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  • richardmitnick 11:50 am on January 27, 2020 Permalink | Reply
    Tags: "This NASA Visualisation of a Black Hole Is So Beautiful We Could Cry", , , , , EHT - Event Horizon Telescope, , ,   

    From NASA via Science Alert: “This NASA Visualisation of a Black Hole Is So Beautiful, We Could Cry” 

    From NASA

    via

    ScienceAlert

    Science Alert

    26 JAN 2020
    MICHELLE STARR

    1
    NASA Visualization Shows a Black Hole’s Warped World

    The first-ever direct image of a black hole’s event horizon was a truly impressive feat of scientific ingenuity. But it was extremely difficult to achieve, and the resulting image was relatively low-resolution.

    Mesier 87*, The first image of a black hole. First-ever direct image of a black hole, Messier 87*. (EHT Collaboration).This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    EHT map

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professor. On the committee for the next iteration of the EHT .

    Techniques and technology will be refined, and it’s expected that future direct images of black holes will improve with time. In September 2019, a NASA visualisation – made for the agency’s Black Hole Week – showed what we might expect to see in high-resolution images of an actively accreting supermassive black hole.

    Supermassive black holes sit at the centres of most large galaxies, and how they got there is a mystery; which came first, the black hole or the galaxy, is one of the big questions in cosmology.

    What we do know is that they are really huge, as in millions or billions of times the mass of the Sun; that they can control star formation; that when they wake up and start feeding, they can become the brightest objects in the Universe. Over the decades, we have also figured out some of their strange dynamics.

    In fact, the very first simulated image of a black hole, calculated using a 1960s punch card IBM 7040 computer and plotted by hand by French astrophysicist Jean-Pierre Luminet in 1978, still looks a lot like NASA’s simulation.

    In both simulations (the one above, and Luminet’s work below), you see a black circle in the centre. That’s the event horizon, the point at which electromagnetic radiation – light, radio waves, X-rays and so forth – are no longer fast enough to achieve escape velocity from the black hole’s gravitational pull.

    4
    (Jean-Pierre Luminet)

    Across the middle of the black hole is the front of the disc of material that is swirling around the black hole, like water into a drain. It generates such intense radiation through friction that we can detect this part with our telescopes – that’s what you are seeing in the picture of Messier 87*.

    You can see the photon ring, a perfect ring of light around the event horizon. And you can see a broad sweep of light around the black hole. That light is actually coming from the part of the accretion disc behind the black hole; but the gravity is so intense, even outside the event horizon, that it warps spacetime and bends the path of light around the black hole.

    You can also see that one side of the accretion disc is brighter than the other. This effect is called relativistic beaming, and it’s caused by the rotation of the disc. The part of the disc that is moving towards us is brighter because it is moving close to light-speed. This motion produces a change in frequency in the wavelength of the light. It’s called the Doppler effect.

    The side that’s moving away from us, therefore, is dimmer, because that motion has the opposite effect.

    “It is precisely this strong asymmetry of apparent luminosity,” Luminet wrote in a paper last year, “that is the main signature of a black hole, the only celestial object able to give the internal regions of an accretion disk a speed of rotation close to the speed of light and to induce a very strong Doppler effect.”

    Simulations such as these can help us understand the extreme physics around supermassive black holes – and that helps us understand what we are seeing when we look at the picture of Messier 87*.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 6:50 am on January 21, 2020 Permalink | Reply
    Tags: "The dynamic behaviour of a black hole corona", "XMM-Newton maps black hole surroundings", , , , Black hole IRAS 13224–3809, , EHT - Event Horizon Telescope, ,   

    From European Space Agency – United space in Europe (2): “The dynamic behaviour of a black hole corona” and “XMM-Newton maps black hole surroundings” 

    ESA Space For Europe Banner

    From European Space Agency – United space in Europe

    1. The dynamic behaviour of a black hole corona

    20/01/2020

    United space in Europe

    1
    XMM-Newton maps black hole surroundings. ESA

    The dynamic behaviour of a black hole corona

    These illustrations show the surroundings of a black hole feeding on ambient gas as mapped using ESA’s XMM-Newton X-ray observatory.

    ESA/XMM Newton

    As the material falls into the black hole, it spirals around to form a flattened disc, as shown here, heating up as it does so. At the very centre of the disc, close to the black hole, a region of very hot electrons – with temperatures of around a billion degrees – known as the corona produced high-energy X-rays that stream out into space.

    A new study has used the reverberating echoes of this radiation, as observed by XMM-Newton, to map the surroundings of a black hole. The study focussed on the black hole at the core of an active galaxy named IRAS 13224–3809, which is one of the most variable X-ray sources in the sky, undergoing very large and rapid fluctuations in brightness of a factor of 50 in mere hours.

    By tracking the X-ray echoes, it was possible to track the dynamic behaviour of the corona itself, where the intense X-ray emission originates from. The corona is shown here as the bright region hovering over the black hole, changing in size and brightness. The study found that the corona of the black hole within IRAS 13224–3809 changed in size incredibly quickly, over a matter of days.

    The Full Story

    2. XMM-Newton maps black hole surroundings

    20/01/2020

    William Alston
    Institute of Astronomy
    University of Cambridge, UK
    Email: wna@ast.cam.ac.uk

    Michael Parker
    European Space Agency
    European Space Astronomy Centre
    Villanueva de la Cañada, Madrid, Spain
    Email: Michael.Parker@esa.int

    Norbert Schartel
    XMM-Newton project scientist
    European Space Agency
    Email: norbert.schartel@esa.int

    Material falling into a black hole casts X-rays out into space – and now, for the first time, ESA’s XMM-Newton X-ray observatory [above] has used the reverberating echoes of this radiation to map the dynamic behaviour and surroundings of a black hole itself.

    Most black holes are too small on the sky for us to resolve their immediate environment, but we can still explore these mysterious objects by watching how matter behaves as it nears, and falls into, them.

    As material spirals towards a black hole, it is heated up and emits X-rays that, in turn, echo and reverberate as they interact with nearby gas. These regions of space are highly distorted and warped due to the extreme nature and crushingly strong gravity of the black hole.

    For the first time, researchers have used XMM-Newton to track these light echoes and map the surroundings of the black hole at the core of an active galaxy. Named IRAS 13224–3809, the black hole’s host galaxy is one of the most variable X-ray sources in the sky, undergoing very large and rapid fluctuations in brightness of a factor of 50 in mere hours.

    “Everyone is familiar with how the echo of their voice sounds different when speaking in a classroom compared to a cathedral – this is simply due to the geometry and materials of the rooms, which causes sound to behave and bounce around differently,” explains William Alston of the University of Cambridge, UK, lead author of the new study.

    “In a similar manner, we can watch how echoes of X-ray radiation propagate in the vicinity of a black hole in order to map out the geometry of a region and the state of a clump of matter before it disappears into the singularity. It’s a bit like cosmic echo-location.”

    As the dynamics of infalling gas are strongly linked to the properties of the consuming black hole, William and colleagues were also able to determine the mass and spin of the galaxy’s central black hole by observing the properties of matter as it spiralled inwards.

    The inspiralling material forms a disc as it falls into the black hole. Above this disc lies a region of very hot electrons – with temperatures of around a billion degrees – called the corona. While the scientists expected to see the reverberation echoes they used to map the region’s geometry, they also spotted something unexpected: the corona itself changed in size incredibly quickly, over a matter of days.

    “As the corona’s size changes, so does the light echo – a bit like if the cathedral ceiling is moving up and down, changing how the echo of your voice sounds,” adds William.

    “By tracking the light echoes, we were able to track this changing corona, and – what’s even more exciting – get much better values for the black hole’s mass and spin than we could have determined if the corona was not changing in size. We know the black hole’s mass cannot be fluctuating, so any changes in the echo must be down to the gaseous environment.”

    The study used the longest observation of an accreting black hole ever taken with XMM-Newton, collected over 16 spacecraft orbits in 2011 and 2016 and totalling 2 million seconds – just over 23 days.

