Astronomers react to black hole images

In one of the biggest scientific announcements of recent times, an international collaboration of astronomers and astrophysicists revealed overnight the first ever image of a black hole.

The image, resembling a bright donut, shows for the very first time the Event Horizon – the point at which no light can escape the gravitational pull of the black hole. It’s this point where some of the most extreme physics occur, say astrophysicists.

The black hole is located in the centre of the Messier 87 galaxy, approximately 55 million light years away. With a mass of around 6.5 billion Suns packed into the space equivalent to our Solar System, the black hole is far more massive than the one found in the centre of the Milky Way.

The discovery was made by the Event Horizon Telescope – a system that linked radiotelescopes around the world and compiled observations to effectively create a single Earth-sized telescope. The data, some 5 petabytes worth, was then compiled using an algorithm developed by Katie Bouman, a postdoctoral researcher formerly of MIT, now with Caltech.

“Astronomers have successfully observed the invisible,” says Alister Graham, a Professor of Astronomy at the Swinburne University of Technology, who was not directly involved with the announcement.

Australian astronomers and astrophysicists have expressed their amazement, intrigue and excitement about the black hole image, saying it opens a whole new level of knowledge about some of the most mysterious features of the cosmos.

Alan Duffy, Swinburne University of Technology

“The worldwide near-decade long experiment is nearly as epic as the prize itself – an impossible picture of a black hole.

Blackholes are black as no light can escape them to reach us so the picture is in fact of the glowing bright material swirling around it.

While we know black holes exist thanks to hearing their collision through gravitational waves we still want this picture and that’s because seeing is believing.

The shape of the shadow of the black hole against the bright material around it can test Einstein’s Theory of General Relativity.

Just imagine if the picture isn’t what we expect, a new era of astrophysics could be revealed! If the picture is as predicted then Einstein was vindicated in a way he couldn’t conceive of being possible a century ago.”

Lisa Harvey-Smith, University of New South Wales and Australia’s Women in STEM Ambassador

“As someone who has studied the environments of supermassive black holes, this long-awaited result from the Event Horizon Telescope is extremely exciting. Although we have been able to measure the properties of supermassive black holes before, this is the first time that we have seen a picture of the light from their very edges.

By using a telescope the size of the Earth, the team has been able to make an exquisite picture, in unprecedented detail, of the light bent around the edge of the black hole in the middle of a nearby galaxy.

This research is particularly important because it has the potential to test Einstein’s theory of gravity to the limits.”

Travel from Earth to the M87 Black Hole

Video from EHT Collaboration

Fred Watson AM, Astronomer-at-Large at the Department of Industry, Innovation and Science

Today, the Event Horizon Telescope has shown us the invisible. On a truly historic day in the annals of astronomy, the world’s media were treated to a remarkable image. It shows the shadow of the event horizon of a 6 billion solar mass black hole at the centre of the active galaxy M87, clearly defined by a telescope the size of the Earth.

While M87 is active in the sense that its black hole is consuming gas and stars around it, it is currently relatively quiescent, allowing the event horizon shadow to be well resolved. The observed ring of light – really high-frequency radio waves – is consistent with the prediction of a photon ring that has only just escaped the clutches of the black hole.
The successful observations were made using an array of eight radio telescopes equipped with special data recorders, atomic clocks and sensitive detectors. As well as the equipment working properly, the weather had to be good at all the sites for the experiment to work. In fact, out of a 10-day allocation of telescope time, only seven days of observation were required. The result was five petabytes of data – the equivalent of 5,000 years-worth of MP3 plays – which have now been reduced to an image of a few kilobytes.

The feat involved a decade of work by a major international collaboration. Project Director Shep Doeleman paid tribute to the many scientists involved, with special praise for the early-career researcher who carried out much of the drudgery of routine data reduction. Asked whether there was a party once the final image had emerged, Doeleman admitted that the overwhelming emotion was surprise that the image was as expected. National Science Foundation Director, France A. Córdova, who had not seen the image prior to the media conference, confessed that it brought tears to her eyes.
The collaboration has also observed the much nearer, but smaller, black hole at the centre of the Milky Way Galaxy known as Sagittarius A*, and data reduction work is continuing on that. There is also the promise of more telescopes being added to the collaboration, together with a move to higher frequencies to improve the resolution.

Watch this space!”

