Feryal Ozel

Zierler:

This is David Zierler, oral historian for the American Institute of Physics. It is November 5, 2020. I’m delighted to be here with Professor Feryal Ozel. Feryal, it’s so nice to meet you. Thank you so much for joining me today.

Ozel:

Thank you for having me. I’m very excited.

Zierler:

To start, would you please tell me your title and institutional affiliations? And I put a ‘s’ on ‘affiliations,’ because I know you have more than one.

Ozel:

I have two departmental affiliations within the University of Arizona. I’m a professor of astronomy and of physics, they are two distinct departments. Astronomy is my primary affiliation, and I have also held visiting positions and NASA-related positions, but right now, those are my titles.

Zierler:

Did you come to Arizona with the plan to be 50/50 between the two departments?

Ozel:

Not really. I actually started out in the physics department. I am a physicist by training. My undergraduate is in physics and applied math, and my PhD is in astrophysics. And my path took me towards a more astronomy-heavy direction—basically, in a direction that my affiliation with the astronomy department at the University of Arizona was more meaningful and stronger. So, that’s how I ended up here. But I feel equally at home in both departments.

Zierler:

So in terms of your overall research agenda—the graduate students that you have, the courses that you teach, the collaborations at the University of Arizona—is it truly a half-half sort of divide between both departments for you?

Ozel:

All the classes that I teach right now are through astronomy, although we do have some joint classes that either advanced undergraduates or graduate students take, like when we teach general relativity or computational methods for astrophysics. There are certainly students from both departments that take those classes. So, my teaching is in astronomy. My committees are all in astronomy. And my graduate students, I would say, are half-half from the two departments.

Zierler:

Feryal, I love to ask this question, because everybody gives a different answer. So, let’s just get our terms on the table, as you understand them, at the outset. There’s astrophysics, there’s astronomy, and there’s cosmology. Where do you understand the overlap of these terms, and where do you understand how those terms fit with your career and your research?

Ozel:

I know that some people make these distinctions. I do sometimes, too. When we say “astronomy,” we refer to the more traditional observational methods that astronomers have used to understand and categorize the universe around us. And over time, this effort to describe and categorize developed more into developing physical models for the things that we observe. And I guess that moves more into the physics domain, so we call that “astrophysics.” Nowadays, some people really feel like they’re traditional astronomers, and a lot of people feel like they’re in this intermediate domain, where they do astrophysics—some physical modeling of the data that they get. I would put cosmology as a subset of astrophysics. I don’t find it to be a completely different way of either obtaining data or making sense of the data. So, I’m not a cosmologist, but I am an astrophysicist. Because my training has been in physics, and I love using the universe as a laboratory to understand how physics works, I just categorize myself in that astrophysics cohort.

Zierler:

Feryal, another spectrum question, both for you and for the most important collaborators that you work with, large-scale and small-scale: where is your research in terms of on the theoretical side and on the experimental side?

Ozel:

It is more on the theoretical side. But you’re right in framing this as a spectrum. I started out doing very heavily theoretical things, and at some point, I was learning how to use certain telescopes in order to be able to obtain the data to either enhance those theories, or test those theories. So, I had a track in my own career that went from very strong theory to more computational work, to, “Sure, I love observations.” I mean, I’m not an observer—that’s not my primary area, but I can certainly dabble in observations. I still lean towards theory.

Zierler:

And in terms of your graduate students, are your graduate students more likely to work in a theoretical realm or an experimental realm?

Ozel:

More likely to work in a theoretical realm, yes. I have close collaborators who are primarily observers, and we work closely in understanding the data and modeling the data. Obviously, the big collaborations have-- For example, the Event Horizon Telescope collaboration that I’m a part of, it has the whole gamut from purely theory to people who build instruments that we actually need on the telescopes to obtain the data to do the observations, etcetera. So, I work closely with those people, but my own students are in theory.

Zierler:

Well, Feryal, let’s take it all the way back to the beginning. I’d like to develop where you come from, with your family background. So, let’s first start with your parents. Tell me a little bit about them and where they’re from.

Ozel:

My parents are from Turkey. I was born in Istanbul, which is the largest city in Turkey, and I grew up there. I went through high school living in Istanbul, and both my parents are medical doctors. They’re anesthesiologists. So, I grew up in a home environment where there was certainly science talk, more medical talk. Dinner conversations were about the surgeries of the day, and things like that.

Zierler:

Were your parents from ethnic Turkish families?

Ozel:

That is so difficult to quantify, when one’s origins are in the Balkans or in the Middle East. My paternal grandparents actually moved from what is currently Greece to a place outside of Istanbul during the population exchange. So, they’re ethnically Turkish. They spoke Turkish, but they lived in in a town north of Thessaloniki. When the war ended and the population exchanges were happening, they decided to move to what is currently Anatolia. My maternal grandparents are from the northern region of Turkey. Again, a mix, because of the centuries of population mixing there. Probably there is some Georgian there, some ethnic Greek and Turkish. So, I’ve never done the DNA testing. [laugh] I’m sure I don’t know what I would find. I consider myself Turkish, as many Turks who live in that geographical area do, but I don’t actually know what ethnicities are actually mixed into that.

Zierler:

And your family comes from a Muslim background as well?

Ozel:

Yes, my family is-- I don’t come from a religious family, but I come from a Muslim family, as far as at least being culturally Muslim, celebrating the holidays and observing cultural traditions. When asked, they would say they’re Muslim. Yes.

Zierler:

Feryal, given the current events we’re experiencing in the United States, I can’t help but think about when you were born, in the mid-1970s, that was a very politically volatile time in Turkey. What were your family’s politics, and how did they fare during that episode in Turkish history?

Ozel:

One of my earlier political memories is the 1980 coup that happened in Turkey. And my parents were left-leaning—always social democratic supporters—so they were anxious during the coup. And I started school really early, so at the age of 5 I was already going to school. And I remember during the 80s and throughout my elementary school and maybe even middle school years, my parents telling me: “If anybody asks you what your political affiliation is, just say, “middle of the road.” We’re centrists. Don’t ever say we’re left-wing or right-wing.” The canned response was, “We’re middle-of-the-road. We’re not a political family.”

So, I definitely grew up with some of that self-censoring happening during that political turmoil when I was a kid in Turkey. And on the bright side though, having lived through that, I really value a democratic society, what it means to have democratic processes, fair elections, equal rights for people. So, even though as a child, I learned to self-censor a little bit, as an adult, that made me become even more outspoken about what I want in a society. And right now, of course, I live in the US. I’ve lived in the US since 1992. In a lot of ways, I’m more American than I’m Turkish, and in my adopted country, I really do try to speak out in favor of democracy and equality.

Zierler:

Feryal, this is such a great opportunity to learn a little bit about the Turkish educational system. So my first question there, in terms of elementary school, is: what impact does a family’s economic status have on the choices of schools available to them?

Ozel:

Huge. Huge impact. I think the family’s investment in education and their current economic status still determines the options that are available to kids in Turkey. Having said that, since the establishment of the republic there, there has been an effort to make science and technology high schools free of charge. So, a lot of merit-based opportunities exist, and this starts as early as elementary school. So if kids show an aptitude for science and technology, then they can go into a middle school, high school, that is free of charge, and develop their abilities. Same thing for some art high schools.

But I’m reluctant to say that that solves any sort of intrinsic problems, in the sense that you still need some basic level of early education and access to books, and even just an interest in-- Like, how does one get interested in science and technology and art and culture and language? It’s only through early exposure. So, I would say that if the kids are lucky enough to be in somewhat privileged families, not necessarily highly privileged families, maybe there is a path for them. But kids in rural areas that have less access and less educated family situations, I think it’s still a struggle for them.

Zierler:

And for you, growing up in a cosmopolitan place like Istanbul, with your parents as doctors, it sounds like you had good educational opportunities available to you.

Ozel:

I did. I went to a good elementary school, and more importantly, I had science books at home. I remember my earliest science encyclopedia. It was like three thin volumes, and it had pictures. It had descriptions. I remember reading about atoms there, nuclei there. I remember reading about some biological systems there. So, just having those books—even if there was no active encouragement or anything like that—in my own case, that certainly helped me. And I would say that when I was growing up, going into basic science was frowned upon. So even in a family with two medical doctors, what I routinely heard was: “Well, do something applied, like engineering or medicine, something that you can make a living out of. What would you possibly do with a basic science degree?” [laugh]

Zierler:

[laugh] Let alone in theoretical astrophysics.

Ozel:

Let alone in theoretical astrophysics. So as I was coming to college in the US, one of the things that I said was: “Don’t worry. I’m going to double major. One of them will be electrical engineering as my fallback position, and then I will study physics as well.” That lasted for about two years. [laugh] And then I told them I really had zero interest in electrical engineering.

