From First Principles - Dr. Michael Blanton on Open Data, Galaxy Surveys, and the Future of Astronomy (EP 43)

Episode Date: June 4, 2026

Hosted by Lester Nare and Krishna Choudhary, this episode is the second interview in our ongoing collaboration series with Carnegie Observatories. Krishna sits down with Dr. Michael Blanton, the new Director of the Carnegie Observatories, for a wide-ranging conversation on how astronomy became one of the most data-rich sciences, how the Sloan Digital Sky Survey helped change the culture around open data, what the next era of astronomical data science and AI could look like, and one of the galaxy mysteries Blanton still wants to solve: why the most massive galaxies in the universe stop forming stars.The conversation starts with Blanton’s Princeton roots and his work connected to the Sloan Digital Sky Survey, then moves into the culture of public astronomical data, the NYU Value-Added Galaxy Catalog, Vera Rubin Observatory, Carnegie’s role in the future of astronomy, the Magellan telescopes, astronomical archives, MaNGA and eBOSS, galaxy formation, dark matter, and even the science behind the black hole visualizations in Interstellar.Audio note: this was one of our first out-of-studio interviews, and there are a few minor audio issues in parts of the conversation. We appreciate your patience, and we’ll be better prepared for future field interviews.Also, if you’re in Los Angeles, Krishna will be giving a talk at Exploring Physics at UCLA, hosted by UCLA’s physics outreach organization Continuum, on Saturday, June 6 at the Fowler Museum. His talk runs from 9:30–10:30 AM.Register here: https://luma.com/3al1hj5h

This episode is brought to you by L'Oreal Group. Beauty is a powerful force that moves us. That's why L'Oreal Group has built a business that is inclusive at its heart with 100% of its brands, championing diversity. With 25,000 professional opportunities for people under 30 worldwide and 54% of leading positions held by women, diversity is a strength that helps L'Oreal Group create the best beauty products for all people. Visit L'Oreal.com to learn more.

Hello, internet. This is your captain speaking, Lester Nare. We have begun preparations for our return to regularly scheduled programming with our resident PhD, Krishna Chowdary, expected back on the pod later this June after some well-deserved family leave. But today, we have our second interview in our ongoing collaboration series with Carnegie Observatories. In this interview, Krishna sat down with Michael Blanton, the new director of the Carnegie Observatories for a conversation about open data, the Sloan Digital Sky Survey, the future of astronomical data science, and the mystery of why the universe's most massive galaxies stop forming stars. And one quick announcement before we jump in, for those of you who are here local to Los Angeles, Krishna will be giving a talk at Exploring Physics at UCLA, hosted by UCLA's physics outreach organization continuum on Saturday, June 6th at the Fowler Museum. This talk will run from 930 to 1030, and we will include a registration link in the description.

So if you're in the neighborhood, come stop by. I will be in the audience. It's sure to be a great talk as we warm back up to our regular episodes. But as always, we are going to learn about the science from the ground up today because this is from first principles. I am joined today by Michael Blanton, the new director of the observatories here at Carnegie Science. Michael, thank you so much for joining us. Thanks for having me. You know, I wanted to start by taking a trip down memory lane because both you, me, and Lester, were...

part of the institution at Princeton University. You got your PhD there in Dayton Hall. I was in the neighboring Jadwin Hall and I was always very jealous of all the astronomers for having such a beautiful building, whereas we got, you know, whatever monstrosity, um, Jadwin Hall was. So one question from one Princeton alum to another Princeton alum, always, um, how often do you go back for reunions? I never go back. You never go back. I was a PhD studio there, and so we existed in a slightly different culture than the undergraduates. Yeah. You know, eating clubs for us.

No, yeah, but Peyton Hall was pretty close to all the eating clubs. So that was, I always, you know. Walk by them on my way to Hockey Haven. Oh, boy. I'm sure you didn't think very highly of the undergrad's there, but we promise. Actually, they were great. I T-Aid while I was there. and they were amazing undergraduates.

