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  • 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 .

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    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 .

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    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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    Please help promote STEM in your local schools.

    Stem Education Coalition

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


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    ESO VLT 4 lasers on Yepun


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    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).


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    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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  • 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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    Please help promote STEM in your local schools.


    Stem Education Coalition

    Visit ESO in Social Media-

    Facebook

    Twitter

    YouTube

    ESO Bloc Icon

    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”.

     
  • richardmitnick 8:53 am on April 1, 2019 Permalink | Reply
    Tags: "Media Advisory: Press Conference on First Result from the Event Horizon Telescope", , , , , EHT - Event Horizon Telescope,   

    From European Southern Observatory: “Media Advisory: Press Conference on First Result from the Event Horizon Telescope” 

    ESO 50 Large

    From European Southern Observatory

    1 April 2019
    Marcin Monko,
    ERC Press advisor
    Brussels, Belgium
    Tel: +32 22 9666 44
    Email: ERC-press@ec.europa.eu

    Katharina Königstein
    Communications Officer — Astrophysics
    Radboud University, The Netherlands
    Tel: +31 24 3652 080
    Email: k.konigstein@astro.ru.nl

    Calum Turner
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6670
    Email: pio@eso.org

    1

    The European Commission, European Research Council, and the Event Horizon Telescope (EHT) project will hold a press conference to present a groundbreaking result from the EHT.

    When: On 10 April 2019 at 15:00 CEST
    Where: The press conference will be held at the Berlaymont Building, Rue de la Loi (Wetstraat) 200, B-1049 Brussels, Belgium. The event will be introduced by European Commissioner for Research, Science and Innovation, Carlos Moedas, and will feature presentations by the researchers behind this result.
    What: A press conference to present a groundbreaking result from the EHT.
    RSVP: This invitation is addressed to media representatives. To participate in the conference, members of the media must register by completing an online form before April 7 23:59 CEST. Please indicate whether you wish to attend in person or if you will participate online only. On-site journalists will have a question-and-answer session with panellists during the conference. In-person individual interviews immediately after the conference will also be possible.

    The conference will be streamed online on the ESO website, by the ERC, and on social media. We will take a few questions from social media using the hashtag #AskEHTeu.

    An ESO press release will be publicly issued shortly after the start of the conference at 15:07 CEST. Translations of the press release will be available in multiple languages, along with extensive supporting audiovisual material.

    A total of six major press conferences will be held simultaneously around the globe in Belgium (Brussels, English), Chile (Santiago, Spanish), Shanghai (Mandarin), Japan (Tokyo, Japanese), Taipei (Mandarin), and USA (Washington, D.C., English).

    The European Commissioner for Research, Science and Innovation, Carlos Moedas will speak in Brussels, the President of the Academia Sinica, James Liao, will speak in Taipei, the ALMA Director Sean Dougherty and the ESO Director General Xavier Barcons will speak in Santiago, and the NSF Director France A. Córdova will speak in Washington DC.

    Due to the importance of this result, we encourage satellite events in the different ESO Member States and beyond. If you wish to arrange a satellite event please contact Katharina Königstein (k.konigstein@astro.ru.nl) for details on the live feed. There are satellite-events currently planned in Madrid, Rome, Gothenburg, Nijmegen and Pretoria.

    For any further information and updates, please also check the Event Horizon Telescope webpage at https://eventhorizontelescope.org.

    More Information

    Members of the press, including online media and broadcasters, may sign up to receive the ESO Media Newsletter. Under normal circumstances this contains ESO press releases sent about 48 hours in advance of public dissemination as well as latest videos and footage from ESO, available for use in documentaries, movies, video news etc. To sign up to the ESO Media Newsletter, please fill out this form.

    Links

    Media registration for the Brussels press conference
    Event Horizon Telescope
    European Southern Observatory (ESO)
    ESO Media Newsletter registration

    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 NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

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

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

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    NSF CfA Greenland telescope

    Greenland Telescope

    Future Array/Telescopes

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    See the full article here .


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

    Please help promote STEM in your local schools.