Zierler:

Feryal, given that your mother was a medical doctor, and the fact that it sounds like you received advice to do things that had more practical applicability, I wonder—to the extent that you did grow up in somewhat of a traditional culture—if, as a girl, you were ever made to feel, applied or not, if science was not an appropriate path of study for you?

Ozel:

You know what my biggest luck was? And I’m a little bit hesitant to put it in these terms, but I’m going to anyway. I went to a private American middle school/high school. It was a 7-year school, 6th through 12th grade, where we were all girls. And it was a difficult school to get into. I tested in 5th grade, along with all the-- it’s a national entrance exam for these coveted schools, I would call them.

Zierler:

Was it an international school?

Ozel:

It was.

Zierler:

There were kids from other countries?

Ozel:

So, when it was established in the 1800s, it was established as an international school. So, it accepted both diplomat kids and foreigners in the country, and Turks who were interested in that education. That really gave me two opportunities. One is I learned English early on. Our 6th grade was an immersion year, and that’s really one of the biggest advantages those schools gave to kids like me, who are in more traditional environments, and you know, they have a little bit less exposure to maybe the outside world.

And the second thing that it did was remove this expectation that boys do one thing; girls do one thing. So, our math team was all girls, and our engineering club was all girls, and our sports team captains were all girls, our drama club was all girls. So, we did everything, and we encouraged each other to do everything. There was absolutely no: “Oh, we don’t do this.” I mean, is that the only way for-- As I said, I’m a little bit reluctant to talk about this, because I don’t want it to come across as having a gender-separated education early on is the only way to ensure that girls reach their potential. Absolutely not. But in my case, did it let me be part of the math competitions, international math competitions in 11th and 12th grade, and be in the science club, and whatever? Yeah, it did. So, I’m a little grateful for that.

Zierler:

It sounds like being in an all-girls’ environment influenced you positively toward science.

Ozel:

It did. Maybe what I should say is: there was nothing that influenced me negatively in my environment. Because what I find is that-- I have two girls. They are now 16 and 14, and I have seen them grow up in Arizona schools. Early on, I’ve been involved in their classrooms and going in to do science nights, and you know, demos and things like that. So, what I find is that in elementary school, the girls are just as interested, and by the time they come to middle school, they’re already receiving the message from their peers or from the culture around them, or whatever it is that is speaking to them negatively about what girls should and should not be doing, they start moving in other directions. And I’ve had this experience with my older daughter, who is really good in math. And at some point, she was talking about her friend group. And she said, “I really like these friends, because I don’t feel like I have to hide the fact that I’m good in math.” And it blew me away. Like, why would a 7th grader ever feel the need to hide [that] she’s good in math? But that’s the reality. So in my case, all I can say is, I loved math and science from a very young age, and nothing really got in my way in my school environment.

Zierler:

Even before you thought about where you might go to college, did you know that you wanted to pursue physics in high school?

Ozel:

As early as 5th or 6th grade, I was talking about studying physics, but then I had a little change of heart. I had an amazing biology teacher in 10th and 11th grade. So, I was like: “Oh, maybe I should do biology.” So, I went through a little bit of soul-searching there, and then I went back to my first love and went on with physics.

Zierler:

What were the opportunities, or even worldview, that was available to you that made pursuing a degree in the United States possible?

Ozel:

Because I was going to an international school—it was called American Academy, even though it was-- it is a school run by Turkey—it exposed me to both the teachers who talked about the US, and just a mindset that our education qualifies us for studying anywhere that we choose. Turkey has great universities too, but especially because I was going in the direction of basic science, I knew that the research opportunities and the career opportunities that would be available outside of Turkey would be valuable to me. I think the exposure was having the teachers there to talk to, and their encouragement, and just becoming aware of—I mean, I’m saying “aware,” but how much did I know? I did not know much. I mean, it was still at the level of, “Oh, these sound like good universities. I should end up there.” So, I don’t want to make it sound like it was so well-researched and conscious decisions. It was more like, “Oh, I should go to the US, Columbia sounds great.”

Zierler:

And it was specifically the United States? You weren’t thinking about schools in Europe?

Ozel:

It was specifically the United States, yeah.

Zierler:

Did you visit the United States? Did you tour universities before you decided on one?

Ozel:

Oh, gosh. No. I applied based on some reading that I had done. And maybe they still exist, I don’t know—these big handbooks of US universities--

Zierler:

Sure.

Ozel:

--where you get a summary of—you know, there was no internet.

Zierler:

[laugh] Right.

Ozel:

So, I remember looking through them and talking to some of my teachers, especially my math teachers and science teachers about: “Hey, what should I try?” And getting some of their advice and then sending in these applications by mail. Once I got the acceptance and a packet that arrived with it, I was like: “Okay. I’m going to New York.” And I arrived with two suitcases at JFK, and luckily somebody I happened to know was on the same flight. She took the bus with me, and a cab with me, to Columbia—helped me move into my dorm. That was that.

Zierler:

Had you been to the United States before?

Ozel:

Nope.

Zierler:

This was brand new.

Ozel:

Brand new. Transatlantic flight.

Zierler:

What were your impressions of New York when you first settled in?

Ozel:

I liked it a lot from the get-go. The one advantage that I have is that Istanbul is a big city, so as far as the size of the city, I was in relatively good shape. The mayhem of it didn’t bother me all that much. And the campus is beautiful. I still love it when I go visit. And having a dorm was nice. But what I will say is that one of my impressions of New York was the number of homeless people that I encountered, just even walking around campus. You don’t have to venture far. I’m talking about 1992, when I arrived, and especially a couple years later, we had a very cold winter. And just seeing homeless people go through that very cold winter was-- I mean, it affected me pretty deeply. In Istanbul, even though it’s a big city, I wasn’t used to seeing a homeless population. There is a little bit more safety net with families. I’m sure there are lots of homeless people too, that I just hadn’t seen it. But yeah, that was one thing that was emotionally difficult for me, but otherwise, New York was fun.

Zierler:

Being in an elite university in the United States, where many of your fellow students were coming from elite private schools, excellent public schools in the United States: how well prepared did you feel, in the science classes specifically, relative to your fellow students?

Ozel:

I felt great in the science classes. I skipped over a whole year of math. I went into accelerated honors physics. That wasn’t a problem. I felt like-- And now looking back, I’m thinking like: why was I so well prepared? I guess the system that we were put through, of multiple years of multiple science classes and math classes, was sufficient. So, I can’t say that I struggled on that front.

Zierler:

And were there any difficulties, aside from the cultural transition? What about coming into a co-ed environment? Were there any difficulties or transitions there for you to deal with?

Ozel:

Yes and no. The difficulties were not because it was a co-ed environment. In the dorms and in my English and other humanities classes—Columbia has a core curriculum, so I went through a lot of masterpieces of western civilization and music, and all of that. So there, being in a co-ed environment didn’t make any difference at all. It was totally fine, it wasn’t an adjustment. But my physics classes, we were one or two girls in the entire class for the majority of my undergrad. So, that’s the reverse shock. Right? I mean, it’s not about having been to an all-girls’ school. It’s about being such a minority in a class. There were really upper-division classes where I would be the only girl in the classroom, out of 15, 20. So, being that kind of a minority makes you feel awkward walking into a classroom. You realize people turn their heads, and they don’t mean anything by it, but it can be uncomfortable.

Zierler:

Who were some of the professors at Columbia that you became close with, or may have served as a mentor to you?

Ozel:

Who were they? So, I have very fond memories of Professor Jacob Shaham--

Zierler:

Ah.

Ozel:

--in the physics department. He was the one who got me interested in the physics of neutron stars. It was his line of work, and he kind of introduced me to this connection between elementary physics, like particle physics and compact objects, which then kind of became one of the themes of my career. So, I have very, very fond memories of him. But interestingly, too, other professors who had a positive influence on me were in the applied math department. So, they weren’t physicists, but they were applied mathematicians working on problems of interest to physics. And I took multiple classes from them. Professor Lorenzo Polvani, who is still there, and Professor Chu, who is no longer with us, and neither is Professor Shaham, unfortunately. But I learned a lot from them. I learned a way of asking mathematical questions and formulating models, and it became my third major, basically, just because I liked that department so much that I finished the requirements.

Zierler:

Feryal, were there any labs or internships or visits to astronomy centers, or anything like that, that were formative in the formation of your identity as a professional physicist, as an undergraduate?

Ozel:

At the time, even though I had this connection with Professor Shaham, and I had this exposure to neutron star questions, I actually wasn’t thinking of going into astrophysics. So, I certainly did not go to telescopes. I didn’t go to astronomy internships, or anything like that. But I did spend my junior summer at CERN. I was one of the CERN undergrad fellows there. And that was a great experience, both in terms of the people that I met and just spending the summer in Switzerland—

Zierler:

Sure.