Well, just as a pitch, you know, there are graduate student alumni reunions at the same time. So you should, you should, you should, I did go to the reunions when I was a PhD student there. They were really great parties, but I haven't been back for any since then. Yeah, of course. Well, so you got your PhD there in astrophysics. One of your advisors was Jeremiah Ostriker. Yeah. And he was seminal in starting, or at least initiating the concept of the Sloan Digital Sky Survey,

which was this monumental effort to map out a large swath of the universe. And one of the things that I've read about the SDSS is that it completely sort of changed the culture of astronomy from, you know, now you guys were just putting out the data for free on this newly formed internet. Could you talk a little bit about what astronomy was like back then and how it's changed today? Yeah, so Jerry was one of my two advisors. And indeed, at that time, he was putting together the Sloan Digital Sky Survey. You know, if you look back at astronomy in the, you know, before around that time was the mid-90. you know, a lot of the data was accumulated in non-digital forms.

So there were still people collecting data on photographic plates. Wow. Like glass plates that had emulsion on them. Yeah. And digital detectors had been introduced and other electronic detectors before, you know, before that. But they really hadn't been. in as large format. You couldn't do like a large, like if you're imaging the sky,

you couldn't get like a really big CCD to actually do that. And so for that reason, a lot of things were still photographic. You know, the, you know, starting around 1990, it became possible to conceive of things which were bigger and digital. And once you are doing something digitally, you are then able to share it in a much, you know, much more broadly, much more easily. Right. And so a few people recognized that that was going to be a possibility. And for example, the people at, you know, the Hubble Space Telescope, which obviously was sending data down digitally.

Of course. They had a lot of, you know, data distribution to the community. And STSS was this other big digital thing that was happening. And partly in order to help fund the survey and motivate the National Science Foundation and the Sloan Foundation to fund it, they promised somewhat rashly maybe to make it all public and freely available. Yeah. And that was very new just because, both because of the technology, but also just because of the culture. And there was a genuine concern among people that like, oh, you're really

giving away the store here. You'll get scooped. Yeah, yeah. Which is, I remember, you know, which is a term I normally associate with, you know, you know, characters in the front page or something, rather than scientists, but, but some scientists are afraid of being scooped. Okay. And, but SDSS really from the beginning had a very different philosophy of, of eventually making the data fully public. This, I was a graduate student of the time. I was doing theory.

Right. So I wasn't, I wasn't part of conceiving of it that way. But when I heard about it, it seemed like so intuitive, like that's the right thing to do. you make the data available, you make it, so any astronomer can get to it, and you're going to get a lot more out of the data. People will be able to collaborate freely, they will do things.

You know, you hadn't thought to do. And there's just too much science with a dataset like that for everybody to do. I think what's been surprising to me over the years is that, so to do that right, you have to really spend enough, money to make it good. I think the genius there was Alex Zillay at Johns Hopkins, who actually, you know, made

the Sky Server and later Sci Server, which really made things accessible to everybody, like middle school students and as well as astronomers. And you have to spend the time and effort to do that. And I think what's been surprising to me over the years is you have to keep telling people that lesson. People still have an instinct to keep their data close and to not spend the effort to make it freely available. And that sort of argument, I thought that that argument was one once and for all. But it was not. It has to be re-argued, you know, almost every project. Yeah. So that was surprising to me because it seemed so natural. I don't know if that answered your question.

No, totally, totally. And I think, you know, modern astronomy has definitely changed a lot, right? Because, I mean, with the Vera Rubin that's coming online, that's very similar in that sense. The data is going to get fed to whatever server very, very quickly as soon as the telescope takes that photo, right? Yes. So for Rubin, you know, as soon as they, you know, as soon as they get the data, they will be sending out alerts publicly. Right. Sometime this year, they'll probably start.

