A Conversation with Kyoto Prize Recipient James Gunn

Mat Kaplan: A memorable conversation with Kyoto Prize recipient, James Gunn, this week on Planetary Radio. Welcome, I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. The Sloan Digital Sky Survey opened up the universe as never before. Jim Gunn helped conceive and create it and then led the international effort for many years. But that's far from all he has accomplished. He and a colleague also led development of the Wide Field and Planetary Camera that helped enable the Hubble Space Telescope to take us so much farther across the cosmos. Jim richly deserved the Inamori Foundation's Kyoto Prize for astronomy and astrophysics, which may be the closest thing to a Nobel Prize for astronomy. A colleague called him the happiest person she'd ever met. I think you'll enjoy my wonderful in-depth conversation with him today. Asteroid Kaplan, said ain't so. Bruce Betts will not reveal all when he joins us for What's Up, but he'll have lots of other great revelations to share.

Mat Kaplan: The biannual Planetary Defense Conference is underway and I've got an invitation for you. The Planetary Society will host the PDC's only public event on Thursday, April 28th at 8:00 AM Pacific, 11:00 AM Eastern and 3:00 PM UTC. We're calling it Earthlings Versus Asteroids, What's the Score? I'll be joined by six international experts on how humanity is working to save our planet from the fate of the dinosaurs. It's free and I hope you'll join us. You'll be able to watch at planetary.org/live on The Planetary Society's Facebook page or on our YouTube channel. The recording will be available on demand right after the live show. A quick look at the down link begins with the ongoing triumph of Ingenuity, The Mars Helicopter. The little flying machine has completed three perfect ascents. As I prepare this week's show, Ingenuity project manager, Mimi Aung, will return as my guest in May. Bill Nelson is a couple of steps closer to becoming the next NASA administrator. The former senator got a friendly reception in his Senate hearing, and Russia has announced that it may end its involvement with the International Space Station. Roscosmos chief, Dmitry Rogozin, says development of an independent station is underway. Russia is also working with China toward human lunar exploration and establishment of a lunar base. You can catch our weekly newsletter every Friday at planetary.org/downlink.

Mat Kaplan: As a young man, James Gunn worked with and for many of the greatest astronomers of the 20th century. You'll hear him mention some of these mentors and colleagues in our terrific conversation. Jim would eventually help develop the digital detectors that have advanced astronomy far beyond the days of photographic plates. That advance would also enable the Sloan Digital Sky Survey that Jim headed for so long. It will be much more interesting to hear these stories from the man himself. You won't wonder why the Inamori Foundation chose to award Jim the Kyoto Prize. Jim Gunn, congratulations on the award of the Kyoto Prize, quite an honor. And it is quite an honor to talk to you as well. Thank you so much for joining us on Planetary Radio.

James Gunn: It's always fun to do these things, Mat, and I like very much to reach out to people and tell them a little bit about what I do and why I do it. So thank you.

Mat Kaplan: That's apparent from what I've already learned about you and from watching your Kyoto Prize lecture, which we will provide a link to from this week's show page at planetary.org/radio. And I encourage everybody to go and take a listen because it it's a wonderful, warm and fascinating conversation. I have so many questions for you, beginning with sky surveys. I mean, really, this is a great human tradition, isn't it? I mean, astronomers, whole civilizations have been charting the skies for about as long as we've been human, right?

James Gunn: Oh yes, absolutely right. And in the beginning, I suppose they were used to keep track of seasons and crops and such things, and then they evolved basically into navigational tools. And of course it wasn't really until, oh, I think the late 18th century, that people began to wonder about... I'm sure people had wondered before about what [inaudible 00:04:49] were and what was going on, but they began to have a little bit of physical and actually 19th century is what I meant, because once photography came along, it became obvious that there were many, many more stars than we could see. They were grouped in funny groups and clusters and people wondered about what they were and where they were. And that of course was the cause of an enormous amount of controversy until the early 20th century. And by then there were already pretty good photographic records of essentially all the sky, because they were being used to look at how stars move, how stars change. Didn't have very much idea what stars really were then, but it became clear I think quite early, that astronomy was basically a statistical thing.

James Gunn: There were lots and lots of very, very different things, but they fell into classes. And if you were going to understand them, you better understand something about the statistics. And now of course, astronomy is an almost entirely statistical subject. You worry about the large scale structure of galaxies in space. It's all very, very complicated statistics. And we wouldn't know anything about this without surveys. I mean, you can study individual objects to death and you don't learn anything about the populations. You don't learn anything about how they evolved. You don't learn anything about how they were formed. So I think surveys are more and more a kind of backbone of astronomy.

Mat Kaplan: I don't know if you know Linda Schweizer, astronomer and author?

James Gunn: Yes. I worked with her on her book. I've worked with her, I provided material for her book. It's a wonderful book. I really quite like it.

Mat Kaplan: Actually, I should've put that question in another way, because she acknowledges you in that book, which we talked about not long ago on this show, Cosmic Odyssey, about those decades of great astronomy performed by the buy-in at the Palomar Observatory, which of course was where this wonderful Palomar Observatory Sky Survey was done. And you, you talked about that a little bit in your lecture. I mean, you're talking about photographing the stars, but not taking the next step. I mean, what was the place of that survey?

James Gunn: Oh, that survey was immensely valuable. I think mostly because of things going on in astronomy that were entirely peripheral to the photographic process, right? Because the survey came along, it really became available in about 1950, I don't remember the exact year. At almost the same time that x-ray astronomy was getting going, that radio astronomy was getting going, that photo electric measurements of brightnesses and colors of things in the sky were getting going. We had not very much idea about what was out there. And the Palomar Survey was of limited use for making precise measurements of things except positions. It was quite good at measuring positions and it was just immensely valuable because you could see it, there was a strong radio source. You would work very hard to figure out where it was in the sky. And maybe you could see it on the Palomar Sky Survey and learn something about what it was, whether it was a galaxy, whether it was some peculiar cluster, whether it was this, that, or the other.

James Gunn: And so it was the sort of primary survey tool for astronomers for a very, very long time, but it was clear that there were serious weaknesses because it was very, very difficult to make precision measurements of colors or brightnesses from it. And so people talked about better ways to do things with electronic detectors that actually made quantitative measurements, but it was a long time before that technology evolved to a place where we could actually do it.

Mat Kaplan: We are going to come to that, of course, because you were the driving force behind that effort when the time came, but I can't leave Palomar yet because like Linda, you talked in your lecture about this wonderful character Fritz Zwicky, who was largely behind that Palomar Survey, those Schmidt instruments. I have a Schmidt telescope sitting downstairs on a tripod. And I wonder if you could just say something about what a character he was. Did you know Fritz Zwicky by the way?

