L'Italo-Americano

L'Italo-Americano THURSDAY, MAY 2, 2019 www.italoamericano.org 4 Ciriaco Goddi is in charge of the BlackHoleCam project, that managed to take the time-defining photo of a black hole in recent weeks @ Ciriaco Goddi BARBARA MINAFRA Continued to page 6 NEWS & FEATURES TOP STORIES PEOPLE EVENTS The black hole at the center of M37 @INAF I t is considered the photo of the century. He has not (yet) won the Pulitzer but has shown Einstein's Gen- eral Relativity. With two super-computers, one at Boston's MIT, and a network of radio tele- scopes from 12 to 30 meters in diameter on the various conti- nents, it immortalized a piece of science fiction: the horizon of events, the distortion of space- time, the shadow of a black hole. A Nobel Prize project. L'Italo-Americano inter- viewed the Sardinian astrophysi- cist in charge of the BlackHole- Cam project. Ciriaco Goddi, 43, degree and PhD in Physics at the University of Cagliari, three years at Harvard, Germany, and in Holland since 2012. All the way to EHT: Event Horizon Telescope, the international pro- ject that measures the enormous mass of the black hole at the cen- ter of a galaxy 55 million light years away from Earth. Italy par- ticipates with several scientists, the National Institute of Astro- physics (Inaf) and the National Institute of Nuclear Physics (Infn). What types of emotions, personal and scientific, do you feel when looking at this part of the universe? During the past weeks, I have understood that a photo of a black hole can give emotions to everyone, even those who are not experts in science or astro- physics. As researchers, we spent decades waiting for this, so ours is a different, more personal type of joy, as we see our dream come true. But even I, who have worked for years on this project, feel a unique emotion when I look at that image, knowing it is a ring of matter and light shaped by space-time deformation, a consequence of the very strong gravity associated with the mas- sive object at its center: a black hole. Not a simulation or an ani- mation — we have seen thou- sand of those — but the very shadow of a black hole, a place from which not even light can escape, just as Einstein had pre- dicted. What can you see beyond that black circle wrapped in incandescent light? Looking at the image, one can imagine what happens to the plasma orbiting around the black hole, rotating at speeds close to that of light, accelerating and gradually descending the spiral staircase that leads it beyond the event horizon, where it disap- pears for ever, swallowed by the black hole itself. It's almost like one can feel (and not just see) the luminous eddy of matter that coils around until it disappears into the deep black of that hole. Someone defined the event horizon the "gates of eternity." It is a beautiful thought, it gives the chills. And the awareness that, from now on, the event horizon is no longer just an immaterial mathematical con- cept — the mathematical solu- tion of a theory — but has become a physical object, observable and measurable by scientific method, is a huge achievement for us astrophysi- cists, and an exciting idea in general. Even if we don't know what happens in there, the mere fact of being able to see it with our own eyes makes science fiction dreams less surreal. Your contribution is a "great step of humanity." What does it feel like to have helped create a new page in the history of astrophysics? When we started, we were aware of the difficulties. We were pushing the limits of cur- rent technology, but at the same time we were sure we would succeed. It was a long journey, an emotional one, at times. This result comes more than 100 years after the publication of Einstein's Theory of General Relativity and Schwarzschild's mathematical solution that pre- dicts the singularity and exis- tence of black holes (at least mathematically). After the pio- neering studies of the 1970s, which used the first simulations to predict black holes' appear- ance (if they could have been observed), in 2000 we had the intuition that observing the super-massive black hole at the center of the Milky Way could have been possible thanks to the technology available. Thoughts went in particular to the very-long baseline inter- ferometry technique (VLBI) used by EHT, which was fol- lowed by a successful technolog- ical development (started about 20 years ago) aimed at applying this technique to high radio fre- quencies (used by EHT). Pro- jects began being developed in the United States and Europe around 4-5 years ago, and they were dedicated exclusively to this goal. They developed first independently and then jointly, with the first global observation campaign taking place in 2017. There was a scrupulous work on the elaboration of the data col- lected in the last 2 years, which finally allowed us to see what seemed invisible: the black hole. Now we know what it looks like. It took a long time, but we've Italian science leads on: Ciriaco Goddi and the crew who photographed a black hole

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