Ozel:

—and being able to contribute to data analysis. At the time, it was ALEPH, the experiment on LEP.

Zierler:

What were you involved with? What was going on with LEP at that time?

Ozel:

I was involved in searching for the supersymmetric decays of the Higgs boson. The Higgs boson wasn’t detected at the time, that didn’t happen until much later when the proton/antiproton collider was built. So, it was still an electron/positron collider with its relatively lower energy, but there were searches for the Higgs, and there were searches for the supersymmetric decays of the Higgs, where basically we looked for missing products from the collision.

Zierler:

Yeah. What year would this have been, when you were at CERN?

Ozel:

The first time I was at CERN, it was the summer of ‘95.

Zierler:

Okay. So, supersymmetry is at the height of excitement right now.

Ozel:

Supersymmetry is definitely the thing to work on at the time.

Zierler:

Yeah. Right. Right.

Ozel:

And so, I got started with that, and then I liked the group that I worked with, the Niels Bohr Institute group. They offered me a graduate fellowship to come back and do my graduate work with them. So, what happened is that in my senior year at Columbia, I applied to a bunch of US schools for a PhD in physics, and I also kept my contact with the Niels Bohr group, and I ended up spending a year there and getting my master’s. So, that’s the second time I was at CERN. Part of the time at CERN, a lot of the time in Copenhagen, living there as a student, and at the end, already then I knew that I wanted to move towards an area where more data was coming in.

You correctly said, “It’s the height of supersymmetry.” One of the reasons it was the height of supersymmetry is that there was really nothing revolutionary coming out of the colliders at the time. LEP was towards the end of its lifetime. The Hadron colliders were still a ways in the future. So, from a theory standpoint, there weren’t that many new ideas that were being generated, whereas in astronomy and astrophysics, it was really the beginning of the golden age.

Zierler:

That’s right.

Ozel:

I mean, NASA’s Great Observatories were launched, and new types of sources were being discovered, new types of phenomena. It was hard to understand everything within the context of the physics that we knew. There were new models for explosions, fast high-energy events, gamma-ray bursts, all sorts of stuff. And I thought: “Hmm, I can still do the physics that I want to do, but really use astronomical data to do it.” So, that’s why my stint at the Niels Bohr Institute was a year. I kind of knew that I was going to come back, so I had deferred my Harvard admission and came back to the US to go to Harvard for a PhD.

Zierler:

Feryal, as an undergraduate, what kind of exposure did you get to string theory?

Ozel:

Hmm.

Zierler:

In other words, was string theory sort of in vogue in the physics department at Columbia at that time? Were a lot of professors working on string theory?

Ozel:

Not that I remember. That is not to say that—I mean, maybe I just wasn’t aware. I remember--

Zierler:

Although, if it was such a big deal, you probably would have been aware.

Ozel:

Probably. I remember people working on numerical QCD, for example. That was a thing. But as far as string theory, do I have any vivid memories of being exposed to it? No, I don’t.

Zierler:

Your intention at the Niels Bohr Institute was that it was simply a gap year for you, essentially. You weren’t planning on pursuing a terminal degree there.

Ozel:

Well, I did a terminal master’s degree there, and I would say that my mind wasn’t made up 100 percent, because I wanted to keep both options open. So, I accepted Harvard, and I said I would like to start in a year. But at the same time, I feel like I really gave a potential PhD at Niels Bohr a fair try. So, if I loved it, and if I found the project that I really wanted to continue on, it was certainly not out of the question. I hadn’t closed the door on it. But I would say towards the middle of the year, I kind of knew that I will get my master’s, and then go to Boston.

Zierler:

Now, were you specifically motivated to go to Harvard because you wanted to work with Ramesh Narayan, or you developed that relationship later on?

Ozel:

I developed it later on. I knew some of the work that was going on in both the Harvard Physics Department and Harvard Astronomy Departments. I was a physics PhD student, so I also looked to see if there are other things that interest me within the physics department. And I had great conversations with people, great contacts that lasted over the years. But ultimately, once I sat down and looked at the particular projects that I could work on and how applicable to the data that we had at that time they would be, I thought: “Hmm, working on black holes and neutron stars is something that suits my personality more,” so that’s the direction that--

Zierler:

How so? In what ways does it suit your personality?

Ozel:

I really like abstract thought, but I also like this process of scientific confirmation. So even if our basic theories are driven by abstract considerations and symmetries and basic tools that we have developed to do physics calculations, ultimately there is a lot of—I get a lot of joy from saying: is there a setting in which I can test this? And is there a way that I can take data that has been either observed in the astronomical setting, or obtained in a lab, and explain it within this context? So, that’s the part that was really exciting about astrophysics at the time. And it still is.

Zierler:

And what was Ramesh working on, at the point that he became your advisor?

Ozel:

He was working on what we called at the time “advection dominated accretion flows.” And what that means is that we see a number of different types of black holes in the universe, both in terms of their masses—so, smaller, like 10 times the mass of the Sun—to anything like billions of times the mass of the Sun. And in terms of how strongly they’re interacting with their environment at the time that we observe them. Some of them are voracious eaters. There’s a lot of gas coming their way, and they’re happy to consume it. They are bright. The gas around them is opaque. They’re just what we call radiatively efficient and geometrically thin disks. But in our nearby universe, where there isn’t that much galactic activity, we are also seeing a lot of sources where gas is kind of trickling in. And one of Ramesh’s huge contributions was in the mid- to late-90s, working out solutions to how black holes interact with this environment as far as how gas gets in, and what the properties of those gases are. And he called those “advection dominated accretion flows,” ADAFs, for short. So, that was his line of work, and I got started on that too, initially.

Zierler:

What was his style as an advisor? When you were thinking about topics for your thesis, was his style that he wanted you to work on a problem that was relevant to his own, or he allowed you to develop your own ideas?

Ozel:

He was definitely very encouraging of things outside of his line of work. So initially, I started working on an ADAF-related project, but even then, I went in some direction that he hadn’t really thought of—I mean, he didn’t give it to me as a project, I came up with it. ADAF models at the time assumed that particles in the accretion flow had a thermal distribution. I was like: “Well, wait a minute. What I know about the particle interactions, there should be some level of particles here, both electrons and protons, that don’t follow a thermal distribution. What about them?” So, I went off in that direction, and he was very supportive. And then I changed to a different topic. I thought: “You know what? These ADAF problems are all fine and dandy, and there are lots of calculations we can do. But there is this new class of sources that defy explanation, which ended up being magnetars. I really want to work on those”—which had nothing to do with his line of work. He said: “Okay.”

Zierler:

What was it about magnetars that was so compelling to you?

Ozel:

We were discovering more and more of them, or rather more and more phenomena associated with some sources that were weird to begin with—sources that show these giant flares, meaning huge outbursts of gamma rays and X-rays. And we were finding a related class of sources called anomalous X-ray pulsars. And all the new X-ray telescopes that were launched in the mid- to late-90s were playing a huge role in finding them, observing the phenomena, and categorizing them. And there were a lot of question marks, as far as whether these could be neutron stars that possessed magnetic fields, above and beyond anything we had seen in the universe. Even radio pulsars that we’ve known since the first discovery of neutron stars possess strong magnetic fields by any standard.

So, compared to the Sun, compared to anything we can generate in a lab, or anything like that—there are many, many, many orders of magnitude higher than that. And the new sources we were finding required yet another maybe three orders of magnitude higher magnetic fields. And the physics that would appear, if the magnetic field was really that strong, wasn’t worked out yet. So of course, I was kind of drawn into that. I thought I could really figure out how emission from these would happen and compare it to the new data. So, that’s the direction that I went toward.

Zierler:

What were some of the major advances in the world of observation that were relevant for your thesis research?

Ozel:

Definitely. A lot was going on. But a couple of the key advances were the Chandra X-ray telescope, which was launched in ‘98, and the Rossi X-ray Timing Explorer, another X-ray telescope with very different qualities than Chandra, which was, again, launched in the mid-90s. So, they kind of opened up a way of collecting data from high-energy sources that weren’t possible before. And Chandra, because it had excellent spatial resolution, we could go into a crowded area—even a neutron star, for example, or a black hole sitting inside of a supernova remnant, or had nearby neighbors—and really find out: okay, what is coming from this source?

