5 facts about the first ever image of a black hole

Niruj RamanujamApr 11, 2019 09:57:03 IST

The Event Horizon Telescope has released the first direct image of a black hole and its neighbourhood. This black hole lurks in the centre of a nearby galaxy called M87. This historic image shows a ring of light coming from the gas falling into the black hole.

The black hole itself is shielded by the event horizon, a boundary from within which nothing can escape, and this is the dark interior in the image.

Though astronomers have had solid evidence for the existence of massive black holes for many years, this historic moment marks the first time that it has been imaged.

5 Facts About the First Ever Image of a Black Hole

The first ever image of a black hole, from the M87 galaxy located in the Virgo constellation in the Milky Way. Image: EHT/NSF

What has the Event Horizon Telescope seen?

The Event Horizon Telescope, or EHT, has imaged the silhouette or shadow of the black hole at the centre of M87, a galaxy 55 million light years from us. To make this image, astronomers combined data from 8 different telescopes across the world in an experiment in April 2017.

The data was taken at a frequency of 230 GHz, or a wavelength of 1.3 mm. Using this, astronomers have formed an image of the black hole for the first time. The event horizon of a black hole is the ultimate boundary. Nothing from within it can escape out.

The ring of fire in the EHT image is light from the gas falling into the event horizon, whose shadow is the dark hole in the centre.

The exact shape of the ring is due to the way the incredible gravity of the black hole bends the light around it, and the incredible speed at which the gas is travelling is why the ring is not uniform in brightness.

5 Facts About the First Ever Image of a Black Hole

Black hole Milky Way Horizon. Image: NASA

How big is the black hole at the centre of M87?

Almost all galaxies have black holes at their centres, and these can be a few million to a few billion times the mass of our Sun.

Our Milky Way galaxy has a fairly small black hole about 4 million times as massive as our Sun. However, the black hole in M87 is a monster, and is 6500 million times the mass of the Sun.

The size of its event horizon is about 20000 million km, which even bigger than our Solar System.

A black hole does not emit any light. Then how do astronomers ‘see’ it or its shadow?

Matter is attracted by the gravity of a black hole, but cannot fall into it easily. In fact, it forms a swirling disk around it, through which it spirals in to the black hole at extremely high speed. While doing so, matter gets heated to enormous temperatures, and this hot magnetised plasma is what emits the intense radiation that we see.

5 Facts About the First Ever Image of a Black Hole

Wavelengths visible of black holes.

EHT has got an image of the radiation from this surrounding gas at a frequency of 230 GHz. However, the image is not as simple as a dark hole in front of a disk of radiating gas.

Since the gravity near the black hole is immense, it can bend the path of the light rays from the surrounding magnetised plasma in peculiar ways. So even light from the gas behind the black hole bends enough to reach us.

This bending of the light, called gravitational lensing, determines the final shape of the ring and the inner shadow that the EHT has imaged.

Why are black holes and their images so important?

Black holes can test physics theories such as the General Relativity theory of Einstein, which relates the motion of bodies due to gravity with the curvature of spacetime. It has passed every test in our Solar System (the accuracy of GPS in our phones is also a good test of the theory) as well as in other astronomical objects.

All this is called the weak gravity case where the curvature of spacetime is small. What astronomers want to do is to test the theory in strong gravity, where the curvature is much higher, and see if the theory still works. The recent detection of gravitational waves from merging black holes is one such example.

Imaging the shadow of super-massive black holes in galactic centres is another.

5 Facts About the First Ever Image of a Black Hole

Black hole size.

First image of a black hole, using Event Horizon Telescope observations of the center of the galaxy M87.

Why was it such a difficult experiment?

The EHT had to image M87 by collecting the radiation over a range of frequencies, and it did so by observing at a frequency of 230 GHz, which corresponds to a wavelength of 1.3 mm. This frequency is more than 2000 times higher than what is used by FM radio stations. This is a pretty special frequency where many factors align favourably.

At much lower frequencies, the inner region of the centre of M87 becomes more opaque and less bright. At higher frequencies, our own atmosphere blocks much of the radiation from coming in. 230 GHz seems just right.

Telescopes at this frequency require incredibly hi-tech hardware, functioning at their limits of performance, including high precision atomic clocks and digital backend.

Is there a single Event Horizon Telescope?

A telescope large enough to image the shadow of the black hole in M87 would have to be as big as the Earth itself. Since that might be a bit difficult, astronomers chose the next best thing.

Using a technique called interferometry, data from many telescopes spread across the Earth were combined in a special way. This enabled astronomers to make images that show detail on as fine a scale as would a single earth-sized telescope.

However, this comes with the cost of enormous computation that requires months of processing on very powerful computers.

