky Way’s central black hole.

    Here is the Event Horizon Telescope Array

    Event Horizon Telescope map

    The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope sites, via University of Arizona at https://www.as.arizona.edu/event-horizon-telescope.

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

    ESO/APEX
    Atacama Pathfinder EXperiment (APEX)

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

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

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Hawaii SAO
    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    Future Array/Telescopes

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Also involved:

    European VLBI

    Of all the black holes that are known in the Universe, the one at our galactic center — Sagittarius A* — is special.

    Sag A* NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way

    From our point of view, its event horizon is the largest of all black holes. It’s so large that telescopes positioned at different locations on Earth should be able to directly image it, if they all viewed it simultaneously. While it will take months to combine and analyze the data from all the different telescopes, we should get our first image of an event horizon by the end of 2017. So what will it looks like? That’s the question of Dan Barrett, who’s seen some illustrations and is a bit puzzled:

    Shouldn’t the event horizon completely surround the black hole like an egg shell? All the artist renderings of a black hole are like slicing a hard boiled egg in half and showing that image. How is it that the event horizon does not completely surround the black hole?

    There are a few different classes of illustrations floating around, to be sure. But which ones, if any, are correct?

    2
    Artwork illustrating a simple black circle, perhaps with a ring around it, is an oversimplified picture of what an event horizon looks like. Image credit: Victor de Schwanberg.

    The oldest type of illustration is simply a circular, black disk, blocking out all the background light from behind it. This makes sense if you think about what a black hole actually is: a collection of mass that’s so great and so compact that the escape velocity from its surface is greater than the speed of light! Since nothing can move that quickly, not even the forces or interactions between the particles inside the black hole, the inside of a black hole collapses to a singularity, and an event horizon is created around the black hole. From this spherical region of space, no light can escape, and so it should appear as a black circle, from any perspective, superimposed on the background of the Universe.

    3
    A black hole isn’t just a mass superimposed over an isolated background, but will exhibit gravitational effects that stretch, magnify and distort background light due to gravitational lensing. Image credit: Ute Kraus, Physics education group Kraus / Axel Mellinger.

    But there’s more to the story than that. Because of their gravity, black holes will magnify and distort any background light, due to the effect of gravitational lensing. This is a more detailed and accurate illustration of what a black hole looks like, as it also possesses an apparent event horizon sized appropriately with the curvature of space in General Relativity.

    Unfortunately, these illustrations are flawed, too: they fail to account for foreground material and for accretion around the black hole. Some illustrations, though, do successfully add these in.

    4
    An illustration of an active black hole, one that accretes matter and accelerates a portion of it outwards in two perpendicular jets, may describe the black hole at the center of our galaxy in many regards. Image credit: Mark A. Garlick.

    Because of their tremendous gravitational effects, black holes will form accretion disks in the presence of other sources of matter. Asteroids, gas clouds, or even entire stars will be torn apart by the tidal forces coming from an object as massive as a black hole. Due to the conservation of angular momentum, and of collisions between the various infalling particles, a disk-like object will emerge around the black hole, which will heat up and emit radiation. In the innermost regions, particles occasionally fall in, adding to the mass of the black hole, while the material in front of the black hole will obscure part of the sphere/circle you’d otherwise see.

    But the event horizon itself isn’t transparent, and you shouldn’t be able to see the matter behind it.

    4
    The black hole, as illustrated in the movie Interstellar, shows an event horizon fairly accurately for a very specific class of rotating black holes. Image credit: Interstellar / R. Hurt / Caltech.

    It might seem surprising that a Hollywood film — Interstellar — has a more accurate illustration of a black hole than many of the professional pieces of artwork created for/by NASA, but misconceptions abound, even among professionals, when it comes to black holes. Black holes don’t suck matter in; they simply gravitate. Black holes don’t tear things apart because of any extra force; it’s simply tidal forces — where one part of the infalling object is closer to the center than another — that does it. And most importantly, black holes rarely exist in a “naked” state, but rather exist in the vicinity of other matter, such as at the center of our galaxy.

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    An X-ray / Infrared composite image of the black hole at the center of our galaxy: Sagittarius A*. It has a mass of about four million Suns, and is found surrounded by hot, X-ray emitting gas. Image credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

    So with all of that in mind, what are the hard-boiled-egg images that have been going around? Remember, we can’t image the black hole itself, because it doesn’t emit light! All we can do is look at a particular wavelength, and see a combination of the emitting light that comes from around, behind and in front of the black hole itself. The expected signal, indeed, does resemble a split hard-boiled egg.

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    Some of the possible profile signals of the black hole’s event horizon as simulations of the Event Horizon Telescope indicate. Image credit: High-Angular-Resolution and High-Sensitivity Science Enabled by Beamformed ALMA, V. Fish et al., arXiv:1309.3519

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

    This has to do with what it is we’re imaging. We can’t look in X-rays, because there are simply too few X-ray photons overall. We can’t look in visible light, because the galactic center is opaque it it. And we can’t look in the infrared, because the atmosphere blocks infrared light. But what we can do is look in the radio, and we can do it all over the world, simulataneously, to get the optimal resolution possible.

    The black hole at the galactic center has an angular size of about 37 micro-arc-seconds, while the resolution of this telescope array is around 15 micro-arc-seconds, so we should be able to see it! At radio frequencies, the overwhelming majority of that radiation comes from charged matter particles being accelerated around the black hole. We don’t know how the disk will be oriented, whether there will be multiple disks, whether it will be more like a swarm of bees or more like a compact disk. We also don’t know whether it will prefer one “side” of the black hole, as viewed from our perspective, over another.

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    Five different simulations in general relativity, using a magnetohydrodynamic model of the black hole’s accretion disk, and how the radio signal will look as a result. Image credit: GRMHD simulations of visibility amplitude variability for Event Horizon Telescope images of Sgr A*, L. Medeiros et al., arXiv:1601.06799.

    We fully expect the event horizon to be real, to be of a specific size, and to block all the light coming from behind it. But we also expect that there will be some signal in front of it, that the signal will be messy due to the messy environment around the black hole, and that the orientation of the disk with respect to the black hole will play an important role in determining what we see.