    This, combined with the strong and short-term variability of the black hole itself, allowed William and collaborators to model the echoes comprehensively over day-long timescales.

    The region explored in this study is not accessible to observatories such as the Event Horizon Telescope [EHT], which managed to take the first ever picture of gas in the immediate vicinity of a black hole – the one sitting at the centre of the nearby massive galaxy Messier 87.

    EHT map

    The result, based on observations performed with radio telescopes across the world in 2017 and published last year, immediately became a global sensation.

    M87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professional. On the committee for the next iteration of the EHT .

    “The Event Horizon Telescope image was obtained using a method known as interferometry – a wonderful technique that can only work on the very few nearest supermassive black holes to Earth, such as those in Messier 87 and in our home galaxy, the Milky Way, because their apparent size on the sky is large enough for this method to work,” says co-author Michael Parker, who is an ESA research fellow at the European Space Astronomy Centre near Madrid, Spain.

    “By contrast, our approach is able to probe the nearest few hundred supermassive black holes that are actively consuming matter – and this number will increase significantly with the launch of ESA’s Athena satellite.”

    ESA/Athena spacecraft depiction

    Characterising the environments closely surrounding black holes is a core science goal for ESA’s Athena mission, which is scheduled for launch in the early 2030s and will unveil the secrets of the hot and energetic Universe.

    Measuring the mass, spin and accretion rates of a large sample of black holes is key to understanding gravity throughout the cosmos.

    Additionally, since supermassive black holes are strongly linked to their host galaxy’s properties, these studies are also key to furthering our knowledge of how galaxies form and evolve over time.

    “The large dataset provided by XMM-Newton was essential for this result,” says Norbert Schartel, ESA XMM-Newton Project Scientist.

    “Reverberation mapping is an exciting technique that promises to reveal much about both black holes and the wider Universe in coming years. I hope that XMM-Newton will perform similar observing campaigns for several more active galaxies in coming years, so that the method is fully established when Athena launches.”

    Science paper:
    A dynamic black hole corona in an active galaxy through X-ray reverberation mapping by W. N. Alston et al.
    Nature Astronomy.

    The study uses data gathered by XMM-Newton’s European Photon Imaging Camera (EPIC).

    See the “dynamic behaviour”full article here .

    See the “Full Story” article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    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 2:21 pm on December 28, 2019 Permalink | Reply
    Tags: , , , , , EHT - Event Horizon Telescope, , Event Horizon, ,   

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

    From Ethan Siegel
    Dec 28, 2019

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

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

    Do black holes ever spit things out at any time?

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

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

    1
    The second-largest black hole as seen from Earth, the one at the center of the galaxy Messier 87, is shown in three views here. At the top is optical from Hubble, at the lower-left is radio from NRAO, and at the lower-right is X-ray from Chandra. These differing views have different resolutions dependent on the optical sensitivity, wavelength of light used, and size of the telescope mirrors used to observe them. These are all examples of radiation emitted from the regions around black holes, demonstrating that black holes aren’t so black, after all. (TOP, OPTICAL, HUBBLE SPACE TELESCOPE / NASA / WIKISKY; LOWER LEFT, RADIO, NRAO / VERY LARGE ARRAY (VLA); LOWER RIGHT, X-RAY, NASA / CHANDRA X-RAY TELESCOPE)

    NASA/ESA Hubble Telescope

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

    NASA/Chandra X-ray Telescope

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

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

    2
    When a black hole and a companion star orbit one another, the star’s motion will change over time owing to the gravitational influence of the black hole, while matter from the star can accrete onto the black hole, resulting in X-ray and radio emissions. (JINGCHUAN YU/BEIJING PLANETARIUM/2019)

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

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

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

    3
    Black holes are not isolated objects in space, but exist amidst the matter and energy in the Universe, galaxy, and star systems where they reside. They grow by accreting and devouring matter and energy, and when they actively feed they emit X-rays. Binary black hole systems that emit X-rays are how the majority of our known non-supermassive black holes were discovered. (NASA/ESA HUBBLE SPACE TELESCOPE COLLABORATION)

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

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

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

    4
    While distant host galaxies for quasars and active galactic nuclei can often be imaged in visible/infrared light, the jets themselves and the surrounding emission is best viewed in both the X-ray and the radio, as illustrated here for the galaxy Hercules A. The gaseous outflows are highlighted in the radio, and if X-ray emissions follow the same path into the gas, they can be responsible for creating hot spots owing to the acceleration of electrons. (NASA, ESA, S. BAUM AND C. O’DEA (RIT), R. PERLEY AND W. COTTON (NRAO/AUI/NSF), AND THE HUBBLE HERITAGE TEAM (STSCI/AURA))

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

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

    5
    An illustration of an active black hole, one that accretes matter and accelerates a portion of it outwards in two perpendicular jets. The normal matter undergoing an acceleration like this describes how quasars work extremely well, while the accretion flows are ultimately responsible for the emitted particles and radiation we observe. (MARK A. GARLICK)

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

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

    6
    The galaxy Centaurus A, shown in a composite of visible light, infrared (submillimeter) light and in the X-ray. This is the nearest active galaxy to the Milky Way, and its bipolar jets are thought to arise from the active, feeding black hole inside. (ESO/WFI (OPTICAL); MPIFR/ESO/APEX/A.WEISS ET AL. (SUBMILLIMETRE); NASA/CXC/CFA/R.KRAFT ET AL. (X-RAY))

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

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

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

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

    The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Event Horizon Telescope Array

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

    ESO/APEX
    Atacama Pathfinder EXperiment

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

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

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

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


    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

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

    Submillimeter Array Hawaii SAO

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

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

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

    NSF CfA Greenland telescope


    Greenland Telescope

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


    ARO 12m Radio Telescope

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

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

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

    8
    In the vicinity of a black hole, space flows like either a moving walkway or a waterfall, depending on how you want to visualize it. At the event horizon, even if you ran (or swam) at the speed of light, there would be no overcoming the flow of spacetime, which drags you into the singularity at the center. Outside the event horizon, though, other forces (like electromagnetism) can frequently overcome the pull of gravity, causing even infalling matter to escape. (ANDREW HAMILTON / JILA / UNIVERSITY OF COLORADO)

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

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

    9
    Visualization of a quantum field theory calculation showing virtual particles in the quantum vacuum. (Specifically, for the strong interactions.) Even in empty space, this vacuum energy is non-zero, and what appears to be the ‘ground state’ in one region of curved space will look different from the perspective of an observer where the spatial curvature differs. (DEREK LEINWEBER)

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

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

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

    9
    The event horizon of a black hole is a spherical or spheroidal region from which nothing, not even light, can escape. But outside the event horizon, the black hole is predicted to emit radiation. Hawking’s 1974 work was the first to demonstrate this, and it was arguably his greatest scientific achievement. (NASA; DANA BERRY, SKYWORKS DIGITAL, INC.)

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

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

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

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

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

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 9:58 am on December 25, 2019 Permalink | Reply
    Tags: , , , , , EHT - Event Horizon Telescope, , ,   

    From ALMA: “In the Shadow of a Black Hole” 

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

    From ALMA

    10 April, 2019

    Nicolás Lira
    Education and Public Outreach Coordinator
    Joint ALMA Observatory, Santiago – Chile
    Phone: +56 2 2467 6519
    Cell phone: +56 9 9445 7726
    Email: nicolas.lira@alma.cl

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
, Tokyo – Japan
    Phone: +81 422 34 3630
    Email: hiramatsu.masaaki@nao.ac.jp

    Bárbara Ferreira
    ESO Public Information Officer
    Garching bei München, Germany
    Phone: +49 89 3200 6670
    Email: pio@eso.org

    Iris Nijman
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Cell phone: +1 (434) 249 3423
    Email: alma-pr@nrao.edu

    The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. In coordinated press conferences across the globe, EHT researchers revealed that they succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.
    This 17-minute film explores the efforts that led to this historic image, from the science of Einstein and Schwarzschild to the struggles and successes of the EHT collaboration. Credit:ESO

    Event Horizon Telescope Array

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

    ESO/APEX
    Atacama Pathfinder EXperiment

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

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

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

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


    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

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

    Submillimeter Array Hawaii SAO

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

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

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

    NSF CfA Greenland telescope


    Greenland Telescope

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


    ARO 12m Radio Telescope

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

    The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Katie Bouman-Harvard Smithsonian Astrophysical Observatory. Headed to Caltech.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small
    ESO 50 Large

     
  • richardmitnick 4:27 pm on June 20, 2019 Permalink | Reply
    Tags: , , , , , EHT - Event Horizon Telescope   

    From Discover Magazine: “The Event Horizon Telescope’s Possible Next Target? Blazars” 

    DiscoverMag

    From Discover Magazine

    June 20, 2019
    Korey Haynes

    1
    A blazar is an active black hole hurling jets of material directly at Earth. (Credit: NASA/Goddard Space Flight Center/CI Lab)

    The Event Horizon Telescope made history on April 10 when it captured the first image of a supermassive black hole’s event horizon at the heart of galaxy Messier 87.