And those will be fully public. And then the data itself eventually becomes public and will be distributed to the partners. Yeah, yeah. I think that's a really cool thing about astronomy that I think other sciences have not totally gotten to where astronomy has, you know, in terms of just public distribution of data. I think that's something that other sciences can probably learn. from? I think so. It's helpful, and this is one of the reasons I think that people who work in data science or machine learning and what have you, I think really like working in astronomy as sort of a sandbox. Yeah. I mean, it's a sandbox stand and it's like our livelihood. But I think,

I think the reason they like that is actually there is a lot of public data and there's no privacy issues. Right. Yeah. So it's sort of, there are many, you know, it's like,

there are many sciences where it's a legitimate problem if the data becomes available. Like in the social sciences, it's not so easy. Totally, yeah. In the neurosciences, too, if you're dealing with human data,

but, you know, there's a place called Allen Brain Institute in Washington. Yeah. They're publishing a lot of, you know, mouse and rotted data freely available.

And that's sort of changed The ice are unlikely to sue. Yes, yes, very much so. You know, keeping on that trajectory, your career has also been one of making large data sets available to people and have those data sets be such that it's easier for astronomers to analyze, right? And one of the things that I'm referring to here is the NYU value-added galaxy catalog. It sounds like a venture capital thing.

You know, what is the value you're adding to my portfolio? But if I were to ask you, what is the value that you added to the SDSS? Yeah, in retrospect, we would have handled that name differently. Visit BetMGM Casino and check out the newest exclusive. The Price is Right Fortune Pick. BetMDM and GameSense remind you to play responsibly, 19 plus to wager. only, please play responsibly. If you have questions or concerns about your gambling or someone

close to you, please contact connects Ontario at 1-866-531-2,600 to speak to an advisor, free of charge. BetMGM operates pursuant to an operating agreement with Eye Gaming Ontario. Well, you're coming to California, so it's the right wording here. I mean, really in that case,

one of my personal obsessions about doing these large, you know, analyzing and taking these large data sets is that for a lot of things you want to do, you don't only want to study, you don't only want to say, oh, I've detected these galaxies, they have these red shifts, whatever. You also need to know exactly what you did, like where you could have seen a galaxy. If there was a galaxy, there, would you have seen it? Right? Because you can only see the galaxies down to a certain brightness.

And that means for a galaxy that is of a certain luminosity, like it's intrinsic brightness, that means there's a distance out to which you can see it. And so when you observe the sky, you're mostly seeing nearby things and fewer far away things. And the things we were trying to do with SDSS at that time was math. the universe on the largest scales.

And if you just took that map, you would be like, wow, everything's near us. Right. And you have to correct for that and correct for the fact that we looked in this part of the sky and not that part of the size. So most of the work of that catalog was very carefully, you know, determining what parts of the universe we had actually been able to see things so that we could then do things like measure the statistical correlations between galaxies over very large distances. So that was sort of the main reason for that catalog.

It was sort of so that statistical analyses, you know, had a firm basis. Yeah, that totally makes sense. And I might be going off on a limb here, but, you know, one of the things that I hear in cosmology all the time, at Princeton, I actually took an undergrad course with Neta Bacal and cosmology. It was great. She's an amazing professor, and I learned a lot. And, you know, one of the things that we learned in that course that was kind of a central

tenant was that the universe is isotropic, you know, whichever way you look, it's about the same. Was your, you know, value-added galaxy catalog part of that conclusion? So, yes. I think that the strongest evidence for that comes from the cosmic microwave bow. Oh, okay, fair. Where it's where it's just very clear that like that art of the sky and that part of the sky, which have never talked to each other, are the same temperature. Yeah. So I think that that is the strongest evidence, but it is true that with the largest volume sample of SDSS, we were able to do that for the galaxies as well. We could answer the

question, like, how homogeneous is the universe? And we did have a quantitative paper, you know, based on the volume we surveyed, which, which showed that it's very, very uniform. Yeah, it is very, very uniform. On those large scales, right? On the small scales, everything's clumped, but once you're at hundreds of millions of light years or a billion light year scales, then And everything is pretty much the same anywhere. It's like soup. Yeah. Yeah.

