Interview with Brian Schmidt Interviewer: Melina Bersten

Interest in Supernova my other one.) I was working Study Dates Back to for him on his project. After Undergraduate Days about a year, I was getting Bersten: First of all, I’d like to the point where I could to congratulate you for the do something useful. One of Nobel Prize. the things they wanted to do Schmidt: Thank was to discover supernovae you very much. in their data set. It was the Bersten: I can Ÿrst digital survey. It was like imagine you are very the Sloan Digital Sky Survey happy. I would like to where the sky transited go back to the origin across the detector and they of it all. How did you moved the information on the get interested in the study detector along with the sky, of supernova? drift scanning as it’s called. I Schmidt: I was an liked the idea of discovering undergraduate at the something new in the data. University of Arizona and So I started looking for that as there was a project run by part of my work for him as an John McGraw who was my undergraduate. undergraduate supervisor. Now, I had not intended (One of two. Tom Swihart was to do that for my Ph.D. thesis and it was when Bob Kirshner Brian Schmidt is Distinguished visited to give the Ÿrst Marc Professor at the Research School Aaronson Memorial Lecture of Astronomy and Astrophysics at the Australian National University, at University of Arizona when formerly known as Mount Stromlo I was Ÿnishing my last year and Siding Spring Observatories. He, together with Saul Perlmutter and of studies there and I was Adam Riess, received the 2011 Nobel trying to Ÿgure out where to Prize in Physics "for the discovery of the accelerating expansion of go to graduate school. Would the Universe through observations I go to Caltech, would I go of distant supernovae". He has also received many other distinguished to Santa Cruz, or would I go awards. In particular, he shared the to Harvard? Those were my 2006 Shaw Prize in Astronomy with Saul Perlmutter and Adam three choices at the end and I Riess. He received his Ph.D. from just could not decide. Harvard University in 1993. He was a postdoctoral fellow at the Harvard- In the end, Bob came and Smithsonian Center for Astrophysics gave a very good talk on from 1993 to 1994. He moved to the Mount Stromlo Observatory in 1995. supernovae and I said“, Well, I

18 Kavli IPMU News No. 20 December 2012 hadn’t really thought of doing Hubble constant to a level supernovae for my Ph.D. thesis, where the systematic error but I do Ÿnd them interesting in the method was about and here is someone who I the same as the statistical can work with at Harvard.” I error. I felt I had got my said to him“, If I can work with answer and there wasn’t you on supernovae then I’ll much else to do with that come to Harvard.” That’s how I method. I was looking to do got started. other things. I was looking Bersten: At the beginning, at how the explosions of you studied Type II supernova. Type II supernovae occur Schmidt: As an undergrad, in by measuring what their Arizona, we were just looking nucleosynthetic output was, for them. We didn’t care relative to their mass, and to what type they were. But, at their explosion energy. Harvard for my Ph.D. thesis, I In 1994, Mario Hamuy did study Type II supernovae. I visited us and showed us measured distances with them the work that they had done in a way that Bob Kirshner in Chile, which essentially did for his Ph.D. thesis. When said you could use Type I came to Harvard, Bob gave Ia supernovae to make me a project to go and look measurements that were at supernova 1987A. I said, roughly two to three times “No, I don’t want to do that. I better than the supernovae I want to do something else. I had used. At the same time, want to measure the Hubble Saul Perlmutter called us up constant and I want to do and said we have an object it using this technique that to look at, which we took a you developed back in your spectrum of with the MMT–I thesis.” I was going to improve was actually at Harvard; it was it. He had a postdoc who Bob Kirshner, Pete Challis, and could model the supernovae Adam Riess. When they said, very accurately and do it with “We think it’s a High-Redshift a radiative transfer code and supernova,” I went and so I was going to work with analyzed it. I got the same Ron Eastman, and to improve answer. the method to measure the Eventually, we found out Hubble constant. That’s what I from Saul Perlmutter that really did for my Ph.D. thesis. that was one of seven objects Bersten: What was the they had discovered. They main reason that made you had been looking for them change the focus into Type Ia since 1988 and suddenly supernova? In other words, they found seven of them. what was the main reason That was a real eye opener that motivated you to form the Interview

High-Redshift Team? Melina Bersten is a postdoctoral Schmidt: When I Ÿnished my fellow at the Kavli IPMU. She is an astronomer studying supernovae Ph.D. thesis, I’d measured the computationally and theoretically.