James Gunn: No, I knew him quite well, actually. And there are various stories and anecdotes. There was a recent biography, which I can't remember who wrote it, which captures him, I think extremely well. He was just incredibly eccentric. You didn't want to cross him. He didn't suffer fools lightly and he thought almost everybody else in the world was a fool. I got on with him actually very well, partly accidentally. There was an edict which came down in the department at Caltech, that retired professors could not have access to the 200-inch telescope. This was aimed entirely at Fritz.

Mat Kaplan: What a way to run science? Okay.

James Gunn: I was a wet behind the ears, young astronomer and Fritz had various things that he wanted observed. And so he would come to me and I would observe them for him. So we got along really, really, quite well. You should tell your listeners that they need to go and read about this man, because he was really one of a kind. He was interested in jet propulsion. He invented JATO, do you remember?

Mat Kaplan: Oh, yes. Jet-assisted take-off.

James Gunn: Fritz invented that-

Mat Kaplan: I'll be darned.

James Gunn: ...during the war while he was working on... And so he was really a universal man. He was interested in engineering. He was interested in... He broke his leg once because he loved to ski and he was trying to invent a new way to do very fast turns coming down a hill very quickly on skis and spirally fractured one leg.

Mat Kaplan: Oh God.

James Gunn: He was just a character and a wonderful, wonderful character, as long as you were not on his bad list.

Mat Kaplan: So I'm glad to hear that you weren't put on his spherical bastard list, as he described so many people.

James Gunn: No, no, no, no, I don't think I was [inaudible 00:11:54].

Mat Kaplan: We should explain, this came up in my conversation with Linda as well, that he said most astronomers were spherical bastards because?

James Gunn: Well, basically because they look the same from his angle. But I don't remember [inaudible 00:12:09].

Mat Kaplan: I think that's it. I think that's it. We'll move on. The way you describe Fritz Zwicky, because he was into so many things, could do anything. Your colleague, Alison Coil at UC San Diego, who just provided the introduction to your Kyoto Prize lecture in the Kyoto Prize symposium that UC San Diego held just a few weeks ago, says that you are that rare combination of theorist and experimentalists and a builder of instruments. Do you agree with her? And-

James Gunn: It's been said many times. So I have been very lucky in my career. When I was a child, my father who was a geophysicist and wandered around the country, had a portable machine shop, which he needed in order to keep his instruments going. And especially during the war, you couldn't find parts. And so I learned very early to be very interested in building things and that has stayed with me. I think it's actually my passion, even more than science. And so things like the Palomar instruments and Sloan, I was really building instruments so that other people could do science. And I love to do that. And people have asked me, "Well, doesn't that make you say that you didn't do more science?" But I built all these cool toys.

Mat Kaplan: That's great. I saw the telescope that I guess you started with your father, which later you actually used and got your first paper published.

James Gunn: Yes, yes, that's right. That's right. Actually, I built that after he died, but we had built several things together before then.

Mat Kaplan: What started your interest in the sky since you were already mechanically inclined?

James Gunn: That's a good question. I think I talked about... I wrote an autobio for annual reviews recently. I don't think I talked about this in my Kyoto lecture. My dad was a geophysicist. And one of the books that I really liked when I was a kid, was his astronomy text. For the life of me, I cannot remember who wrote the book. I will eventually perhaps discover this before I leave this mortal coil. But the subject was of course not very well developed and he had been a college student in the 1920s. And of course there was a lot going on in astronomy, but this book was mostly just descriptive, lots of pictures of planets and galaxies. The galaxies fascinated me.

James Gunn: And there was a children's book called The Stars for Sam, which I'm happy to say is still experimenting and has been updated and things. And so it just caught my fancy enormously, and because he liked to build things, we talked about it and we started building little telescopes. And so I began my amateur astronomy career at the age of 10 or nine or 10 or something like that. And it just really never, maybe I wasn't clever enough, original enough to think about something else because [inaudible 00:15:46] that really caught my heart, and I just stuck with it.

Mat Kaplan: Well, that's good for the rest of us. I have to say it worked out pretty well. I'm glad you weren't distracted by too much. You got to Caltech as a grad student, what, in the early '50s, thereabouts?

James Gunn: Nope. Let me think. I graduated, I did physics and mathematics at Rice and I think I graduated in '60.

Mat Kaplan: Oh yeah. I'm too early. That's right.

James Gunn: Then I got my degree at Caltech, I think in '65 of that order, '65, '66, yeah.

Mat Kaplan: What was the state of cosmology as you got to Caltech where you thought you were going to work on general relativity, but didn't get the chance?

James Gunn: And unfortunately, HB Robertson died before I arrived and he was the only relativist on campus, but I was very lucky since I had earlier been a very active amateur and had done astrophotography and build telescopes that tracked and things like this. I sort of got a head start on my colleagues because I knew about telescopes. And so Bob Kraft, who was an astronomer at the Mt. Wilson Observatory, and at that time that family was very closely knit. And so I started working almost right away on a project with him to do stellar spectroscopy, but I was also very interested in cosmology. And so I sort of kept up, I learned things on my own. There was a general relativity course taught by a wonderful man from JPL called Frank Estorba. And so I was able to learn about the things that I wanted to learn about.

James Gunn: And when it came time to do a thesis, I was also quite interested in statistics and surveys and things, already then. And so I did a thesis on the statistical structure of galaxies in space, I think one of Jim Peebles and I started the subject, but he got there first, that's just the way it was, but cosmology was not in a good state. I mean, we didn't know about dark matter. We didn't know within a factor of two or maybe more, how old the universe was and what the Hubble Constant was and all of these things that we now know toward the order of a percent. At that time, I could not [inaudible 00:18:24] that we would progress to the extent that we have.

Mat Kaplan: But we didn't know about dark energy, right?

James Gunn: Oh no. We certainly didn't know about dark energy. We didn't even [inaudible 00:18:36] dark matter, right? That kind of slowly developed and the subject at the time was very strange. And the contrast with the subject today is just incredibly marked. The subject then was the province of a few powerful men who had access to the world's biggest telescopes, Allan Sandage, [inaudible 00:19:07]. And it was very difficult to know whether any of those characters was correct or not. They published a lot, but there was no way to find out whether a particular thing that they claimed was white or not, because they were the only people who had access to the tools to do the experiment. The whole idea of science as being something, you do an experiment, somebody else does the same experiment, they get the same answer. And you have some idea about whether it's right or not, those checks and balances simply didn't think they existed.

Mat Kaplan: I saw a great quote from you, "Cosmology may look like a science, but it isn't a science, a basic tenet of science is that you can do repeatable experiments and you can't do that in cosmology," said Jim Gunn.