Brad Tucker, Australian National University

“Black holes are some of the most fascinating objects in the Universe. In the past few years, we’ve made great progress in understanding these objects. And today we make another big leap – being able to see the effects of a black hole.

The direct image of the event horizon is amazing. It allows us to directly measure how black holes affect gravity and time. I never thought we would be able to see something that has been so mysterious.”

Steven Tingay, ICRAR at Curtin University

“The Event Horizon Telescope (EHT) project has just released the first direct image of material disappearing across the event horizon of a supermassive black hole in a galaxy approximately 55 million light years away (one of our closest neighbour galaxies).

For decades, we have been studying black holes but could only indirectly see the effects of their extreme masses and gravitational fields. In the last few years, we have famously seen black holes merging, via the LIGO and VIRGO gravitational wave observatories, confirming the predictions of Einstein from one hundred years ago from his theory of General Relativity.

The EHT images show, for the first time, the point close to the black hole from which nothing can escape, even light, the so-called event horizon. The simple but astonishing images show a ring of radio emission that hugs the black hole event horizon, again confirming the predictions of General Relativity.

The EHT is composed of a collection of radio telescopes operating at very high frequencies, scattered around the world, generally in remote and high elevation locations, posing very challenging problems in engineering and data processing to effectively build a telescope with a diameter equal to the Earth’s diameter.  This is an astonishing result, obtained in record time, built on international collaboration and multi-disciplinary efforts. There is clearly lots of room for improvement and I expect we will see in the near future even better images from the EHT, uncovering more of the mystery of black holes.”

David Gozzard, Australian National University

“This is really exciting because it is the first time we have got a clear look at a black hole. The black hole’s event horizon is where the laws of physics as we know them break down. Studying this region is crucial to understanding what goes on inside a black hole, what happened at the moment of the Big Bang, and the deeper underlying laws of nature. But this is just the start. The image is still pretty blurry. It’s like looking through frosted glass. As we work to make our telescopes get bigger and more powerful, we can expect many more exciting images and discoveries to come.”

Fiona Panther, UNSW Canberra

“The image that you see of the supermassive black hole comes from material that has teetered on the brink of a supermassive black hole. This material emits millimetre radio waves, that reach telescopes on Earth after a journey that took 55 million years. Collecting and analysing these radio waves is a challenging task and these remarkable images are a testament to how human curiosity about our universe, and our ability to collaborate, can be harnessed to do incredible things. The new challenge will be to interpret what has been observed, and to investigate how the new knowledge we have gained fits into our current understanding of how black holes work.”

Richard de Grijs, Macquarie University

“The technical challenges were formidable, but that didn’t stop an international team of more than 200 scientists to link together essentially all existing submillimetre telescopes – as far south as the South Pole – to create a virtual telescope the size of the Earth.

Basic physics tells us that the larger a telescope is, the smaller the details are that one can observe. With a truly Earth-sized telescope, the Event Horizon Telescope (EHT) team took the ultimate picture and, in the process, proved Einstein right once again.

Training their facilities on the centre of the massive elliptical galaxy Messier 87, in one of the most densely populated regions of the Virgo Cluster of galaxies some 55 million light-years from Earth, the EHT recorded the first-ever image of the ‘event horizon’, the point of no return on an imaginary journey towards the galaxy’s central black hole.

Nothing, not even light, can escape from inside the event horizon. Yet, when matter falls into the event horizon, it becomes superheated and outshines pretty much everything else nearby. The image shown today shows a slightly blurred ring, but one should keep in mind that given the small size of the event horizon at the distance of Messier 87, this is a truly remarkable measurement.

Today represents indeed an historic moment: it marks the confirmation that black holes exist and that support for Einstein’s theory of general relativity is as strong as ever. This could only have been achieved by collaborating internationally, by putting science on a pedestal irrespective of political, religious or other controversies. Once again, this team has proven that science diplomacy is a viable means of bringing people together to work on common goals while overcoming numerous challenges against almost insurmountable odds.”

The EHT, a planet-scale array

Video from EHT Collaboration

Adam Deller, Swinburne University of Technology

“This was an amazing technical feat – to make it work, the EHT team used radio telescopes that are thousands of kilometres apart and lined up the signals they receive to around a millionth of a millionth of a second! When they do, they’re able to make phenomenally sharp images – if your digital camera was this good, you could take a photo of a person hundreds of kilometres away and make out individual strands of hair on their head.