Very cool. So now I want to talk about your transition to Carnegie. You've got a new job now. Congratulations, by the way. Thanks. You left New York for the best city on the planet, Los Angeles. Okay. I mean, you know, Leshera and Nader.

It's out, but, you know. Not to us. So I grew up here and, you know, I've always loved it. So welcome to Southern California. This is an institution. Hubble walked these halls, you know. Why make the move? What about Carnegie brought you here?

The astronomy? Yeah. So it's an department of physics at NYU. That's right. And one of the things I've, even in this first month, is just really clear, is just, just every morning there, you know, there is, there is, such a range of experts here talking about every single aspect of the astronomy. You know, yesterday someone's talking about very large-scale structure.

People are talking about exoplanets. It's really like that. So one of the main draws for me was just that environment where I'm learning something new every day from the people around here. and and so that's actually the fundamental thing. Another thing is just simply the resources in terms of the engineering resources. Las Can's Companis Observatory is an amazing facility. And SDSS actually partnered with Las Campanis.

We actually now, you know, in SDSS-5, they're completely using the 100-inch telescope. And that's a, you know, so I've had a, you know, a long, you know, a decade or so of experience working with Carnegie already through that. Right. And then in terms of the job itself, like a director job, I was, I, you know, I started in SDSS as like, you know, writing software, which actually kind of stuff. do. But in a previous phase of SDSS, I was the director. And I sort of learned at that time that I kind of liked enabling science. I got a satisfaction from making it possible for people, as you said, get their data, but also get the science they wanted done out of the project.

And so it's an admit, like, that was an administrative and leadership role, but very close to the science. So, like, not like, you know, offense to any deans, but not like being a dean. Yeah. Like, like really, like very close to the scientific decisions. And, and I think, and this job being director here, I think has that same flavor. You're very close to what people are doing and, you know, the sorts of. decisions they have to make that require scientific judgment. And so I like that place where it's a leadership role and you're really, it's enabling science,

but you're sort of close to, you know, what's actually happening. Right, yeah. I mean, just before we were filming in this room, there was, I think, a journal club meeting. Yeah, the team. Yeah, they were discussing the bullet cluster data from the James Webb. Yeah. And I was just eavesdropping. And it was such a cool conversation that, you know, everybody was just gathered around talking about one paper.

So it is an incredible institution. Well, this is an amazing thing about astronomy, which is different than other fields, is that, well, I don't know how different it is from other fields. But I think it's different is that, you know, when you're an astronomer, you kind of have to know all the bits of astronomy. Like, they actually all end up being relevant in some way. So it is relevant to the people who study stars. what's happening in the bullet cluster. Like that turns out there are enough connections to like how galaxies form

and then how stars form and the elements that are in stars that those things are connected enough that you really have to, you know, have some knowledge of what's happening across the field. Yeah, so it's not just like dark matter guys or girls but could have the bullet cluster. It's like everyone. Yeah.

No, no, I think it's certainly very relevant to the people who study galaxies, then that is connected to the people who study stars, which is connected to the people who study planets. And it's very hard to, you know, you're kind of expected as an astronomer to have some handle on all of that. And that, I think, is, and partly it's because it's, you know,

there's only whatever, tens of thousands of professional astronomers in the world. So it just is a small field. but that I really like about it, that you sort of have a connection to almost every astronomer that you meet. Right, yeah, that makes sense. So you've been, you're a very new director here.