19 to me that you could discover computer hardware that we The second day is useless. If that we would go through them and we knew how to could all use together was a it’s cloudy at the second day, to discover these supernovae use them. I literally, when problem. We got around it by then the Ÿrst day image just because we didn’t have a I found those things out, working really, really hard. But sits there. home base we could ship dropped everything that I was that was part of the difŸculty We needed to have a them to–and just have stable doing and said“, There is an of having someone young place that was guaranteed software–that was a real, real opportunity to go and measure like myself going and running to give us two clear nights. nightmare. q0, the deceleration parameter, things. The good part is that Chile, the Atacama Desert, The other problem in 1995 right now.” To me, that was this was the one thing I was was really the only place that was that we didn’t have just the big thing to do and it working on. And not just me, gives that good of weather, access to the Keck 10 meter was the most exciting thing Adam Riess, Peter Garnavich, guaranteed. Plus that new telescopes. Now in 1995, I could think of doing. It was you know, we were young detector meant we could do Bruno Leibundgut and Jason measuring what’s the ultimate and we worked on this one it. And, of course, the team at Spyromilio with the ESO fate of the universe. I dropped thing. We worked on it night Cerro Tololo means we knew NTT, in very good conditions, everything I was doing to go and day and that was the only the instrument and telescope managed to get a spectrum measure that. thing we worked on. That very well. So that’s where of our supernova at a redshift Bersten: At that moment you was one of the reasons we we decided to work. Saul’s of 0.48. They spent almost all were quite young. Was that a were able to make progress– team had not yet realized night and it took them about problem for being a leader of that we were not distracted the possibilities at Cerro a month to reduce the data the program? by other things. Tololo at that point. So we and actually see that it was Bersten: Could you tell me a applied, and after we made a Type Ia supernova. But that little about the methodology our Ÿrst discovery (SN 1995K), was an all-night affair in very As a Young Leader, Organized the High-Redshift and how many telescopes you they realized the natural good conditions–in reality the Team like Organizing a Party used–and also, identify which advantages of working at 4-meter telescopes were too Schmidt: I was the leader was the most difŸcult task CTIO, and presumably thought, small to get spectra of these of the team but not in a during the program? “Geez, that’s a good place to high-redshift supernovae on a traditional sense. I wasn’t a Schmidt: In 1994 when we work. We should do that too.” consistent basis. general telling everyone what started, we had these new The challenge of actually In the meantime, Keck to do. I was the consensus CCDs, and I was down in discovering supernovae had come online and Saul leader of a bunch of people Chile talking to Nick Suntzeff, was hard. The software I Perlmutter’s group had access working together as friends. who was one of the leads had written wasn’t very to Keck and they completely I had to organize people, but of the Calán/Tololo Survey good. It worked, but I had killed us in 1995. They found it was like organizing a party. that had Ÿgured out how to written it in Australia and all these objects at the end You’d just tell people to show use Type Ia supernovae. We got it working in Australia. of 1995, and they were able up, and they do. They do that discussed using the CTIO When it was shipped to the to get spectra of all of them. because that’s just the way 4-meter. CTIO 4-meter had computers in Chile, many We had a bunch of objects, things work. It wasn’t like I a new 2k x 2k CCD, so, 4 of the libraries didn’t work. but we couldn’t get spectra was a general. million pixels. I knew that the They had different operating of them. We ended up with Was there a problem being weather at Cerro Tololo was systems. Everything broke. two lousy spectra–where 27? There were some issues. pretty much cloud free from It was a nightmare. Every they ended up with like 11. I didn’t have the ability to November through March. time I would show up there, I was very worried“, Oh my go out and write a grant One of the problems that you things would break differently God, without Keck, we’re that could pay for all of our have when you go out and try because the computer system dead.” Alex Filippenko had activities. Every group got to Ÿnd supernovae is that you had changed. I think in the asked to join our team early its own bit of money and need two images. You need end that was the hardest in 1995. Because the teams showed up and worked a before image and an after part. Then, I’d go to Hawaii were competitive and he was together that way. That image. If it’s cloudy one of and the same thing. Things at Berkeley I said“, No, you inability to have a bunch of those days, then you’re dead. would break again. The effort need to continue to work at

