Into the Impossible With Brian Keating - Is Earth Truly One of a Kind? Exploring Exoplanets with Josh Winn [Ep. 463]

Episode Date: October 27, 2024

Please join my mailing list here 👉 https://briankeating.com/list to win a meteorite 💥 Is Earth truly one of a kind?  This question has fascinated humans for decades, and with today's advanced technology, we're finally able to explore it scientifically. In this episode, renowned astrophysicist Josh Winn joins us to discuss the fascinating world of exoplanets, planetary systems, and the quest to discover other habitable planets. Josh shares the latest breakthroughs in exoplanet research, from unexpected discoveries like hot Jupiters to the ongoing efforts to detect Earth-like planets around distant stars. He also explores the challenges of studying planets light-years away and the exciting future missions that could reveal more about the universe beyond our solar system.  Tune in to learn more about exoplanets and life beyond our solar system! Key Takeaways:  00:00:00 Intro 00:00:34 Rare Earth Hypothesis  00:06:04 The role of stars in exoplanet habitability  00:13:23 Judging a book by its cover  00:16:50 Could aliens detect Tokyo?  00:19:42 The Habitable Worlds Observatory  00:22:06 Methods for detecting exoplanets  00:25:21 The lazy method  00:30:03 Avi Loeb and Oumuamua 00:36:08 The nuts and bolts of Josh's work  00:44:29 The role of technology in detecting exoplanets  00:52:48 Why should young people be interested in exoplanets? 00:57:22 Outro Additional resources:  📚 Get The Little Book of Exoplanets by Josh Winn: https://a.co/d/9PK4XFV  ➡️ Follow me on your fav platforms: ✖️ Twitter: https://twitter.com/DrBrianKeating  🔔 YouTube: https://www.youtube.com/DrBrianKeating?sub_confirmation=1  📝 Join my mailing list: https://briankeating.com/list  ✍️ Check out my blog: https://briankeating.com/cosmic-musings/  🎙️ Follow my podcast: https://briankeating.com/podcast  Into the Impossible with Brian Keating is a podcast dedicated to all those who want to explore the universe within and beyond the known. Make sure to follow/subscribe so you never miss an episode! Learn more about your ad choices. Visit megaphone.fm/adchoices

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Just tell the manager you'll sue. Instant room upgrade. Stop taking bad travel advice. Start comparing hundreds of sites with kayak and get your trip right. Bad advice? You talking to me? Kayak, got that right. exploring exoplanets, they probably think we're out there visiting them. That's totally out of the

question. All we can do is trying, we're stuck here on the Earth, all we can do is use telescopes and cameras and our ingenuity to try to figure out whether planets do exist around nearby stars. So it's kind of amazing that there are five or six different ways that all work pretty well. Any sufficiently advanced technology is indistinguishable from magic. Open the pod bay doors, hell. So we're going to get to your book, Josh, but we're going to start with the rare earth hypothesis, which is something I've always wanted to ask, someone of your incredible intellect and breadth of knowledge. And that's that the conditions that allow complex life on Earth are so specific that intelligent life, certainly, maybe life at all, is very likely uncommon in the universe.

And I wonder how you would react to this statement. If you got a letter from God or Mother Nature, and it said, life is only existent on Earth, everything else is barren, cold, and lifeless. Would you still say there's a point to studying exoplanets? I think so. I think that the search for life is definitely one of the fields' great kind of animating principles. And that's true of the public. And it's also true of scientists.

It's a thrill to be able to be part of this very long-term quest. And I remain interested in that question. I don't happen to work on it personally. I am not really on a day-to-day basis trying to find life on other planets. Mostly about trying to find the planets and study their properties. And there are a bunch of reasons to do it that have nothing to do with life. One of them is just generally exploratory. What is out there?

We all learn in elementary school about the properties of the planets and the solar system and each one has its own story. You know, Saturn has rings and Uranus is typical. on its side. So what are the other planetary systems like? What kind of surprising features do they have? Do the planets resemble the ones in our solar system or not? And the field has been very good to us in providing lots of surprises and lots of planets that do not resemble any of our friends in the solar system. So there's an exploratory purpose. And then there's a more kind of scientific purpose, which is to try and figure out where planets come from. You know, if we didn't

already know planets existed, if we just knew the laws of physics, and we were told, okay, you're in a galaxy, there's clouds of hydrogen and helium, there's a little bit of heavier elements sprinkled around, what happens next? I'm not sure. It would take a long time before anybody would venture to predict that planets would exist. they're the outcome of a really complicated, really interesting set of processes that we only dimly understand. So a lot of the here and now in this field is not about trying to find extraterrestrial life, but it's trying to explore the properties of other planetary systems and figure out where planets come from. I want to talk about the only planet we know has life, which is the Earth. And you talk towards the end of the book about Carl Sagan.