    Stem Education Coalition

    Visit ESO in Social Media-

    Facebook

    Twitter

    YouTube

    ESO Bloc Icon

    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”.

    ESO La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun)

    ESO/HARPS at La Silla

    ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    MPG/ESO 2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres

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

    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 VLT 4 lasers on Yepun

    Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT.

    ESO/NTT at Cerro La Silla, Chile, at an altitude of 2400 metres

    Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light.
    Credit: ESO/Y. Beletsky, with an elevation of 2,635 metres (8,645 ft) above sea level

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

    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

    A novel gamma ray telescope under construction on Mount Hopkins, Arizona. a large project known as the Cherenkov Telescope Array, composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile. The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the University of Wisconsin–Madison, and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev

     
  • richardmitnick 5:06 pm on March 29, 2019 Permalink | Reply
    Tags: , EHT - Event Horizon Telescope, , , SO-2 and SO-38 circle SGR A*Image UCLA Galactic Center Groupe via S. Sakai and Andrea Ghez at Keck Observatory   

    From Science News: “4 things we’ll learn from the first closeup image of a black hole” 

    From Science News

    March 29, 2019
    Lisa Grossman

    Event Horizon Telescope data are giving scientists an image of the Milky Way’s behemoth.

    1
    FIRST LOOK The first image from the Event Horizon Telescope may show that the black hole at the center of our galaxy looks something like this simulation.

    The Event Horizon Telescope, a network of eight radio observatories spanning the globe, has set its sights on a pair of behemoths: Sagittarius A*, the supermassive black hole at the Milky Way’s center, and an even more massive black hole 53.5 million light-years away in galaxy Messier 87 (SN Online: 4/5/17).

    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

    Sgr A* from ESO VLT

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

    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 NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

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

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Hawaii SAO
    Submillimeter Array Hawaii SAO

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

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    NSF CfA Greenland telescope

    Greenland Telescope

    Future Array/Telescopes

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    In April 2017, the observatories teamed up to observe the black holes’ event horizons, the boundary beyond which gravity is so extreme that even light can’t escape (SN: 5/31/14, p. 16). After almost two years of rendering the data, scientists are gearing up to release the first images in April.

    Here’s what scientists hope those images can tell us.

    What does a black hole really look like?

    Black holes live up to their names: The great gravitational beasts emit no light in any part of the electromagnetic spectrum, so they themselves don’t look like much.

    But astronomers know the objects are there because of a black hole’s entourage. As a black hole’s gravity pulls in gas and dust, matter settles into an orbiting disk, with atoms jostling one another at extreme speeds. All that activity heats the matter white-hot, so it emits X-rays and other high-energy radiation. The most voraciously feeding black holes in the universe have disks that outshine all the stars in their galaxies (SN Online: 3/16/18).

    3
    TOO BIG, TOO SOON Supermassive black holes that are actively feeding on gas and dust, like the one shown in this artist’s rendition, have been spotted in the early universe — before they should have had time to grow. NAOJ.


    A CAMERA THE SIZE OF EARTH How did scientists take a picture of a black hole? Science News explains.

    The EHT’s image of the Milky Way’s Sagittarius A*, also called SgrA*, is expected to capture the black hole’s shadow on its accompanying disk of bright material. Computer simulations and the laws of gravitational physics give astronomers a pretty good idea of what to expect. Because of the intense gravity near a black hole, the disk’s light will be warped around the event horizon in a ring, so even the material behind the black hole will be visible.

    And the image will probably look asymmetrical: Gravity will bend light from the inner part of the disk toward Earth more strongly than the outer part, making one side appear brighter in a lopsided ring.

    Does general relativity hold up close to a black hole?

    The exact shape of the ring may help break one of the most frustrating stalemates in theoretical physics.

    The twin pillars of physics are Einstein’s theory of general relativity, which governs massive and gravitationally rich things like black holes, and quantum mechanics, which governs the weird world of subatomic particles. Each works precisely in its own domain. But they can’t work together.