20 Kavli IPMU News No. 20 December 2012 Berkeley–I wouldn’t want to the primary thing that the didn’t know we were getting Nobel Prize? poach you.” At the end of cosmological constant did. the same answer as him, but Schmidt: No, one does not 1995, he called me up again That was taught to me in we knew he was getting expect a Nobel Prize. To and said“, I really want to school. It was taught to me because he showed it at some my mind, I was genuinely work with your team–I am a as“, Look at these people talk in preliminary form–his surprised because when supernova physicist like you who messed up, look at data had changed effectively. you make a discovery of guys.” At that point I said, these people who messed I have to admit, still being acceleration–well, what “Okay,” because without up, look at these people unsure, I knew what our data causes the acceleration? Keck, we weren’t going to be who messed up, they all said, but I kept on thinking Well, we give it a name– able to compete with Saul, had bad observations, and there must be something dark energy–but we and Alex had a lot to offer they thought it was the we’re missing. There must don’t understand it yet. to our team in terms of his cosmological constant.” be something no one has I would not be surprised knowledge of supernova and I didn’t really worry too thought of; not just us, but if we don’t understand it their spectra. much about it. It was sort the whole Ÿeld that we’ve left during my lifetime. Without Bersten: Did you need to be of an ongoing joke within out. understanding it, I felt it in Berkeley to have access to cosmology. Bersten: When did you wouldn’t be worthy of a Keck? At the end of the 1997 change your feeling that Nobel Prize. The fact that it Schmidt: Berkeley and Caltech when Adam sent me a Ÿgure something could have been was given pretty timely–you had access to Keck, and all of that had the data clearly wrong? know, I was only 44 last year– the University of California showing a cosmological Schmidt: That feeling really was a bit of surprise. Put it schools. The only person constant, I just assumed that didn’t go away until 2000. I this way, I wasn’t waiting up who studied supernovae in we had made a mistake. I mean after 6 months, I said, for the call. the whole system was Alex didn’t say“, Oh, a cosmological “Okay, maybe we’re right. Bersten: How did you know Filippenko and, of course, constant!” I said“, Ah, what We haven’t done anything that you obtained the Nobel Saul’s group. For us, he was have we done wrong?” We really stupid.” Then in 2000, Prize? of the same culture that we went through that bit-by-bit when the cosmic microwave were, and the fact that he and it suddenly started sinking background came out and Received a Call from came back and said“, I still in“, No, this isn’t going to go showed that the universe was Stockholm While Cooking Dinner want to come and join your away.” In the end when we žat, deŸnitively žat. When team,” saved us. Without Alex had gone through everything I saw that, I realized that it Schmidt: They make the and his ability to get spectra, several times, it didn’t go made it almost impossible announcement at 11:45 am we weren’t going to survive away. Then, I was resigned to for our observations to in Stockholm. I didn’t used to because we just couldn’t the fact, and I said“, Okay,” show anything other than know this, but I know it now. compete. then I got excited. We’re acceleration. It pushed things, That is 8:45 pm in Australia. Bersten: Which was your going to have to tell the world so the only sensible solution My son had been out at an reaction when you found the about this. I was like“, No one was that the universe was athletic event and we had acceleration of the universe? is going to believe us.” accelerating. At that point I gotten home. My wife and I Did you immediately At the same time, Saul said“, I’ll be damned, we’re were cooking dinner. I was understand the implications Perlmutter’s group had right.” That was in May of making a green Thai curry of these results or…? published a paper in 1997 2000 when BOOMERANG with my wife. I was stir-frying. saying the universe was and MAXIMA came out The phone rang. I answered The Data Showed decelerating. We were getting and showed the Ÿrst peak it and I had a Swedish accent Accelerating Universe in a crazy answer. He was of the cosmic microwave saying“, Is this Schmidt?” 1997; Convinced in 2000 getting something sensible. I background deŸnitively. Now earlier in the day, I had Schmidt: Yeah. We had didn’t know what to make of That’s when I said“, Wow, my graduate student giving Interview known that the cosmological it. Then suddenly, we realized we’re right!” Before that I just me his wedding invitation. constant gave you Saul was getting more or less wasn’t sure. His wedding was on the acceleration. That was the same answer as us. He Bersten: Did you expect the 10th of December. He said