    2

    While there’s only one other target close enough to image that way – the black hole at the center of our own Milky Way – there are plenty of other targets where EHT’s sharp gaze can still make breakthroughs.

    Astronomers are proposing to use EHT to image the jets of a blazar called PKS 1510-089 more than 4 billion light-years away. A blazar is one of many names for a black hole that is actively consuming material, resulting in high-energy jets shooting out of the top or bottom of the black hole. With a blazar, the jets are pointed almost directly at Earth, making them especially bright.

    This particular blazar is one of the brightest known, and it’s also highly variable, meaning its brightness changes on short time scales. Many blazars vary on the scale of months to days, but PKS 1510-089 varies on the scale of minutes to hours. Scientists think the powerful, variable jets are the result of the black hole twisting magnetic field lines, but they’ve lacked the technology to peer close enough to discern the details — until now.

    Nicholas MacDonald, from Germany’s Max Planck Institute for Radio Astronomy, presented the case for observing PKS 1510-089 with EHT on June 20 at the annual meeting of the Canadian Astronomical Society in Montreal, Quebec, Canada.

    Bright jets

    In 2008, the Fermi Gamma-Ray Telescope launched, opening a new era of exploration of the high-energy universe. “The big discovery of the last decade,” says MacDonald, “was that blazars dominate the gamma-ray sky. These classes of objects are all bright, but [PKS 1510-089] is one of the brightest.”

    That makes it a good target for EHT, which is a network of telescopes spanning the globe, acting together as one giant telescope the size of the planet. MacDonald wants to use EHT plus ALMA, a radio observatory in Chile composed of yet another 66 telescopes networked together. The ALMA array is much smaller in overall size though, spreading out across only between 500 feet and 10 miles, depending on the movable telescopes’ configuration.

    The problem with EHT acting as one telescope the size of the planet is that it’s not actually one telescope. It’s a telescope with massive holes in it, and that makes the data less reliable. Because ALMA is farther south than most of the EHT telescopes, and is composed of a dense cluster of telescopes itself, it can drastically improve EHT’s results by essentially filling in gaps in EHT’s coverage.

    Event Horizon Telescope Array

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

    ESO/APEX
    Atacama Pathfinder EXperiment

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

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

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

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


    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

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

    Submillimeter Array Hawaii SAO

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

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

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

    NSF CfA Greenland telescope


    Greenland Telescope

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


    ARO 12m Radio Telescope

    Astronomers ultimately hope to understand what creates the powerful jets they observe, and that means taking the closer look with EHT.

    “The idea is you have a central supermassive black hole, millions of times the mass of the sun,” MacDonald explains. The black hole is not just consuming gas and dust in a whirlpool, but yanking spacetime itself along for the ride. Researchers think the jets are produced when magnetic fields also get caught and twisted up in this motion, launching relativistic beams of charged material. But they don’t know what it looks like in detail.

    D-brief

    « Third Falcon Heavy Launch Set for Next Week A Molecule Long Thought Harmless Plays a Role in Pancreatic Cancer, Could Hint at Cure »
    The Event Horizon Telescope’s Possible Next Target? Blazars
    By Korey Haynes | June 20, 2019 12:30 pm
    1
    flat disk of material with jet shooting out perpindicular
    A blazar is an active black hole hurling jets of material directly at Earth. (Credit: NASA/Goddard Space Flight Center/CI Lab)

    The Event Horizon Telescope made history on April 10 when it captured the first image of a supermassive black hole’s event horizon at the heart of galaxy M87. While there’s only one other target close enough to image that way – the black hole at the center of our own Milky Way – there are plenty of other targets where EHT’s sharp gaze can still make breakthroughs.

    Astronomers are proposing to use EHT to image the jets of a blazar called PKS 1510-089 more than 4 billion light-years away. A blazar is one of many names for a black hole that is actively consuming material, resulting in high-energy jets shooting out of the top or bottom of the black hole. With a blazar, the jets are pointed almost directly at Earth, making them especially bright.

    This particular blazar is one of the brightest known, and it’s also highly variable, meaning its brightness changes on short time scales. Many blazars vary on the scale of months to days, but PKS 1510-089 varies on the scale of minutes to hours. Scientists think the powerful, variable jets are the result of the black hole twisting magnetic field lines, but they’ve lacked the technology to peer close enough to discern the details — until now.

    Nicholas MacDonald, from Germany’s Max Planck Institute for Radio Astronomy, presented the case for observing PKS 1510-089 with EHT on June 20 at the annual meeting of the Canadian Astronomical Society in Montreal, Quebec, Canada.
    Bright jets

    In 2008, the Fermi Gamma-Ray Telescope launched, opening a new era of exploration of the high-energy universe. “The big discovery of the last decade,” says MacDonald, “was that blazars dominate the gamma-ray sky. These classes of objects are all bright, but [PKS 1510-089] is one of the brightest.”

    That makes it a good target for EHT, which is a network of telescopes spanning the globe, acting together as one giant telescope the size of the planet. MacDonald wants to use EHT plus ALMA, a radio observatory in Chile composed of yet another 66 telescopes networked together. The ALMA array is much smaller in overall size though, spreading out across only between 500 feet and 10 miles, depending on the movable telescopes’ configuration.

    The problem with EHT acting as one telescope the size of the planet is that it’s not actually one telescope. It’s a telescope with massive holes in it, and that makes the data less reliable. Because ALMA is farther south than most of the EHT telescopes, and is composed of a dense cluster of telescopes itself, it can drastically improve EHT’s results by essentially filling in gaps in EHT’s coverage.

    Astronomers ultimately hope to understand what creates the powerful jets they observe, and that means taking the closer look with EHT.

    “The idea is you have a central supermassive black hole, millions of times the mass of the sun,” MacDonald explains. The black hole is not just consuming gas and dust in a whirlpool, but yanking spacetime itself along for the ride. Researchers think the jets are produced when magnetic fields also get caught and twisted up in this motion, launching relativistic beams of charged material. But they don’t know what it looks like in detail.

    “Is it highly ordered, or disordered?” MacDonald wonders. The options are that the magnetic field lines are either turbulent and snarled, or, alternatively, highly ordered in a helical structure. Theorists can reproduce the blazar behavior observed by telescopes with either ordered or disordered computer models of the magnetic fields. So they need to look closer to figure out what’s really going on.

    “The big game changer is ALMA,” MacDonald says, and especially ALMA’s cooperation with the other EHT telescopes. “And so we’re able to – for the first time – resolve down to the scales where we can distinguish where the field is ordered or disordered.”

    MacDonald was approved once for these observations, but weather at multiple points around the globe cheated him of his images. He’s trying again, and the observations, if approved, would be taken sometime between October 2019 and September 2020.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 4:16 pm on May 11, 2019 Permalink | Reply
    Tags: , , , , EHT - Event Horizon Telescope,   

    From Ethan Siegel: “How Does The Event Horizon Telescope Act Like One Giant Mirror?” 