    One side is brighter as the disk rotates towards us; one side is fainter as the disk rotates away. The entire “outline” of the event horizon may be visible as well, thanks to the effect of gravitational lensing. Perhaps most importantly, whether the disk is seen “edge-on” or “face-on” with respect to us will drastically alter the signal, as the 1st and 3rd panels below illustrate.

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    The orientation of the accretion disk as either face-on (left two panels) or edge-on (right two panels) can vastly alter how the black hole appears to us. Image credit: ‘Toward the event horizon — the supermassive black hole in the Galactic Center’, Class. Quantum Grav., Falcke & Markoff (2013).

    There are other effects we can test for, including:

    whether the black hole has the right size as predicted by general relativity,
    whether the event horizon is circular (as predicted), or oblate or prolate instead,
    whether the radio emissions extend farther than we thought,

    or whether there are any other deviations from the expected behavior. This is a brand new frontier in physics, and we’re poised to actually test it directly. One thing’s for certain: no matter what it is that the Event Horizon Telescope sees, we’re bound to learn something new and wonderful about some of the most extreme objects and conditions in the Universe!

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

     
  • richardmitnick 1:11 pm on April 15, 2017 Permalink | Reply
    Tags: , , , Black Holes, , , ,   

    From ESO: “Taking the First Picture of a Black Hole” 

    ESO 50 Large

    European Southern Observatory

    30.3.2017

    1. What are the Event Horizon Telescope and the Global mm-VLBI Array?

    At the centre of our galaxy lurks a cosmic monster: a supermassive black hole called Sagittarius A* with a mass about four million times that of the Sun.

    Sag A* NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way

    Its gravity is so intense that not even light can escape its pull, but if it wasn’t for its strong gravitational influence on the stars and gas around it, we would have no idea that it was there! Now, an ambitious new endeavour is underway to take a never-seen-before image, of the event horizon of the black hole itself.

    Two international collaborations of radio telescopes have linked up to create Earth-sized virtual telescopes: the Event Horizon Telescope (EHT) and the Global mm-VLBI Array (GMVA), working at different wavelengths.

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    This infographic details the locations of the participating telescopes of the Event Horizon Telescope and the Global mm-VLBI Array. Credit: ESO/O. Furtak

    Global mm-VLBI Array

    Event Horizon Telescope Array

    Event Horizon Telescope map

    The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope sites, via University of Arizona at https://www.as.arizona.edu/event-horizon-telescope.

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

    ESO/APEX
    Atacama Pathfinder EXperiment (APEX)

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

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

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Hawaii SAO
    Submillimeter Array Hawaii SAO

    Future Array/Telescopes

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    The impressive line-up of telescopes, which stretch across the globe from the South Pole to Hawaii to Europe, will work together to target the supermassive black hole at the heart of the Milky Way.

    To do this, astronomers will exploit a technique known as Very-long-baseline Interferometry (VLBI), where telescopes thousands of kilometres apart can link together and act as one.

    European VLBI

    This cooperative technique can achieve a far higher resolution than any single facility could obtain on its own — a resolution 2000 times that of the NASA/ESA Hubble Space Telescope! This super-high resolution is crucial for detecting the black hole, which — despite being about 20 times bigger than the Sun — lies a long way away, over 26 000 light-years from Earth.

    The plan to image a black hole has been in the works for years, but it’s only recently that technology has brought the ambitious endeavour within reach. Plus, a radio telescope heavyweight has just joined the team: the Atacama Large Millimeter/submillimeter Array (ALMA).

    Located high up on the Chajnantor plateau in Chile’s Atacama Desert, ALMA’s 66 antennas and exquisite receivers make it the largest and most sensitive component of the EHT/GMVA collaboration, increasing the overall sensitivity by a factor of 10. Despite being a state-of-the-art facility, ALMA has undergone several upgrades to take part in the collaboration. Specialist equipment has been installed, including new hard drives that are necessary to store the sheer amount of data produced by the observations, as well as an extremely accurate atomic clock, which is critical to link ALMA to the entire VLBI network.

    The first groundbreaking observations will be made in April 2017: observations at 3 millimetre wavelengths will be made with the GMVA from 1–4 April 2017, and with the EHT at 1.3 millimetre wavelengths from 5–14 April 2017. The GMVA will investigate the properties of the accretion and outflow around the Galactic Centre, while the EHT will attempt to image, for the very first time, the shadow of the black hole’s event horizon.

    There is a long, hard road ahead to process the massive amounts of data that will be acquired during the observation periods, and results are expected to become available towards the end of 2017.

    The outcome of these observations is eagerly awaited by the astronomy community worldwide, as their scientific potential is incredibly exciting and the collaboration are pursuing some awesome goals. These could include testing Einstein’s theory of general relativity, which predicts a roughly circular “shadow” around the black hole. Other goals include learning about how material accretes around black holes, as well as the formation of extremely fast jets of gas that blast out from them.

    3
    Simulated images of the shadow of a black hole: General relativity predicts that the shadow should be circular (middle), but a black hole could potentially also have a prolate (left) or oblate (right) shadow. Future EHT images will test this prediction. Credit: D. Psaltis and A. Broderick.

    This is the first post of a blog series that will take you along for the astronomical ride, giving insight into how cutting-edge research is done and what risks are involved.

    In the following posts, we’ll explore questions such as: What makes black holes so interesting? How do radio telescopes see the Universe? And what do we really know about the supermassive monster lurking at the centre of the Milky Way?

    11.4.2017

    2. What is a black hole?

    Right now, astronomers are attempting to take the first image of the event horizon of the supermassive black hole at the centre of the Milky Way — but what exactly are black holes?

    Black holes are some of the most bizarre and fascinating objects in the Universe. Essentially, they’re reality-bending concentrations of matter squeezed into a very tiny space, creating an object with an immense gravitational pull. Around a black hole is a boundary called an event horizon — the surface beyond which nothing can escape the black hole’s clutches, not even light.

    Take a tour of the anatomy of a black hole with our handy infographic:

    4
    Credit: ESO, ESA/Hubble, M. Kornmesser/N. Bartmann

    Since no light can escape from a black hole, we can’t see them directly. But their huge gravitational influence gives away their presence. Black holes are often orbited by stars, gas and other material in tight paths that become more crowded and frantic as they’re dragged closer to the event horizon. This creates a superheated accretion disc around the black hole, which emits vast amounts of radiation of different wavelengths.

