German Nobel Prize in Physics Winner

German Nobel Prize in Physics Winner

"It's Unbelievable All That's Going On at the Moment in Astronomy"

 

German astrophysicist Reinhard Genzel was just awarded the Nobel Prize in physics. In an interview, he talks about how he discovered the black hole at the center of the Milky Way.

 

Interview Conducted by Johann Grolle und Christoph Seidler

 

Spiegel International

15.10.2020,

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Depiction of a black hole: "It's important to get people excited about research," says Reinhard Genzel.

Foto: All About Space Magazine / Future Publishing / Getty Images

 

DER SPIEGEL: Professor Genzel, congratulations on receiving the Nobel Prize in physics. What were you doing when you received the call from Stockholm?

 

Genzel: The same thing that we scientists have been doing all day everyday for the last six months: Zoom, Zoom, Zoom. I was sitting with 25 other people in the Zoom conference of a virtual committee belonging to the Max Planck Society.

 

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DER SPIEGEL: And your telephone rang right in the middle of the conference?

 

Genzel: It was almost funny. I was sitting in front of the screen, knowing that I would have to spend the next six hours doing the same. Then the phone rang, and somebody said: "This is Stockholm." Then, the call started breaking up. It took some time before I could hear the "sekreterare" again. During that time, I went over to the window and started thinking: "This damned pandemic. Now I've started hallucinating."

 

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Reinhard Genzel was born just outside of Frankfurt and is now director of the Max Planck Institute for Extraterrestrial Physics in Munich. For his discovery of the supermassive black hole Sagittarius A* in the center of our galaxy, the Milky Way, he received the 2020 Nobel Prize in physics, along with co-discoverer Andrea Ghez.

 

DER SPIEGEL: It's a Tuesday in early October, shortly after 11 a.m. - time for the Nobel Prize in physics to be announced. And you want us to believe that you didn't know who was on the line?

 

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Genzel: No. You have to believe me. This year, I wasn't thinking about it at all. In previous years I was, like in 2011. We had come a long way with our measurements that year and I thought to myself: It could really be our turn. I'm pretty sure that we were close that time.

 

DER SPIEGEL: And after the call, you returned jubilantly to your Zoom call to tell everyone?

 

Genzel: No, no, everything goes according to a strict protocol. Twenty minutes pass between informing the winner and announcing the prize. During that time, you're not allowed to tell anyone. They really insist on that.

DER SPIEGEL: So you acted as if nothing had happened?

 

Genzel: Well, I didn't exactly do that either. I said to the committee chairman, a vice president of the Max Planck Society: "Mr. Blaum, I have to take care of something. Maybe you should turn on the television in about a quarter of an hour."

 

DER SPIEGEL: Why is it that you were hoping for a Nobel Prize in 2011 but weren't expecting one in 2020?

 

Genzel: There are several reasons for that. For one, I was out of the running in a sense since I had received the Crafoord Prize eight years ago. For Sweden, that is the equivalent to the Nobel Prize for fields of research that don't fit into the Nobel categories - things like mathematics, earth sciences and my field, astronomy. Accordingly, I didn't think I had a chance any longer, and certainly not this year.

 

DER SPIEGEL: What is different about this year?

 

Genzel: If you look at the Nobel Prize for physics over the last five years, you'll see that they have been awarded for neutrinos, gravitational waves, cosmology and exoplanets. Was it to be astrophysics again? You can perhaps imagine that people in other fields of physics might start grumbling.

 

DER SPIEGEL: We are apparently living in the golden age of astronomy.

 

Genzel: Absolutely. It is unbelievable all that is going on at the moment. And it will continue. Take just exoplanets, for example. We are currently experiencing a downright explosion in knowledge. And GRAVITY, our interferometer at the Very Large Telescope (VLT) in Chile is part of this explosion. We have just recently measured the atmospheres of some exoplanets. We are on the brink of being able to practice astrochemistry on planets outside our Solar System.

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Astrophysicist Reinhard Genzel: "You have to believe me. This year, I wasn't thinking about it at all."

Foto: Roderick Aichinger / DER SPIEGEL

 

DER SPIEGEL: There is another reason why people may have been surprised that you were awarded the Nobel Prize. Your discovery of the black hole in the middle of the Milky Way was overshadowed by the spectacular image of a black hole published by the Event Horizon Telescope team last year. Why were they not rewarded?

 

Genzel: It was good that their image received a lot of attention. It is important to get people excited about research. And astronomy has a special role to play.

 

DER SPIEGEL: Are you trying to say that the image was good for attracting an audience, but wasn't all that important from a scientific point of view?

 

Genzel: No, I wouldn't say that. It is true, though, that such a beautiful, orange picture is enticing, even if it can't be clearly interpreted. An open discussion is still ongoing among experts: Are we really sure of what we are looking at in this picture?

 

DER SPIEGEL: Wherever black holes are discussed, that picture is shown. And you are now telling us that we don't really even know what it is?

 

Genzel: Exactly. It could be that we are looking at the shadow of a black hole, as it is commonly portrayed. But it could also be the outer wall of a jet that is coming directly at us at the speed of light. To know for sure, we need additional measurements. But we have a problem at the moment: the corona pandemic. Most Earth-based telescopes have been switched off.

 

DER SPIEGEL: Tell us a little bit about your research. What is the importance of a black hole at the center of the Milky Way?

 

Genzel: We are talking here about a supermassive black hole around which gravity is particularly strong. Most interesting, of course, would be to take measurements from inside of it. That, though, isn't possible. There is a natural limit: the event horizon. Our goal is thus to creep as close as we can to this limit in an extreme environment where everything is moving at around half the speed of light, a place where the tidal forces of gravitation are so strong that they tear everything apart. By studying such black holes increasingly precisely, we are gaining a better and better understanding as to why our Milky Way is a rotating spiral galaxy while other galaxies have the form of an ellipse. Because black holes play a decisive role in that difference.

DER SPIEGEL: When did you become interested in supermassive black holes?

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