    From Ethan Siegel
    May 11, 2019

    1
    The Allen Telescope Array is potentially capable of detecting a strong radio signal from Proxima b, or any other star system with strong enough radio transmissions. It has successfully worked in concert with other radio telescopes across extremely long baselines to resolve the event horizon of a black hole: arguably its crowning achievement. (WIKIMEDIA COMMONS / COLBY GUTIERREZ-KRAYBILL)

    If you want to observe the Universe more deeply and at higher resolution than ever before, there’s one tactic that everyone agrees is ideal: build as big a telescope as possible. But the highest resolution image we’ve ever constructed in astronomy doesn’t come from the biggest telescope, but rather from an enormous array of modestly-sized telescopes: the Event Horizon Telescope. How is that possible? That’s what our Ask Ethan questioner for this week, Dieter, wants to know, stating:

    “I’m having difficulty understanding why the EHT array is considered as ONE telescope (which has the diameter of the earth).
    When you consider the EHT as ONE radio telescope, I do understand that the angular resolution is very high due to the wavelength of the incoming signal and earth’s diameter. I also understand that time syncing is critical.
    But it would help very much to explain why the diameter of the EHT is considered as ONE telescope, considering there are about 10 individual telescopes in the array.”

    It’s made up of scores of telescopes at many different sites across the world. But it acts like one giant telescope. Here’s how.

    Event Horizon Telescope Array

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

    ESO/APEX
    Atacama Pathfinder EXperiment

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

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

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

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


    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

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

    Submillimeter Array Hawaii SAO

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

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

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

    NSF CfA Greenland telescope


    Greenland Telescope

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


    ARO 12m Radio Telescope

    Constructing an image of the black hole at the center of Messier 87 is one of the most remarkable achievements we’ve ever made. Here’s what made it possible.

    2
    The brightness distance relationship, and how the flux from a light source falls off as one over the distance squared. The Earth has the temperature that it does because of its distance from the Sun, which determines how much energy-per-unit-area is incident on our planet. Distant stars or galaxies have the apparent brightness they do because of this relationship, which is demanded by energy conservation. Note that the light also spreads out in area as it leaves the source. (E. SIEGEL / BEYOND THE GALAXY)

    The first thing you need to understand is how light works. When you have any light-emitting object in the Universe, the light it emits will spread out in a sphere upon leaving the source. If all you had was a photo-detector that was a single point, you could still detect that distant, light-emitting object.

    But you wouldn’t be able to resolve it.

    When light (i.e., a photon) strikes your point-like detector, you can register that the light arrived; you can measure the light’s energy and wavelength; you can know what direction the light came from. But you wouldn’t be able to know anything about that object’s physical properties. You wouldn’t know its size, shape, physical extent, or whether different parts were different colors or brightnesses. This is because you’re only receiving information at a single point.

    3
    Nebula NGC 246 is better known as the Skull Nebula, for the presence of its two glowing eyes. The central eye is actually a pair of binary stars, and the smaller, fainter one is responsible for the nebula itself, as it blows off its outer layers. It’s only 1,600 light-years away, in the constellation of Cetus. Seeing this as more than a single object requires the ability to resolve these features, dependent on the size of the telescope and the number of wavelengths of light that fit across its primary mirror. (GEMINI SOUTH GMOS, TRAVIS RECTOR (UNIV. ALASKA))

    Gemini Observatory GMOS on Gemini South


    Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    What would it take to know whether you were looking at a single point of light, such as a star like our Sun, or multiple points of light, like you’d find in a binary star system? For that, you’d need to receive light at multiple points. Instead of a point-like detector, you could have a dish-like detector, like the primary mirror on a reflecting telescope.

    When the light comes in, it’s not striking a point anymore, but rather an area. The light that had spread out in a sphere now gets reflected off of the mirror and focused to a point. And light that comes from two different sources, even if they’re close together, will be focused to two different locations.

    3
    Any reflecting telescope is based on the principle of reflecting incoming light rays via a large primary mirror which focuses that light to a point, where it’s then either broken down into data and recorded or used to construct an image. This specific diagram illustrates the light-paths for a Herschel-Lomonosov telescope system. Note that two distinct sources will have their light focused to two distinct locations (blue and green paths), but only if the telescope has sufficient capabilities. (WIKIMEDIA COMMONS USER EUDJINNIUS)

    If your telescope mirror is large enough compared to the separation of the two objects, and your optics are good enough, you’ll be able to resolve them. If you build your apparatus right, you’ll be able to tell that there are multiple objects. The two sources of light will appear to be distinct from one another. Technically, there’s a relationship between three quantities:

    the angular resolution you can achieve,
    the diameter of your mirror,
    and the wavelength of light you’re looking in.

    If your sources are closer together, or your telescope mirror is smaller, or you look using a longer wavelength of light, it becomes more and more challenging to resolve whatever you’re looking at. It makes it harder to resolve whether there are multiple objects or not, or whether the object you’re viewing has bright-and-dark features. If your resolution is insufficient, everything appears as nothing more than a blurry, unresolved single spot.

    4
    The limits of resolution are determined by three factors: the diameter of your telescope, the wavelength of light your viewing in, and the quality of your optics. If you have perfect optics, you can resolve all the way down to the Rayleigh limit, which grants you the highest-possible resolution allowed by physics. (SPENCER BLIVEN / PUBLIC DOMAIN)

    So that’s the basics of how any large, single-dish telescope works. The light comes in from the source, with every point in space — even different points originating from the same object — emitting its own light with its own unique properties. The resolution is determined by the number of wavelengths of light that can fit across our primary mirror.

    If our detectors are sensitive enough, we’ll be able to resolve all sorts of features on an object. Hot-and-cold regions of a star, like sunspots, can appear. We can make out features like volcanoes, geysers, icecaps and basins on planets and moons. And the extent of light-emitting gas or plasma, along with their temperatures and densities, can be imaged as well. It’s a fantastic achievement that only depends on the physical and optical properties of your telescope.

    4
    The second-largest black hole as seen from Earth, the one at the center of the galaxy Messier 87, is shown in three views here. At the top is optical from Hubble, at the lower-left is radio from NRAO, and at the lower-right is X-ray from Chandra. These differing views have different resolutions dependent on the optical sensitivity, wavelength of light used, and size of the telescope mirrors used to observe them. The Chandra X-ray observations provide exquisite resolution despite having an effective 8-inch (20 cm) diameter mirror, owing to the extremely short-wavelength nature of the X-rays it observes. (TOP, OPTICAL, HUBBLE SPACE TELESCOPE / NASA / WIKISKY; LOWER LEFT, RADIO, NRAO / VERY LARGE ARRAY (VLA); LOWER RIGHT, X-RAY, NASA / CHANDRA X-RAY TELESCOPE)

    NASA/ESA Hubble Telescope

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

    NASA/Chandra X-ray Telescope

    But maybe you don’t need the entire telescope. Building a giant telescope is expensive and resource intensive, and it actually serves two purposes to build them so large.

    The larger your telescope, the better your resolution, based on the number of wavelengths of light that fit across your primary mirror.
    The larger your telescope’s collecting area, the more light you can gather, which means you can observe fainter objects and finer details than you could with a lower-area telescope.

    If you took your large telescope mirror and started darkening out some spots — like you were applying a mask to your mirror — you’d no longer be able to receive light from those locations. As a result, the brightness limits on what you could see would decrease, in proportion to the surface area (light-gathering area) of your telescope. But the resolution would still be equal to the separation between the various portions of the mirror.

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


    ALMA is perhaps the most advanced and most complex array of radio telescopes in the world, is capable of imaging unprecedented details in protoplanetary disks, and is also an integral part of the Event Horizon Telescope.

    This is the principle on which arrays of telescopes are based. There are many sources out there, particularly in the radio portion of the spectrum, that are extremely bright, so you don’t need all that collecting area that comes with building an enormous, single dish.