    By observing this radiation from the activity around black holes, astronomers have determined that there are two main types: stellar mass and supermassive.

    A stellar mass black hole is the corpse of a star more than about 30 times as massive as our Sun. At the end of its life, such stars violently collapse and don’t stopped collapsing until all of their constituent matter has condensed down into an unimaginably tiny space. It’s easiest to discover stellar mass black holes that are part of an X-ray binary system, where the black hole is guzzling down material from its companion star.

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    Artist’s impression of the formation of a stellar black hole in a binary system. Credit: ESO/L. Calçada/M.Kornmesser

    The second type is called a supermassive black hole. These gargantuan black holes are up to billions of times more massive than an average star, and how they formed is much less clear and is a matter of ongoing study. One theory proposes they formed from enormous clouds of matter that collapsed when galaxies first formed; another theory suggests that colliding stellar mass black holes can merge into one enormous object.

    Today, these supermassive monsters reside at the centres of almost every galaxy — including our own Milky Way. They exert tremendous influence on their home galaxies, especially when they gorge on gas and stars.

    6
    Artist’s impression of a gas cloud after a close approach to the black hole at the centre of the Milky Way. The star orbiting the black hole are shown, along with blue lines that mark their fast, tight orbits. Credit: ESO/MPE/Marc Schartmann

    26 000 light-years away from Earth, Sagittarius A* (Sgr A* for short) is the supermassive black hole in the hot, violent centre of the Milky Way. It’s over 4 million times more massive than our Sun, over 20 million kilometres across, and is spinning at a large fraction of the speed of light. It’s shrouded from optical telescopes by dense clouds of dust and gas, so observatories that can observe different wavelengths — either longer (such as ALMA) or shorter (X-ray telescopes) — are essential to study its properties.

    Soon, through the combined power of ALMA and other millimetre-wavelength telescopes across the globe, we may become much better acquainted with the monstrous heart of our galaxy. The Global mm-VLBI Array is currently investigating the process of how gas, dust and other material accrete onto supermassive black holes, as well as the formation of the extremely fast gas jets that flow from them. The Event Horizon Telescope, on the other hand, is working towards a different goal: imaging the shadow of the event horizon, the point of no return.

    This is the second post of a blog series following the EHT and GMVA projects. Stay tuned to find out more about why the event horizon of a black hole is so interesting!

    Event Horizon Telescope website
    GMVA website
    BlackHoleCam — an EU-funded project to finally image, measure and understand astrophysical black holes
    Read more about ALMA
    Find out more about ALMA’s VLBI capabilities

    See the full article here .

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

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

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

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

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

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert

     
    • Nikola Milovic 8:48 am on April 16, 2017 Permalink | Reply

      I wish I could make contact with scientists who are trying to learn something more about black holes. The main reason for this contact is my view that science still does not know what a black hole is and how and why it occurs.
      It is true that this is a place where even light can not escape. But, one must know the limits of long acting black hole and what happens within those boundaries towards the center of the black hole and outside those borders where both matter and light still “confused” and do not know which way to go. To be deciphered. What if scientists to “see” with new telescopes, is again out of the black hole and its limits where the “forbidden transition both sides of the border.
      It is true that this is an enormous amount of gravity, but how and why this occurs, science can not know if you do not know the structure of the universe.
      The black hole has a spherical shape and is situated so that all sides around this sphere can “suck every form of matter. The fact that science sees as the horizon, not what is in reality, neither of the black hole can form any kind of matter, nor can they be two black holes collide.

      Like

  • richardmitnick 8:18 am on March 31, 2017 Permalink | Reply
    Tags: , , , Black Holes, , , direct collapse black hole ala Avi Loeb   

    From COSMOS: “When giants warped the universe” 

    Cosmos Magazine bloc

    COSMOS

    31 March 2017
    Graham Phillips

    1
    They don’t make them like they used to: supermassive black holes emerged billions of years earlier than thought. Getty Images

    They gobble stars, bend space, warp time and may even provide gateways to other universes.

    Black holes fire the imagination of scientists and science-fiction aficionados alike. But at least one thing about them wasn’t all that mind-bending: we’ve long understood black holes to be the end point in the life of a big star, when it runs out of fuel and collapses on itself.

    However, in recent times astronomers have been confronted with a paradox: gigantic black holes that existed when the universe was less than a billion years old.

    Since average-sized black holes take many billions of years to form, astrophysicists have been scratching their heads to figure out how these monsters could have arisen so early. It now seems that rather than being the end game in the evolution of stars and galaxies, supermassive black holes were around at their beginnings and played a major role in shaping them.

    Recommended reading: The bright side of black holes

    It was the little known English clergyman and scientist John Michell who, in 1783, first articulated the idea of “dark stars” whose gravity was so great they would prevent light from escaping them. The concept was astonishingly prescient even if parts of his theory – particularly those based on Newton’s idea that light particles had mass – were flawed.

    The first accurate description of black holes came in 1916 from German physicist and astronomer Karl Schwarzschild. Schwarzschild was serving in the German Army at the time, despite already being over 40 years of age.

    After seeing action on both the western and eastern fronts, Schwarzschild was sent home due to a serious auto-immune skin disease, pemphigus.

    It was late 1915 and Einstein’s theory of General Relativity had just been published. Inspired, Schwarzschild lost no time writing a paper that predicted the existence of black holes; it was published just months before he succumbed to his disease in May 1916.

    According to Einstein’s theory, the force of gravity was the result of a mass distorting the fabric of space-time. In the same way that a bowling ball dimples the fabric of a trampoline, a star’s mass dimpled the space-time fabric of its system, keeping planets circling around it.

    The theory was underpinned by equations laying out the interaction of energy, mass, space and time. Schwarzschild’s achievement was to apply Einstein’s equations to a simplified scenario: a perfectly spherical star. One of the things that jumped out of his mathematical musings was an object with such a strong gravitational pull that not even light could escape it.

    While Schwarzschild’s idea made sense in the theoretical realm of mathematics, most physicists did not expect to find an exemplar in the real universe.