    “General relativity as it is and quantum mechanics as it is are incompatible with each other,” says physicist Lia Medeiros of the University of Arizona in Tucson. “Rock, hard place. Something has to give.” If general relativity buckles at a black hole’s boundary, it may point the way forward for theorists.

    Since black holes are the most extreme gravitational environments in the universe, they’re the best environment to crash test theories of gravity. It’s like throwing theories at a wall and seeing whether — or how — they break. If general relativity does hold up, scientists expect that the black hole will have a particular shadow and thus ring shape; if Einstein’s theory of gravity breaks down, a different shadow.

    Medeiros and her colleagues ran computer simulations of 12,000 different black hole shadows that could differ from Einstein’s predictions. “If it’s anything different, [alternative theories of gravity] just got a Christmas present,” says Medeiros, who presented the simulation results in January in Seattle at the American Astronomical Society meeting. Even slight deviations from general relativity could create different enough shadows for EHT to probe, allowing astronomers to quantify how different what they see is from what they expect.


    CONSIDERING ALL POSSIBILITIES Physicists expect black holes to follow Einstein’s rules of general relativity, but it might be more interesting if they don’t. This computer simulation shows one possibility for how a black hole would look if it behaved unexpectedly.

    Do stellar corpses called pulsars surround the Milky Way’s black hole?

    Another way to test general relativity around black holes is to watch how stars careen around them. As light flees the extreme gravity in a black hole’s vicinity, its waves get stretched out, making the light appear redder. This process, called gravitational redshift, is predicted by general relativity and was observed near SgrA* last year (SN: 8/18/18, p. 12). So far, so good for Einstein.

    5
    BLACK HOLE SUN Einstein’s theory of gravity was upheld in measurements of a star that recently made a close pass by the supermassive black hole at the center of the Milky Way, as shown in this artist’s conception illustrating the star’s trajectory over the past few months.

    SO-2 and SO-38 circle SGR A*Image UCLA Galactic Center Groupe via S. Sakai and Andrea Ghez at Keck Observatory

    An even better way to do the same test would be with a pulsar, a rapidly spinning stellar corpse that sweeps the sky with a beam of radiation in a regular cadence that makes it appear to pulse (SN: 3/17/18, p. 4). Gravitational redshift would mess up the pulsars’ metronomic pacing, potentially giving a far more precise test of general relativity.

    “The dream for most people who are trying to do SgrA* science, in general, is to try to find a pulsar or pulsars orbiting” the black hole, says astronomer Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va. “There are a lot of quite interesting and quite deep tests of [general relativity] that pulsars can provide, that EHT [alone] won’t.”

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

    Despite careful searches, no pulsars have been found near enough to SgrA* yet, partly because gas and dust in the galactic center scatters their beams and makes them difficult to spot. But EHT is taking the best look yet at that center in radio wavelengths, so Ransom and colleagues hope it might be able to spot some.

    “It’s a fishing expedition, and the chances of catching a whopper are really small,” Ransom says. “But if we do, it’s totally worth it.”

    How do some black holes make jets?

    Some black holes are ravenous gluttons, pulling in massive amounts of gas and dust, while others are picky eaters. No one knows why. SgrA* seems to be one of the fussy ones, with a surprisingly dim accretion disk despite its 4 million solar mass heft. EHT’s other target, the black hole in galaxy M87, is a voracious eater, weighing in at about 2.4 trillion solar masses. And it doesn’t just amass a bright accretion disk. It also launches a bright, fast jet of charged subatomic particles that stretches for about 5,000 light-years.

    “It’s a little bit counterintuitive to think a black hole spills out something,” says astrophysicist Thomas Krichbaum of the Max Planck Institute for Radio Astronomy in Bonn, Germany. “Usually people think it only swallows something.”

    Many other black holes produce jets that are longer and wider than entire galaxies and can extend billions of light-years from the black hole. “The natural question arises: What is so powerful to launch these jets to such large distances?” Krichbaum says. “Now with the EHT, we can for the first time trace what is happening.”