Why did the EHT not image the black hole in our own Galaxy?

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The black hole in the centre of our Milky Way is about 1000 times less massive than the one in M87, and hence also smaller by the same factor.

However, it is only 26000 light years away from us and hence appears to be a bit bigger on the sky than the black hole in M87.

EHT had also observed the Milky Way black hole, but since its brightness varies much more rapidly, even during the observation duration, the data processing to make the image is more difficult.

Why did the telescopes have to be so far apart?

The EHT experiment had eight telescopes operating together at sub-mm wavelengths. These were as far apart as Hawaii, mainland USA, Chile, Mexico and even the South Pole. All of them had to look at M87 together at the same time and record their data. The telescopes functioning together in this way are jointly called the Event Horizon Telescope.

The size of the ring seen by EHT is around 40 micro-arcsecond – which is the angle made by the thickness of a sheet of paper viewed edge-on from around 100 km away. The black hole in M87 is the largest in the local Universe and is therefore, a good bet.

To image such a small region, we need a telescope that has an enormous magnification, so that details within the image can be captured well. In the technique used to combine data from different telescopes, the magnification is higher if the telescopes are farther apart. The farthest apart they can be, of course, is the size of the Earth itself.

  The magnification of the EHT image is enough for you to sit in New Delhi and read a book which is in Kanyakumari.

Why Indian telescopes were not part of EHT?

India does not have a telescope working in the sub-mm wavelengths. Though India has two of the world’s largest radio telescopes (Giant Metrewave Radio Telescope near Pune and Ooty Radio Telescope), they operate at centimetre and metre wavelengths and will be completely blind at the shorter wavelengths of sub-mm.

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First ever black hole image released

By Pallab Ghosh Science correspondent, BBC News

5 Facts About the First Ever Image of a Black Hole Image copyright EHT Image caption The first ever picture of a black hole: It's surrounded by a halo of bright gas

  • Astronomers have taken the first ever image of a black hole, which is located in a distant galaxy.
  • It measures 40 billion km across – three million times the size of the Earth – and has been described by scientists as “a monster”.
  • The black hole is 500 million trillion km away and was photographed by a network of eight telescopes across the world.
  • Details have been published today in Astrophysical Journal Letters.
  • It was captured by the Event Horizon Telescope (EHT), a network of eight linked telescopes.
  • Prof Heino Falcke, of Radboud University in the Netherlands, who proposed the experiment, told BBC News that the black hole was found in a galaxy called M87.
  • “What we see is larger than the size of our entire Solar System,” he said.

“It has a mass 6.5 billion times that of the Sun. And it is one of the heaviest black holes that we think exists. It is an absolute monster, the heavyweight champion of black holes in the Universe.”

5 Facts About the First Ever Image of a Black Hole

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Media captionM87: The significance of the first ever image of a black hole

The image shows an intensely bright “ring of fire”, as Prof Falcke describes it, surrounding a perfectly circular dark hole. The bright halo is caused by superheated gas falling into the hole. The light is brighter than all the billions of other stars in the galaxy combined – which is why it can be seen at such distance from Earth.

The edge of the dark circle at the centre is the point at which the gas enters the black hole, which is an object that has such a large gravitational pull, not even light can escape.

The Story Behind the First Picture Taken of a Black Hole

On Wednesday, April 10th, the world was treated to something unprecedented – the first-ever image of a black hole! Specifically, the image captured the Supermassive Black Hole (SMBH) at the center of M87 (aka. Virgo A), a supergiant elliptical galaxy in the Virgo constellation.

Already, this image is being compared to pictures like the “pale blue dot” taken by the Voyager 1 mission or the “Earthrise” image taken by Apollo 8. Like these images, the picture of the M87 black hole has captured the imagination of people all around the world.

This accomplishment drew on years of hard work involving astronomers, observatories and scientific institutions from all around the world. As with most accomplishments of this caliber, countless people played a role and deserve credit for making it happen.

5 Facts About the First Ever Image of a Black Hole

But as always, there were a handful of people whose contributions really stand out. In addition, capturing the first-ever image of a black hole depended a lot of specialized technology and scientific methods, which also deserve attention. You might say that his historic accomplishment had a historic buildup!

Those Who Made it Happen:

Since the EHT project released the first image of a black hole, Katherine Bouman has become something of a household name. But just who is this black hole hunter whose work has helped us to look into the face of one of the most mysterious phenomena in the Universe?

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RELATED: KATIE BOUMAN: THE BRILLIANT MIND THAT BROUGHT US THE IMAGE OF A BLACK HOLE

Bouman received her Ph.D. Electrical Engineering and Computer Science at the Massachusetts Institute of Technology (MIT) in 2017. Since then, Bouman has worked as a postdoctoral researcher with the Event Horizon Telescope project, where she applied emerging computational methods to push the boundaries of imaging technology.