And X-ray Timing Explorer, because it didn’t have spatial resolution, but it had phenomenal timing resolution—so we could really find things that were pulsating or that had, where the emission from them had some periodic changes, and we could categorize those. Those were really helpful to me and to my colleagues studying anomalous X-ray pulsars, soft gamma-ray repeaters, magnetars in general. And even beyond that, once—even if all the data is not there, once you open up this possibility of, there might be a realm in the universe where this new theoretical thing might happen, then you can run off with it. So, that’s kind of where I was, too.

Zierler:

Feryal, of course, with a thesis dissertation, there’s always the balance between being hyper-focused in your own little niche of what you’re working on, but then also connecting your research to the larger discipline out there. So in that regard, what were some of the larger research questions that were being raised in the field? And how did your dissertation respond to them?

Ozel:

You’re absolutely right that one needs to become an expert at something, better than anybody else in the world in some ways, when you write a dissertation on it. But there’s also the breadth question: how does it compare to everything else that we’re seeing? Did I consciously make that connection to the larger questions of the field? Probably not, but what I did know was that at the time? We were dealing with sources—both my work on black holes during my PhD and neutron stars—that possessed some extreme characteristics.

For example, extreme gravitational fields. There is no place in the universe, other than perhaps the big bang—where we encounter strength of gravitational potentials and the curvature of spacetime—that compares to the immediate environments of black holes and neutron stars. Neutron stars have this additional aspect that there is no place in the Universe where we encounter magnetic fields that come anywhere close to what we see in neutron stars. So, I knew that as far as the connection to the big questions, what I wanted to know was: when you go to an environment that is extreme, in as far as the limits of our theories go, both general relativity at the extreme of the event horizons of black holes and the surfaces of neutron stars, and classical electroweak theory in extremely strong magnetic fields, how does physics change? I guess I had that drive in terms of connecting what I do to the big questions.

Zierler:

Besides Ramesh, who else was on your thesis committee?

Ozel:

On my thesis committee? Irwin Shapiro was at my defense. And wait, I am blanking on his name right now. He works on planet atmospheres…

Zierler:

Sure.

Ozel:

Dimitar Sasselov.

Zierler:

Ah, okay.

Ozel:

Dimitar was on my thesis committee, which was really good, because even though his own area of research is not on neutron star structure or atmospheres or anything, there are surprisingly numerous similarities between how you model the outermost layers of any star that is gravitationally bound. So, whether you’re doing this for planets, or stars, or neutron stars, or even an accretion disk, the know-how really translates. So, Dimitar being an expert on radiative transfer was really nice.

Zierler:

Feryal, on the social side of things: at what point did you think that the United States would become your adopted country? When were you stopping thinking about perhaps going back to Turkey or somewhere else besides the United States?

Ozel:

Early on, I would say. I think that I imagined a career in the US after my PhD, early on. I knew that the type of work that I wanted to do was—I’m not going to say it wasn’t possible elsewhere. Of course, it is. But it was a lot more plausible here. So, as far as postdoctoral fellowships, for example, I only applied in the US.

Zierler:

What postdocs did you apply to? What was most compelling to you?

Ozel:

I applied to fellowships. I knew that I had a pretty strong thesis, and I was already giving conference talks and even colloquia in places. So, at the time, there weren’t nearly as many fellowships as there are now, but there were some good ones that one would apply to, like the Hubble Fellowship that NASA offered. And the Institute for Advanced Study and the UC Berkeley Miller Institute has a well-known fellowship in the sciences. I applied to a few more. I can’t remember what they were, but I feel like I applied to maybe five or six of these.

Zierler:

And what was most exciting about the institute for you? Why did you ultimately end up there?

Ozel:

Yes, I ended up being a Hubble Fellow at the Institute, but I was selected as an IAS member independent of that as well.

Zierler:

What is the institutional connection between the Hubble fellowship and the Institute?

Ozel:

There is none. One can take Hubble fellowships to any institution that is willing to host them, and the fellowship is implemented as an agreement between that institution and NASA. So, there is an institutional commitment that any university or a place like the IAS makes, as far as hosting a Hubble fellow or any NASA fellow.

Zierler:

So, you were funded by Hubble.

Ozel:

I was funded by Hubble. Yes. Having said that, I actually went to the Institute before my Hubble fellowship started. I was an Institute member for a while, and then when I officially graduated, deposited my thesis, and my Hubble fellowship started, I switched to that. I knew I wanted to be at the Institute, so I put it as my number one choice on the Hubble fellowship application, and when I got it, I took it there.

Zierler:

Was there anyone in particular at the Institute who you wanted to work with?

Ozel:

John Bahcall was head of astrophysics at the time. He’s since passed away, unfortunately. And I was very excited to be in the group that he had created, but one of the most amazing things about the Institute is that it is basically a postdoc-run place. Yes, there are faculty, esteemed people, good resources. You can discuss pretty much anything with them, and even somebody like Freeman Dyson—who was retired but still very much around when I was a fellow there. And string theorists like Juan Maldacena was there, and even though our research didn’t have a direct overlap, we certainly had lots of black hole conversations and GR conversations. But you don’t go to the Institute just for that. You really go because it’s all about the postdoc interactions. It’s about your fellow fellows, and you decide on what to do over science coffee, and what journal clubs to run, and what collaborations you initiate between the different members. So, I would say that is one of the most attractive things about the IAS.

Zierler:

What were your impressions when you got there? It’s such a unique place. What were your impressions of the overall research culture, the culture of collaboration there?

Ozel:

I found my cohort to be very open. We really had great discussions about anything from clusters of galaxies to the smallest things, like how to detect certain features in planets. So, in terms of the astrophysical scale, anything from the smallest to the largest, then in terms of the physics, really, the whole range. And we had a lot of fruitful directions that we all explore. Everybody did their own thing, too. I mean, certainly whatever we were experts in, we continued to publish on that. But there was a great camaraderie, I would say, between the Institute postdocs at the time.

I should also add, of course, the presence of the Princeton Astrophysics department is also a huge asset. It’s basically within walking distance and there are joint events. So, there is also the whole faculty of Princeton Astrophysics that we routinely interacted with. I loved talking to Bohdan Paczynski, for example, one of the most creative minds of that era. I mean, the number of new things that he’s suggested and discovered—what an amazing person. I love talking to Neta Bahcall, David Spergel, lots of different people.

Zierler:

Did you spend time much at the physics department at Princeton?

Ozel:

I wouldn’t say I spent much time. I loved the Institute setting and I had my office there, but I certainly went to talks at the department, and they came over for talks and Tuesday lunches, the famous gathering of everybody in that area in astrophysics. And I went to offices and coffee and meetings, but I didn’t really spend my days there—I didn’t have an office at the department at Princeton.

Zierler:

To what extent, for your postdoc, did you see this as an opportunity to take on new research interests, and to what extent was it an opportunity to expand and improve upon your thesis research?

Ozel:

I think I did some of both. Some of the stuff that I had started as part of my thesis—some of the new directions, calculations, etcetera—I certainly pursued them during my postdoc years at the Institute. But I also started whole new lines of thinking in my research about compact objects and their gravitational effects and masses, and things like that. That turned into, I would say, the next 20 years of my career, since then. So, my first black hole and neutron star papers are around years 2000 and 2001, and here we are in 2020. So, it had many reincarnations in the meantime, and some of that happened at the Institute.

Zierler:

Feryal, as you were entering the job market and you were thinking about your identity as a physicist and the kinds of positions that would be most interesting and relevant for your work, where was physics at that point in terms of available positions and the kinds of things that departments were looking to add, in terms of new faculty?

Ozel:

I would say it was a time when cosmology was hot, and a larger number of cosmologists were being hired. Not to the exclusion of everything else, but there was definitely a wave of people who worked on the CMB or other aspects of cosmology that were in high demand at the time. But I didn’t feel like positions were not open to other fields and there was enough interest in my subfield.

Zierler:

What positions were open at that time, in 2004?

Ozel:

I don’t remember. I mean, there weren’t so few that I could list them now.

Zierler:

So, the market was good at that point. You had options.

Ozel:

It was reasonably good, but the other thing that played a role in my path and my decision was that I was in a two-body situation.

Zierler:

Yeah.

Ozel:

As I was starting my postdoc, before I was thinking too much about applying for faculty jobs, my husband already had an offer from Arizona. But I wasn’t ready to go to Arizona yet, I wanted to be at the Institute. So, he deferred his position for a year—he was a 5-year member at the Institute at the time—and then he went a year ahead of me to Arizona, and I stayed an extra year at IAS.

Zierler:

What is your husband’s field?

Ozel:

He is also in theoretical and primarily high-energy astrophysics.

Zierler:

Ah, so it’s a true two-body problem. [laugh]

Ozel:

It is a true two-body problem, yes. And we both knew that whoever got a better position, the other would accommodate—I mean, we knew that we would both apply, and we would make it clear that we would need two positions. But because Arizona is such a great place for astrophysics, and because they had already verbally told me that they would be interested in hiring me, I didn’t apply as widely as I would have otherwise.