    By the 1960s, however, expectations were changing. Astronomers discovered the existence of extremely dense objects known as neutron stars. Detected by their unusual pulsing of electromagnetic radiation, they were the dense corpses of large stars that had exhausted their fuel. Without the force of the burning fuel pushing against their own gravity, they collapsed, compressing their matter until only the pressure of neutron against neutron halted the crush.

    Neutron stars got astrophysicists thinking back to Schwarzschild’s idea. What happens when really big suns with even stronger gravity cave in? All the matter would be squeezed down to a point with an extraordinarily strong gravitational field.

    Sometime in the 1960s, physicists coined the term “black hole”, and the hunt for something more than just a mathematical artefact was on.

    The first evidence that black holes weren’t just theoretical came in 1964, when a rocket decked with sensitive instruments was shot into sub-orbital space. It detected suspicious X-rays emanating from the constellation of Cygnus (the swan).

    The X-ray source became known as Cygnus X-1. By the early 1970s most astronomers inferred the X-rays were radiated by super-heated matter being sucked into the gravitational field of the black hole. It would take decades more, however, before the first conclusive evidence that black holes exist and obey Einstein’s equations of general relativity.

    This came in September 2015 with the detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States.



    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

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


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

    These ripples in the fabric of space-time had been generated by two black holes colliding 1.3 billion years ago. Theorists had predicted that if such a titanic event occurred somewhere in our galaxy, the reverberations should be measurable on Earth.


    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    LIGO’s detection of gravitational waves thus also confirmed the existence of black holes. Yet even as the evidence that black holes truly exist has firmed up, our understanding of how they arise seems to be crumbling.

    The cracks in the theory grew gradually as astronomers accumulated evidence for the existence of a very different kind of black hole. While most black holes have a mass that is equivalent to 10-100 times that of our Sun, these monsters were equivalent to a million or a billion solar masses. With typical prosaicness, astronomers dubbed them supermassive black holes.

    Unlike smaller black holes, they also resided at the centres of galaxies. Most surprising of all, far-reaching telescopes like the European Southern Observatory’s Very Large Telescope detected them in extremely distant galaxies.


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

    Because of the extreme length of time it takes for their light to reach Earth, these galaxies provide snapshots of the universe in its infancy.

    “A billion years after the big bang you have black holes that are as massive as the biggest black holes we find around us today,” says Avi Loeb, an astrophysicist at Harvard University.

    That simply doesn’t make sense according to the accepted understanding that black holes come only at the end of a star’s life. “It’s sort of like going to the delivery room in a hospital and finding giant babies.”

    Were these monster babies the result of many black holes colliding? Or did they arise from moderately sized black holed that ballooned by feeding on gas and other stars? Neither of these scenarios sits well with astrophysicists.

    “Getting from even a hundred solar masses up to several billion solar masses in less than a billion years is quite challenging,” says Mitch Begelman, an astrophysicist from the University of Colorado. “Black holes are not vacuum cleaners. That’s a popular misconception. It’s very difficult to get a black hole to swallow lots of stuff [in a short period of time].”

    Loeb, who has been captivated by supermassive black holes since he got into astrophysics, thinks he might have a solution to the mystery: in 1994, he came up with the idea that a different kind of process gave birth to black holes in the early universe.

    In the modern universe, a black hole takes billions of years to form. The black hole’s precursor star (which must be greater than 10 solar masses to muster the required gravitational force) must first burn through its fuel, then explode as a supernova before it collapses.

    But while the biggest stars today reach the size of 300 solar masses, the early universe might have blazed with stars equivalent to as much as a million solar masses. Such a super star, according to Loeb’s calculations, would burn so feverishly it would use up its fuel in just a million years.

    Then it would collapse directly into a black hole a million times the mass of the Sun – what Loeb calls “a direct collapse black hole”.

    According to Loeb, the reason super stars were formed only in the embryonic universe, is because back then stars were made of simpler stuff: “The gas was pristine. It came from the big bang and had only hydrogen and helium,” he explains.

    Lacking heavier elements to radiate heat, the clouds stayed relatively warm. That allowed them to grow without fragmenting, forming super stars.

    By contrast, in today’s universe star dust contains heavy atoms like carbon, silicon and oxygen – forged in the nuclear furnaces of the first generation of stars and blown throughout the cosmos when those stars exploded.

    As result, modern-day dust clouds can cool to extremely low temperatures and fragment, mostly forming stars about the size of the Sun.

    If Loeb is right, early super stars gave rise to the direct collapsers, which gave rise to supermassive black holes. These monsters have had an enormous influence on how the universe evolved. They shaped galaxies in two ways.

    First, they gobbled up clouds and stars in their immediate vicinity. Second, like some cosmic air blower, they beamed out jets of energy that propelled dust and gas out of their galaxy.

    “Within tens of millions of years the black holes can remove the gas from the host galaxy,” Loeb says. By cleaning the galaxy of the raw material for star creation and growth, the black holes have capped the size of galaxies.

    If not for the supermassive black hole at the centre of the Milky Way, Loeb estimates, our galaxy could have grown a thousand times bigger than it is today. That would be some night sky to look up at.

    “The growth of black holes seems to be a crucial element in galaxy formation,” Begelman agrees. “Galaxies would look very different if there weren’t these black holes.”

    Of course, the absolute proof that direct collapse black holes exist will come when one is observed.

    In the past year astronomers have seen some tantalising clues. One is a galaxy known as CR7, which hosts a source of light much brighter than its stars – perhaps the radiation caused by a black hole sucking in gas.

    “You see evidence for a galaxy that has mainly hydrogen and helium,” Loeb says. “That could potentially be the birthplace of a direct collapse black hole.”

    See the full article here .

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  • richardmitnick 1:31 pm on March 28, 2017 Permalink | Reply
    Tags: , Black Holes, , , , , SUPERRADIANCE   

    From PI via GIZMODO: “Mind-Blowing New Theory Connects Black Holes, Dark Matter, and Gravitational Waves” 

    Perimeter Institute
    Perimeter Institute

    GIZMODO

    3.28.17
    Ryan F. Mandelbaum

    The past few years have been incredible for physics discoveries. Scientists spotted the Higgs boson, a particle they’d been hunting for almost 50 years, in 2012, and gravitational waves, which were theorized 100 years ago, in 2016. This year, they’re slated to take a picture of a black hole. So, thought some theorists, why not combine all of the craziest physics ideas into one, a physics turducken? What if we, say, try to spot the dark matter radiating off of black holes through their gravitational waves?