Very new. What are you looking forward to in your tenure here? So there's, you know, the things that are going on here, really the main observational event, right, now is Magellan, two six and a half meter telescopes and the SDSS program at the DuPont. And what I think, you know, our challenge, one of our challenges is, you know, with any, you know, any large telescope like this, really any telescope, you want to make sure that the things that are happening at it are

continue to be cutting edge. So I think one of the things we really have to figure out is the strategy for for keeping the telescope functioning. It was built in the 90s. It's got all of the, you know, it's got some 90s technology still in there. There are things like that which are,

which really have to be done. There are sort of more on the technical, you know, infrastructure side. Right. But then there's also there are new opportunities for instrumentation now. There is there's instrumentation that that you could build better now and be able to look at fainter things, look at things over, you know, wider swaths of

sky. And I think that, you know, in the in the, in that those sorts of timescales, I think we have to figure out how to build those instruments. And and one of the things about that is that, and I think this is borne out by some of the successful efforts, recent efforts, is that you really have to do this collaboratively. Like, you know, Carnegie has to be working with, you know, and this, this, this is part of, like, the way Carnegie has worked with SDSS, which has brought a lot of new instrumentation and energy to certain parts of Carnegie. And I think this is true at Magellan as well, the six and a half meters is I think you have to be working with other parts of the community to build the things that are cutting edge. You don't do it alone anymore. So that's one aspect. I think there's another

aspect, which is that I really think that, you know, we are sitting on a pile of data. It's a huge pile of data and facilities that, you know, that can create them. And I think that There's a lot of work in, you know, I sort of think of it as astronomical data science, but that would include everything from, from, you know, telescope software to, you know, data reduction software to machine learning, to, you know, AI applied to the data. Like, I think that is something where I think Carnegie should have, like, a really strong position in. And so that, that's something I would really like to see happen. Yeah.

Do you have, do you have any plans with all the photographic plates in your basement? I think, no, the answer to that is no. Yeah, I mean, it's serious. It's a hassle. So, so there, there are programs, like, hard. Harvard has a program for their library where they're digitizing all of these things. I think that is in principle interesting. I think you have to do it in a science-driven way.

I think because it's such a big problem. I mean, you've seen. Yeah, it was all sorts of things, all sorts of different data, all sizes and GOPs. And so you really would, you want to approach that with. I really want to study X and I'm going to do something. Yeah. I think that's the way you approach that. Yeah.

And for what it's worth, I mean, any astronomer can request Carnegie for like a specific plate and things like that, right? You have some way of doing it? I don't know the answer to that question. That's one of the things I should probably know. Okay. Well, I might be misremembering, but last time when we got a tour, they were like, you know, people come in and they say,

oh, I want to look at this part of the sky, you know, and there was somebody to play. You hope we say yes to that. Yeah. That would be great. I think you do, but maybe, I don't know. Maybe. Yeah.

Yeah, no, absolutely we should. And there, you know, there are definitely things in astronomy where people have studied this star for hundreds of years. And this is a hundred year period where, especially if it's something significant enough that people are doing that. Yeah, there probably is information in an archive about it. Yeah. Definitely. I mean, your archives here are just spectacular. So one of the things that you talked about was that, you know, as director, you're not like, you're not someone like just pure administration. You're making scientific decisions.

You were the director of SDSS4. Yeah. Right. So could you give an example of like a scientific decision that you, you know, it was the buck stops with you and you had to make that decision? and what were the things that you weighed when making that decision? So, I think there... And it doesn't have to be from SDSS, if any way... Yeah, I think SDSS probably has the examples I could most easily talk about.

You know, I think there was... Just tell me if this is too far in the weeds, But, you know. We love the weeds on the podcast. Okay. You like the weeds. Good. So in SSS4, we had two programs that were using what we call the dark time, which is when the moon is new. Oh, okay.

It's on the other side of the earth. Well, it's on, yeah, it's on, it's on the day side. The sun. Yeah. Right. So it's when the sky is dark. Yes. Right.