And when he and other collaborators turned the Galileo spacecraft in on itself, he liked to do that. I mean, I think he did the Voyager spacecraft and it came to the pale blue dot, as you know about. And you mentioned in the book the kind of signs of life. There's two of them in particular that you mentioned, but I want to highlight a third one. We get to it. Gases in the Earth's atmosphere detectable through spectroscopy are indicative of life. and liquid water, while not directly, a proof of life is the indicator of strong potential habitability. Why are we so obsessed with, you know, with Earth-like planets in terms of what could be out there?

I mean, surely as, you know, as they say in Star Trek, you know, could be life, but not as we know it. So how is it possible to really make any conclusions from a sample size of one that would guide you in your research? How do you handle such endeavors? Yeah, it is a very good question. And there is this concept that we talk about all the time, the habitable zone of a star, the range of distances from the star where an Earth-like planet would have just the right temperature to have liquid water. I don't know how seriously to take that concept. It sounds like maybe you don't either. We don't have a theory that tells us how life got started here.

So we do not know what was required here. And likewise, we don't know even if there is an identical planet somewhere else, whether that would be enough to guarantee the formation of life elsewhere. So because we don't know either of those things, all we can do is guess based on what we do know for sure, which is that life. exist here on the Earth. I think about it not as a kind of scientific advance to say that we're going to explore the habitable zone, but more as a prioritization of resources. If we have limited time and limited resources and we want for life elsewhere, which planets deserve the most emphasis? Which ones should we build our telescopes specifically to study? Maybe those should be the

ones that resemble the earth in what we think are the key respects. I wouldn't go any further than that. I don't know how much increasing the odds of success by doing that, but it does seem logical to follow that path, while also being open-minded enough to the possibility of surprise. What's the role of a star on an exoplanet? You talk about the various types of arrangements, I'd say family dynamics, be with stars. And in fact, I want to cover the planet, exoplanet, probably the first one, right, that was discovered around a pulsars. Is that not correct? So what is the relationship with a host star to the exoplanet and its potential habitability? Yeah. So the first thing to know is that

most of our knowledge is about stars that resemble the sun. And that's for mainly technological reasons. Detecting planets is very difficult. We can get into why it's so difficult. And so we have to use very high technology. We have to make very precise measurements. And naturally, all of our optics, all of our telescopes are geared towards visible light. And stars like the sun are the ones that put out most of their energy and visible light. So I can tell you a lot about the planets that exist around stars that are, say, between half the mass of the sun and maybe one and a half times the mass of the sun. But that's a pretty narrow range. There's all kinds of other stars. There's a lot of excitement about trying to find planets. around really tiny stars, maybe a tenth of the mass of the sun, because they're very common and they're very convenient in a lot of ways. And there's also a lot of interest, although not much activity, in trying to find planets around stars much more massive, stars that will eventually become supernovaeate that will explode someday.

And then, as you said, there's also been some surprises about the types of stars where you never would think you'd find an exoplanet, but you actually do find at least, at least, you know, a few systems. One of them was the pulsar, neutron star. There is at least one planet that's known around a white dwarf star. And another one that is orbiting a very tight orbit around a helium-burning star, which is a very surprising place to find one for reasons I can explain. You ask about habitability.

And so that brings up that same issue that we don't really know. what that means really. We don't know whether a planet is truly habitable if it has certain characteristics or if that's just kind of projection from what we know here on the Earth. But that doesn't stop people from thinking about it and arguing about it and trying to make forecasts to help guide our future efforts. So there's a big argument going on right now, for example, about low mass stars. If you find a planet close to to a star that's a red dwarf, only, you know, a tenth of the mass of the sun. And it's close enough to that star, so that even though the star is hardly putting out any

energy, planet does have the right temperature for liquid water, should we consider such a planet to be habitable? We really don't know, and there's a lot of arguments in the literature back and forth. You know, on the one hand, if the temperature's right, water could be liquid, great. But on the other hand, if most of that end, if most of that end, it's a temperature's right, water could be liquid, great. on the other hand, if most of that energy from the star is at infrared wavelengths, could you really develop a kind of light harvesting organism that feasts on infrared rather than visible light? As you know, infrared light is a little bit harder on kind of general thermodynamic grounds to take advantage of.