21 to me“, When they call you changes your opportunities, Now that I am one of those think it has a real vibrancy. It’s tonight, just tell them you’re but does not necessarily people, I could see that being surprisingly western for better busy.” I looked at him and I increase your scientiŸc the Nobel Prize winner inspires and for worse. But, it’s still had no idea what he meant. opportunities. It actually people. It’s like they were Japanese. It’s not so western I said“, What do you mean?” hurts science because the part of the discovery. It feels as not to be Japanese. He said“, When the guys in fundamental thing that you kind of weird to me. I feel like Bersten: Yeah, we have tea–I Sweden call you tonight, tell need to make progress in I am living in someone else’s mean green tea (laughs). them you’re busy,” because science is time. That is the body. But, it’s important. That Schmidt: Yeah. I thought it his wedding turned out to thing that young people have inspiration is really important. was further out from Tokyo. be on the day that the Nobel in the Ÿeld, the time to focus I do feel I have a role of It’s actually much easier to Prize ceremony. Now, I have and to answer questions. doing what Hans Bethe and get here than I expected. Of to admit I still was a little What the Nobel Prize gives Dudley Herschbach, and the course, the autumn colors are confused, but he explained it you is the increase in scope of people I met when I was beautiful. It’s a great time to to me. When I got home and who will listen to your ideas. young did for me, because it be here. I got this call from a Swedish It gives you the opportunity was an important part of my Bersten: I agree with that. woman, I have to admit my to make representations upbringing, meeting those Here in the institute, we have Ÿrst thought was, this is a to government about why people and being inspired by different Ÿelds together, practical joke by my graduate science is important, why them. people from string theory, student who had set me up education is important, about Bersten: I hope you inspire people from mathematics and earlier in the day. the big directions that science me also. astrophysics. Do you think that I said“, Yes, this is Brian is going in the country. Schmidt: Well, we’ll see. this type of interaction can Schmidt,” and then she said, That doesn’t help me Bersten: I know that you help to Ÿnd a great discovery “Are you sure this is Schmidt? make my little telescope didn’t have much time to and so on, for example in This is a very important phone (SkyMapper) run better, it know the Kavli IPMU. But, the case of acceleration of call from Sweden.” That was turns out. But it does give what was your impression the universe? Have you got a kind of funny thing to say. I me the opportunity, I think, to about this institute? some interaction with people responded“, I am sure that it improve the way we approach in other Ÿelds that help is,” thinking this is a practical science at the national level. A Diversity of Kavli IPMU Is to deeper understand the Helpful to Work on the joke. Then she put on another lot of my time has been spent Question of Accelerating phenomenon? person, a much older Swedish doing things like that over the Universe Schmidt: The accelerating gentleman, and then I was last year, meeting with people Schmidt: Well for me, it’s universe is a special case like“ Geez, I can’t believe, my and government, explaining great to see such a diverse because it’s very clearly a graduate student could have how they need to look at the group of people here. One question that goes across got two people from Sweden education system, how we of the features of coming astronomy and fundamental to do a practical joke.” Then teach physics in high school, to Japan, which I’ve been physics. As an astronomer, they told me and it became how we fund universities, to many times, has been I know what the universe is very apparent that it wasn’t a how we fund research, everyone has been Japanese, doing. I know how to measure practical joke. I have to admit why funding of research is except for who is visiting on it. But, the real fundamental I felt it’s very much like when important. the day. When you come to string theory or quantum Ÿeld my Ÿrst son was born. It was The other thing with the the Kavli IPMU, it is incredibly theories and gravity theories very exciting, but I felt sick Nobel Prize is–in some way diverse. People from all over may link into it. Being able to in my stomach, too much that doesn’t really make sense the world, very clearly. It’s a solve a problem, like what is excitement. to me, but I felt myself–quite lovely building, very new and causing cosmic acceleration, Bersten: I can imagine it was! inspirational to people. I met sleek, and seems to have very really requires theory–which is In what sense does obtaining a few Nobel Prize winners good facilities. There’s lots more non-astronomy theory, the Nobel Prize change your when I was young and I was of discussion at coffee. Not but more particle physics scientiŸc career? genuinely inspired by them. everyone holed up in their theory–combined with the Schmidt: Well, the Nobel Prize I don’t know why. I just was. ofŸce like I used to see a lot. I knowledge the astronomers