So, so one was called manga, which is another naming. the house anime? Yeah, it's spelled the same way. It makes it hard to. What was the full form? The mapping nearby galaxies

at Apache Point Observatory. Okay. Yeah. Yeah, that's, okay. Yeah, yeah. But it was observing nearby galaxies. Great. And then there was eBoss,

which was like the last Redshift survey we did. Another great name? Yeah, yeah. EBoss, yeah. That was the extended boss survey. Okay. So anyway, retrospectively. But what was happening, we had to make a decision between this, you know, how much time we were spending on each.

Right. And, you know, there was a question of the competition for each of these two. And basically, manga, actually, for a data set like that, the way, the amount of information we're getting per galaxy, the number of galaxies. It actually, this program ended in 2021, but there's still nothing that's comparable to it even now. Right. Whereas with E-BOS, it was our last Rage-Siff survey, and another Rage-Servie called DESE was starting up near the end of when we were ending, but not, but, you know, it was going to be a small overlap. And our E-BOS team was like, you know what? Like, we all want to work on this other project.

Yeah. You know, and we really want to close down eBoss sooner, but we want to reach our goals. Yeah. And so the decision there was sort of, let's bring forward eBoss and just spend, you know, I forget exactly, but spend like a whole year just doing that, don't do any manga, and then wait for manga to do in the last year of the survey. I'm getting the exact timing wrong. I know. So we're back. There's a whole report to the Sloan Foundation about it.

But that was a decision where it's like, we're going to put your data taking on hold so we can get these people done and then we'll go back to you, which is quite risky because at that time we didn't have enough money to finish the project. Oh, wow. Yeah, yeah. So it was, we didn't have enough money to finish the project until maybe 18 months before we finished. Wow.

But part of that, so that's a scientific decision. It's like, do you prioritize? this thing and put the other thing at risk. And then you sort of say, well, we'll give you a little more time if you'll take it later. Yeah. And so you work it out that way. And it also became a selling point to the DOE to give us a little more money, the Department of Energy, to give us a little more money to finish EBoss. Right.

And so that's an example where it's a scientific decision because of the timing of these projects. Yeah. And but it's somehow intimately tied to the funding decision. Like that only works if you can actually get a little money that helps you close your budget. And so that's an example where it's like it's not just an administrative decision or a scientific decision. They're intimately connected. Right. And just to be clear, these are two programs that are asking different questions scientifically.

Totally different. They're trying to use the same telescope. They're using exactly the same telescope. Right. And e-boss is the redshift. Yeah. So that's the one that's just like charting galaxies far away. It's wrapping the universe on the largest scales.

Right. At the time. Yeah, at the time. But I guess DESE was coming on. And I think DESE is at in Tucson, right? In Kitpeak. Yeah, it's like Kipi. So it's like nearby.

It's nearby. And it was the same team of people. Like the team of people's... Oh, okay. E-Boss were the people, a key part of the team that had proposed Desi. Okay, so. And they'd already gotten time, so they're like, let's just finish up. Yeah, they were sort of, you know, we're going to, we really want to move on to this other thing.

And, and, you know, because for good reasons. Yeah. And so that was their motivation. Okay. Very cool. And then, I guess, manga was nearby galaxies. Yeah. What was the question?

Because I imagine with Redshift, you're trying to answer, you know, Hubble's constant expansion of the universe. Yep. cosmology at the biggest scales kind of thing. Yeah, pretty much. What was manga's prerogative? Mongo was, in manga's tagline was the galaxy survey for people who love galaxies. Okay. So it was getting, so it was this much smaller number of galaxies.

I think by the time we finished the SDSS redshift surveying at the end of EBOS, we had maybe somewhere between three and four million galaxy red shifts. Manga observed 10,000 galaxies. Okay. which is much smaller number. Yeah. But for each galaxy, you are observing not just, you know, the redshift survey just takes the spectrum of the center of the galaxy.

Right. It's like the mean. It's just get one redshift and get, and you get more information. You get something about the overall age of the stars, the metallicity of the stars, something about the gas in the galaxy. But manga, you had these fiber bundles where you put the whole fiber bundle. they're not this big, they're like that big. Yeah.