James Gunn: Yes. Yes. Yes. Well, that's just the whole picture of the universe. What we can do is take the science we learn in the lab and locally and the solar system, because we can do some exploration, and try to generalize it, to expand it to the whole universe. We can be lucky sometimes and we can be unlucky sometimes, but proof is something that's very, very hard to come by in astronomy. You can make theories that fit the observations, but for elaborate science, you can repeat the experiment, but there's only one experiment here, it's just the universe. And so you don't know whether you're being lucky that your theory fits the things you know today or whether it's just a fluke, right? The fact that we are making such detailed models now, that seem to fit what we see, I think is saying that cosmology is becoming more and more of a science. It was not a slant when I started this thing, they were just a million crazy ideas, right? There's still crazy ideas that come out of the woodwork, but my faith in the subject has increased a lot just because of what we understand, the precision with which we understand it. And we can kind of predict what's going to happen next. I mean, the Event Horizon Telescope, for example, right? That black hole looks like we thought it should [inaudible 00:21:40] so that's I think pretty amazing.

James Gunn: The most amazing thing to me actually, is that when Jim Peebles wrote down, who I think incidentally is the greatest astronomer of this century, his cosmology [inaudible 00:21:56] he wasn't really an observational astronomer, but certainly the greatest cosmologist. He had been fascinated from the beginning, from its discovery in whatever it was 67 or so of the cosmic microwave background, how it arose from the Big Bang, the structure that one should see in it when he first proposed the cold dark matter paradigm, which is essentially the way we will believe the universities today, except that he didn't know about dark energy. He predicted these acoustic modes that came from the universe very, very early and by God they were there. And it's just amazing.

Mat Kaplan: I hear the emotion in your voice. Because of the profound, what, beauty of this?

James Gunn: The beauty and correctness. I mean, it says that we understand basically what went on in the early universe. That's completely remote from the physics of our understanding, but Jim put it all together and predicted essentially exactly what we see. So it's amazing.

Mat Kaplan: It's wonderful to hear that you can still be so overwhelmed by a discovery like this, that we mere humans are capable of this kind of work.

James Gunn: [inaudible 00:23:27] these things, that's right. That's right.

Mat Kaplan: We're The Planetary Society. We tend to talk about small round hard cold things, but we do get to talk on this show anyway, now and then, about these largest of structures in our universe, galactic clusters, I can tell this is still a lifelong fascination for you, right?

James Gunn: Oh, yes, yes, yes. It is. I sort of got into exoplanets and things were discovered late in my career and I never... I'm fascinated by the subject, but I never worked in it. It's certainly a sort of... It's a major tenet of astronomy these days. And I regret that I didn't, but I was pretty old [inaudible 00:24:10].

Mat Kaplan: And yeah, the Sloan Survey, as we will talk about in a few minutes, has contributed at that level is so-

James Gunn: I think the [inaudible 00:24:21] stuff is just wonderful from Sloan and it was nothing that we imagined it would look like.

Mat Kaplan: Well, we'll come back to that. We also much more regularly on this show, we talk about spectra. We talk about spectroscopy all the time. Not long ago on the show, I was talking about the spectra of rocks on Mars that have been zapped by lasers. Your use of spectroscopy has been on a somewhat larger scale than individual rocks.

James Gunn: But we slung looked at rocks too.

Mat Kaplan: But it was a key point, right? In the upgrade that because of this progress that was needed following the Palomar Observatory Survey that did a wonderful job, but you knew and you and others knew that we needed to build on that, particularly through spectroscopy?

James Gunn: Right. Right. Well, and also photometry. I mean, you could do photometry or photographs, but there were only two colors. And so it was very limited and the accuracy was very limited just because of the photographic process. So what we needed was something that was very much more quantitative. I don't know, we will probably talk about this later, but at some point it occurred to me early on that the same telescope that was doing the imaging, which was the thing that I thought of first, and it just then came to me that, that very telescope would also be an incredibly useful spectroscopic instrument. So that's basically where the idea of Sloan came from.

Mat Kaplan: We had to wait for technology to catch up with the need to learn these things. I'm thinking of the way you and I are looking at each other right now, CCDs, charge-coupled devices. How did you realize that here was a device that might enable the kind of work that you were hoping to do?

James Gunn: Well, I think it was pretty obvious from the beginning. Jim Westfall, who was a friend and probably the most important mentor in my career, he was actually a planetary scientist, were very interested in working on detectors. And so we worked on datacoms and various things. Somewhere in the middle of this detector work that was going on in '70s, RCA made a tube called a silicon vidicon, which had a silicon target very much like a CCD, photon comes in, makes a pair, the pair, the electron deposits on the back and you use an electron beam to read it. So it was a sensitive vidicon, but the read noise was very, very large. It was useful for bright things. And Jim was interested in bright things because he was a planetary scientist. And I worked very hard for a while trying to figure out how to take exposures longed enough, that there was enough signal that you could read them reasonably well, but that came to nothing.

James Gunn: A couple of years after the silicon vidicon came along, I think it was RCA first, but the real work was done at Tektronix, no at-

Mat Kaplan: Bell Labs?

James Gunn: Well, Bell Labs invented the device, Bell Labs invented the CCD. And I think that was during the time that the whole telephone industry was being taken apart by the government because of anti-trust things. They never really got into the commercial business of building these things, but RCA started making them for commercial purposes and Texas Instruments started making them for scientific and military purposes. NASA was putting a lot of money into the effort at Texas Instruments. They built the first really good detectors and they went on the [inaudible 00:28:33] mission. There were lots, lots of places where they went, but since JPL was sort of right there and Westfall had been working with them a lot on the silicon vidicons, we sort of had an inside track to this development. And of course, JPL were very invested in people using these things so that they could find out how they worked, because they could test them in the lab, but they couldn't test them on the sky in any reasonable way. So Jim Westfall and I started working with them and built a couple of cameras using 500 by 500 thin devices, the thinning is very important, and built a camera for Calla Markel Fuji, which was prime focus, universal extra galactic instrument.

Mat Kaplan: I love it.

James Gunn: The combination camera and spectrograph, they're called parallel beam boxes these days and they're very common, but I think that was the first one. And then we got word that a project that was just called Space Telescope at the time, that's now Hubble, was in trouble. They were going to use a camera built around one of these big vidicons. It wasn't a silicon vidicon, but it worked sort of the same way. It was called a secondary electronic conduction vidicon, and the target in this vidicon was potassium chloride, very thin salt window. And it was incredibly [inaudible 00:30:08]. The thought of this thing withstanding launch loads and things like... just absurd. And it was being done at Princeton, under the aegis of Lyman Spitzer, who had been a major mover, of course, in the project. But NASA really got, they just knew it wasn't going to work. They didn't exactly take the project away from Princeton, but they said we need a plan B.