Zierler:

What was exciting about what Arizona was doing with regard to astrophysics at that point?

Ozel:

Arizona has always had a huge astronomy tradition, meaning the more traditional optical and infrared astronomy—both building telescopes with our mirror lab here, and in terms of using big telescopes to do a lot of work on cosmology, galaxies, quasars, stars. Also, some of my colleagues a little bit older than me academically and whom I liked were getting positions in Arizona, and that was attractive to me. I mean, I knew the quality of the work that they did. So, it was attractive to me to be with really high-quality faculty as well as my own peers who had just accepted jobs there, maybe two, three, four years prior to me. As far as a strength in theoretical astrophysics or a strength in gravity and compact objects, I can’t say that there was much. But that’s okay. I mean, when you’re starting a faculty position, I think part of the idea is that you start something new.

Zierler:

Right. Right.

Ozel:

It’s great if you’re going to a place that already has a lot of resources in exactly what you’re doing, but it’s also okay if you’re going to a place where you’re expected to create more resources. And that’s kind of what happened when we arrived in Arizona. I think that both my husband and I contributed to building the theory group here, hiring others, bringing computational resources to campus, and making connections with observational facilities that weren’t there before. Especially in terms of studying of black holes. We built up the Event Horizon Telescope collaboration, with our colleague Dan Marrone, at we’re at a point where Arizona is contributing three telescopes, in addition to all the theory and analysis work. So yeah, I think I helped build a direction here that wasn’t really there before.

Zierler:

And were you involved with high-performance computing at this point, when you started at Arizona?

Ozel:

I was. My thesis was pretty heavily computational, but it was at a time when there weren’t widespread clusters. I mean, there were some centers that one could apply for supercomputing time, but I didn’t, as a grad student. But I had a poor man’s cluster. Basically, I had accounts on pretty much all the machines of a particular type in the department, and when people went home, I launched jobs on them to run overnight. It was pretty hilarious, actually, that the jobs would run overnight, and I would either put them at lower priority or stop them for a while so people could actually use their own computers. But there were certain, fast enough computers that I did my own distributed computing. And after arriving in Arizona, I think the codes that I helped develop and got involved in were even larger, so then we started applying for supercomputing time with my students and postdocs, and eventually building our own resources on campus, too.

Zierler:

When did you start taking on graduate students? Was it right away?

Ozel:

It was right away, yes. 2005, January, is the official start of my faculty position. And that year, I already started taking students.

Zierler:

And in what ways, in this new role for you to be an advisor-- In what way did taking on graduate students positively affect your own research agenda, the kinds of things that you wanted to work on?

Ozel:

To support a research group you have to write proposals for external funding and that is an important component of being an advisor. I have a love/hate relationship with writing proposals–perhaps like most people. I don’t like the nitty-gritty of writing proposals, but I like how it crystallizes ideas that I had in my mind into certain projects that my students can work on. So, the act of sitting down and writing a scientific roadmap that then turns into my students’ projects actually really helped me. So, even my earliest NSF and NASA proposals, when I look back, I was like: “Oh, yeah. That became that student’s project. That became that student’s project.” And of course, things don’t go exactly as planned, and they’re not meant to. But it just gives me an overview of the responsibility of having to assign it to my students, and therefore thinking it through and putting it down in a funding proposal that would support them, and then having to look back and assess. Did I actually produce what I thought I would produce? I kind of like that process, even though, like I said, the act of writing the proposals is annoying, or time-consuming, I should say.

Zierler:

Yeah.

Ozel:

But I like having students from that point of view, not just because the work gets done by more people, because honestly, training somebody to do the work takes more time than doing it yourself. But just taking the responsibility of thinking more broadly about, “Where is this research going? What could we be doing? Is this worthy of somebody’s PhD thesis?” is a satisfying exercise.

Zierler:

On the topic of proposals and funding: when would it make more sense to go to the NSF, and when would it make more sense to go to NASA?

Ozel:

In my field, NASA theory proposals have to have a component that has something to do with NASA goals and/or NASA facilities. So, if the particular theoretical calculation, model, or interpretation that you want to work on involves some NASA data or relates to NASA data then you can apply to NASA for funding. Even if you’re not going to actually analyze the data but you’re going to build a framework that is relevant to it. Obviously, if you’re going to use a NASA telescope, you apply to NASA for funding—both for telescope time and for funding. NSF is broader. NSF astronomy and NSF physics cover areas that are just pretty much anything one could work on in astronomy and physics. And even there, there’s a little bit of programmatic thinking as far as, like, what is the most timely right now, and what is the most interesting for the community? But in principle, they could fund anything.

Zierler:

I’m curious. This is right around the time when the Department of Energy starts to fund astrophysics. I’m thinking about Saul Perlmutter at Lawrence Berkeley. Was the Department of Energy ever useful as a resource for you?

Ozel:

Not for me personally, but you’re absolutely right that the Department of Energy has been involved in certain subjects within astrophysics. That includes dark energy surveys, which is related to what Saul Perlmutter is doing, and it has provided funding for that. There are some other areas of astrophysics DoE funds—such as supernova explosions—for people who actually model the radiation and the hydrodynamics of how these explosions happen and what the observables are. I have colleagues who receive funding from the DOE for that reason as well. But I have not, personally.

Zierler:

On the undergraduate side, Feryal, what have been some of your most enjoyable classes to teach undergraduates?

Ozel:

Ooh. I love teaching math methods in physics, again, maybe because I had such a great experience in the applied math department at Columbia. Equipping undergrads with tools that then they can apply to different problems in physics and science is just like teaching them some linear algebra, some concepts in symmetries and Hilbert spaces and solving differential equations. So, it is more tools-based, but we go through so many different applications. Here’s a quantum physics application. Here is something else, even things outside of immediate physics, like population modeling—I really enjoy teaching that class. At the graduate level, I really love teaching radiative processes and radiative transfer. It covers the basics of theoretical astrophysics, but especially when it comes to how radiation interacts with the stuff in the universe and how it’s generated by matter in the universe in the first place.

Zierler:

Feryal, I want to ask you about gender politics in the department at Arizona. Of course, you know, many departments over the years have experienced many problems in this regard. Did you ever have any issues with regard to being a woman, feeling like you were accepted among your peers, or did you feel like those things were pretty much well worked out by the time you joined the faculty?

Ozel:

I am going to focus specifically on the astronomy department when I answer this question, because as I said, my committees and my main tenure line and my teaching comes through astronomy. So, I interact a lot more with colleagues in astronomy. I like the environment here. I would say that I encountered either discrimination or some sort of harassment a lot more outside of my department as a more senior person, and certainly outside of my department as a student, than I ever have here. So, I don’t feel like there was ever a meeting where I thought: “Hmm, they didn’t listen to me because of my gender,” or: “That was really disrespectful to me.” It’s a really good department to be in. I have a lot fewer interactions with the physics faculty as a whole, so the setting there probably is different. But I’m not going to say anything positive or negative without being sure. But Arizona astronomy, I would say—we all take turns taking leadership of things, and it’s usually respectful. And when we disagree, it’s for good reasons, and it’s just a nice department to be in.

Zierler:

On the mentor side, to undergraduates, do you ever see yourself as a role model to women undergraduates who might be interested in a career in science?

Ozel:

I think so. I mean, that’s just the nature of the beast. They have to see somebody to imagine themselves pursuing it, and because of the relatively few number of women in astrophysics and relatively few number of women in physics in general, it’s inevitable that having an advisor, a mentor, or even a classroom professor who resembles them in some way is influential. So, I try to reach out to minority groups on campus, both through—I do this myself, like Women in STEM on campus, just giving a dinner speech or joining their activities or recruiting students from them, or as part of a more concerted effort to get minorities involved in, for example, the NSF PIRE project for the Event Horizon Telescope, the black hole research that we do at the University of Arizona. We actively recruit women. We actively recruit students of Hispanic origin, and students of color.

So, you asked me specifically about a gender role model, but it goes a little bit beyond that. I think I understand what it means to be a minority, whether it’s gender-based, or because somebody’s a first-generation college student, or because they’re an ethnic minority. So, our recruitment efforts aren’t just towards women undergrads, but also for these other minority communities.

Zierler:

And of course, being at an enormous public university, the diversity of the student body has many, many opportunities also.

Ozel:

It does. It really does—I love that aspect of being in a public serving institution. We have a diverse student body. So, with enough effort, hopefully we’ll be able to recruit some of that diversity into astrophysics in particular and into STEM in general, so I like that.