But, um, optic, these are optic fibers. Optical fibers. Not the string theory fiber bundles. That is, yeah, there's no Lee algebra here. The creation of these fiber bundles. Yes.

Um, the, these fiber bundles are pieces of glass. Um, and, and, and they're put on the galaxy in the focal plane of the telescope. And we would do 17 of them at a time. Uh,

and get information across the face of the galaxy. Oh, very cool. So you could get a rotation curve. Yeah. You could get, you know, the gradients of the gas distribution and the metallicity distribution. So it's like much more information about, like if there was an active galactic nucleus, which is like a super massive black hole at the center of the galaxy, you could get that separately

from the rest of the galaxy. Right. Yeah. So before there was just one spectrum and the entire galaxy, all of its spectrum was coming through. you're getting this thing. Now you're sort of like pixelating a galaxy and tiling it. Yeah. Because the spectro over here, because it's moving, you know, maybe it's rotating this way,

is different from the spectro over here. Yeah. Is different from the center. If there's some black hole that's acting up. Yeah. Very cool. I see. Yeah.

That's, that's super fascinating. I wanted to wrap up with two questions. Okay. One was, you know, with your tenure coming up in Carnegie, What is like one mystery of the universe that you personally are super, you know, curious about and you hope that your efforts can lead to an answer? I mean, there are many. Yeah. If you were to pick, you know, one.

If I'm going to pick one personally. Personally. Yeah. Then I grew up as a galaxy person. Yeah. And I'm still fascinated by galaxies. and I, well, it's really two things. One, one is that, which is really just about the galaxies,

which is that, and this has been a mystery since I was a graduate student. Okay. And is still, as far as I'm concerned, still mysterious, even if we have some better knowledge, which is that the most massive galaxies in the universe are not forming any stars. There are no stars forming in them. They are filled with old stars that mostly formed billions of years ago.

Okay. And although you would think they would have available gas, in some cases you see the available gas, which is normally what new stars form out of, they're not actually doing that. And that problem, which existed in the 90s, is still not as far as I'm. I'm concerned explained today. And that has consequences like those galaxies don't get as massive as your theoretical expectation would be. Now, there is a theory that is that that is sort of, if there is a generally accepted theory, it would be this, which is that somehow the supermassive black holes that are accreting matter at the centers of these very massive galaxies,

are preventing star formation from happening. Okay. And somehow. Somehow. Somehow. And so there are like, you know, at least half a dozen different numerical simulation methods where people incorporate this and successfully stop the stars from forming in these most massive galaxies. All of the models work.

Okay. And they're all different. Okay. Yeah. Got it. So they all start with, there's a black hole at the center of the galaxy, and it's doing something. And then they all do different things. And then the end result is that they get the galaxies to have the right mass.

Okay. And, but the ways in which they do that in detail are all different. Okay. And that to me is, you know, I would like to know which of those answers is correct. This spring, denim gets a softer, lighter update. Introducing Old Navy's drapey denim wide leg, a new fit that moves with you. It's everything you want denim to feel like for summer. Easy, breathable, and effortlessly cool.

With a fit that creates natural movement and a wide leg that feels modern, not overwhelming. Plus, that signature, wait, for this price, moment. Old Navy's drapey denim wide leg. Yeah, that's so interesting. So that seems counterintuitive. I mean, big galaxies should just have... Yeah. Because the Milky Way is forming stars, right?

The Milky Way is not one of these. The Milky Way is maybe 10 times less massive than when this size. Then this happens, depending on exactly how you count. Understood. But, yeah, so the Milky Way is in this mass range where some galaxies aren't forming stars, some are, and Milky Way is actually kind of in the middle. But these guys, it's like no one is forming stars in this poppy. Very rare for them to be forming stars.