    Instead, you can build an array of dishes. Because the light from a distant source will spread out, you want to collect light over as large an area as possible. You don’t need to invest all your resources in constructing an enormous dish with supreme light-gathering power, but you still need that same superior resolution. And that’s where the idea of using a giant array of radio telescopes comes from. With a linked array of telescopes all over the world, we can resolve some of the radio-brightest but smallest angular-size objects out there.

    EHT map

    This diagram shows the location of all of the telescopes and telescope arrays used in the 2017 Event Horizon Telescope observations of M87. Only the South Pole Telescope was unable to image M87, as it is located on the wrong part of the Earth to ever view that galaxy’s center. Every one of these locations is outfitted with an atomic clock, among other pieces of equipment. (NRAO)

    Functionally, there is no difference between thinking about the following two scenarios.

    The Event Horizon Telescope is a single mirror with a lot of masking tape over portions of it. The light gets collected and focused from all these disparate locations across the Earth into a single point, and then synthesized together into an image that reveals the differing brightnesses and properties of your target in space, up to your maximal resolution.
    The Event Horizon Telescope is itself an array of many different individual telescopes and individual telescope arrays. The light gets collected, timestamped with an atomic clock (for syncing purposes), and recorded as data at each individual site. That data is then stitched-and-processed together appropriately to create an image that reveals the brightnesses and properties of whatever you’re looking at in space.

    The only difference is in the techniques you have to use to make it happen, but that’s why we have the science of VLBI: very long-baseline interferometry.

    9
    In VLBI, the radio signals are recorded at each of the individual telescopes before being shipped to a central location. Each data point that’s received is stamped with an extremely accurate, high-frequency atomic clock alongside the data in order to help scientists get the synchronization of the observations correct. (PUBLIC DOMAIN / WIKIPEDIA USER RNT20)

    You might immediately start thinking of wild ideas, like launching a radio telescope into deep space and using that, networked with the telescopes on Earth, to extend your baseline. It’s a great plan, but you must understand that there’s a reason we didn’t just build the Event Horizon Telescope with two well-separated sites: we want that incredible resolution in all directions.

    We want to get full two-dimensional coverage of the sky, which means ideally we’d have our telescopes arranged in a large ring to get those enormous separations. That’s not feasible, of course, on a world with continents and oceans and cities and nations and other borders, boundaries and constraints. But with eight independent sites across the world (seven of which were useful for the M87 image), we were able to do incredibly well.

    10
    The Event Horizon Telescope’s first released image achieved resolutions of 22.5 microarcseconds, enabling the array to resolve the event horizon of the black hole at the center of M87. A single-dish telescope would have to be 12,000 km in diameter to achieve this same sharpness. Note the differing appearances between the April 5/6 images and the April 10/11 images, which show that the features around the black hole are changing over time. This helps demonstrate the importance of syncing the different observations, rather than just time-averaging them. (EVENT HORIZON TELESCOPE COLLABORATION)

    Right now, the Event Horizon Telescope is limited to Earth, limited to the dishes that are presently networked together, and limited by the particular wavelengths it can measure. If it could be modified to observe at shorter wavelengths, and could overcome the atmospheric opacity at those wavelengths, we could achieve higher resolutions with the same equipment. In principle, we might be able to see features three-to-five times as sharp without needing a single new dish.

    By making these simultaneous observations all across the world, the Event Horizon Telescope really does behave as a single telescope. It only has the light-gathering power of the individual dishes added together, but can achieve the resolution of the distance between the dishes in the direction that the dishes are separated.

    By spanning the diameter of Earth with many different telescopes (or telescope arrays) simultaneously, we were able to obtain the data necessary to resolve the event horizon.

    The Event Horizon Telescope behaves like a single telescope because of the incredible advances in the techniques we use and the increases in computational power and novel algorithms that enable us to synthesize this data into a single image. It’s not an easy feat, and took a team of over 100 scientists working for many years to make it happen.

    But optically, the principles are the same as using a single mirror. We have light coming in from different spots on a single source, all spreading out, and all arriving at the various telescopes in the array. It’s just as though they’re arriving at different locations along an extremely large mirror. The key is in how we synthesize that data together, and use it to reconstruct an image of what’s actually occurring.

    Now that the Event Horizon Telescope team has successfully done exactly that, it’s time to set our sights on the next target: learning as much as we can about every black hole we’re capable of viewing. Like all of you, I can hardly wait.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 12:22 pm on May 11, 2019 Permalink | Reply
    Tags: BlackHoleCam project, EHI-Event Horizon Imager, EHT - Event Horizon Telescope, , , Radboud Universiteit Nijmegen, Radio telescopes in space   

    From From Radboud Universiteit Nijmegen via EurekAlert “Telescopes in space for even sharper images of black holes” 

    From From Radboud Universiteit Nijmegen

    via

    6-May-2019

    Freek Roelofs
    f.roelofs@astro.ru.nl
    31-243-652-808

    Astronomers have just managed to take the first image of a black hole, and now the next challenge facing them is how to take even sharper images, so that Einstein’s Theory of General Relativity can be tested. Radboud University astronomers, along with the European Space Agency (ESA) and others, are putting forward a concept for achieving this by launching radio telescopes into space. They publish their plans in the scientific journal Astronomy & Astrophysics.

    The idea is to place two or three satellites in circular orbit around the Earth to observe black holes. The concept goes by the name Event Horizon Imager (EHI). In their new study, the scientists present simulations of what images of the black hole Sagittarius A* would look if they were taken by satellites like these.

    2
    In space, the EHI has a resolution more than five times that of the EHT on earth, and images can be reconstructed with higher fidelity. Top left: Model of Sagittarius A* at an observation frequency of 230 GHz. Top right: Simulation of an image of this model with the EHT. Bottom left: Model of Sagittarius A* at an observation frequency of 690 GHz. Bottom right: Simulation of an image of this model with the EHI.
    Credit F. Roelofs and M. Moscibrodzka, Radboud University

    More than five times as sharp

    “There are lots of advantages to using satellites instead of permanent radio telescopes on Earth, as with the Event Horizon Telescope (EHT),” says Freek Roelofs, a PhD candidate at Radboud University and the lead author of the article. “In space, you can make observations at higher radio frequencies, because the frequencies from Earth are filtered out by the atmosphere. The distances between the telescopes in space are also larger. This allows us to take a big step forward. We would be able to take images with a resolution more than five times what is possible with the EHT.”

    Sharper images of a black hole will lead to better information that could be used to test Einstein’s Theory of General Relativity in greater detail. “The fact that the satellites are moving round the Earth makes for considerable advantages,” Radio Astronomy Professor Heino Falcke says. “With them, you can take near perfect images to see the real details of black holes. If small deviations from Einstein’s theory occur, we should be able to see them.”

    The EHI will also be able to image about five additional black holes that are smaller than the black holes that the EHT is currently focussing on. The latter are Sagittarius A* at the centre of our Milky Way and Messier 87* at the centre of Messier 87, a massive galaxy in the Virgo Cluster.

    Technological challenges

    The researchers have simulated what they would be able to see with different versions of the technology under different circumstances. For this they made use of models of plasma behaviour around the black hole and the resulting radiation. “The simulations look promising from a scientific aspect, but there are difficulties to overcome at a technical level,” Roelofs says.

    The astronomers collaborated with scientists from ESA/ESTEC to investigate the technical feasibility of the project.

    ESA Estec

    “The concept demands that you must be able to ascertain the position and speed of the satellites very accurately,” according to Volodymyr Kudriashov, a researcher at the Radboud Radio Lab who also works at ESA/ESTEC. “But we really believe that the project is feasible.”

    Consideration also has to be given to how the satellites exchange data. “With the EHT, hard drives with data are transported to the processing centre by airplane. That’s of course not possible in space.” In this concept, the satellites will exchange data via a laser link, with the data being partially processed on board before being sent back to Earth for further analysis. “There are already laser links in space,” Kudriashov notes.

    Hybrid system

    The idea is that the satellites will initially function independently of the EHT telescopes. But consideration is also being given to a hybrid system, with the orbiting telescopes combined with the ones on Earth. Falcke: “Using a hybrid like this could provide the possibility of creating moving images of a black hole, and you might be able to observe even more and also weaker sources.”