22 Kavli IPMU News No. 20 December 2012 have. I think being able to where I can do something the expected science was to Ÿnd stars that are thrown work together on questions that I think is unique. In 2002, actually done in Australia out when they get to close to like that is very helpful. I started a project to map by the 2dF Redshift Survey the supermassive black hole There are some problems the southern sky in a way before they got to it. But on in the Milky Way. SkyMapper which are mainly astronomy. analogous to what the Sloan the other hand, the Sloan can go out and Ÿnd those There are some problems Digital Sky Survey did in the Digital Sky Survey had even things systematically which are mainly particle northern hemisphere. But my a bigger impact than they because there’re stars out physics. But, there are observatory burned down expected, because it made that shouldn’t be there and techniques that have been destroying the telescope a huge impact in areas they SkyMapper has the ability developed in the different and the instrument that was did not expect. That was to measure the radius of the Ÿelds that are useful. There are going to do this survey. Since because it allowed them star, its temperature, and its techniques of how you build 2003, I have been leading to do everything. They did chemical composition. The instruments that astronomers a project to rebuild a new large scale structure, they radius and the temperature have done, that are useful telescope, a mapping facility did asteroids, they did stars, tell you how bright it is, within particle physics and vice called SkyMapper. SkyMapper they did galaxies. They even therefore how far away it is. versa. There are data reduction is about a very precise eventually did supernovae. We can go out and we can techniques that are useful. photometric survey of the And they did these things very literally pick out and say“, That There are statistical techniques southern sky. well, indeed. star is chemically rich out at a the mathematicians typically It is able to do supernovae The thing that really very large distance. Why is it will know. As we’re asking and map them out in interests me on SkyMapper there? It shouldn’t be there.” bigger and bigger problems, the nearby universe very is both the metal-poor stars Then when you look at those you really need to look accurately in a way that no tracing out the birth of our things, those things inevitably at them from a broader one else is really doing. But, it Milky Way, but, then there is are the stars that were thrown perspective. I think having that also allows us to do galactic also all this supernova stuff out by the black hole in the expertise around is very helpful physics, that is how the galaxy we can do. We’re going to Milky Way’s center. By getting for everyone because you formed, being able to pick be able to discover several a bunch of those things, we get insights of how to solve out the most chemically poor hundred supernovae a year can measure, for example, problems that are beyond your stars in our galaxy that were and get really the most how much they slow down on Ÿeld, and that’s where you’re formed right after the Big comprehensive set of data the way out because they’ve liable to have a revolution in Bang, piece together how for a set of objects ever. been thrown directly out from understanding, when you take the supernovae enriched our Get spectra of all of them– the center. a new idea and bring it in. galaxy and how our galaxy every single one. That will It also gives us an idea– That’s the advantage of having formed. That is a project be a wealth to understand is the Milky Way black hole people in related Ÿelds, but which I am spending most of supernova physics, and that binary or is it just one? not the same, all collocated. my time working on. It will is very close to my heart. But, Because if it’s a binary… Bersten: I agree. I would like take almost a petabyte of I really think being able to go Bersten: The central black now to ask something related data. That’s a lot of data. through and Ÿnd every metal- hole? to your current work. In which Bersten: You say that you poor star in the Milky Way so Schmidt: Yeah, the central project are you working now are not only focusing on that we can Ÿgure out how super-massive black hole, it and which is the fundamental supernovae, but on galaxies, the Milky Way formed and could be a binary. This is a good question that you want to which is the main goal of the how supernovae, which make way to check it, because if it answer? project that you mostly work? the heavy elements, enriched is a binary, the stars won’t all Schmidt: The project probably the universe right at the be thrown out in all directions has several goals. The main beginning. Well, that s really equally. They ll be thrown out in SkyMapper Project for ’ ’ Precise Photometric Survey goal of the Sloan Digital exciting to me too. That’s one a plane. I think those are really Interview of the Southern Sky Sky Survey was to measure of the goals of that program. cool things to do. Schmidt: As an astronomer, I the large-scale structure of And it really is meant to do Bersten: Do you think that am always looking at places the universe, but much of lots of other things. It’s meant obtaining a Noble Prize in the