James Gunn: And so they put out a proposal for this and Westfall and I had been working with CCDs enough to know that that's the way you've got to [inaudible 00:30:44] that's the only thing you can do. So we put in a successful proposal for the Wide Field Planetary Camera and the rest, as they say, is history. So we worked a lot with Texas Instruments on CCDs, learned how they worked, did a lot of good astronomy, I think. And we got money from NASA for the same reason, to put these things on the sky. We built Fuji first, which was the single CCD instrument, and then we built a quite massive instrument called Four Shooter that used four CCDs with the same kind of image splitter that was going to be used in the Wide Field Planetary Camera on Hubble. And that was very successful. We found very high Richard quasars. We did a survey for clusters of galaxies.

James Gunn: And so I had forgotten about the survey business, but Martin Schmidt and Don Schneider and I did a high Richard quasar survey, John Hessel and other people and I did a hybrid shift cluster survey, the hybrid shift quasar survey was spectroscopy. It was done in a slitless mode with this instrument that's a little hard to explain, but you have a spectrograph but you don't have a slit and so it images. And so what you get is a little spectra on the sky background. So you can't work terribly faint, but you can cover an enormous area. And so we found the highest Richard quasars known at the time of Richard's around five. And the cluster survey was just done. You take a picture, you move, you take a picture, you move, you take a picture, you move. But we also developed at that time, we didn't develop actually, we utilized a technique called TDI, which means time delay and integrate. And it's a military technology, and time delay and integrate has absolutely nothing to do with what it does. But now one of the beautiful things about a CCD is that the photons come in, they make charge. And then you read this device by moving those photons along a row at a time in the detector. And then the last row, you read out to an amplifier and there could be more than one amplifier, but in those days there was only one.

James Gunn: The beautiful thing about this technique is that you never stop. It was developed for reconnaissance on the ground. The satellite or the airplane flies along, there is a CCD which is doing this and you have to move the charge at exactly the right rate. So the image of a tank or something is on exactly the same pixel as you move. Do it on the sky star stays on the same pixel as you move. And so for both Fuji and Four Shooter, we implemented this technique. And so basically it makes a tapestry of the sky. So you never waste time stopping, closing the shutter, reading the device, the device is reading the whole time. And so it increases the efficiency of light gathering by a very, very large factor. And we were the first people, seriously I think, other people had a little bit to use it [inaudible 00:34:16].

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Mat Kaplan: We're back with James Gunn. Before we leave the Hubble Space Telescope, what became the Hubble Space Telescope and your contribution to it that first Wide Field Planetary Camera for HST, I came across this wonderful term, what some of you I think called yourselves, are you a whiff picker?

James Gunn: Yes, yes, yes. Because that's what we built.

Mat Kaplan: So much cutting-edge technology. I mean, not just CCDs. Fiber optics, computer processing. Was it during this period that you realized, okay, now we can take on this giant jump over the Palomar Survey, which would become the Sloan Digital Sky Survey?

James Gunn: No, no, it wasn't until probably later. And that's a story also, which I told in this annual review's article, but I'm just trying to place this in time.

Mat Kaplan: Sure.

James Gunn: Yes, it was before the launch because the launch wasn't until '92. I had left Caltech and come to Princeton and was mostly working on theoretical things. Although I was still working at Palomar with Martin Schmidt and Don Schneider on the quasar Survey and with other people at Caltech on the cluster survey. And they were nice enough to even... They wouldn't give Uncle Fritz time on the [inaudible 00:36:58]. I was doing this work with Caltech colleagues, so that was okay. Anyway, one of those trips to California, I walked into my friend Jim Westfall's office, and we were talking about the Wide Field Planetary Camera, because that's what we were doing and Morley Blouke, who was the chief engineer, CCD engineer at Texas Instruments, completely unannounced knocks on the door, comes in and says, "Oh, Jim, I'm glad you're here, both Jims, I want to show you [inaudible 00:37:37]." So Morley reaches in his briefcase and pulls out a chip carrier, and it's about this size, in it there is a single chip with a single CCD, two and a half inches across. And the things we had been doing before were a centimeter across.

Mat Kaplan: No, wait, was this TI or was it Tektronix by this point?

James Gunn: This was Tektronix, beacuse Morley had left TI and had gone to Tektronix. Tektronix wanted to develop big CCDs to make really super fast oscilloscopes. So you could write on this thing with an electron beam and take your time reading it later. You didn't have to read the signals in real time. That apparently never worked out, but they made a lot of money on them because the CCDs are incredibly sensitive x-ray detectors. They were able to make mammography x-rays that expose the patient to a tiny tiny dose compared to other photographic technology basically [inaudible 00:38:48] it's the same reason. So quantum efficiency one versus quantum efficiency 1000.

Mat Kaplan: Were you blown away when he showed this to you?

James Gunn: That was when I knew, and on my way from Caltech to a meeting at Kitt Peak, where they were trying to figure out how they could use a three and a half meter honeycomb mirror. They had been working on this honeycomb technology, Roger Angel's technology. I sat there the whole time during this meeting, trying to figure out how to make these huge CCDs. They were not real yet. Morley said, "This thing doesn't work." That was basically how Sloan was born, because I knew I can make a telescope that would do this TDI, mosaic, scanning of tapestry scanning. And it wasn't till a little later that I realized these devices, that the match between the photometric instrument, because I was just thinking about imaging the sky. I was going to replace the sky survey with a CCD survey. It'd go deeper. It had much much better photometry and many more colors. And then I don't remember exactly how it happened and it may not have been even my idea. But anyway, it came to be, that I realized that these detectors were also marvelous for spectroscopy and on two and a half meters telescope, which turned out to be the sweet spot for the... Back up a little bit.

James Gunn: Princeton had just become involved in Apache Point Observatory in New Mexico. And it was a good site, but not a great site. It turns out that when you consider the size of the pixels, the read noise, the sky brightness, all of these things, there is a kind of sweet spot for a telescope, for a survey telescope anyway, and that turned out to be a little smaller than I was thinking about originally. Two and a half meters was about right. With a two and a half meter telescope and the kind of spectrographs I knew you could build, we could reach down to about 88 magnitude. And that's about a million galaxies. Then the various people interested in the project divided into two. There were the people interested in the imaging and there were the people interested in the spectroscopy, but we talked to one another quite a lot. The beauty of it that we hadn't realized at the beginning was that the weather at Apache Point is okay, but it's not great. So when it's great, you image and when it's not great, you do spectroscopy and your frequency is enormously improved because you can use the telescope, not all the time, because sometimes it's really sucked in, but when it's really clear, we were always able to work. And that's one of the big reasons plan Sloan was a success one.

Mat Kaplan: So you had the right location, you now had the right detector or at least the beginnings of it. This was such an ambitious huge project. I mean, there was a consortium to put together?