Zierler:

I want to ask some questions about the state of the field, since you started at Arizona up to the present. So, let’s start first with neutron star astrophysics. What have been some of the major advances in the field since you joined the faculty at Arizona?

Ozel:

We know a lot more about what makes up neutron star interiors. We still haven’t completely pinned it down as far as what is the composition and interactions of matter in the neutron star interior, but I think we’re getting closer. Part of it is the new X-ray measurements, and part of it is LIGO. The fact that we’ve seen two binary neutron star mergers through gravitational waves is a whole new way of studying them that my students and I have been excited about and we’re employing. We know a whole new class of sources called fast radio bursts. Do we know exactly what they are? Well, there was a paper just two days ago saying that they have linked fast radio bursts finally to a magnetar, which of course, I enjoy. I’m not actively working on it right now, but I enjoy seeing it—because magnetars are capable of some of the most bizarre phenomena we see in the universe.

What else do we know? We know that-- So, even when I started, I would say—that’s now 2004, 2005—we didn’t really know what the mass distribution of neutron stars was. We now know that there are 2-solar-mass neutron stars, and as low as probably 1.2-solar-mass neutron stars. So, this old paradigm postulating that they’re all born with 1.4 solar masses, because of some peculiarity about the explosion, it’s just not true. They are more diverse than that. What else? I’m sure I’m forgetting some new, exciting stuff.

Zierler:

And to go back to that question of the interplay between theory and observation/experimentation, for neutron stars, for the last 15 years, has the theory been driving the experiment and observation, or more vice-versa?

Ozel:

I think the field is developing so fast that both are happening. I mean, there is certainly a lot of wonderful data coming out of telescopes and observatories that we try to incorporate into our theoretical understanding. But then, we in turn say: “Okay, here is what we think about the framework that produced the signal.” And then, the turnaround time is fast enough that our observer colleagues can go and obtain new data if we make certain predictions about it, whether this is outcome of merging neutron stars, or how a magnetar should behave, or the size of the star itself, or whatever the case might be. So, I think it’s really happening hand-in-hand.

Zierler:

Feryal, of course there’s so many different subfield specialists who work on black holes.

Ozel:

Yes.

Zierler:

How do you see your area of expertise, going all the way back to graduate school? What is your research agenda, and how do you apply that to greatest benefit to these massive collaborations, in terms of furthering research in black holes?

Ozel:

Well, you’re absolutely right. We encounter and study black holes in so many different contexts that two different people working on black holes might have very little in common. I am specializing in building models for the immediate environment of black holes, how the gas falls into them. That is interesting in and of itself. There are so many unsolved aspects of a problem seemingly as simple as this: There are nearby stars. A black hole can attract gas from them. How does it make its way down into the black hole and become part of it? How does the black hole environment look, and how does it grow? So, there are some basic questions in that field that are interesting and unsolved. That is one of my goals.

But the other goal has been, once we understand that, how can we use the observational data that we get from the immediate environment of a black hole in order to understand whether Einstein’s theory is correct? So, we know that general relativity is our description of gravity today. We know that it works in most settings when we test it in the solar system, when we test it with binary pulsars. But the most extreme prediction of general relativity is the existence of black holes. Once we understand black hole environments and the behavior of the gas, we can use it to turn it around and ask about the properties of the spacetime. If these dark massive objects that we call black holes, within general relativity, if they have the properties that the theory really ascribes to them. What are the observational signatures of an event horizon? What would it look like if the spacetime wasn’t described by the Kerr metric, but something else? Or, the “no hair” theorem, that a black hole is specified by two quantities only: mass and spin. And charge, but we usually say, in the astrophysics context, that charge is not important. What if there are other “hairs” that we can ascribe to a black hole?

So again, using that environment as a test of one of the most bizarre physical theories that we deal with today, the one that is not compatible with quantum mechanics and the way we formulate our three forces, and one that predicts a singularity—is something wrong or incomplete in our understanding? So, that’s what I work on.

Zierler:

When did you join the Event Horizon collaboration?

Ozel:

Event Horizon Telescope collaboration has been very organic in terms of how it came to be. Various people working on different aspects of the problem at different institutions formed a collaboration that eventually became worldwide. My first paper on the image sizes of black holes and the optimal wavelengths in which we could see down to the horizon, was a paper in 2000, when I was a graduate student. And so, as early as 2000, I was thinking about imaging black holes and communicating with colleagues who were observers to try to push the limits of what observations can do in terms of getting resolution on scales that are comparable to the event horizon of a black hole. There were already some size measurements at longer wavelengths. My work with Dimitrios Psaltis and Ramesh Narayan developed a way of understanding why black holes looked as big as they did at those wavelengths and translated them into a wavelength dependence that we should expect for black hole images. I concluded that we should be observing at 1 millimeter to see the event horizon, which ended up becoming the EHT observing wavelength.

After that, I focused on neutron stars for a few years, and I didn’t do too much on black holes. But in 2005, I started working on new numerical models to understand the black hole environment. And one of my first students wrote a new code—an algorithm for a new way of modeling those environments. And his papers are in 2006, 2007. So, it’s a continuous process. And we continued to build up the group and resources in Arizona. We had the first collaboration meeting—what we call the inaugural EHT meeting—in 2012 in Tucson, but it wasn’t until 2016 or 2017 when we actually had membership agreements.

So, I’ve been there from the start—like I said, it developed organically, because it’s a worldwide effort. It’s not like LIGO or CERN, for example, where you build one facility, and everybody is there. This is more like: “Okay, now we secured this telescope. Now we have this telescope. Now we have observing capabilities that connect this network.” And here are the theoretical models that predict how the observations should go. So, that all happened over a 20-year period.

Zierler:

Feryal, I’d like to ask your feelings about the significance of that first photograph of the black hole. There’s two perspectives on that. One is we can go back to LHC and the Higgs. The two perspectives are: you know, “This is amazing. We saw it.” And the other is: “Well, we knew we were going to see it, so it’s not that big of a deal.” Right? What was your feeling when you actually-- I mean, it’s not as if the photograph proved the existence of black holes. That was known. And yet, at the same time, there was now a physical reality to it that wasn’t there before. So, I wonder if you can reflect on your reactions to when that happened.

Ozel:

Sure. I agree with you that as a photograph, it doesn’t prove something about black holes that we didn’t suspect before. Even then, I would say the physical reality of it that you’re referring to—which is that our theory tells us that there should be a void at the center, a darkness, which we see in the image, is remarkable. We lack words to describe it, but the closest we come is calling it the “shadow,” because it’s the absence of light, when the light is really sucked into the black hole. And there is a point, a physical scale inside of which we should see nothing but a darkness. To see that in the data is remarkable, I think. At least, we were excited. And you might think: “Well, because you worked on it for so many years, of course you are excited.” But it’s beyond that. I don’t think the data had to be that clear. It didn’t have to be: “Oh, look. Yes, it’s bright where we thought it would be bright, and really, there’s an absence of light, like this darkness at the center, that we associate with the shadow of the black hole.”

Having said all that, it is the quantitative things that we did with the image that are far more interesting for a physicist, and even to communicate to the public. I mean, it’s great that the public loved the image, and it was widely shared, etcetera. But the story that we wanted to get across is that we are using this to make a measurement. It’s not the fact that we made this picture that is interesting. It is that we had a particular prediction for the size of the ring, and the size of the darkness—which is the size of the shadow—and that we can make a statistical comparison between that prediction and what we are measuring.

And in fact, in order to do that comparison, we don’t even need the image. We use directly the raw interferometric quantities that we got from the telescopes. And what I mean by that is, when you hook up telescopes, you don’t obtain the image directly. You measure little components of it in what is called the Fourier space, and our actual data looks like some amplitudes and phases as a function of separation. So, we directly modeled that and said: is this consistent? How consistent is it with what general relativity predicted? Not just that there is a darkness, but is that darkness the size that we expected it to be? So, we ended up doing tests of gravity in a regime that wasn’t possible before, and in the sense that this is the first billion-solar-mass black hole with its own curvature and potential, but also things that would not have been accessible to solar-system tests or tests that we’ve done with pulsars and other objects. So, it is brand new, and this is—you know, as far as doing an “experiment,” that’s the exciting part.

Zierler:

Feryal, I want to ask a broad question about your advisory work. You’re involved in so many things, you know, within both your own subfield and even in more general pursuits, such as being a member of the JASON Group. What are the advisory roles that you serve in that are most compelling to you from a research perspective, and which are most compelling to you from that broader, sort of science and society perspective, contributing broadly to using science to advance human society?