    The research is part of the BlackHoleCam project, which is an ERC Synergy Grant awarded in 2013 to a team of European astrophysicists to image, measure and understand black holes. BlackHoleCam is an active partner of the Event Horizon Telescope collaboration.

    See the full article here .

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    Radboud University has seven faculties and enrols over 19.900 students in 112 study programs (37 bachelor’s and 75 master’s programs).[8]

    As of September 2013, the university offers 36 international master’s programs taught in English and several more taught in Dutch. There are nine bachelor’s programs taught fully in English: American Studies, Artificial Intelligence, Biology, Chemistry, Computing Science, International Economics & Business, International Business Administration, English Language and Culture, and Molecular Life Sciences. International Business Communication, Psychology and Arts and Culture Studies offer English-language tracks. All other bachelors are in Dutch, although most of the required literature is in English. Some exams, papers and even classes may be in English as well, despite the programs being Dutch-taught. All master’s programs have been internationally accredited by the Accreditation Organization of the Netherlands and Flanders (NVAO).

     
  • richardmitnick 11:54 am on April 12, 2019 Permalink | Reply
    Tags: , , , , EHT - Event Horizon Telescope, ,   

    From ESOblog: “Photographing a black hole” 

    ESO 50 Large

    From ESOblog

    Messier 87 supermassive black hole from the EHT

    10 April 2019

    Today, the Event Horizon Telescope team announced that they have “imaged” a black hole for the first time ever. The black hole lies 55 million light-years away at the centre of the massive galaxy Messier 87. Such an incredible feat has taken decades of collaboration between people and telescopes around the world — requiring patience, persistence and perseverance. And the story doesn’t end here. Rubén Herrero-Illana and Hugo Messias, two ESO/ALMA fellows, tell us about how they were involved at the front line of this endeavour, and about the enormous efforts involved in such an astonishing achievement.

    Q. Firstly, could you tell us a bit more about the Event Horizon Telescope?

    Rubén Herrero-Illana (RHI): The Event Horizon Telescope — or EHT — is an experiment that uses eight telescopes around the world to observe some of the closest supermassive black holes with an unprecedented resolution. The scientific goal of the EHT is to find out what happens in the extreme environments around supermassive black holes, which are some of the most intriguing objects in the Universe.

    The EHT uses a technique called very long baseline interferometry (VLBI), in which we make several radio telescopes, separated by thousands of kilometres, observe the same object in the sky simultaneously. By combining the signals from each telescope in a particular way, we are able to mimic a telescope as large as the Earth. To explain just how amazing this is — the resolution that we obtain this way would allow us to stand in Chile and see through the eye of a needle in Spain!

    The participating stations in the EHT include ESO’s APEX telescope and ALMA, which ESO is a partner in.

    3
    Consisting of 66 antennas, ALMA is revolutionising the way that we see the Universe. As well as helping to image black holes, ALMA gives astronomers an unprecedented capability to study the cool Universe — molecular gas and dust as well as the relic radiation of the Big Bang. ALMA studies the building blocks of stars, planetary systems, galaxies, and life itself. Credit: ESO/S. Guisard (www.eso.org/~sguisard)

    Q. What were your roles in the project?

    RHI: For the last two years, we have been involved in the preparation and execution of the observations at ALMA. This involves actually observing on site using the telescope. We have also been part of the group that calibrates the ALMA data and checks their quality before sending them to the correlators, which are the supercomputers th combine the signals from every station.

    Q. What do you mean by ‘calibrating’ the data?

    Hugo Messias (HM): We correct the raw data from the telescope for any system imperfection or inhomogeneous behavior. There are many things to correct for: for example, light is distorted and partially absorbed as it travels through Earth’s turbulent atmosphere, making the image blurrier and fainter. And even though the telescope system is state-of-the-art, it may introduce other imperfections in the light we receive from the Universe. We need to correct for all of these things to ensure that we have great data!

    Q. So has it been difficult to schedule observations of the black hole at the centre of Messier 87?

    4
    Analogue signals collected by the antenna are converted to digital signals and stored on hard drives together with the time signals provided by atomic clocks. The hard drives are then flown to a central location to be synchronised. Credit: ALMA (ESO/NAOJ/NRAO), J.Pinto & N.Lira

    RHI: Yes! The individual telescopes that make up the EHT are not fully dedicated to the EHT project; they are cutting-edge telescopes that astronomers use all year long to observe a variety of different objects. Once per year, all these telescopes agree to create a gap in their schedules to observe together as part of the EHT. But the observing time is very limited.

    During observing campaigns, we must decide every day if an observation is going to be triggered or if we are going to wait until the next day. If we decide to wait, all stations will continue their usual observations, but if we get the green light, everyone will observe the agreed black hole targets and a part of the valuable time set aside for the EHT is consumed. This decision is mainly based on the weather forecast, and it is a tough one. After all, it is not that common to have good weather in so many places in both hemispheres at the same time! Furthermore, there are some small details that make things even more interesting. For instance, communication with the South Pole Telescope in the middle of Antarctica is not steady, but restricted to the limited windows when telecommunication satellites pass above the telescope. Last minute decisions are not always an option.

    HM: During the observations, a plan is sketched and distributed among all observing facilities. This schedule has to be followed to very precise timings, so we know that all telescopes are pointing at the same source at the same time. When finished, the data obtained are sent to the data-combining correlators. The challenge is that some of the stations might have been shut due to poor weather conditions, or that the data take months to arrive. An extreme example of the latter is that data from the South Pole Telescope arrive at the correlators only 6–8 months after observation!

    Q. Thirteen partner organisations and more than 200 people are involved in this project. Why does it require such a huge international effort?

    HM: Imaging a black hole is incredibly difficult. Even though the black hole at the centre of Messier 87 is 6.5 billion times the mass of the Sun, it is very dense, and therefore relatively small. And it is 55 million light-years away, so from Earth it looks tiny! We have been trying to image the event horizon — the ‘point of no return’ around a black hole, beyond which light can’t escape. But to discern something so small, we need a huge telescope. And as we are measuring light that has wavelengths on the order of millimetres, we need a telescope the size of the Earth! This is physically impossible, so we used interferometry — which is the same technique that ALMA uses on a smaller scale — to connect telescopes around the globe to mimic an Earth-sized telescope. And that takes a huge international effort.

    Q. How are the telescopes synchronised?

    RHI: When using the technique of interferometry, it is essential to combine the signals from each telescope at the exact same time. One way to ensure the synchronisation is to connect every station with a fibre-optic link to a central supercomputer. But considering the remote locations of the EHT telescopes, this would clearly not have been an option! Instead, each telescope was equipped with an ultra-precise hydrogen maser atomic clock that precisely timed each observation. This made it possible to combine data later on.

    4
    The locations of the participating telescopes of the Event Horizon Telescope (EHT) and the Global mm-VLBI Array (GMVA). Credit: ESO/O. Furtak

    Q. Was it difficult to collaborate with other institutions all around the world?

    RHI: There are always challenges in coordination and communication among the many different people working in an observatory: astronomers, engineers, administrators and computing teams, to name just a few. Everyone must work together towards the same goal. ALMA is a huge observatory, with hundreds of workers from more than ten different countries, and some of the other observatories involved in the EHT project are almost as big. Now imagine eight of these observatories working together on a time critical, cutting-edge project, and you will get a grasp of how much fun a project like the EHT can be!

    Q. How does it feel to be part of an international collaboration that has made such an incredible discovery?

    HM: I feel honoured, proud, fulfilled, and hopeful. The latter is more related to the fact that we are showing that, despite the cultural differences, a team comprising individuals with distinct backgrounds had a common goal, and achieved it. That teaches the world another key lesson, besides the one being reported.