James Gunn: That's right. Well, the consortium that already begun because the Apache Point Observatory existed some years before Sloan happened. So the prime mover was University of Chicago and Don York. And there was Princeton, there was University of Washington, there was Washington state. I think that was the partnership at the beginning. A three and a half meter telescope also using this Angel white mirror technology was already underway. We built a spectrograph for that telescope in the process of doing Sloan. But fortunately we did not have to put this consortium together right from the beginning, but it was a big enough project that we needed a lot more partners. And so we got [inaudible 00:43:05] involved, which was I think in the end, not a mixed blessing. I think it was a real blessing, but it was dueled for various reason. And so the consortium just began to grow.

James Gunn: We had no idea how much this thing was going to cost. Just no idea. I mean, nothing had ever been done before. We knew how much the telescope would cost. We knew we were negotiating with Tektronix about the detectors and they gave us a quite good deal on the detectors. But the thing that we were very naive about was how much it was going to cost to store and reduce the data, the software, because it was a huge, huge job that we just didn't really have proper appreciation for. I think the first realistic budget. No, no, that's not the right word, sort of semi-thought out budget that we had was around 20 million and the project cost 80 in the end. It was really very difficult because during the project, there were several occasions when we did not know that we could pay the next... We had money for the next payroll. On the other hand, if we had said upfront that this project is going to cost $80 million, it probably would not have been funded, so-

Mat Kaplan: That works out. That works out. Thank goodness, thank God, it was funded. And you began this great work, which resulted in this enormous database, which is still so important today. Can you talk a little bit about how big a jump this was over the earlier Palomar Survey?

James Gunn: The Palomar survey, various people had tried scanning these plates and there were databases. I don't think of anything like the whole sky, but the accuracy just wasn't there. NASA had been in this business for a long time. So the IRF satellite that data were taken, they were stored, they were reduce, it wasn't anything like this big, but we can't claim that we went there first.

Mat Kaplan: And that was the infrared astronomy satellite, right? That did this work from orbit obviously?

James Gunn: Right, right. Because you couldn't store a bunch of photographic prints in your room from that because they didn't exist. So it was a really enormous step. I don't know a factor, but I think it was at least 100 times bigger than any other astronomical database. One thing that we learned very early... I was project scientist in this thing the whole time that it was going on. And I was pretty intransigent about doing the very best job we could do, which not all of our colleagues agreed with because they were interested in saving money. And sometimes doing things... It's my opinion that you always win by doing things right. Because if you do things not right, it just costs you more later because you realize that the data is... And my Princeton colleagues were very, very much with me. And so the thing that we tried to realize was that, in the software, the data are the photons. And so there are a finite number of photons. And so there is finite accuracy that can be achieved. And that was the accuracy we wanted to achieve.

Mat Kaplan: To the photon?

James Gunn: To the photon. And I don't know that we've succeeded to 100%, but we did a pretty damn good job. And that has just enabled so much as time has gone on, the asteroid stuff, all of the galaxy morphology stuff, the galaxy spectra, nobody really believed we could do the spectroscopic job that we did with a telescope this size because other spectrographs were not so efficient. So we worked very, very hard on getting the photons to the CCD and also having software that can extract the information.

Mat Kaplan: But it wasn't just software. You had one slide, you spent maybe 10 seconds mentioning this in your Kyoto Prize lecture, but I was just blown away. And I know that there has been work done like this since then, but you were the pioneers, you mentioned that you made these plates and that holes were drilled in the plates that exactly corresponded to the positions of the galaxies that were being observed in the telescope, and then you had to put fiber optics behind this, what? I mean, how many of those plates did you have to make? How many holes had to be drilled?

James Gunn: There were a couple of 3000 plates and each one in Sloan had 640 holes.

Mat Kaplan: Oh my gosh.

James Gunn: But let me tell you my favorite story about that. There are several good stories. Early on in the project, the most fun meetings would be when we would get together and try to figure out how to get the fibers in a parallel plane. And there were cockamamie ideas. There were wonderful things, right? Fancy robots and things. We finally decided, we knew that a CNC milling machines could place the holes to the accuracy we wanted.

Mat Kaplan: Those computer-driven milling machines, very accurate, yeah.

James Gunn: Yeah. Very accurate. It was tricky because the focal plane is curved. The light doesn't come in exactly perpendicular to the focal plane. So the plate has to be bent at a different angle when you're drilling from an angle and the telescope. Engineers who did this, they were just wonderful. And it's quite simple mechanism that does this. We knew how much that was going to cost roughly. And we knew how much a not particularly well-trained person who would just plug fibers into the holes cost. And the big problem was what if they plug them into the wrong hole? So somebody had the bright idea that we... What you do, you have the plate and you have the fibers plugged in. You don't care which hole, you just plug the fibers in. And the fibers go to a slip and the fibers are arranged along the slit in order, one to 640. You shine a laser along the slit and you watch the fiber on the plate-

Mat Kaplan: Brilliant.

James Gunn: ...in video, isn't it brilliant?

Mat Kaplan: Yes. Yes. You just reversed the flow of the photons.

James Gunn: My wife claims to be the one who has this idea. And I think, correct, she's [inaudible 00:50:23].

Mat Kaplan: Good for her.

James Gunn: And that solved the problem.

Mat Kaplan: Fascinating.

James Gunn: The other really cool [inaudible 00:50:30] was that we got the image were going first and it was going for a few months first. And we drilled the very first plate, which was a bunch of reasonably bright galaxies in the coma cluster. And we put the plate on the telescope and we got 640 spectra, the very first plate.

Mat Kaplan: Wow.

James Gunn: And that was amazing.

Mat Kaplan: God, it's like landing on the moon or Mars.

James Gunn: But pretty cool.

Mat Kaplan: Yeah. Very cool. How do you measure your success? I mean, how much of the sky was eventually imaged? How many objects did you get images of or spectra of?

James Gunn: I should know those numbers more accurately than I do. We got the whole northern sky above 30 degrees, galactic latitude. We got a big chunk of the southern sky. We basically got all the sky that could be reached with reasonable quality from the site, except for the galactic plane. And we simply could not cope with the data. Later in Sloan Two, there was a project called Segway that did go into the plane and we had some success with that, but the software is just incredibly complicated. There's 40,000 degrees in the sky. I think we, in the end, did something like 20,000 degrees. The original survey, which has now been surpassed with later embodiments, did a few more than a million galaxy redshifts and about 120,000 quasar redshifts.

James Gunn: The way this worked was that we took the images first, did the astrometry on the images. So we knew where to drill the holes in the plates. For galaxies you could see that it was a galaxy, for quasars, it was a little trickier because we had to depend on colors to be different enough from a star. Basically we took spectra of almost everything we could whose colors did not look like stars. Most of those were quasars. So that's basically how it worked. We did the imaging first, we reduced the imaging then went after the spectroscopy.