By the numbers: First-ever image of black hole’s event horizon

5 Facts About the First Ever Image of a Black Hole Scientists working with the Event Horizon Telescope collaboration have taken the first-ever image of a black hole. This supermassive black hole (left inset) at the center of the Messier 87 galaxy (location of black hole marked with a white box) is surrounded by a ring of swirling hot gas and dust that sits just outside of the gravitational pull of the event horizon. (Photo: EHT collaboration; NASA/CXC/Villanova University)

On April 10th, researchers from the Event Horizon Telescope (EHT) collaboration released the first image collected of a black hole’s event horizon. The breakthrough image of a supermassive black hole and its shadow at the center of the Messier 87 galaxy was collected using a series of radio telescopes spread across the globe to create an “Earth-sized virtual telescope.”

The black hole, nicknamed Pōwehi, which means “embellished dark source of unending creation” in Hawaiian, has already generated a lot of excitement in the news and in the scientific community, even becoming immortalized in meme form. 

Here are some key facts and figures to better understand what went into collecting this first-ever image and what it means for the future of astronomy.

    • 6.5 billion The number of suns equal to the mass of the Messier 87 black hole. This meets the criteria for being a supermassive black hole, where such a large amount of matter has been squeezed into such a small area that the resulting force of gravity becomes so strong that nothing can escape, not even light. 

    First-ever image of a black hole

    Max Planck researchers involved in direct observation of the massive gravity trap in the Messier 87 galaxy

    Black holes swallow all light and are therefore invisible. What sounds plausible is fortunately a little different in practice for astronomers. Because black holes are surrounded by shining gas discs and therefore stand out from the dark background, similar to a black cat on a white sofa.

    In this way, the Event Horizon Telescope has now succeeded for the first time in photographing a black hole. This worldwide network of eight ground-based radio telescopes focused on the galaxy Messier 87, about 55 million light years away.

    Researchers from the Max Planck Institute for Radio Astronomy and the Institute for Radio Astronomy in the Millimetre Range (IRAM) are also involved in the observation.

    View of a mass monster: this image is the first direct visual evidence of a black hole. This particularly massive specimen is at the centre of the massive galaxy Messier 87 and was recorded with the Event Horizon Telescope (EHT), a network of eight ground-based radio telescopes distributed around the globe.

    Black holes swallow all light and are therefore invisible. What sounds plausible is fortunately a little different in practice for astronomers. Because black holes are surrounded by shining gas discs and therefore stand out from the dark background, similar to a black cat on a white sofa.

    In this way, the Event Horizon Telescope has now succeeded for the first time in photographing a black hole. This worldwide network of eight ground-based radio telescopes focused on the galaxy Messier 87, about 55 million light years away.

    Researchers from the Max Planck Institute for Radio Astronomy and the Institute for Radio Astronomy in the Millimetre Range (IRAM) are also involved in the observation.

    In April 2017, the scientists linked eight telescopes around the globe for the first time, thus forming a virtual telescope with an aperture almost as large as the diameter of the Earth.

    Very Long Baseline Interferometry (VLBI) is the name of this technique, in which the signals of the individual antennas are superimposed. This synchronization takes place with the aid of high-precision atomic clocks accurate to the nanosecond.

    An extreme angular resolution of less than 20 micro arc seconds can be achieved; if our eyes had such a power, we could see the individual molecules in our hands.

    The network of this so-called Event Horizon Telescope (EHT) included the 30-meter IRAM mirror in Spain and the APEX telescope in Chile, in which the Max Planck Institute for Radio Astronomy is involved.

    In 2017 alone, the telescopes recorded a total of about four petabytes of data – such a large amount that postal transport is actually faster and more efficient than sending the data via the Internet.

    The measurement data were calibrated and evaluated at the Max Planck Institute for Radio Astronomy in Bonn using a supercomputer, the correlator.

    “For the first time, the results give us a clear view of a supermassive black hole and mark an important milestone in our understanding of the fundamental processes that determine the formation and evolution of galaxies in the universe,” says Anton Zensus, Director at the Max Planck Institute in Bonn and Chairman of the EHT Collaboration Council. Zensus said it was remarkable that in this project astronomical observations and theoretical interpretations led faster than expected to the expected result.

    This is the first ever photo of a black hole

    Astronomers around the world celebrated today’s unveiling. “Having spent about 20 years helping to visualize the high-energy universe, I am seeing this silhouette of a black hole. That it happened in my lifetime is incredible,” says Kim Kowal Arcand, visualization and emerging-tech lead for the Chandra Observatory.