    EHT’s measurements of Messier 87’s black hole will help estimate the strength of its magnetic field, which astronomers think is related to the jet-launching mechanism. And measurements of the jet’s properties when it’s close to the black hole will help determine where the jet originates — in the innermost part of the accretion disk, farther out in the disk or from the black hole itself. Those observations might also reveal whether the jet is launched by something about the black hole itself or by the fast-flowing material in the accretion disk.

    Since jets can carry material out of the galactic center and into the regions between galaxies, they can influence how galaxies grow and evolve, and even where stars and planets form (SN: 7/21/18, p. 16).

    “It is important to understanding the evolution of galaxies, from the early formation of black holes to the formation of stars and later to the formation of life,” Krichbaum says. “This is a big, big story. We are just contributing with our studies of black hole jets a little bit to the bigger puzzle.”

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 12:31 pm on January 22, 2019 Permalink | Reply
    Tags: , , , , EHT - Event Horizon Telescope, , Our Galaxy's Supermassive Black Hole Could Be Pointing a Relativistic Jet Right at Us, ,   

    From Science Alert: “Our Galaxy’s Supermassive Black Hole Could Be Pointing a Relativistic Jet Right at Us” 

    ScienceAlert

    From Science Alert

    22 JAN 2019
    MICHELLE STARR

    1
    A black hole simulation (Bronzwaer/Davelaar/Moscibrodzka/Falcke/Radboud University)

    Things are officially getting exciting. New science has just come in from the collaboration to photograph Sagittarius A*, the supermassive black hole at the centre of the Milky Way, and it’s ponying up the secrets at our galaxy’s dusty heart.

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

    The image below is the best picture yet of Sgr A* (don’t worry, there’s more to come from the Event Horizon Telescope), and while it may look like just a weird blob of light to you, astrophysicists studying the radio data can learn a lot from what they’re looking at – and they think they’ve identified a relativistic jet angled towards Earth.

    EHT map

    Because the image taken of the region is the highest resolution yet – twice as high as the previous best – the researchers were able to precisely map the properties of the light around the black hole as scattered by the cloud.

    “The galactic centre is full of matter around the black hole, which acts like frosted glass that we have to look through,” astrophysicist Eduardo Ros of the Max Planck Institute for Radio Astronomy in Germany told New Scientist.

    Using very long baseline interferometry to take observations at a wavelength of 3.5 millimetres (86 GHz frequency), a team of astronomers has used computer modelling to simulate what’s inside the thick cloud of plasma, dust and gas surrounding the black hole.

    1
    Above: The bottom right image shows Sgr A* as seen in the data. The top images are simulations, while the bottom left is Sgr A* with the scattering removed.
    (S. Issaoun, M. Mościbrodzka, Radboud University/ M. D. Johnson, CfA)

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

    GMVA The Global VLBI Array

    It revealed that Sgr A*’s radio emission comes from a smaller region than previously thought.

    Most of it is coming from an area just 300 milllionth of a degree of the night sky, with a symmetrical shape. And, since black holes don’t emit detectable radiation on their own, the source is most likely one of two things.

    “This may indicate that the radio emission is produced in a disk of infalling gas rather than by a radio jet,” said astrophysicist Sara Issaoun of Radboud University in The Netherlands.

    “However, that would make Sgr A* an exception compared to other radio emitting black holes. The alternative could be that the radio jet is pointing almost at us.”

    Active black holes are surrounded by a swirling cloud of material that’s falling into it like water down a drain. As this material is swallowed by the black hole, it emits jets of particles from its rotational poles at velocities approaching light speed.

    We’re not quite sure how this happens, but astronomers believe that material from the inner part of the accretion disc is channelled towards and launched from the poles via magnetic field lines.

    Since Earth is in the galactic plane, having a jet pointed in our direction would mean that the black hole is oriented quite strangely, as if it’s lying on its side. (Nearby galaxy Centaurus A, for instance, has jets shooting perpendicular to the galactic plane.)

    But this orientation has been hinted at before. Last year the GRAVITY Collaboration described flares around Sgr A* consistent with something orbiting it face-on from our perspective – like looking at the Solar System from above.