    It’s really not that strange of an idea. Now that scientists have detected gravitational waves, ripples in spacetime spawned by the most violent physical events, they want to use their discovery to make real physics observations. They think they have a way to spot all-new particles that might make up dark matter, an unknown substance that accounts for over 80 percent of all of the gravity in the universe.

    The basic idea is that we’re trying to use black holes… the densest, most compact objects in the universe, to search for new kinds of particles,” Masha Baryakhtar, postdoctoral researcher at the Perimeter Institute for Theoretical Physics in Canada, told Gizmodo. Especially one particle: “The axion. People have been looking for it for 40 years.”

    Black holes are the universe’s sinkholes, so strong that light can’t escape their pull once it’s entered. They’ve got such powerful gravitational fields that they produce gravitational waves when they collide with each other. Dark matter might not be made from particles (specks of mass and energy), but if it was, we might observe it as axions, particles around one quintillion (a billion billion) times lighter than an electron, hanging around black holes. Now that you understand all the terms, here’s how the theory works.

    Baryakhtar and her teammates think that black holes are more than just bear traps for light, but nuclei at the center of a sort of gravitational atom. The axions would be the electrons, so to speak. If you already know about black holes, you know they have incredibly hot, high-energy discs of gas orbiting them, produced by the friction between particles accelerated by the black hole’s gravity. This theory ignores that stuff, since axions wouldn’t interact via friction.

    Keeping with the atom analogy, the axions can jump around the black hole, gaining and losing energy the same way that electrons do. But electrons interact via electromagnetism, so they let out electromagnetic waves, or light waves. Axions interact via gravity, so they let out gravitational waves. But like I said earlier, axions are tiny. Unlike a tiny atom, the black hole in these “gravity atoms” rotates, supercharging the space around it and coaxing it into producing more axions. Despite the axion’s tiny mass, this so-called superradiance process could generate 10^80 axions, the same number of atoms in the entire universe, around a single black hole. Are you still with me? Crazy spinning blob makes lots of crazy stuff.

    Craziest of all, we should be able to hear a gravitational wave hum from these axions moving around and releasing gravitational waves in our detectors, similar to the way you see spectral lines coming off of electrons in atoms in chemistry class. “You’d see this at a particular frequency which would be roughly twice the axion mass,” said Baryakhtar.

    There are giant gravitational wave detectors scattered around the world; presently there’s one called LIGO (Laser Interferometer Gravitational Wave Observatory) in Washington State, another LIGO in Louisiana, and one called Virgo in Italy that are sensitive enough to detect gravitational waves, and with upgrades, to detect axions and prove their theory right.



    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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



    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Scientists would essentially need to record data, play it back, and tune their analysis like a radio to pick up the signal at just the right frequency.

    There are other ways the team thinks it could spot this superradiance effect, by measuring the spins in sets of colliding black holes. If black holes really do produce axions, scientists would see very few quickly-spinning black holes in collisions, since the superradiance effects would slow down some of the colliding black holes and create a visible effect in the data, according to the research published this month in the journal Physical Review D. The black hole spins would have a specific pattern which we should be able to spot in the gravitational wave detector data.

    Other scientists were immediately excited about this paper. “I’m always super excited about new ways to detect my favorite pet particle, the axion! Also, SUPERRADIANCE!” Dr. Chanda Prescod-Weinstein, the University of Washington axion wrangler, told Gizmodo in an email. “It’s so cool, and I haven’t read a paper that talked about [superradiance] in years. So it was really fun to see superradiance and axions in one paper.”

    There are a few drawbacks, as there are with any theory. These theorized black hole atoms would have to produce axions of a certain mass, but that mass isn’t an ideal one for the axion to be a dark matter particle, said Prescod-Weinstein. Plus, the second detection idea, the one that looks at the spin rate of colliding black holes, might not work. “They say [in the paper] that they don’t take into account the potential influence of another black hole” in the colliding pair, Dr. Lionel London, a research associate at Cardiff University School of Physics and Astronomy specializing in gravitational wave modeling, told Gizmodo. “If this does turn out to be a significant effect and they’re not including it, this could cast doubt on their results.” But there’s hope. “There’s good reason to believe the effect of a companion [black hole] won’t be large.”

    When would we spot these kinds of events? As of now, the LIGO and Virgo gravitational wave detectors probably aren’t ready. “With the current sensitivity we’re on the edge” of detecting axions, said Baryakhtar. “But LIGO will continue improving their instruments and at design sensitivity we might be able to see as many as 1000s of these axion signals coming in,” she said. Thousands of hums from these black hole-atoms.

    So, if you’ve gotten all the way to this point of the story and still don’t understand what’s going on, a recap: We’ve got these gravitational wave detectors that cost hundreds of millions of dollars each, that are good at spotting really crazy things going on in the universe. Theorists have come up with an interesting way to use them to solve one of the most important interstellar mysteries: What the heck is dark matter? As with most new ideas in theoretical physics, this is something cool to think about and isn’t ready for the big time… yet.

    “I think that timescale is always a concern, but we’re just getting started with LIGO discoveries,” said Prescod-Weinstein. “So who knows what’s around the corner over the next 10 years.”

    See the full article here .

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    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 10:26 am on March 16, 2017 Permalink | Reply
    Tags: , , , Black Holes, ,   

    From MIT: “Scientists identify a black hole choking on stardust” 

    MIT News

    MIT Widget

    MIT News

    March 14, 2017
    Jennifer Chu

    1
    In this artist’s rendering, a thick accretion disk has formed around a supermassive black hole following the tidal disruption of a star that wandered too close. Stellar debris has fallen toward the black hole and collected into a thick chaotic disk of hot gas. Flashes of X-ray light near the center of the disk result in light echoes that allow astronomers to map the structure of the funnel-like flow, revealing for the first time strong gravity effects around a normally quiescent black hole.
    Image: NASA/Swift/Aurore Simonnet, Sonoma State University

    Data suggest black holes swallow stellar debris in bursts.

    In the center of a distant galaxy, almost 300 million light years from Earth, scientists have discovered a supermassive black hole that is “choking” on a sudden influx of stellar debris.

