Interview with Brian Schmidt

Transcription

1 with Brian Schmidt er : Melina Bersten Interest in Supernova Study Dates Back to Undergraduate Days Bersten: First of all, I d like my other one.) I was working for him on his project. After about a year, I was getting 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 first 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. (One of two. Tom Swihart was Now, I had not intended to do that for my Ph.D. thesis and it was when Bob Kirshner Brian Schmidt is Distinguished Professor at the Research School of Astronomy and Astrophysics at the Australian National University, formerly known as Mount Stromlo and Siding Spring Observatories. He, together with Saul Perlmutter and Adam Riess, received the 2011 Nobel Prize in Physics "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae". He has also received many other distinguished awards. In particular, he shared the 2006 Shaw Prize in Astronomy with Saul Perlmutter and Adam Riess. He received his Ph.D. from Harvard University in He was a postdoctoral fellow at the HarvardSmithsonian Center for Astrophysics from 1993 to He moved to the Mount Stromlo Observatory in Kavli IPMU News No. 20 December 2012 visited to give the first Marc Aaronson Memorial Lecture at University of Arizona when I was finishing my last year of studies there and I was trying to figure out where to go to graduate school. Would I go to Caltech, would I go to Santa Cruz, or would I go to Harvard? Those were my three choices at the end and I just could not decide. In the end, Bob came and gave a very good talk on, Well, I supernovae and I said

2 hadn t really thought of doing supernovae for my Ph D thesis but I do find them interesting and here is someone who I can work with at Harvard I said to him If I can work with you on supernovae then I ll come to Harvard That s how I got started Bersten At the beginning you studied Type II supernova Schmidt As an undergrad in Arizona we were just looking for them We didn t care what type they were But at Harvard for my Ph D thesis I did study Type II supernovae I measured distances with them in a way that Bob Kirshner did for his Ph D thesis When I came to Harvard Bob gave me a project to go and look at supernova 1987A I said No I don t want to do that I want to do something else I want to measure the Hubble constant and I want to do it using this technique that you developed back in your thesis I was going to improve it He had a postdoc who could model the supernovae very accurately and do it with a radiative transfer code and so I was going to work with Ron Eastman and to improve the method to measure the Hubble constant That s what I really did for my Ph D thesis Bersten What was the main reason that made you change the focus into Type Ia supernova? In other words what was the main reason that motivated you to form the High-Redshift Team? Schmidt When I finished my Ph D thesis I d measured the Hubble constant to a level where the systematic error in the method was about the same as the statistical error I felt I had got my answer and there wasn t much else to do with that method I was looking to do other things I was looking at how the explosions of Type II supernovae occur by measuring what their nucleosynthetic output was relative to their mass and to their explosion energy In 1994 Mario Hamuy visited us and showed us the work that they had done in Chile which essentially said you could use Type Ia supernovae to make measurements that were roughly two to three times better than the supernovae I had used At the same time Saul Perlmutter called us up and said we have an object to look at which we took a spectrum of with the MMT I was actually at Harvard it was Bob Kirshner Pete Challis and Adam Riess When they said We think it s a High-Redshift supernova I went and analyzed it I got the same answer Eventually we found out from Saul Perlmutter that that was one of seven objects they had discovered They had been looking for them since 1988 and suddenly they found seven of them That was a real eye opener Melina Bersten is a postdoctoral fellow at the Kavli IPMU She is an astronomer studying supernovae computationally and theoretically 19

3 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 first 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 difficulty 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 q 0 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 As a Young Leader Organized the High-Redshift Team like Organizing a Party little about the methodology and how many telescopes you used and also identify which our first discovery (SN 1995K) they realized the natural advantages of working at was an all-night affair in very good conditions in reality the 4-meter telescopes were too Schmidt I was the leader was the most difficult 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 figured 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 find 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

4 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 field 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 Keck? cosmology At the end of the 1997 Bersten When did you change your feeling that wouldn t be worthy of a Nobel Prize The fact that it Schmidt Berkeley and Caltech had access to Keck and all of when Adam sent me a figure that had the data clearly something could have been wrong? was given pretty timely you 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 Saul s group For us he was constant! I said Ah what have we done wrong? We We haven t done anything really stupid Then in 2000 that you obtained the Nobel Prize? of the same culture that we went through that bit-by-bit when the cosmic microwave were and the fact that he came back and said I still want to come and join your and it suddenly started sinking in No this isn t going to go away In the end when we background came out and showed that the universe was flat definitively flat When Received a Call from Stockholm While Cooking Dinner 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 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 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 Accelerating Universe in 1997 Convinced in 2000 decelerating We were getting a crazy answer He was getting something sensible I and showed the first peak of the cosmic microwave background definitively it and I had a Swedish accent saying Is this Schmidt? Now earlier in the day I had Schmidt Yeah We had known that the cosmological didn t know what to make of it Then suddenly we realized That s when I said Wow we re right! Before that I just my graduate student giving 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

5 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 scientific 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 field 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 first thought was this is a to government about why people and being inspired by different fields 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 find 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 is thinking this is a practical joke Then she put on another person a much older Swedish improve the way we approach science at the national level A lot of my time has been spent doing things like that over the Diversity of Kavli IPMU Is Helpful to Work on the Question of Accelerating Universe in other fields that help to deeper understand the phenomenon? 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 field my first 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 scientific 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 office like I used to see a lot I knowledge the astronomers 22 Kavli IPMU News No 20 December 2012

6 have I think being able to where I can do something the expected science was to find 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 find 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 fields 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 field 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 fields 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 find 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 figure 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 answer? which is the main goal of the project that you mostly work? how supernovae which make the heavy elements enriched way to check it because if it is a binary the stars won t all Schmidt The project probably the universe right at the be thrown out in all directions SkyMapper Project for Precise Photometric Survey of the Southern Sky has several goals The main goal of the Sloan Digital Sky Survey was to measure beginning Well that s really exciting to me too That s one of the goals of that program equally They ll be thrown out in a plane I think those are really 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

7 supernova field 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 find 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 field has grown improve our constraints by problem in the supernova really works I think that s tremendously during my lifetime When I finished my about a factor of 2 by doing that well field that if solved may lead to a revolution like the a real big question Is it a 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 who finished their Ph D in supernovae of that year you mean? Schmidt Nearby I mean out to a redshift of 0 1 beyond a Scientific Revolutions Come from Not Knowing we do is we keep on doing the best job we can and then 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 done It s so much it s hard to Einstein s theory of general relativity being a little different causes the Type Ia supernova to explode? Now do I think do we spend money on basic 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 figure 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 don t have very many objects to measure how gravity is behaving at the scales of it reaches the Chandrasekhar mass? Is rotation important to ask you more questions! Unfortunately we have to The objects we have observed hundreds of megaparsecs and does the thing actually finish 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