    This means the long-awaited picture of the shadow of a black hole will – hopefully – be breathtakingly detailed.

    Meanwhile, studying data such as these help build a comprehensive picture of how these mysterious cosmic objects work.

    “Understanding how black holes work … takes more than the picture of its shadow (although incredible in its own right),” Issaoun wrote on Facebook. “It takes observations at many different wavelengths (radio, X-ray, infrared etc) to piece together the entire story, so every piece counts!”

    The team’s paper has been published in The Astrophysical Journal..

    So “Maybe this is true after all,” said Radboud University astronomer Heino Falcke, “and we are looking at this beast from a very special vantage point.”

    Hopefully, when the Event Horizon Telescope releases the first images of Sgr A*’s event horizon – something we are expecting very soon – they will reveal more. And, in case you were starting to get worried, the 1.4-millimetre wavelength (230 GHz) will reduce the light scattering by a factor of 8.

    See the full article here .

    See also here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 12:15 pm on December 23, 2018 Permalink | Reply
    Tags: , , , , , EHT - Event Horizon Telescope, , New fellowships, ,   

    From Perimeter Institute: “New fellowships to fuel fundamental physics with radio telescopes in Canada” 

    Perimeter Institute

    From Perimeter Institute

    December 20, 2018

    Perimeter Institute and Canada’s National Research Council have created a pair of postdoctoral fellowships for exceptional emerging radio astronomers.

    As radio astronomy enters a transformative new era, Perimeter Institute and Canada’s National Research Council (NRC) have launched two new fellowships to accelerate the research of young scientists conducting theory, data analysis, or instrument development.

    The new initiative is a collaboration between Perimeter and NRC’s Dominion Radio Astrophysical Observatory (DRAO), the site of Canada’s revolutionary Canadian Hydrogen Intensity Mapping Experiment (CHIME) Telescope.

    CHIME Canadian Hydrogen Intensity Mapping Experiment -A partnership between the University of British Columbia, the University of Toronto, McGill University, Yale and the National Research Council in British Columbia, at the Dominion Radio Astrophysical Observatory in Penticton,British Columbia

    Instruments like CHIME and forthcoming experiments possess unprecedented statistical power, promising to open new windows into fundamental physics questions, including dark matter, gravity, and neutrinos. These instruments will be used to tackle new challenges in data analysis and high-performance computing, and will help scientists resolve deep astronomical puzzles, such as the origin of fast radio bursts (FRBs).

    The Perimeter-DRAO partnership will bring together theorists, data analysts, and instrumentalists at the leading edge of this very exciting field.

    One of the postdoctoral fellows will be based at the DRAO, with the other at Perimeter Institute; each will be encouraged to spend time at the other institution to deepen the partnership and strengthen the connections between the institutions.

    Perimeter Institute is part of a number of radio astronomy collaborations, including CHIME/FRB, HIRAX (Hydrogen Intensity and Real-time Analysis Experiment), and the EHT (Event Horizon Telescope), among others.

    SKA HIRAX prototype dishes at Hartebeesthoek Astronomy Observatory near Johannesburg.

    EHT map

    EHT APEX, IRAM, G. Narayanan, J. McMahon, JCMT/JAC, S. Hostler, D. Harvey, ESO/C. Malin

    Perimeter researchers associated with these initiatives include Avery Broderick, Ue-Li Pen, Will Percival, Daniel Siegel, Kendrick Smith, and Neil Turok.

    In addition to hosting CHIME in British Columbia and several other radio telescopes, DRAO features laboratories and specialized equipment for the design and construction of all aspects of radio-frequency instrumentation, from highly sensitive antennae and receiver systems to high-speed digital signal processing hardware and software. This national facility is home to astronomers, astrophysicists, engineers, and technologists, as well as visiting researchers and students from universities and astronomical observatories around the world.

    The deadline to apply for the fellowships is January 31, 2019. Find more information and apply here.

    See the full article here .


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    Please help promote STEM in your local schools.
    stem
    Stem Education Coalition

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

     
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