    In a paper published today in Astrophysical Journal Letters, researchers from MIT, NASA’s Goddard Space Flight Center, and elsewhere report on a “tidal disruption flare” — a dramatic burst of electromagnetic activity that occurs when a black hole obliterates a nearby star. The flare was first discovered on Nov. 11, 2014, and scientists have since trained a variety of telescopes on the event to learn more about how black holes grow and evolve.

    The MIT-led team looked through data collected by two different telescopes and identified a curious pattern in the energy emitted by the flare: As the obliterated star’s dust fell into the black hole, the researchers observed small fluctuations in the optical and ultraviolet (UV) bands of the electromagnetic spectrum. This very same pattern repeated itself 32 days later, this time in the X-ray band.

    The researchers used simulations of the event performed by others to infer that such energy “echoes” were produced from the following scenario: As a star migrated close to the black hole, it was quickly ripped apart by the black hole’s gravitational energy. The resulting stellar debris, swirling ever closer to the black hole, collided with itself, giving off bursts of optical and UV light at the collision sites. As it was pulled further in, the colliding debris heated up, producing X-ray flares, in the same pattern as the optical bursts, just before the debris fell into the black hole.

    “In essence, this black hole has not had much to feed on for a while, and suddenly along comes an unlucky star full of matter,” says Dheeraj Pasham, the paper’s first author and a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research. “What we’re seeing is, this stellar material is not just continuously being fed onto the black hole, but it’s interacting with itself — stopping and going, stopping and going. This is telling us that the black hole is ‘choking’ on this sudden supply of stellar debris.”

    Pasham’s co-authors include MIT Kavli postdoc Aleksander Sadowski and researchers from NASA’s Goddard Space Flight Center, the University of Maryland, the Harvard-Smithsonian Center for Astrophysics, Columbia University, and Johns Hopkins University.

    See the full article here .

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    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 9:02 am on March 2, 2017 Permalink | Reply
    Tags: , , Black Holes, , , Rapid changes point to origin of ultra-fast black hole winds   

    From ESA: “Rapid changes point to origin of ultra-fast black hole winds” 

    ESA Space For Europe Banner

    European Space Agency

    1 March 2017
    Markus Bauer








    ESA Science and Robotic Exploration Communication Officer









    Tel: +31 71 565 6799









    Mob: +31 61 594 3 954









    Email: markus.bauer@esa.int

    Michael Parker
    Institute of Astronomy, Cambridge, UK
    Email: mlparker@ast.cam.ac.uk

    Andrew Fabian
    Institute of Astronomy, Cambridge, UK
    Email: acf@ast.cam.ac.uk

    Norbert Schartel
    XMM-Newton project scientist
    Email: Norbert.Schartel@esa.int

    1
    Black hole with ultrafast winds. No image credit

    ESA and NASA space telescopes have made the most detailed observation of an ultra-fast wind flowing from the vicinity of a black hole at nearly a quarter of the speed of light.

    Outflowing gas is a common feature of the supermassive black holes that reside in the centre of large galaxies. Millions to billions of times more massive than the Sun, these black holes feed off the surrounding gas that swirls around them. Space telescopes see this as bright emissions, including X-rays, from the innermost part of the disc around the black hole.

    Occasionally, the black holes eat too much and burp out an ultra-fast wind. These winds are an important characteristic to study because they could have a strong influence on regulating the growth of the host galaxy by clearing the surrounding gas away and therefore suppressing the birth of stars.

    Using ESA’s XMM-Newton and NASA’s NuStar telescopes, scientists have now made the most detailed observation yet of such an outflow, coming from an active galaxy identified as IRAS 13224–3809.

    ESA/XMM Newton
    ESA/XMM Newton

    NASA/NuSTAR
    NASA/NuSTAR

    The winds recorded from the black hole reach 71 000 km/s – 0.24 times the speed of light – putting it in the top 5% of fastest known black hole winds.

    XMM-Newton focused on the black hole for 17 days straight, revealing the extremely variable nature of the winds.

    “We often only have one observation of a particular object, then several months or even years later we observe it again and see if there’s been a change,” says Michael Parker of the Institute of Astronomy at Cambridge, UK, lead author of the paper published in Nature this week that describes the new result.

    “Thanks to this long observation campaign, we observed changes in the winds on a timescale of less than an hour for the first time.”

    The changes were seen in the increasing temperature of the winds, a signature of their response to greater X-ray emission from the disc right next to the black hole.

    Furthermore, the observations also revealed changes to the chemical fingerprints of the outflowing gas: as the X-ray emission increased, it stripped electrons in the wind from their atoms, erasing the wind signatures seen in the data.

    “The chemical fingerprints of the wind changed with the strength of the X-rays in less than an hour, hundreds of times faster than ever seen before,” says co-author Andrew Fabian, also from the Institute of Astronomy and principal investigator of the project.

    “It allows us to link the X-ray emission arising from the infalling material into the black hole, to the variability of the outflowing wind farther away.”

    “Finding such variability, and finding evidence for this link, is a key step in understanding how black hole winds are launched and accelerated, which in turn is an essential part of understanding their ability to moderate star formation in the host galaxy,” adds Norbert Schartel, ESA’s XMM-Newton project scientist.

    The response of relativistic outflowing gas to the inner accretion disk of a black hole,” by M. Parker et al. is published in Nature.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 6:27 pm on February 19, 2017 Permalink | Reply
    Tags: , , , Black Holes, , , NAOJ Nobeyama Radio Observatory, Supernova Remnant W44   

    From EarthSky: “Hints of a quiet, stray black hole” 

    1

    EarthSky
    Via NAOJ Nobeyama Radio Observatory
    No writer credit

    1
    Supernova Remnant W44. https://earthspacecircle.blogspot.com/2015/12/supernova-remnant-w44.html

    Graduate student Masaya Yamada and professor Tomoharu Oka, both of Keio University, led a research team that was surveying gas clouds around the supernova remnant W44, located 10,000 light-years away from us, when they noticed something unusual. Their statement explained:

    “During the survey, the team found a compact molecular cloud with enigmatic motion. This cloud, [nicknamed] the ‘Bullet,’ has a speed of more than 100 km/second [60 miles/second], which exceeds the speed of sound in interstellar space by more than two orders of magnitude. In addition, this cloud, with the size of two light-years, moves backward against the rotation of the Milky Way galaxy.”