Ozel:

Hmm, very interesting question. I think I have been lucky enough that all the advisory roles that I’ve taken on—even though the overall goal is serving science and society in general, I’ve always benefited scientifically from them. There has always been a lot of new thought and directions that came out of those interactions—even if it’s not my immediate research area, and I’m never going to publish a paper on it, and maybe the big advances are not even going to happen in my lifetime. Well, hopefully in my lifetime, but maybe not in my [laugh] working career, like the Lynx Observatory study that I co-chaired for NASA. It was not to serve my own career, but did I learn new things, and did I benefit scientifically? Yes, immensely. I learned a lot about detector development and mirrors, and even subject areas, like cycling of metals in galaxies, that even if I’m not going to write a paper on it, I enjoyed a lot scientifically. And I think we had a great product at the end.

Similarly for the NASA Astrophysics Advisory Committee, I learned a lot from just being on, then chairing, that committee—a lot more about NASA, Science Mission Directorate activities, that I wouldn’t have known otherwise. Certainly, the service to my community and society was the leading reason for taking it on but it led to some fruitful ideas, even for my own research, like some intersections of black hole physics with heliophysics. JASON is a whole other story. Of course, I think all members of JASON do it because it is a service to the country, but I love thinking broadly about problems when I work on different studies.

Zierler:

Did you feel like it was a boys’ club, or it had been sufficiently well integrated, starting with Claire Max and going from there, when you joined JASON?

Ozel:

Hmm. How do I answer this? [laugh] I really, really appreciate having women colleagues who are older than me in JASON, and they are very successful, very influential, good role models. But it’s still a bit of a boys’ club. I think my generation has enough of a subject diversity and a bit more gender diversity, that maybe now we are turning the corner. Maybe.

Zierler:

I want to ask. You know, even since graduate school, when you first got involved with high-performance computing, it’s hard to overstate, you know, the advances that had been made in computational power over the last 20 years. So, I wonder what you might point to, to illustrate the point about what supercomputing does for you now, that even 10 years ago, 20 years ago—what wasn’t even imaginable?

Ozel:

What I would say is that the advances took place on multiple fronts. One is simply the CPU processors becoming faster, so being able to just run jobs faster—on a given number of CPUs. The other is interprocessor communications became much faster. So, the ability to scale up a particular computation became much stronger. Think of it this way: it doesn’t matter that a particular processor is fast, if I’m wasting most of my time talking to my neighbor, that becomes the bottleneck. So, the new architectures really sped up the communication that we have between processors, so when we say “parallel computing,” now we can do really massively parallel computing.

The third thing that I would say is: we’re not just limited to CPUs anymore. There are different, massively parallel architectures within the chip, such as tensor technologies and graphics processors units. So, the type of code that we can write, and the speedups that we can get, are, again, immense compared to five years ago, 10 years, ago, let alone 20 years ago, when I was hijacking other people’s desktops to do my calculations. I think what we’ve seen is that the predictive capabilities that we developed became better, in very complex astrophysical systems like those of black hole environments and formation of galaxies, their interaction with their central objects and star formation, for example. How do stars form, and how does the life cycle of a star work? And how do they explode? All of these saw tremendous benefits from all these three directions that technology went in, and high-performance computing went in.

In my own case, when we built the GPU cluster with NSF support on the University of Arizona campus in 2012, it enabled us to do the first massive rendering of black hole environments in terms of observables—images, spectra, light curves—that hadn’t been done before, because of that huge leap in capability. Now, GPUs are almost commonplace, but we still look at the next architecture and look how we can couple the various bits of physics that we need to worry about in that complex environment.

Zierler:

Feryal, I’d like to ask about your interest in science communication and serving as a public intellectual for your field. Right? This is obviously extracurricular kind of stuff. This is nothing that you would ever be expected to do, so it clearly comes from a place of genuine interest and desire to communicate those things. And so, I want to ask you generally—either if it’s through social media or it’s giving lectures to either school-age kids or a broad lay audience, or appearing in documentaries—what are some of the broad motivations that you have, where you want to do this, where you want to devote your precious time to doing these kinds of things, to communicating these science ideas beyond your peers, beyond your collaborators?

Ozel:

I love sharing what I know. When I was very little and first learned to read and write, my grandmother grew up in an era where she learned how to read Arabic, and only with the purpose of, you know, reading religious documents. And she could not read in Turkish. She could not write her name. She couldn’t sign. And as a, whatever, five-year-old, I was appalled by the fact that I was given the opportunity to learn to read and write, and here my wonderful grandmother, just because of the time she was born, the environment she grew up in, she didn’t have that. So, I taught her how to read and write. I was like: we’re going to sit down, and we’re going to do this. And you know, she could read for the rest of her life.

So, I feel it’s-- I don’t know. Maybe it’s just the excitement that I feel about knowing something, having understood something, or having the privilege of having thought about something, and it’s not fair if I don’t share it. So, I think it’s coming from that really raw feeling of it’s not enough to do science so we gain the recognition of our colleagues. It’s really here for everybody to know what we found out about the universe, or diseases, or whatever—earthquakes, or whatever the case might be. So, I think that’s where I’m coming from. I always enjoyed sharing.

Zierler:

And because so much of your outreach is interactive—in other words, you can get a sense of the kinds of things your audiences are curious about—what are those things, generally, that your audience wants to know about the universe, where you feel well-positioned to explain?

Ozel:

I don’t know if it’s because they are the audiences that show up in my talks, but it seems like the public loves black holes. They’re genuinely curious about how these bizarre things can be out there, and they’re also a little bit worried about whether there is any danger that it poses to us. I think over the years, that worry went down. Maybe some years ago, there would definitely be a question from the audience about how worried they should be. Where is the closest black hole, can we fall into it, etcetera. Now, it’s more of a sense of wonder, and what else can we find out about them, and is Einstein right? So, those are the types of questions that I feel like I can answer and I can share with the people. I often get an alien-life type of question from the audience. I don’t work on it. Just like any other person, or maybe as a scientist, I can review where we are, as far as how close we are to detecting life elsewhere. We haven’t, of course, but there’s a lot of effort going on in that direction. What else are they curious about?

Zierler:

What about some of the philosophical questions? You know, like knowing so much about the universe—does that tell us anything about why the universe might exist, or what, if anything, created the universe?

Ozel:

I got that question a couple times, and not from the public, actually. I think I was on a BBC program the first time I was asked. I don’t think science asks, “Why?” Science is about the “How?” If we can explain how certain things happen and build a framework that is predictive, that’s the basis of science. I don’t ask about if or how things were created. That, to me, is not the interesting part of science. And certainly, our tools aren’t designed to answer that. So, we’ll leave that to philosophers.

Zierler:

[laugh] I want to ask a time management question. Given the fact that you’re involved in so many different research endeavors, outreach, teaching, advisory—is your work style on the research side-- Do you tend to compartmentalize things, or do you tend to work on many things at the same time?

Ozel:

I am happier when I compartmentalize things, because I really think that is the better way to make progress, to really immerse oneself in one thing and allow myself to think about it uninterrupted. But I don’t have that luxury all the time. There are pockets of time, sometimes over the summer, sometimes maybe a week here and there, where I carve out the time to immerse myself in one thing and one thing only. And it’s very satisfying. But most of the time, I think the reality of it is that as an academic, my life is very fragmented. So, I have to do my best to remember where a particular conversation was left off, and what we said we were going to try, and what I did on my code or calculation the last time I worked on it, and do the best that I can.

Zierler:

When do you feel-- I mean, in the world of theoretical astrophysics, when you don’t have that feeling of completeness, of completing an experiment or making an observation or analyzing the data—when you’re working in a purely theoretical framework, going back to the question of time management: how do you know when to continue pushing forward, and how do you know when to say, “Okay, I’ve gone far enough on this. Now it’s time to move on to something else.”? What are those feedback mechanisms in the world of theory, that you might rely on to inform how you devote your time and resources?

Ozel:

I think having real data helps in that. If there are still aspects of data that have not been satisfactorily explained, and it could point to something interesting, I feel the drive to keep going. And sometimes, it’s just, you know, I lost interest. Like, it’s not that there weren’t more questions that can be answered, but I’m going to move on to something else. So, that happens. That’s the thing about doing open-ended research, and something that most beginning students, going from undergraduate to graduate, that’s a transition that they have to make. It’s no longer a problem set that somebody assigns, and once you put the last period on the solution of a problem, you’re done. It is always open-ended, and sometimes it’s grinding work, small steps at a time. And once in a while, it is a real breakthrough, and you have a better understanding of something—a new result, a new way of calculating, or a new way of understanding the data—and you know, it keeps you going for a while through the more grinding work.

Zierler:

Given that you started in this field, as you said, when you felt so strongly that there was a real frontier mentality, that this was just opening up, that there was so much to discover. So, on that point, what have been the most intellectually satisfying breakthroughs that you’ve been a part of, where you can say, “We really didn’t understand something before, and as a result of what we’ve done, now we truly do understand it”? What have been some of those research endeavors where you’ve had that intellectual satisfaction?