23 supernova Ÿeld gives an extra carefully and as uniformly as a only good way to do this a billion years later after the motivation for new projects high redshift. I do think there’s right now. That is a way of thing slows down a bit? in supernova? In that sense, still an opportunity which I testing general relativity in a Those are all active scenarios also, I would like to know want to use SkyMapper to regime where it hasn’t been and I can’t tell you which one your opinion related with the measure the expansion in the tested before. I think that’s is right. possibility to continue the universe very accurately in the another interesting thing that I just Ÿnd that amazing, use of Type Ia supernova for nearby universe so we can we’re going to try to do with given how much effort has obtaining better precision. tie it in to the distant objects SkyMapper. been put into it. There doesn’t Schmidt: Yeah. I think the better. I think we can probably Bersten: Can you identify a appear to be an answer that supernova Ÿeld has grown improve our constraints by problem in the supernova really works. I think that’s tremendously during my about a factor of 2 by doing Ÿeld that, if solved, may a real big question. Is it a lifetime. When I Ÿnished my that well. lead to a revolution like the revolution? No. Revolutions Ph.D. in 1993, I was literally Bersten: By nearby, what do accelerating universe? come from surprises. What the person in the world you mean? we do is we keep on doing who Ÿnished their Ph.D. in Schmidt: Nearby, I mean out Scienti€c Revolutions Come the best job we can and then from Not Knowing supernovae of that year to a redshift of 0.1; beyond a the surprise will come from because there were only redshift of 0.03, closer to the Schmidt: I think that someplace where we least a handful of us. I mean I redshift of 0.1. I also think revolutions usually come as expect it. That’s the beautiful know everyone from that the other thing supernovae a surprise. You can’t easily thing of basic research and era, everyone, because there provide an opportunity to predict revolutions. If you why it’s so important. The was only a few people do is to measure how gravity could there wouldn’t be any, revolution comes from not doing it. Since the discovery behaves on large scales. One it wouldn’t be a revolution. knowing what the future is, of acceleration, there are of the things where dark There are some fundamental not predicting it. many, many people studying energy could potentially be things. Today, we still don’t People say“, Well, why don’t supernovae. I don’t know lurking is that it isn’t dark understand what makes the governments just fund the everyone anymore. I don’t energy at all. If it’s really Type Ia supernova. What things that they know? Why know all the work that’s being Einstein’s theory of general causes the Type Ia supernova do we spend money on basic done. It’s so much, it’s hard to relativity being a little different to explode? Now, do I think research? Why don’t we just keep track of. than we expect out at large that’s going to revolutionize fund how to make better X, I think the Nobel Prize distances, that is something dark energy? No. But, we have Y, or Z?” Well, the answer itself probably won’t change we can potentially test been working for 20 years is because if you always are that. I think that had already using supernovae. Because now to try to Ÿgure that out trying to do what you already occurred before the Nobel they measure very precise and it’s still a mystery. Is it one know, then you just make a Prize. I do think that with distances, it means that by large star donating material better X, Y, and Z. You don’t Type Ia supernovae there are comparing the expansion rate to a white dwarf and then it invent the Internet. You don’t some interesting things they with the distance, we can reaches the Chandrasekhar invent Wi-Fi, which was done can still do. I think using them measure a velocity that’s been mass and explodes? Is it two by astronomers in Australia. to do more work at high induced by gravity. white dwarfs coming together You don’t have that revolution redshift is pretty tough now. With hundreds of these to exceed the Chandrasekhar that comes from basic The measurements have really objects, we can actually mass and exploding? Is it a research. You need to have been very well done out there measure the average motion star that donates material in both. The revolutions come and we are limited now by of every part of space using the form of helium and the from not knowing. systematic uncertainties. But the supernovae as test helium detonates and causes Bersten: Thank you very in the nearby universe, there particles. That gives us a way the thing to explode before much. I wish I had more time is a sweet spot where we just to measure how gravity is it reaches the Chandrasekhar to ask you more questions! don’t have very many objects. behaving at the scales of mass? Is rotation important Unfortunately we have to The objects we have observed hundreds of megaparsecs. and does the thing actually Ÿnish now. have not been observed as Supernovae are really the quit growing and blow up Schmidt: Okay. Thank you.

24 Kavli IPMU News No. 20 December 2012