    The energy of motion of the Bullet is many times larger than that injected by the original W44 supernova. The astronomers think this energy must come from a quiet, stray black hole, and they proposed two scenarios to explain the Bullet:

    ” In both cases, a dark and compact gravity source, possibly a black hole, has an important role. One scenario is the ‘explosion model’ in which an expanding gas shell of the supernova remnant passes by a static black hole. The black hole pulls the gas very close to it, giving rise to an explosion, which accelerates the gas toward us after the gas shell has passed the black hole. In this case, the astronomers estimated that the mass of the black hole would 3.5 times the solar mass or larger.

    The other scenario is the ‘irruption model’ in which a high speed black hole storms through a dense gas and the gas is dragged along by the strong gravity of the black hole to form a gas stream. In this case, researchers estimated the mass of the black hole would be 36 times the solar mass or larger. With the present dataset, it is difficult for the team to distinguish which scenario is more likely.”

    Via NAOJ Nobeyama Radio Observatory

    ASTE Atacama Submillimeter telescope
    ASTE Atacama Submillimeter telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Telescope

    3
    (a) CO (J=3-2) emissions (color) and 1.4 GHz radio continuum emissions (contours) around the supernova remnant W44. (b) Galactic longitude-velocity diagram of CO (J=3-2) emissions at the galactic latitude of -0.472 degrees. (c -f): Galactic longitude-velocity diagrams of the Bullet in CO (J=1-0), CO (J=3-2), CO (J=4-3), and HCO+ (J=1-0), from left to right. Galactic longitude-velocity diagrams show the speed of the gas at a specific position. Structures elongated in the vertical direction in the diagrams have a large velocity width. Credit: Yamada et al. (Keio University), NAOJ

    4
    Schematic diagrams of two scenarios for the formation mechanism of the Bullet. (a) explosion model and (b) irruption model. Both diagrams show a part of the shock front produced by the expansion of the supernova remnant W44. The shock wave enters into quiescent gas and compresses it to form dense gas. The Bullet is located in the center of the diagram and has completely different motion compared to the surrounding gas. Credit: Yamada et al. (Keio University)

    These astronomers published their findings in January, 2017 in the peer-reviewed Astrophysical Journal Letters.

    A black hole is a place in space where matter is squeezed into a tiny space, and where gravity pulls so hard that even light can’t escape. Black holes are black. No light comes from them. Up to now, most known stellar black holes are those with companion stars. The black hole pulls gas from the companion, which piles up around it and forms a disk. The disk heats up due to the enormous gravitational pull by the black hole and emits intense radiation.

    On the other hand, if a black hole is floating alone in space – as many must be – its lack of light or any sort of emission would make it very, very hard to find.

    See the full article here .

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  • richardmitnick 1:46 pm on February 8, 2017 Permalink | Reply
    Tags: Black Holes, ,   

    From CfA: “A Middleweight Black Hole is Hiding at the Center of a Giant Star Cluster” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    February 8, 2017
    Christine Pulliam
    Media Relations Manager
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu

    1
    In this artist’s illustration, an intermediate-mass black hole in the foreground distorts light from the globular star cluster in the background. New research suggests that a 2,200 solar-mass black hole resides at the center of the globular cluster 47 Tucanae. CfA / M. Weiss

    2
    This artist’s conception shows another representation of the intermediate-mass black hole that may lurk in the center of the globular cluster 47 Tucanae. B. Kızıltan & T. Karacan

    All known black holes fall into two categories: small, stellar-mass black holes weighing a few Suns, and supermassive black holes weighing millions or billions of Suns. Astronomers expect that intermediate-mass black holes weighing 100 – 10,000 Suns also exist, but so far no conclusive proof of such middleweights has been found. Today, astronomers are announcing new evidence that an intermediate-mass black hole (IMBH) weighing 2,200 Suns is hiding at the center of the globular star cluster 47 Tucanae.

    “We want to find intermediate-mass black holes because they are the missing link between stellar-mass and supermassive black holes. They may be the primordial seeds that grew into the monsters we see in the centers of galaxies today,” says lead author Bulent Kiziltan of the Harvard-Smithsonian Center for Astrophysics (CfA).

    This work appears in the Feb. 9, 2017, issue of the prestigious science journal Nature.

    47 Tucanae is a 12-billion-year-old star cluster located 13,000 light-years from Earth in the southern constellation of Tucana the Toucan. It contains hundreds of thousands of stars in a ball only about 120 light-years in diameter. It also holds about two dozen pulsars that were important targets of this investigation.

    47 Tucanae has been examined for a central black hole before without success. In most cases, a black hole is found by looking for X-rays coming from a hot disk of material swirling around it. This method only works if the black hole is actively feeding on nearby gas. The center of 47 Tucanae is gas-free, effectively starving any black hole that might lurk there.

    The supermassive black hole at the center of the Milky Way also betrays its presence by its influence on nearby stars. Years of infrared observations have shown a handful of stars at our galactic center whipping around an invisible object with a strong gravitational tug. But the crowded center of 47 Tucanae makes it impossible to watch the motions of individual stars.

    The new research relies on two lines of evidence. The first is overall motions of stars throughout the cluster. A globular cluster’s environment is so dense that heavier stars tend to sink to the center of the cluster. An IMBH at the cluster’s center acts like a cosmic “spoon” and stirs the pot, causing those stars to slingshot to higher speeds and greater distances. This imparts a subtle signal that astronomers can measure.

    By employing computer simulations of stellar motions and distances, and comparing them with visible-light observations, the team finds evidence for just this sort of gravitational stirring.

    The second line of evidence comes from pulsars, compact remnants of dead stars whose radio signals are easily detectable. These objects also get flung about by the gravity of the central IMBH, causing them to be found at greater distances from the cluster’s center than would be expected if no black hole existed.

    Combined, this evidence suggests the presence of an IMBH of about 2,200 solar masses within 47 Tucanae.

    Since this black hole has eluded detection for so long, similar IMBHs may be hiding in other globular clusters. Locating them will require similar data on the positions and motions of both the stars and any pulsars within the clusters.