Mat Kaplan: But short of those that you got spectra from, weren't there hundreds of millions of objects?

James Gunn: I mean, the spectrographs were only powerful enough to go down to about 80th magnitude and the [inaudible 00:53:10] went down to 20 seconds. So there were about a billion objects that we got photometry for.

Mat Kaplan: Is there anything much more beautiful in nature than galaxies?

James Gunn: Oh, I think all of nature is extremely beautiful.

Mat Kaplan: Good answer.

James Gunn: But galaxies are very beautiful.

Mat Kaplan: Where I'm going kind of, is that I've seen, in fact, in your lecture, you took a piece of sky and zoomed in on it and zoomed and zoomed and zoomed until we saw these beautiful individual objects, the hundreds of billions of the hundred billion or so of them across the sky. And it's just, I mean, you can see it in those deep sky fields taken by the Hubble Space Telescope as well. It just blows you away.

James Gunn: Yup. Yup. Now we have a big mosaic on our wall from the Hyper Supreme Cam. We're somewhat involved in that and a big Japanese camera on Super and it's mind boggling and you get close and we're almost at the confusion limit. The galaxies are overlapping.

Mat Kaplan: Those objects that you weren't looking for. Thousands of asteroids discovered by Sloan, but I'm also thinking of those little stars that people pretty much knew existed, I guess, but you know what I'm talking about, the brown dwarfs.

James Gunn: Brown dwarfs, that's right. That's right. The amazing thing there was that people had been thinking they knew that the atmospheres of these stars, that the spectra of these stars would be dominated by methane. And we knew what the methane spectrum looked like, they're very cool stars. And so people thought, well you find them in the infrared, but the infrared part of the spectrum is basically wiped out by the methane absorption. So it's much easier to find them in the far red and the visible than it is to find them in the infrared. And that's why it's accessible.

Mat Kaplan: Those asteroids, I need to bring those up again because I'm with The Planetary Society and we care a lot about asteroids. We're still finding them. Did Sloan help us to understand how many of these rocks there are?

James Gunn: I think so. And that was a very controversial subject. [Jelco Ivezich 00:55:36] who was a postdoc here working on that subject, he had not come here particularly interested in asteroids, but was fascinated as soon as they started showing up and they were just a nuisance to begin with, because they had very funny colors because they were moving. And we were trying to find quasars and trying to take... And of course you go back to an asteroid and take a spectrum and I didn't care because [inaudible 00:56:06]. There were two controversies going on, one, it was known that there were several orbital families of asteroids, which I don't think we understand at all yet exactly how the asteroids came to be, but there were several orbital families, and there was a little bit of data on photometry, but not a lot. And so, as soon as the Sloan, as soon as we discovered hundreds of them, we very quickly discovered that these orbital families also were chemically different just from the colors. That was, I think probably the major thing, but the other thing that really upset the community, and we were sort of interlopers in this community [inaudible 00:56:51] doing asteroid.

James Gunn: We discovered that there were very many fewer asteroids in the inner part of the solar system than had been thought before. That has immediate impact on a lot of people's research because of Earth-crossers, there were many fewer Earth-crossers.

Mat Kaplan: I was going to say, no pun intended impact, yeah.

James Gunn: Precisely, precisely. So people wanted to prove us wrong because they were getting money from NASA to work on Earth-crossers.

Mat Kaplan: Still plenty of them out there for us to worry about, but also fascinating and an unintended result. I'm thinking of other impacts that Sloan had beyond the data that you collected that are still with us today, just in how science big science is conducted, big astronomy is conducted.

James Gunn: I think that's a very important question. And one that I like very much to talk about.

Mat Kaplan: Please.

James Gunn: When we started, astronomy in particular physics less so, because physics had these huge experiments with hundreds of people on, but in astronomy, most papers had one author, some fair fraction had two or three, people working on NASA projects, there were lots of authors because NASA was doing these surveys, but for ground-based astronomy, it was very much a sort of one or a few person subject. And as I said, the field had been dominated for a long, long time by great men. The thing that Sloan changed and which I am actually as proud of as I am of the science, is that we really opened up things. The data, we had a small proprietary period to make sure that it was okay, but even within the collaboration, people would get together with various talents, with various specialties, because it was required to make this work. And so there were large groups, papers already with large groups of people on them, including, and this is an important thing, including the people who built things. Mt. Wilson, somebody built that telescope, somebody built that spectrograph, but their name wasn't on the paper. It was just the people who got the data and we thought about it. We said at the beginning, "This is not a good idea, this is not fair. This is not putting the credit and the blame if something doesn't work."

James Gunn: Anyway, and we were quite successful with that. And I think it's become a kind of general thing. But then of course, when the data become public, everybody can work on it. One of the other things that we did that I'm very proud of, other projects and NASA projects even as well, the people who were involved in the project could carve out a fif, and that was their stuff. And we said from the beginning in Sloan, we're not going to do this. Anybody can do anything they want to, right, wrong, whatever. We reviewed the papers, but there was no formal censorship, we would point it out but there were all sorts of errors, and we would plan it out years and it has just worked incredibly well and made the subject so very much richer than it was before.

Mat Kaplan: I think of this as sort of a democratization of science and scientific data.

James Gunn: That's a very good yes. Right, right. Right.

Mat Kaplan: And even beyond sharing with other researchers, I know that you are a fan of citizen science projects and I'm thinking specifically of Galaxy Zoo.

James Gunn: Galaxy Zoo, yes, yes. And it's been I think quite incredibly useful. And of course it raises the awareness of science and the way science is done in the public, which I think is enormously important. So yeah, that wasn't my... The Galaxy Zoo wasn't, but I'm very proud that it happened and was part of Sloan.

Mat Kaplan: This was toward the end of your Kyoto lecture. You wanted to give credit because you were being recognized with this prize. Well-deserved, in my opinion, you wanted to give credit to the many members of the team, some of whom you've mentioned, but you singled out the younger members and the delight that you got from having young people as part of a project like Sloan.

James Gunn: Yes, yes, yes. No, that's certainly true. And it comes back to this question about science versus building things, project things, software things like this, it became apparent to me quite early, this was probably pretty close to the end of my scientific career because the project was taking so much time that I couldn't do it. And then I had to think about, did this matter? And indeed I came to the conclusion that it didn't matter. The important thing is that the science get done. So let's open this up. It was already pretty clear that we had to open things up and it was just so wonderful to see young people come along postdocs and graduate students. The highest redshift quasar for a long time in Sloan was found by a graduate student in Joey fund.

Mat Kaplan: And you say the highest redshift, therefore, the farthest back in the history of the universe?