And again, you need a lot of energy to stop the gas from flowing in its forming stars. You need to like heat it up or blow it out. You need a lot of energy. So people are like, these black holes, they can generate a lot of energy, which is a really good argument. But the exact way in which that happens is still a mystery. is still a mystery. That's cool. So that's one thing.

And I would say the other thing really for me, which is also related to galaxies, is that I really think dark matter is a gigantic mystery. Of course. Everybody is. And one of the things that motivates me about studying galaxies, although they're very complicated and annoying in the way that it's hard to make predictions about them,

I do feel like if we really want to, to know more about dark matter, we better understand the physics of galaxies a lot better than we do today. Otherwise, I don't think we're making progress without sort of understanding the way the regular material works. Yeah. Yeah. All right. Totally. That's a fascinating problem. Well, all the best to you and Carnegie, there's one last question that I want to ask. I want to go back down memory lane to your undergrad days at Cornell. Yes. You did. You did. And, you did. And engineering physics, right? Yeah.

But you actually were in the research group where they were doing numerical relativity. Yeah, right. Right. So have you seen Interstellar, the movie? I have. I have. And what did you think about those visualizations? Because I imagine that's kind of, you know, the supermass, you were looking at numerical

simulations around holes. Yeah, actually. Yeah, we were. What did you think about that? We were doing visualization. Right. But with a much smaller computer, I bet. It was a much smaller computer.

We did them. We would, in fact, we had to, we did most of our work on green terms. Like these, you know what these are? You know what these are? You don't know. I don't know, actually. It's just, you've got a keyboard. It's got a monitor that's 24 by 80 car.

Oh my gosh. Okay. Yeah, it's like, you know, like in war games or whatever. Like, it was one of those. And then you were making these images. And then to see the images, you walk over to a room where the monitor was. Okay. Anyway, it was a while ago.

And then you wanted to put that video, and then we would make videos for professors to show at conferences. Right. And like, there was a whole other room where it was like, you slowly frame by frame, put this onto a VHS. Yeah. Anyway. So it was, so the visualization has gotten better.

Yeah, definitely. So what Interstellar does, I believe, and which is a really neat thing, is showing you, like, how the light actually, how you would see it if you were in that space time. Yeah. And so, would they come? Yeah, like, do all the ray tracing. Yeah. So, so we did do ray tracing, like, similar to that.

We were doing it, but we didn't do that for our visualization. We were doing that because there was a scientific question. We were asking about, basically we're asking, like, if you take to. things, well, you know, we had these simulations that the graduate students in postdocs had run of like matter collapses, forms a black hole. At that time, you couldn't make them do this. They could only come straight together. And they would form a black hole, but it's like, when does the black hole form? Right. You only, the definition of a black hole is the inventant horizon is when light can't get out. No matter what. Like it forever,

can't get out. And if you think about it, that's not really a local thing. You can't just say, oh, in this frame of this simulation at this particular moment, there's a black hole anywhere. You have to figure out, if I shine light here, can it eventually get out? And if the things in motion, if the stuff is still flowing, then it's not obvious. Right. Right. So, which frame are you talking about? Well, yeah. It's like, well, it sort of depends. on what these two clumps of matter do. If they're moving away from each other, maybe the light's fine.

If they're coming together, there will be a black hole there and this light won't get out. So we were doing ray tracing to figure out the answer to that question, like where the black hole actually formed. That was our job in the undergraduate group. But it was way, like we could do a few thousand traces

through this space time. We did not have, the computing to like render an image through ray tracing that that was that was beyond our capability so the stuff in interstellar is is amazing in that way where these days you can you can literally make a picture of of what what you would see in in these situations yeah and i think katea group actually did publish a few scientific results through the you know yeahization process of Interstellar, which I think is fascinating. Yeah.

Well, it's been a great conversation with you. Thank you so much for taking time. We really look forward to what you're going to do here at Carnegie. So do I. Yeah, and yeah, we'll see what happens. Thank you. Great. Thanks. Are you one of those media strategy people

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