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Q&A: Professor and astronomer receives $875,000 to study supermassive black holes

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Peter Behroozi is an assistant professor of astronomy at the University of Arizona and an assistant astronomer at the Steward Observatory. He recently received a grant from the David and Lucile Packard Foundation for $875,000 to study supermassive black holes.

University of Arizona Assistant Professor of astronomy Peter Behroozi received a $875,000 grant from the David and Lucile Packard Foundation. The foundation provides funding to scientists who are still within the early stages of their careers as researchers. Behroozi, who also works as an assistant astronomer at the UA's Steward Observatory, will use the money to study supermassive black holes.

The Daily Wildcat spoke to him about his research plans. 

Daily Wildcat: How did you become interested in astronomy?

Peter Behroozi: It was totally by accident. I went to Stanford [University] for graduate school in physics. The way the program works is that there's a rotation with up to three different professors your first year, and all the people who I wanted to work with doing laser physics didn't have any openings. 

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I said, "Why not? I'll try astronomy," because there's another professor who did simulations of the entire universe on big computers, and I thought that sounded super cool. So I tried that and then I loved it so much that I stuck with that professor. I didn't even try going back to research physics, and that began my career. 

DW: How did you get the Packard grant? 

PB: That's a competition both at the {University of Arizona] and then also nationwide. The first stage is for the UA to pick two people to send to the Packard competition, so I was very lucky to be one of those. The Packard Foundation picks among the hundred applicants, so basically 50 universities and two people at each, and the Packard Foundation has very famous and also very old people – you can find a picture of them on the Packard Foundation website – to decide among those hundred candidates, and they picked 22 for this year. 

DW: How long did that application process take?

PB: The competition at the UA started in January. So, they just announced the fellowship now, in the middle of October.

DW: What were some of the requirements for application?

PB: They wanted to see a list of my accomplishments, really, and previous positions, as well as a two-page summary of my research and then three letters of recommendation.

DW: How would you explain what you plan to research in the simplest way possible?

PB: The project I proposed was to study the growth history of supermassive black holes. Black holes are pieces of the universe that have gotten so dense, so much matter in the same spot, that they've created a region where not even light can escape. Anything that passes within something called the event horizon in a black hole gets sucked inside and can never escape.

The UA recently was part of a collaboration that took the first picture that we have of a black hole that's surrounded by matter that's falling in. That was earlier this year with the Event Horizon Telescope. We know these strange parts of the universe exist and I want to uncover what was the history, how did they form inside galaxies?

We believe the center of every galaxy, like our galaxy the Milky Way, that there exists one of these supermassive black holes. The way I study this is that it's impossible to look at a single black hole and figure out what its history was — that is, how fast it grew over time. 

We can see growing black holes, or at least the matter falling into black holes, all across the history of the universe. I built models of the entire universe to try to capture the growth of black holes and compare those models to the real thing. 

I generate entire simulated universes where I know how black holes grow, and I compare those to the real universe and see, "Do they look the same? Do they not look the same?" If they do look the same, then I've been able to verify that my guess for how black holes grow matches what is happening in the real universe. 

Just to make an analogy to something that's maybe more familiar, if you think about human growth, how humans have changed or evolved over time, you can't take a single human and say, "This was your history," but if you look deeper and deeper into the surface, you see things that seem to be related to humans, like our ancestors, the Neanderthals, and so on, as you go earlier and earlier into the history of Earth. 

So I'm doing something similar to black holes and looking for the ancestors of black holes that existed at earlier and earlier times in the history of the universe, and then trying to construct the evolutionary pathways of black holes from that. 

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DW: How long have you had this research idea in mind?

PB: I've actually had this idea for quite a long time. I would say five years. It's been very hard to find funding for it because it's someone outside of the field for which I'm best known.

I do most of my work in galaxy formation and that's why I was hired at the UA. The research I proposed for the Packard fellowship is with supermassive black holes. What happens usually when one applies to traditional grants through the government or other places, people look at your past work to see, "Have you done anything with black holes?" If you haven't, then they view your application with a little more skepticism. 

Because success rates are so low, people end up effectively being very risk-averse, so they fund the projects that only seem very likely to succeed, but they also tend to fund projects where the people proposing them have had clear paths to success in that field. Even though my method was very interesting, and the comments I got suggested it was very interesting, people are somewhat hesitant to fund someone who's never done black hole research before. 

The Packard Foundation had been unique in that they care less if you've been very successful in a field and more about, "Does the approach sound interesting and creative and new and likely to push the whole field in a new direction?"

I was very lucky that they exist and fund that kind of research, otherwise I wouldn't be able to do it.

DW: How long do you anticipate this project taking?

PB: It'll probably be around five years. It'll be different stages of getting closer and closer to the real answer that we're hoping to achieve over those five years.

DW: The grant is $875,000 over five years – why does your research require that amount of funding?

PB: For most people, me included, that's an almost unimaginable amount of money. Actually, if you ask, "How much does it cost to hire a student and post-doctoral fellow to work?" That's actually then enough to fund one student and fellow for five years. If you divide it up each year, it's about $175,000 and split that across two people's salaries plus benefits plus retirements plus everything, it ends up being eaten up very quickly.

DW: What do you hope to find from your research?

PB: Definitely, I want to understand how black holes grew and why they grew. Another hope that I have with this research is to learn a little more about, "What are the seeds of these supermassive black holes?"

For context, when I talk about a supermassive black hole, I'm talking about something that can be up to 10 billion times the mass of our sun. Researchers of the UA have found that these enormous black holes exist, even when the universe was maybe 5 to 10% of its current age. In other words, in not very much time, the universe created these really enormous black holes for no light to escape. It's been a puzzle for a long time why that could be, and there are several different ways people have thought up for this to happen.

I hope with my research to be able to find out which way it is to understand what was the tiny seed that eventually grew so much to become these enormous, supermassive black holes very early in the history of the universe.

DW: How do you think your research will contribute to our current understanding of black holes?

PB: The answer to the previous question depends on how matter falls into black holes and how fast black holes spin out as that matter falls onto them. We have very unclear ideas because it's very difficult to see exactly where matter is falling into black holes. 

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We can see the light that's produced. The same way that if someone has a light bulb and it's a mile away, you can see that there's light but you can't really see what's emitting that light. These supermassive black holes are so far in the distance, we can tell that there's light but we can't see details about what's happening; as matter falls in, it heats up and releases a lot of light in that process.

My work will help tell us about how fast black holes grew, and that will also give us some more insight about what's happening that we can't see today but which we hope to understand how do black holes grow. 

This interview has been edited slightly for clarity.


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