James Gunn: I mean, the farthest away in space. Yes. Right. It's just so rewarding to see young people come along and grab the stuff and run and see all of this wonderful science getting done. And I don't really miss not being in the thick of that at all, far prouder to have done what I've done right.

Mat Kaplan: What are you most excited about what's to come? I mean, here we have a whole new generation of giant ground-based telescopes now being built first light not far off, but also these new space telescopes, maybe finally James Webb Space Telescope launching later this year, but what I'm really thinking of with you in mind is the Nancy Grace Roman, formerly known as the Wide-Field Infrared Survey Telescope, or survey telescope, WFIRST, do these excite you?

James Gunn: Yes. James Webb excites me quite a lot, because to find out what's going on early in the universe at very high redshift, you have to look farther and farther into the infrared. It doesn't very much survey capability. The field is too small, but it will certainly tell us a lot about the way galaxies form and how they evolve early. Lots and lots of papers are written about this from ground-based data, but there's always an enormous amount of speculation and extrapolation to do because we just don't have the data and Webb will give it to us. I am somewhat less excited by, and I'm sorry to be saying this, because many of my colleagues at Princeton are very involved in LSST or Nancy Roman Telescope. I think when you're looking very far away and trying to figure out what's wrong, [inaudible 01:04:32] what's wrong, that was [inaudible 01:04:35] what's going on. It isn't necessary to look at the whole sky because you get such an enormous volume going deep.

James Gunn: And so we've been involved for a while in this Hyper Supreme Camera on Subaru with the Japanese. And I'm not entirely sure that the Roman Telescope is going to tell us very much more than we know from this. The depth is comparable. They certainly cover a lot more sky, but we're so far from, I mean, we're pretty far from exhausting Sloan, and we're just infinitely far from exhausting HSC. I'm a little worried that there's going to be so much data that people get drowned. I don't know. And I'm not sure that it's going to be so unique. Now, that's unfair, because one thing that looking at the whole sky does for you is enabled you to discover extremely rare objects. But as far as the statistics of galaxies and the origin of galaxies and all of these things, I'm really not sure that it's going to tell us very much that we won't find out in other ways. I could well be terribly wrong, but that's what I think.

Mat Kaplan: Right upfront, I mentioned your colleague at UCSD, Alison Coil, who talked about you being sort of a master of many trades, but she also said that when she was at Princeton and she was in the astronomy department in the astronomy building there, she used to see this guy, bearded guy, usually in the basement. And he seemed so happy. He was whistling all the time. And she thought, oh, he's a technician. He's building instruments. Turned out it was you. But she said you seem to be the happiest person that she had ever seen.

James Gunn: Well, that was when we were building the Sloan camera and I was pretty happy.

Mat Kaplan: You still sound like a pretty happy guy.

James Gunn: Yeah, yeah, yeah. I am. And I really love doing what I'm doing. I mean, this physical business is sort of getting to me, I'm very weak, but it's improving. So we'll see what happens.

Mat Kaplan: I'm glad Jim, and I sure thank you for what has proven to be a wonderful conversation. I really have enjoyed this. I hope you have too.

James Gunn: I have enjoyed it. I always do, but this was very, very nice, Mat.

Mat Kaplan: Thank you. And I hope that both of us get to find out whether the Roman Telescope, WFIRST, whether it maybe surpasses your expectations but-

James Gunn: When really that happens, right? There are a few instruments which kind of fall on their faces, but generally if they're well done, and I think both of those are very, very well done. They end up surprising you in the end, certainly Sloan. It just did so enormously more than any of us thought it would.

Mat Kaplan: Regardless of the success of any new single instrument, I bet you would agree that there's a heck of a lot of great science ahead of us. Some of which we don't even suspect?

James Gunn: Oh yeah. Most of which we don't even suspect, I think. Yes, yes. Right, right, Mat. Absolutely. Yeah.

Mat Kaplan: Thank you, Jim.

James Gunn: Thank you, Mat. It was really, really lovely. Thanks. Bye. Bye.

Mat Kaplan: Jim Gunn is Emeritus Eugene Higgins professor of astrophysical sciences at Princeton University. He is also the most recent recipient of the Kyoto Prize for astronomy and astrophysics. As another astronomer who spent time at Palomar Observatory, Bruce Betts is moments away from joining me for What's Up. Time again for What's Up on Planetary Radio. Here is the chief scientist of The Planetary Society. We're going to talk about stuff that flies later on today, but I guess you could say the stuff that is up there in the night sky for us to look up is flying, right?

Bruce Betts: Sure. We'll talk about flying planets today and flying meteors, they'll fly until they burn up. Let's go ahead and start with the meteor shower on a peaking on May 6th and 7th are the ADA aquaroids and they're an above average shower, maybe 60 meteors per hour at its peak from a very dark site. You're going to want to be in the Southern Hemisphere for this one. You can see it for much of the Northern Hemisphere, but not as many, not as well. It's produced by dust particles left behind by our friend Comet Halley. So that's a peak on May 6th and 7th.

Bruce Betts: We also got planets. You can see from all over the place in the evening, sky Mars, still dimming, but still looking like a fairly bright reddish star, still hanging out in the Southwest in the early evening near reddish stars. Well, kind of near reddish stars Aldebaran and tourists in Betelgeuse in Orion, making for the red triangle and in the pre-dawn sky, we've got super bright Jupiter hanging out in the east, along with Saturn to it's upper right Saturn looking yellowish, there'll be around with us for many months in the pre-dawn and then moving to the middle of the night. And then in the early evening, in several months from now, something to look forward to.

Mat Kaplan: Speaking of meteors, big rocks, big dangerous rocks, sometimes in the sky, Planetary Defense Conference, you're participating as we speak. Well, near when we speak, right? It's happening this week.

Bruce Betts: It is indeed happening this week, virtual conference hosted by the United Nations in Vienna, people all over the world tuning in and experts in all aspects of defending the earth from asteroid impact.

Mat Kaplan: So I mentioned upfront that the public event that is part of the Planetary Defense Conference being brought to you about to be produced by The Planetary Society. You can catch it at planetary.org/live or on our Facebook page. Just look for the video link there. You're going to be one of my panel, quite a distinguished group of panelists, a big group too.

Bruce Betts: I thought it was just me?

Mat Kaplan: No, I'm sorry. You're going to have company, but they're all people you like, I think.

Bruce Betts: Yes they are. And they all are experts in this field. I'm looking forward to it.

Mat Kaplan: Anyway, that's it? 8:00 AM Brighton early Pacific Time anyway, 8:00 AM tomorrow, 11:00 AM Eastern Daylight Time. And I believe, gosh, I hope I have this right. 3:00 PM or 1500 UTC.

Bruce Betts: Yes, that is correct.

Mat Kaplan: Thank you.

