The Fantastic Story of M87’s Black Hole Photo (Astronomy)

Radboud University astrophysicist Heino Falcke, among the protagonists of the Event Horizon Telescope project and the first image of a black hole, has reconstructed the milestones of that historic milestone in the best-seller “The enigma of black holes. Discovering the universe and human nature ”, now also available in Italian bookstores. Corrado Ruscica interviewed him for us

On the morning of April 10, 2019, millions of people from all over the world followed the press conference live in which Heino Falcke , professor of astrophysics at Radboud University in Nijmegen and guest-professor at the Max Planck Institute for Radio Astronomy in Bonn, presented the first “Photo” of a black hole , the one at the center of the galaxy M87 – an image that has now become iconic. A grandiose scientific result made possible thanks to a titanic enterprise, born from an idea of ​​Falcke himself, which made it possible to coordinate eight observatories by virtually creating a single radio telescope the size of the Earth: Eht, the Event Horizon Telescope. A historic milestone whose fundamental stages are told by Falcke in the book The enigma of black holes. Discovering the universe and human nature , a best-seller now also available in Italy, published by Mondadori.

Traveling on an adventurous journey through space and time, from the study of black holes to the still unsolved mysteries of the universe, the author delves into an elusive and exciting enigma, questioning the doubts and certainties of science without neglecting a reference to the wedding ring. A surprising virtual itinerary, in which scientific rigor is combined with simple and fluent writing, vibrant with wonder and poetry. A path that is at the same time the dream of a man with his gaze turned towards the firmament and that makes us rediscover the fundamental questions with which we have always “knocked hard on the gates of heaven”. Media Inaf interviewed him.

Professor Falcke, what was your reaction when you first saw the image of the ring of light?

“It was a moment of awe, wonder and fear. Amazement, because we were looking at an exotic world never seen before until a few moments ago. Wonder and gratitude that it really worked and fear that we could have been misled. It sounded too good to be true. The image was surprisingly familiar. A bit like the photo of your biggest, secret love that you’ve never seen in person but always had in mind. And now you are in front of “her” for the first time and you see that she is more beautiful than you imagined ».

What have we learned from this image?

“That these dark, supermassive monsters residing at the center of galaxies are indeed black holes, or at least they show up as our theories predict. We see the light literally disappearing into the darkness of the event horizon. We can also test general relativity with higher accuracy than we are able to do within the solar system. Einstein’s theory works very well when applied to stellar-sized black holes , which we can “hear” through gravitational wave detectors such as Ligo and Virgo, but also to supermassive black holes., which have a mass 100 million times higher than the solar one and which we can observe with Eht. This is what we call the scale invariance of general relativity, which holds over a truly impressive wide range of values ​​».

Did you expect to find something different?

“Indeed, yes. The black hole’s shadow could be much smaller, the gas could hide the shadow, and even the predictions of general relativity could be wrong. We have never observed this region of space-time in detail. Eventually, hopefully things may turn out differently, because you want to be surprised. But to be the start, it’s comforting that things went as planned. Apparently, we did everything well but we will continue to look for any deviations from what we expect ».

Astrophysicist Heino Falcke with the English edition of his book, “Light in the Darkness: Black Holes, the Universe, and Us” © INAF

Eht was his idea. How did you manage to set up this great group of researchers?

“I was the first to point out that we could have seen the shadow of a black hole at certain radio frequencies by virtually building a telescope the size of the Earth. This goes back 25 years. Ultimately, it was a joint effort by several parties, growing over the years. But to do this you have to convince others that it is a good idea, then you have to create a group that wants to reach the goal together, wait for the radio telescopes to be built, have funds for the experiment and finally be sure not to stay. cut off. Science is also competition. Americans have a lot of financial resources, telescopes and excellent researchers. They definitely pursue their goals and require leadership. As Europeans, I believe we need to be able to have our say. For this project we have had excellent collaboration from excellent radio astronomy institutes in Germany, Italy and other European countries, and in addition we have received great support from the European Research Council. This time we acted as a team ».

Why do you think the world stopped that day and millions of people were thrilled to see the image of the black hole?

“Black holes go beyond science. They are modern, mythological objects that arouse mystery. They create a morbid fascination of death and destruction. They confront us with the limits of knowledge. And then they represent an exotic world so different from ours. “Seeing them” for the first time is like discovering a new continent ».

Why is it so important to study black holes?

“I believe the future of physics will be decided on the far edge of black holes. The problem of reconciling the two major theories of the universe, on the one hand quantum physics which describes infinitely small objects, and general relativity, which describes the largest objects and the entire universe, is still a mystery today. It is precisely in the vicinity of black holes that the discrepancy between the two theories becomes more evident ».

He said physics is on the verge of a paradigm shift. What exactly do you mean?

“The past century was the century of particle physics. The century we live in could be that of the physics of space-time. For the first time, we have experiments – gravitational wave detectors and the Event Horizon Telescope – that allow us to study physical phenomena at the extreme edge of the event horizon. We now have real data. While Einstein’s theory will not be overturned in some time, the ability to evaluate new theories alone represents enormous creative potential for scholars. Perhaps all of this is inspiring a new Einstein somewhere in the world, or a new Einstein has already been born when we showed the image of the black hole. “

Do you think Einstein and his theory will triumph forever?

“Of course, Einstein’s theory will still stand, but it will have to be changed in some regimes. This is similar to Newton’s theory of gravity, which describes physical phenomena within the solar system very well. But when real precision measurements are made, such as the orbit of Mercury, only then do we discover that a better description is needed. The same thing will happen with Einstein’s theory. If we go into the early epochs of cosmic history, if we look at the expansion of the universe or if we explore the event horizon of black holes, we will eventually need a more complete theory. “

What do you expect for the near future?

“We took the first step and showed the feasibility of the experiment, but science is made up of long paths. If we can make more images, we can reduce uncertainties by a factor of 3-10 over the next decade. To do this, it will take hard work and a lot of patience. It is necessary to optimize the set of radio telescopes and build one or more of them in Africa. Then, the next step will be to go into space to virtually make an antenna larger than the size of the Earth. It is not a crazy idea and we are working on it ».

Featured image: “The enigma of black holes. Discovering the universe and human nature “. By Heino Falcke and Jorg Romer. Mondadori, 2021. 336 pages, 22 euros © INAF

Provided by INAF

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