    Q. Is there anything else you would like to mention?

    HM: Aside from the people included in the author list of the papers, many other individuals enabled this discovery to happen. We are not only “standing on the shoulders of giants” who carved out the path towards the techniques and technology we currently use, but also on shoulders of hard-working people who build and maintain the antennas, correlators and software at these remote sites. This is what enabled the discovery to happen. To them, I say a big thank you, as well as to the curious society that provided the will and, of course, the funding. These contributions were key to making this feat a reality!

    See https://sciencesprings.wordpress.com/2019/04/10/from-european-southern-observatory-astronomers-capture-first-image-of-a-black-hole/ for lists with links.

    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”.

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo,


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

    ESO VLT 4 lasers on Yepun


    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.

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

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).


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

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    ESO Speculoos telescopes four 1m-diameter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level


    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
  • richardmitnick 6:10 pm on April 11, 2019 Permalink | Reply
    Tags: , , , , EHT - Event Horizon Telescope, , , , , ,   

    From Nautilus: “First Black-Hole Image: It’s Not Looks That Count” 

    Nautilus

    From Nautilus

    Apr 11, 2019
    Sabine Hossenfelder

    1
    FIRST LOOK: The Event Horizon Telescope measures wavelength in the millimeter regime, too long to be seen by eye, but ideally suited to the task of imaging a black hole: The gas surrounding the black hole is almost transparent at this wavelength and the light travels to Earth almost undisturbed. Since we cannot see light of such wavelength by eye, the released telescope image shows the observed signal shifted into the visible range.Event Horizon Telescope Collaboration.

    “The Day Feynman Worked Out Black-Hole Radiation on My Blackboard”
    2
    After a few minutes, Richard Feynman had worked out the process of spontaneous emission, which is what Stephen Hawking became famous for a year later.Wikicommons.

    The Italian 14th-century painter, Giotto di Bondone, when asked by the Pope to prove his talent, is said to have swung his arm and drawn a perfect circle. But geometric perfection is limited by the medium. Inspect a canvas closely enough, and every circle will eventually appear grainy. If perfection is what you seek, don’t look at man-made art, look at the sky. More precisely, look at a black hole.

    Looking at a black hole is what the Event Horizon Telescope has done for the past 12 years. Yesterday, the collaboration released the long-awaited results from its first full run in April 2017. Contrary to expectation, their inaugural image is not, as many expected, Sagittarius A*, the black hole at the center of the Milky Way. Instead, it is the supermassive black hole in the elliptic galaxy Messier 87, about 55 million light-years from here. This black hole weighs in at 6.5 billion times the mass of our sun, and is considerably larger than the black hole in our own galaxy [1,000 times the size of SGR A*]. So, even though the Messier 87 black hole is a thousand times farther away than Sagittarius A*, it still appears half the size in the sky.

    The Event Horizon Telescope (EHT) is not less remarkable than the objects it observes. With a collaboration of 200 people, the EHT uses not a single telescope, but a global network of nine telescopes. Its sites, from Greenland to the South Pole and from Hawaii to the French Alps, act in concert as one. Together, the collaboration commands a telescope the size of planet Earth, staring at a tiny patch in the northern sky that contains the Messier-87 black hole.

    Event Horizon Telescope Array

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

    ESO/APEX
    Atacama Pathfinder EXperiment

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

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

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

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


    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

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

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile [recently added]

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL [recently added]

    Future Array/Telescopes

    NOEMA (NOrthern Extended Millimeter Array) will double the number of its 15 meter antennas of its predecessor from six to twelve, located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope


    Greenland Telescope

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


    ARO 12m Radio Telescope

    In theory, black holes are regions of space where the gravitational pull is so large that everything, including light, becomes trapped for eternity. The surface of the trapping region is called the “event horizon.” It has no substance; it is a property of space itself. In the simplest case, the event horizon is a sphere—a perfect sphere, made of nothing.

    In reality, it’s complicated. Astrophysicists have had evidence for the existence of black holes since the 1990s, but so far all observations have been indirect—inferred from the motion of visible stars and gas, leaving doubt as to whether the dark object really possesses the defining event horizon. It turned out difficult to actually see a black hole. Trouble is, they’re black. They trap light. And while Stephen Hawking proved that black holes must emit radiation due to quantum effects, this quantum glow is far too feeble to observe.

    But much like the prisoners in Plato’s cave, we can see black holes by observing the shadows they cast. Black holes attract gas from their environment. This gas collects in a spinning disk, and heats up as it spirals into the event horizon, pushing around electric charges. This gives rise to strong magnetic fields that can create a “jet,” a narrow, directed stream of particles leaving the black hole at almost the speed of light. But whatever strays too close to the event horizon falls in and vanishes without a trace.

    At the same time black holes bend rays of light, bend them so strongly, indeed, that looking at the front of a black hole, we can see part of the disk behind it. The light that just about manages to escape reveals what happens nearby the horizon. It is an asymmetric image that the astrophysicists expect, brighter on the side of the black hole where the material surrounding it moves toward us, and darker where it moves away from us. The hot gas combined with the gravitational lensing creates the unique observable signature that the EHT looks out for.

    The experimental challenge is formidable. The network’s telescopes must synchronize their data-taking using atomic clocks. Weather conditions must be favorable at all locations simultaneously. Once recorded, the amount of data is so staggeringly large, it must be shipped on hard disks to central locations for processing.

    The theoretical challenges are not any lesser. Black holes bend light so much that it can wrap around the horizon multiple times. The resulting image is too complicated to capture in simple equations. Though the math had been known since the 1920s, it wasn’t until 1978 that physicists got a first glimpse of what a black hole would actually look like. In that year, the French astrophysicist Jean-Pierre Luminet programmed the calculation on an IBM 7040 using punchcards. He drew the image by hand.

    Today, astrophysicists use computers many times more powerful to predict the accretion of gas onto the black hole and how the light bends before reaching us. Still, the partly turbulent motion of the gas, the electric and magnetic fields created by it, and the intricacies of the particle’s interactions are not fully understood.

    The EHT’s observations agree with expectation. But this result is more than just another triumph of Einstein’s theory of general relativity. It is also a triumph of the astronomers’ resourcefulness. They joined hands and brains to achieve what they could not have done separately. And while their measurement settles a long-standing question—yes, black holes really do have event horizons!—it is also the start of further exploration. Physicists hope that the observations will help them understand better the extreme conditions in the accretion disk, the role of magnetic fields in jet formation, and the way supermassive black holes affect galaxy formation.

    When the Pope received Giotto’s circle, it was not the image itself that impressed him. It was the courtier’s report that the artist produced it without the aid of a compass. This first image of a black hole, too, is remarkable not so much for its appearance, but for its origin. A black sphere, spanning 40 billion kilometers, drawn on a background of hot gas by the greatest artist of all: Nature herself.

    See the full article here .

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    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 10:08 am on April 10, 2019 Permalink | Reply
    Tags: , Although the telescopes are not physically connected they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations., , , , BlackHoleCam, , Data were flown to highly specialised supercomputers — known as correlators — at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory to be combined., EHT - Event Horizon Telescope, , , Sagittarius A* the supermassive black hole at the center of our galaxy, VLBI-very-long-baseline interferometry   

    From European Southern Observatory: “Astronomers Capture First Image of a Black Hole” 

    ESO 50 Large

    From European Southern Observatory

    10 April 2019

    Heino Falcke
    Chair of the EHT Science Council, Radboud University
    The Netherlands
    Tel: +31 24 3652020
    Email: h.falcke@astro.ru.nl

    Luciano Rezzolla
    EHT Board Member, Goethe Universität
    Germany
    Tel: +49 69 79847871
    Email: rezzolla@itp.uni-frankfurt.de

    Eduardo Ros
    EHT Board Secretary, Max-Planck-Institut für Radioastronomie
    Germany
    Tel: +49 22 8525125
    Email: ros@mpifr.de

    Calum Turner
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Email: pio@eso.org

    ESO, ALMA, and APEX contribute to paradigm-shifting observations of the gargantuan black hole at the heart of the galaxy Messier 87.

    1
    The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. Today, in coordinated press conferences across the globe, EHT researchers reveal that they have succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.