Bruce Betts: All right. We move on to this week in space history and in 1928, future planetary scientist, Gene Shoemaker was born and expert in figuring out that all those pesky craters like meteor crater and craters on the moon were actually from asteroid and comet impacts. We have just announced a new round in our grants program named after Gene Shoemaker, the Gene Shoemaker Near Earth Object Grants Program, which funds astronomers around the world to upgrade their observatories, to do planetary defense research. So you can find out more about that at planetary.org/neogrants, N-E-O-G-R-A-N-T-S.

Mat Kaplan: And I bet you're going to talk about that in our public event tomorrow, which by the way, I think is called Humans Versus Asteroids, because we're going to talk about the status of planetary defense.

Bruce Betts: What's the score? All right. So we move on to animal space, right?

Mat Kaplan: It's a nice new approach.

Bruce Betts: It's hard to coming up with something vaguely new after all this time. As we are recording this, 27, April, 2021, there are six spaceships attached to the International Space Station. I just think that's impressive. You got two Space X crew Dragon vehicles, Northrop Grumman Cygnus cargo aircraft, and two Russian Progress resupply ships and a Soyuz cruise ship. Within a few days, we'll be down to four because one of the resupply ships will be packed with trash and sent to burn up the atmosphere. And the first Space X crew Dragon cruise, it will be headed back. Operational crew will be headed back to earth.

Mat Kaplan: Great RSF. I love to think of that as sort of a parking lot up there and 11 people inside the station right now, at least for a couple more days.

Bruce Betts: Yeah. It's good stuff. Speaking of good stuff, I asked you what was the first successful flight on another planet? So it'll be unpowered, don't count parishes or heat shields or other things designed primarily to land on the surface. How do we do Mat?

Mat Kaplan: You going to love this. We got this answer and most of them were kidding, from four people, William Malkemus in Pennsylvania, Lauren Privet in Maryland, John Guyton in Australia, maybe Mel Powell in California said it best. But if BB will accept our moon as a planet for this contest, our Shepherd's golf balls predate what I think is the correct answer by 14 years. "Do I win?" says Mel. "No," says Bruce, he predicts.

Bruce Betts: Survey says, no, no, you do not. For the purpose of one question, we will not be reclassifying the moon as a planet.

Mat Kaplan: Here is the answer, hidden away at the end of Jean Lewin's poetic contribution this week, Jean up in Washington. The ears of Radar O'Reilly perked up the other day, detecting the hum of a chopper lifting from the marsh and clay. But back in the 1985, an Aero bot took flight released to an acidic sky at a 50-kilometer height. Vega 1 and 2 released one each through the darkness, they did creep. And since I'm a fan of The Herculoids, I would have named them Gloop and Gleep.

Bruce Betts: I love the twist at the end. I didn't see it coming.

Mat Kaplan: So the cartoon trivia there, is that correct? Those two balloons?

Bruce Betts: That is correct, with Vega 1 technically being first four days before Vega 2 entered the atmosphere and they hung out for tens of hours communicating before batteries died, floating around way up in the Venus atmosphere.

Mat Kaplan: That's going to make Kevin Leigh here in California very happy because Kevin, you're a first-time winner. Kevin, you are going to be the first to win a copy of that new pocket atlas of Mars, including an overlay, probably an overlay of the state of California, which is what I got with mine. It's great. I've got it right here. We're going to give away one more as we'll mention again, in a moment or two, some other interesting stuff. Lad Bogdanov in British Columbia, Jacques Blamo had a dream of a balloon flying high up in the Venusian atmosphere, decades of collaboration with the Soviet Union and NASA brought this dream to life, shocked Blamo. The great French scientist, very appropriately Mark Little in Northern Ireland, pointed out that it happened 1985 was about 202 years after the first balloon carried humans into the air. Thanks to the Montgolfier brothers in France.

Bruce Betts: Cool.

Mat Kaplan: Bedard Bacchae, he knows we love innovative units of measurement and comparison. We haven't heard any wild. So here we go. The tether connecting the balloons to the gondola was 13 meters long, which is just a little bit less than the length of both our cars, our two daughters, my wife and me all laid out in a line. Sorry, no picture available.

Bruce Betts: No, but that really helps me visualize it.

Mat Kaplan: Of course, Hudson Ansley asks, "What if they ran into any phosphene?"

Bruce Betts: I don't know. I don't think they had things to detect that.

Mat Kaplan: Finally, one more bit of verse from our poet Laureate, Dave Fairchild in Kansas. The Vega program sent to Venus wasn't just a dream. They were made of polytetrafluoroethylene floating in an atmosphere of toxic acid rain measuring the pressure of the wind speed hurricane.

Bruce Betts: Wow. Nice pronunciation.

Mat Kaplan: Thank you. On hurricane or polytetrafluoroethylene?

Bruce Betts: Show off.

Mat Kaplan: I love saying that. That's fun to say. We're ready for a new one.

Bruce Betts: Who was the asteroid Kaplan named after?

Mat Kaplan: No.

Bruce Betts: K-A-P-L-A-N. Who was the asteroid Kaplan named after? Go to planetary.org/radiocontest.

Mat Kaplan: No, no, no, no, no. There can't be, because I want one, everybody knows I want an asteroid named after me.

Bruce Betts: Well, maybe it's named after you, Mat. Maybe this is the greatest surprise ever. Or maybe it's just going to be really really disappointing. We'll find out with the contest in a couple of weeks.

Mat Kaplan: It's too far past my birthday. So I have a feeling I'm going to be disappointed. Anyway-

Bruce Betts: They can still name an astroid Matthew Kaplan or some such permutation.

Mat Kaplan: That'd be okay. That's fine. I would even let them use my middle name, which I generally avoid mentioning.

Bruce Betts: And what was that again?

Mat Kaplan: We'll just move on here. You have until May 5th, that would be Wednesday, May 5th at 8:00 AM. Pacific Time to get us the answer to this one, which might be kind of personal. One more time, we're going to give the winner, the Mars pocket atlas from Henrik Hargitai and a Euro plan at the Central European Hub. It is gorgeous and yeah, you might just get that overlay of the region that you happen to live in here on earth, so that you can compare it to places on Mars.

Bruce Betts: All right, everybody. Go out there and look up in the night sky and think about Mat's middle name. Thank you and goodnight. Go ahead, what's your response, man?

Mat Kaplan: I will provide that middle name if someone, even if it doesn't contain that name, I will provide it if someone names an asteroid after me, preferably the IAU. That's Bruce Betts. He's the chief scientist for The Planetary Society who joins us every week here for What's Up. Planetary Radio is produced by The Planetary Society in Pasadena, California, and it's made possible by its members who gaze across the universe, become part of their vision at planetary.org/join. Mark Hilverda is our associate producer. Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser. Ad astra.