Ozel:

It depends on the magnitude of that satisfaction that you’re asking about. I’ve certainly felt that multiple times, but on the grand scale of things, would I ever say, “That’s it. We put the period at the end of the sentence, and now we understand it in a way that doesn’t require anything more.” I wouldn’t say that. I certainly would say we understand black hole and neutron star populations in our galaxy a lot more, in a way that we didn’t understand before. I would say we understand general relativity and what it predicts around black holes better, and we’ve taken some pretty amazing steps in terms of bringing a new way of studying them into the mix. We did not image black holes before, and now we do. And we have the tools to turn it into real science results.

We understand magnetic fields and compositions of neutron stars definitely better, that I don’t think anybody doubts that very strong magnetic fields associated with neutron stars exist anymore. There was a lot of doubt when I started out, and that they really do a bunch of crazy stuff. But have we understood those phenomena exactly? No, I wouldn’t say that. So again, it’s like, have we taken pretty good steps? Yes. Have we said the last word on the problem? No.

Zierler:

Feryal, maybe an easier way to answer the question is to just look at the word “breakthrough” in the extraordinary recognition you’ve received this year from Science magazine, and of course from the Breakthrough Prize. So, maybe an easier way to answer that question is: to the extent that this recognition is a recognition by your peers, by the field broadly, that you’re involved in some of the most exciting work that’s happening in theoretical astrophysics now, how does the larger community of science look at what you’re doing and say, “This really does represent a breakthrough in ways of understanding the universe that we didn’t understand before”?

Ozel:

I think there is that recognition. I think people are genuinely excited about—you’re referring specifically to imaging black holes that the Event Horizon Telescope has enabled, and the theoretical work that surrounds it, in terms of interpreting it. Yes, those recognitions by our peers and the community was extremely generous, and it makes us want to keep going. Having said that, I think science really works in a way where we are very excited about our result, and then we start questioning it.

Take the accelerated expansion of the universe, for example. When the Type 1a supernova results first started coming out, and we said, “Wow, this really points to a non-zero cosmological constant.” But immediately the community also started thinking of other ways the data could be explained. And until we ruled out those possibilities, and until we established the concordance with the cosmic microwave background results and multiple things pointed to the same thing, the community didn’t say: “Yeah, we’re done.” So, with the recognitions for the black hole work, on the one hand, yes, we are getting these recognitions that it is some of the most exciting work happening. And at the same time, it is just making it clear that we have more to do, whether this is repeated observations, or observing at a different wavelength, or checking consistency with gravitational waves, or just other ways of verifying our results.

Zierler:

Feryal, now that we’re talking about 2020, and we’ve brought the narrative right up to the present, I want to ask you, for the last part of our talk, a broadly retrospective question about your career, and then one that’s forward-looking. So, I want to ask you—in terms of the research you’ve done so far—if you can reflect on how that research contributes to some of the major ongoing question marks in physics, in astrophysics, in cosmology—things about understanding dark matter, understanding dark energy, figuring out how to integrate gravity into the standard model. If you could broadly reflect on your wide-ranging research in neutron stars and black holes and magnetars, in what ways does your research base contribute to those broader fundamental questions that occupy the minds of so many physicists coming from so many different subfields?

Ozel:

One of the outstanding questions of our times, as far as physics as a whole, is how we can’t make gravity compatible with our understanding of the subatomic world. We can’t quantize gravity. It is a problem that we kind of push to the back of our minds when we work on the subatomic physics and gravity on large scales. But it is one that is actually quite bothersome. And where my research fits in is trying to see, especially in places where there could be signatures of that breakdown in our understanding of either theory, like the black hole horizon environments and neutron star surfaces, whether we can get some clues as to what might be incomplete. That’s one of my overall goals, as far as why I like studying the extreme gravity environment of black holes and trying to understand everything else about them, so that we can turn it around and use it as—is our understanding of gravity complete?

You also mentioned dark matter and dark energy. These are two cases where our understanding of the astrophysics of it, and our predictions from gravity did not match one another. Galaxy rotation curves, clusters of galaxies, and distant supernovae—when we compared the light that we see from these things with the gravitational prediction, there was a mismatch. In one case, we solved it by adding more matter, that we called “nonluminous,” or “dark.” And in the other case, we solved it by changing the gravity equations, which we called “dark energy,” by adding either a gravitational constant or some variant of it. We don’t know what the dark matter particles are, but we think that it is not the incompleteness of the gravity theory but it’s actually a new particle.

And with dark energy, at the weakest gravity scales, we saw that the distant supernova become dim faster than we expected. Is there an astrophysical reason for this? No, we don’t think so. So, we fixed it by changing our gravity theory. Around black holes, will the same thing happen? I mean, will we encounter a disconnect between our gravitational predictions and what we are seeing? And if so, is it going to have a reason that allows us to push our understanding of physics forward, like is the field equation missing another term? Or is it some sign of things that happen around horizons that prevent a singularity? Is it some string theory effects that actually become visible at much larger scales than the Planck scale? I mean, wouldn’t it be wonderful if that happened? And if it doesn’t, I think it’s a fruitful place to look, so we will keep doing it.

Zierler:

And on that note, Feryal, for my last question, going forward the broader question is: what are you personally most excited about, in terms of advancing fundamental understanding for the universe, broadly conceived—in other words, as an astrophysicist, as a theoretician? And what are you most excited about as an individual, as a scholar, in terms of the kinds of things that you specifically want to work on, insofar as those things will inform and advance those broader questions, going into the future?

Ozel:

What am I excited about as an astrophysicist in general, or —

Zierler:

Yeah, as a duality. In other words, there are things that you’re excited about that will motivate your own research project. Right?

Ozel:

Yes.

Zierler:

But then, there are those broader things to be excited about that would make you sort of part of a very large collaboration, where you’re one piece of the puzzle. So, both in terms of the immediacy of the things that you want to devote your time to individually, and your excitement about the larger world in which you work, and your contributions to that, and what those large contributions will do to help us understand even further how the universe works.

Ozel:

I mean, I’m an easily excitable person, so there is really [laugh] very little that’s happening in astrophysics right now that I don’t find really remarkable. I mean, whether this is-- Perhaps we’re on the cusp of detecting gravitational waves with pulsars, in addition to direct detections with LIGO and Virgo. I genuinely enjoy the ongoing efforts to quantify dark energy better. And again, is it a cosmological constant, or is it something more? Is there an additional field that we’re not aware of, or we haven’t been able to quantify, and we will get there? I think a lot about these questions about gravity, and I think there is a lot of excitement there. And certainly, when we launch the next generation of telescopes, like James Webb, but we will find out about the early universe, how galaxies, and black holes in the early universe grew and somewhat interacted. It will give us some limited information. Of course I’m really excited about that.

And right now, our own neighborhood is interesting as far as extrasolar planets, just the fact that they’re everywhere, and they seem to come in all sizes, and some are bound to be habitable. So, how can you not be excited about that? [laugh] So yeah, as I said, I think we live in a really rapidly evolving and fun time. As far as what drives my research, there’s quite a bit that I will continue to do with black hole images, not the least of which is the black hole at the center of our galaxy, and then repeated observations to answer certain questions that were formulated. I am excited about the synergy with gravitational waves. I think coming at it from both sides will increase our confidence in what we’re finding. There is quite a bit more neutron star research to be done too, from both X-ray observations and gravitational waves. But who knows? I mean, I have kind of gone in completely new directions as far as--

Zierler:

And it sounds like part of the challenge is to keep an open mind--

Ozel:

Yeah.

Zierler:

--in terms of what avenues might open up that are worth thinking about in the future, that you might not have thought about in the past.

Ozel:

Absolutely. I mean, we—my students and I—have adapted the questions that we are asking, based on the developments that we hear about, and the availability of data. So, if a new direction becomes fruitful, then one needs to be adaptable, so I think I’m happy to go in a new direction if there’s a discovery. I think fast radio bursts, FRBs, is the one area that I have consciously said: “I’m not going to work on it right now.” It’s super interesting. It’s an unsolved problem. But you know, I’m already stretched thin, so I’m following as an observer, no pun intended. But other than that, yeah, I get my hands on something new when it happens.

Zierler:

Well, Feryal, it’s been so fun spending this time with you. I’m so glad that we connected and that you were able to do this, and it will be wonderful to include all of your insights and recollections into our collection. So, thank you so much for spending this time with me. I really appreciate it.

Ozel:

Thank you for the great questions. I enjoyed it, too.

Zierler:

Wonderful.