    This breakthrough was announced today in a series of six papers published in a special issue of The Astrophysical Journal Letters. The image reveals the black hole at the centre of Messier 87 [1], a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5 billion times that of the Sun [2].

    The EHT links telescopes around the globe to form an unprecedented Earth-sized virtual telescope [3]. The EHT offers scientists a new way to study the most extreme objects in the Universe predicted by Einstein’s general relativity during the centenary year of the historic experiment that first confirmed the theory [4].

    “We have taken the first picture of a black hole,” said EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian. “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”

    Black holes are extraordinary cosmic objects with enormous masses but extremely compact sizes. The presence of these objects affects their environment in extreme ways, warping spacetime and superheating any surrounding material.

    “If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow — something predicted by Einstein’s general relativity that we’ve never seen before,” explained chair of the EHT Science Council Heino Falcke of Radboud University, the Netherlands. “This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and has allowed us to measure the enormous mass of Messier 87’s black hole.”

    Multiple calibration and imaging methods have revealed a ring-like structure with a dark central region — the black hole’s shadow — that persisted over multiple independent EHT observations.

    “Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, superheated matter and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well,” remarks Paul T.P. Ho, EHT Board member and Director of the East Asian Observatory [5]. “This makes us confident about the interpretation of our observations, including our estimation of the black hole’s mass.”

    “The confrontation of theory with observations is always a dramatic moment for a theorist. It was a relief and a source of pride to realise that the observations matched our predictions so well,” elaborated EHT Board member Luciano Rezzolla of Goethe Universität, Germany.

    Creating the EHT was a formidable challenge which required upgrading and connecting a worldwide network of eight pre-existing telescopes deployed at a variety of challenging high-altitude sites. These locations included volcanoes in Hawai`i and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the Chilean Atacama Desert, and Antarctica.

    The EHT observations use a technique called very-long-baseline interferometry (VLBI) which synchronises telescope facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope observing at a wavelength of 1.3mm. VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a café in Paris [6].

    The telescopes contributing to this result were ALMA, APEX, the IRAM 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope [7]. Petabytes of raw data from the telescopes were combined by highly specialised supercomputers hosted by the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory.

    Max Planck Institute for Radio Astronomy Bonn Germany

    MIT Haystack Observatory, Westford, Massachusetts, USA, Altitude 131 m (430 ft)

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

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

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

    East Asia Observatory James Clerk Maxwell telescope, Mauna Kea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    The University of Massachusetts Amherst and Mexico’s Instituto Nacional de Astrofísica, Óptica y Electrónica
    Large Millimeter Telescope Alfonso Serrano, Mexico, at an altitude of 4850 meters on top of the Sierra Negra

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

    U Arizona Submillimeter Telescope located on Mt. Graham near Safford, Arizona, USA, Altitude 3,191 m (10,469 ft)

    South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including the University of Chicago, the University of California, Berkeley, Case Western Reserve University, Harvard/Smithsonian Astrophysical Observatory, the University of Colorado Boulder, McGill University, The University of Illinois at Urbana-Champaign, University of California, Davis, Ludwig Maximilian University of Munich, Argonne National Laboratory, and the National Institute for Standards and Technology. It is funded by the National Science Foundation. Altitude 2.8 km (9,200 ft)

    European facilities and funding played a crucial role in this worldwide effort, with the participation of advanced European telescopes and the support from the European Research Council — particularly a €14 million grant for the BlackHoleCam project [8]. Support from ESO, IRAM and the Max Planck Society was also key. “This result builds on decades of European expertise in millimetre astronomy”, commented Karl Schuster, Director of IRAM and member of the EHT Board.

    The construction of the EHT and the observations announced today represent the culmination of decades of observational, technical, and theoretical work. This example of global teamwork required close collaboration by researchers from around the world. Thirteen partner institutions worked together to create the EHT, using both pre-existing infrastructure and support from a variety of agencies. Key funding was provided by the US National Science Foundation (NSF), the EU’s European Research Council (ERC), and funding agencies in East Asia.

    “ESO is delighted to have significantly contributed to this result through its European leadership and pivotal role in two of the EHT’s component telescopes, located in Chile — ALMA and APEX,” commented ESO Director General Xavier Barcons. “ALMA is the most sensitive facility in the EHT, and its 66 high-precision antennas were critical in making the EHT a success.”

    “We have achieved something presumed to be impossible just a generation ago,” concluded Doeleman. “Breakthroughs in technology, connections between the world’s best radio observatories, and innovative algorithms all came together to open an entirely new window on black holes and the event horizon.”
    Notes

    [1] The shadow of a black hole is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across.

    [2] Supermassive black holes are relatively tiny astronomical objects — which has made them impossible to directly observe until now. As the size of a black hole’s event horizon is proportional to its mass, the more massive a black hole, the larger the shadow. Thanks to its enormous mass and relative proximity, M87’s black hole was predicted to be one of the largest viewable from Earth — making it a perfect target for the EHT.

    [3] Although the telescopes are not physically connected, they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations. These observations were collected at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced enormous amounts of data – roughly 350 terabytes per day – which was stored on high-performance helium-filled hard drives. These data were flown to highly specialised supercomputers — known as correlators — at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory to be combined. They were then painstakingly converted into an image using novel computational tools developed by the collaboration.

    [4] 100 years ago, two expeditions set out for Principe Island off the coast of Africa and Sobral in Brazil to observe the 1919 solar eclipse, with the goal of testing general relativity by seeing if starlight would be bent around the limb of the sun, as predicted by Einstein. In an echo of those observations, the EHT has sent team members to some of the world’s highest and most isolated radio facilities to once again test our understanding of gravity.

    [5] The East Asian Observatory (EAO) partner on the EHT project represents the participation of many regions in Asia, including China, Japan, Korea, Taiwan, Vietnam, Thailand, Malaysia, India and Indonesia.

    [6] Future EHT observations will see substantially increased sensitivity with the participation of the IRAM NOEMA Observatory, the Greenland Telescope and the Kitt Peak Telescope.

    [7] ALMA is a partnership of the European Southern Observatory (ESO; Europe, representing its member states), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences(NINS) of Japan, together with the National Research Council (Canada), the Ministry of Science and Technology (MOST; Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA; Taiwan), and Korea Astronomy and Space Science Institute (KASI; Republic of Korea), in cooperation with the Republic of Chile. APEX is operated by ESO, the 30-meter telescope is operated by IRAM (the IRAM Partner Organizations are MPG (Germany), CNRS (France) and IGN (Spain)), the James Clerk Maxwell Telescope is operated by the EAO, the Large Millimeter Telescope Alfonso Serrano is operated by INAOE and UMass, the Submillimeter Array is operated by SAO and ASIAA and the Submillimeter Telescope is operated by the Arizona Radio Observatory (ARO). The South Pole Telescope is operated by the University of Chicago with specialized EHT instrumentation provided by the University of Arizona.

    [8] BlackHoleCam is an EU-funded project to image, measure and understand astrophysical black holes. The main goal of BlackHoleCam and the Event Horizon Telescope (EHT) is to make the first ever images of the billion solar masses black hole in the nearby galaxy Messier 87 and of its smaller cousin, Sagittarius A*, the supermassive black hole at the centre of our Milky Way. This allows the determination of the deformation of spacetime caused by a black hole with extreme precision.

    More information

    This research was presented in a series of six papers published today in a special issue of The Astrophysical Journal Letters.

    The EHT collaboration involves more than 200 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

    The EHT consortium consists of 13 stakeholder institutes; the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.

    Links

    ESO EHT web page
    EHT Website & Press Release
    ESOBlog on the EHT Project

    Papers:

    Paper I: The Shadow of the Supermassive Black Hole
    Paper II: Array and Instrumentation
    Paper III: Data processing and Calibration
    Paper IV: Imaging the Central Supermassive Black Hole
    Paper V: Physical Origin of the Asymmetric Ring
    Paper VI: The Shadow and Mass of the Central Black Hole

    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 EEuropean Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

     
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