    “This is to me the cherry on top of an amazing rush of astronomical discovery: moving from what was in the realm of science fiction to science fact.”

    The image was created using radio astronomy. Most radio astronomy is done using large dishes that capture radio waves hitting Earth. But creating an image of the black hole required a telescope quite a bit larger. Researchers needed one the size of our planet.

    That’s why the Event Horizon Telescope combined measurements from radio observatories on four separate continents.

    The array is currently made up of sites in North America, South America, Europe, and Antarctica, with other locations being included over its life cycle.

    When all dishes take measurements at the same time, they can be combined into a conglomeration of data, similar to what’s taken on a smaller scale in radio dishes. (Check out a great explainer video that goes into more detail here.)

    The information used to make the image revealed today comes primarily from data taken in April 2017.

    Over the past two years, researchers have worked to turn that information into the clearest image possible by syncing up the measurements taken concurrently around the world.

    In 2018, an observatory in Chile was added to help create a clearer photo, after the initial results that came back were a tad foggy.

    Darkness Visible, Finally: Astronomers Capture First Ever Image of a Black Hole

    Continue reading the main story

    Astronomers announced on Wednesday that at last they had captured an image of the unobservable: a black hole, a cosmic abyss so deep and dense that not even light can escape it.

    For years, and for all the mounting scientific evidence, black holes have remained marooned in the imaginations of artists and the algorithms of splashy computer models of the kind used in Christopher Nolan's outer-space epic “Interstellar.” Now they are more real than ever.

    “We have seen what we thought was unseeable,” said Shep Doeleman, an astronomer at the Harvard-Smithsonian Center for Astrophysics, and director of the effort to capture the image, during a Wednesday news conference in Washington, D.C.

    The image, of a lopsided ring of light surrounding a dark circle deep in the heart of a galaxy known as Messier 87, some 55 million light-years away from Earth, resembled the Eye of Sauron, a reminder yet again of the implacable power of nature. It is a smoke ring framing a one-way portal to eternity.

    To capture the image, astronomers reached across intergalactic space to Messier 87, or M87, a giant galaxy in the constellation Virgo. There, a black hole several billion times more massive than the sun is unleashing a violent jet of energy some 5,000 light-years into space.

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    Black hole picture captured for first time in space breakthrough

    Astronomers have captured the first image of a black hole, heralding a revolution in our understanding of the universe’s most enigmatic objects.

    The picture shows a halo of dust and gas, tracing the outline of a colossal black hole, at the heart of the Messier 87 galaxy, 55m light years from Earth.

    Quick guide

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    • Black holes were first predicted by Einstein’s theory of general relativity, which reimagined gravity as the warping of space and time by matter and energy. 
    • The equations predicted that, beyond a certain threshold, when too much matter or energy is concentrated in one place, space and time collapse, leaving behind a sinkhole through which light and matter can enter but not escape. 
    • At first these were thought to be mathematical oddities, rather than real astronomical objects, but in the past century overwhelming evidence has confirmed that black holes are out there.

    The edge of the black hole is defined by its so-called event horizon. This is the point at which escaping would require something to travel at faster than the speed of light – which as far as we know nothing does – so it is the point of no return.

    Black holes are surrounded by an accretion disk of dust and gas, orbiting at close to the speed of light. A lot of this material is destined for oblivion, although some of it is ejected as powerful jets of radiation.

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    The black hole itself – a cosmic trapdoor from which neither light nor matter can escape – is unseeable. But the latest observations take astronomers right to its threshold for the first time, illuminating the event horizon beyond which all known physical laws collapse.

    The breakthrough image was captured by the Event Horizon telescope (EHT), a network of eight radio telescopes spanning locations from Antarctica to Spain and Chile, in an effort involving more than 200 scientists.

    Sheperd Doeleman, EHT director and Harvard University senior research fellow said: “Black holes are the most mysterious objects in the universe. We have seen what we thought was unseeable. We have taken a picture of a black hole.”

    Astronomers reveal first-ever picture of a black hole – video

    France Córdova, director of the US National Science Foundation and an astrophysicist, said that the image, which she had only seen as it was unveiled at the press briefing she was chairing, had brought tears to her eyes. “We have been studying black holes for so long that sometimes it’s easy to forget that none of us has seen one,” she said. “This will leave an imprint on people’s memories.”

    The image gives the first direct glimpse of a black hole’s accretion disc, a fuzzy doughnut-shaped ring of gas and dust that steadily “feeds” the monster within.

    The EHT picks up radiation emitted by particles within the disc that are heated to billions of degrees as they swirl around the black hole at close to the speed of light, before vanishing down the plughole.

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