They used this capability to capture the shadow that a supermassive black hole casts – it’s the first time astronomers have ever really “seen” a black hole.  When you think about it, the photons that travelled almost 60 million years to hit the EHT telescopes in 2017 and make this image were extremely lucky – they were born right next door to a monstrous black hole and nearly, nearly fell in. The shadow we see in the image is the absence of photons right next to them that weren’t so lucky, they fell over the black hole’s event horizon and no-one will ever see them again.”

Adam has previously been a co-author on a couple of papers with some of the authors of these papers, on some semi-related work (millimetre images of the black hole in the middle of our galaxy).  He has also developed some of the instrumentation that was used in part of the data analysis in this work (the DiFX software correlator) so is acknowledged in the paper.

Ilya Mandel, Monash University

“It was hugely exciting to see the fantastic results from the Event Horizon Telescope.

Using a network of radio telescope around the Earth and incredibly precise interferometry, the EHT team imaged the central black hole in the galaxy M87, more than 50 million light years away.  Their image matched the predictions of Einstein’s general theory of relativity: in the image of radiation from a disk of matter spiralling into the black hole, this supermassive black hole itself casts a gargantuan shadow.

The size of the shadow has been used to get the most precise measurement of the black hole’s mass: a whopping 6 billion times the mass of the Sun. It’s a monster, but a very law-abiding one, precisely following the rules laid out by general relativity. ”

Samuel Hinton, University of Queensland

“For decades cosmological models have predicted black holes, and black holes have been validated over and over again with indirect evidence. So it’s easy to lose sight of the fact that – until now – we’ve never actually seen one. But the Event Horizon Telescope has peeled back the curtain and given us our first direct image of an event horizon – the boundary in spacetime that wraps a singularity – the boundary at which, once passed, nothing can ever leave. And we’ve got it on picture. Lying in the heart of supergiant galaxy Messier 87 is a supermassive black hole dwarfing anything inside the Milky Way, a black hole more than six billion times the mass of our sun. Surrounded by a fiery maelstrom of infalling matter over a hundred billion degrees in temperature, we see the event horizon, a region of deathly calm in the most chaotic region of space ever imaged. This black hole allows us to measure Einstein’s General Theory of Relativity in the drastically curving region of spacetime around an event horizon, and Einstein’s Theory passes yet one more test with flying colours.”

James Miller-Jones, ICRAR at Curtin University

“An international team of astronomers have, for the first time, peered into the heart of a black hole, imaging the dark region corresponding to its event horizon—the point from which light can no longer escape.

Creating a telescope by combining the data from multiple antennas spanning the entire globe, the Event Horizon Telescope collaboration made an image of the supermassive black hole at the centre of the nearby galaxy Messier 87.

With a mass 6.5 billion times that of the Sun, this black hole has an event horizon roughly the size of our entire solar system. Located at a distance of 55 million light years, the magnifying power of the telescope required to see the black hole’s shadow was the equivalent of being in Perth and reading the writing on a coin located in Sydney.

The image confirms that black holes do have event horizons as opposed to dim but solid surfaces, and was in full agreement with predictions from Einstein’s theory of general relativity, allowing this century-old theory to pass yet another rigorous test with flying colours.

The centre of the galaxy Messier 87 is known to launch extremely powerful jets that travel at close to the speed of light, carrying energy away to distances of thousands of light years.

Emanating from a region no larger than our solar system, these jets affect the entire galaxy, as well as its surrounding environment.

This new measurement is proof that a black hole is indeed responsible for launching such energetic jets, which in other, more distant galaxies, are known to shape some of the most massive structures in our Universe.”

Michael Brown, Monash University

“Astronomers have been accumulating evidence for black holes for almost half a century. The simplest explanation for quasars and certain X-ray binary stars is that they are powered by black holes. We can see stars zipping around an unseen mass at the centre of our own galaxy, and we similar evidence of stars and gas orbiting vast unseen masses in other galaxies too (including Messier 87). The creation of black holes produces gravitational waves, which were observed for the first time just a few years ago.

But we haven’t had an image of a black hole and its surrounds until now.

This intriguing image of Messier 87’s black hole may not be as impressive as its CGI cousin from the movie “Interstellar.” However, it is consistent with what theoreticians have been expecting. We can see a ring of light around a circular shadow, the result of luminous plasma near the black hole moving at close to light speed and light being deflected by the black hole’s vast gravitational pull.”

This article was first published on Australia’s Science Channel, the original news platform of The Royal Institution of Australia.

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