    See the full article here .

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

     
  • richardmitnick 4:07 pm on February 2, 2017 Permalink | Reply
    Tags: , , , Black Holes, , , Tail of Stray Black Hole hiding in the Milky Way   

    From NAOJ: “Tail of Stray Black Hole hiding in the Milky Way” 

    NAOJ

    NAOJ

    2017 Feb 02
    No writer credit found

    By analyzing the gas motion of an extraordinarily fast-moving cosmic cloud in a corner of the Milky Way, astronomers found hints of a wandering black hole hidden in the cloud. This result marks the beginning of the search for quiet black holes; millions of such objects are expected to be floating in the Milky Way although only dozens have been found to date.

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    Figure 1. Artist’s impression of a stray black hole storming through a dense gas cloud. The gas is dragged along by the strong gravity of the black hole to form a narrow gas stream. Credit: Keio University

    It is difficult to find black holes, because they are completely black. In some cases black holes cause effects which can be seen. For example if a black hole has a companion star, gas streaming into the black hole piles up around it and forms a disk. The disk heats up due to the enormous gravitational pull by the black hole and emits intense radiation. But if a black hole is floating alone in space, no emissions would be observable coming from it.

    A research team led by Masaya Yamada, a graduate student at Keio University, Japan, and Tomoharu Oka, a professor at Keio University, used the ASTE Telescope in Chile and the 45-m Radio Telescope at Nobeyama Radio Observatory, both operated by the National Astronomical Observatory of Japan, to observe molecular clouds around the supernova remnant W44, located 10,000 light-years away from us. Their primary goal was to examine how much energy was transferred from the supernova explosion to the surrounding molecular gas, but they happened to find signs of a hidden black hole at the edge of W44.

    NAOJ Atacama Submillimeter Telescope Experiment (ASTE)  deployed to its site on Pampa La Bola, near Cerro Chajnantor and the Llano de Chajnantor Observatory in northern Chile
    NAOJ Atacama Submillimeter Telescope Experiment (ASTE) deployed to its site on Pampa La Bola, near Cerro Chajnantor and the Llano de Chajnantor Observatory in northern Chile

    NAOJ Nobeyama Radio Observatory, located near Minamimaki, Nagano at an elevation of 1350m
    NAOJ Nobeyama Radio Observatory, located near Minamimaki, Nagano at an elevation of 1350m

    During the survey, the team found a compact molecular cloud with enigmatic motion. This cloud, named the “Bullet,” has a speed of more than 100 km/s, which exceeds the speed of sound in interstellar space by more than two orders of magnitude. In addition, this cloud, with the size of two light-years, moves backward against the rotation of the Milky Way Galaxy.

    To investigate the origin of the Bullet, the team performed intensive observations of the gas cloud with ASTE and the Nobeyama 45-m Radio Telescope. The data indicate that the Bullet seems to jump out from the edge of the W44 supernova remnant with immense kinetic energy. “Most of the Bullet has an expanding motion with a speed of 50 km/s, but the tip of the Bullet has a speed of 120 km/s,” said Yamada. “Its kinetic energy is a few tens of times larger than that injected by the W44 supernova. It seems impossible to generate such an energetic cloud under ordinary environments.”

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    Figure 3. (a) CO (J=3-2) emissions (color) and 1.4 GHz radio continuum emissions (contours) around the supernova remnant W44. (b) Galactic longitude-velocity diagram of CO (J=3-2) emissions at the galactic latitude of -0.472 degrees. (c -f): Galactic longitude-velocity diagrams of the Bullet in CO (J=1-0), CO (J=3-2), CO (J=4-3), and HCO+ (J=1-0), from left to right. Galactic longitude-velocity diagrams show the speed of the gas at a specific position. Structures elongated in the vertical direction in the diagrams have a large velocity width. Credit: Yamada et al. (Keio University), NAOJ

    The team proposed two scenarios for the formation of the Bullet. In both cases, a dark and compact gravity source, possibly a black hole, has an important role. One scenario is the “explosion model” in which an expanding gas shell of the supernova remnant passes by a static black hole. The black hole pulls the gas very close to it, giving rise to an explosion, which accelerates the gas toward us after the gas shell has passed the black hole. In this case, the astronomers estimated that the mass of the black hole would 3.5 times the solar mass or larger. The other scenario is the “irruption model” in which a high speed black hole storms through a dense gas and the gas is dragged along by the strong gravity of the black hole to form a gas stream. In this case, researchers estimated the mass of the black hole would be 36 times the solar mass or larger. With the present dataset, it is difficult for the team to distinguish which scenario is more likely.

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    Figure 4. Schematic diagrams of two scenarios for the formation mechanism of the Bullet. (a) explosion model and (b) irruption model. Both diagrams show a part of the shock front produced by the expansion of the supernova remnant W44. The shock wave enters into quiescent gas and compresses it to form dense gas. The Bullet is located in the center of the diagram and has completely different motion compared to the surrounding gas. Yamada et al. (Keio University)

    Theoretical studies have predicted that 100 million to 1 billion black holes should exist in the Milky Way, although only 60 or so have been identified through observations to date. “We found a new way of discovering stray black holes,” said Oka. The team expects to disentangle the two possible scenarios and find more solid evidence for a black hole in the Bullet with higher resolution observations using a radio interferometer, such as the Atacama Large Millimeter/submillimeter Array (ALMA).

    These observation results were published as Yamada et al. Kinematics of Ultra-high-velocity Gas in the Expanding Molecular Shell adjacent to the W44 Supernova Remnant in the Astrophysical Journal Letters in January 2017.
    The research team members are: Masaya Yamada, Tomoharu Oka, Shunya Takekawa, Yuhei Iwata, Shiho Tsujimoto, Sekito Tokuyama, Maiko Furusawa, Keisuke Tanabe, and Mariko Nomura, from Keio University, Japan.

    This research was supported by a Grant-in-Aid from the Japan Society for the Promotion of Science (No. 15H03643).

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

    NAOJ Subaru Telescope

    NAOJ Subaru Telescope interior
    Subaru

    ALMA Array
    ALMA

    sft
    Solar Flare Telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Observatory

    Nobeyama Solar Radio Telescope Array
    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

     
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