So that and there's all kinds of other quibbles about the conditions that might exist around low-mass stars. Are you familiar with this debate that goes on about red dwarfs? I've heard some of this, and it'll bring us to discussion of the research done by Jill Tarter eventually and brown dwarfs and so forth. But, yeah, very vaguely, so why don't you explain how that controversy plays out in your field for the benefit of the audience that might not be as familiar? Like I said before, the great thing about red dwarfs, and astronomers know them is M dwarfs, but I like to just call them red dwarfs. they're red. They're cool relative to the sun. They are only 3,000 or 4,000 degrees Kelvin instead of 6,000 Kelvin.

So that means that they're putting out most of their energy at the very reddest end of the spectrum and it's in the infrared. They're very low luminosity. They're hardly putting out any wattage to the sun. And they're small. And the smallness in particular is actually an advantage for a planet hunter. We haven't talked about how you find planets yet, but one of the most powerful ways we have is based on eclipses. That these stars are so far away that we cannot just snap a picture of the star and see the star and see the little planets going around it. That has worked in some cases, but it is not the main way that we get this information.

The way that we get, so we know of about 6,000 X-8 planets so far, maybe about 5,000 coming. from eclipses. Those very rare cases when planet's orbit carries it directly in front of the star. And now we cannot see that happening as like watching a movie, but we can tell it's happening because the star appears to get slightly fainter. It's peak pollination season, and my business is scaling fast. To keep the nectar flowing, I need a phone plan with top priority data speeds. That's why I chose GoogleFi wireless. My connections stay strong, even when the hive is buzzin. Plus, unlimited plans started $35 a month. Now, that's a deal that doesn't stay. Explore GoogleFi Wireless plans today. Plus taxes and government fees. GoogleFi Wireless is not

subject to data traffic deprioritization during times of high network usage. The planet's blocking some of the light that would usually reach us. So, for example, if we were watching the solar system from very far away and the Earth passed in front of the sun. The sun would appear to get fainter by about 0.01%. So a tiny amount, but potentially detectable. But if you make the star smaller, then a planet of a given size blocks a larger fraction of the starlight. So if you make the sun 10 times smaller, like one of these red dwarfs,

then that means that the planet will actually block 100 times more light. compared to that same planet around the sun. So a 0.01% signals suddenly a 1% signal. And that's something that is actually quite straightforward to detect. The small sizes of these stars give them a lot of advantages if you're hunting for planets like the Earth. Can you explain the challenges of doing photometry at that level? If a star gets faintier by 10%,

you can see that with your eyes. you don't need any special equipment. If a star gets fainter by 1%, okay, now you need a digital camera, you need a proper telescope, but you don't need a professional telescope. You can buy something out of the pages of the Sky and Telescope magazine

that will allow you to measure brightness changes of 1%. If you want 0.01%, right, that's what you need in order to detect a planet, as small as the Earth, a starlight, sun. Okay, now you need a space telescope.

You need to spend tens of millions, hundreds of millions of dollars, get a telescope above the Earth's atmosphere, which would otherwise corrupt our brightness measurements. And that's when you can detect such tiny variations in the brightness of a star. So, Josh, as you know on this podcast, we love to do what you're forbidden to do in polite society, which is to judge a book by its cover. But this book is not only little, it's also beautiful. It's full of color plates, hand-drawn, or not hand-dron, but custom-made images, squashed Jupiters, all sorts of cool things. It even taught one of my kids, Kepler's Equal Area Law, which I struggled with for a very long time. Talk about the origin of the name of the book. Are you forced to name books in this way when you write for Princeton University Press?

And then describe the cover illustration. and there is no subtitle, but what would you have used as a subtitle, perhaps? This is part of a series that's published by Princeton University Press. There's a little book of Black Holes. There's a little book of cosmology. Now there's a little book of Exoplanets. I didn't set out to write a book in this series, but I approached the editor there to say,

I wanted to write a book that tells the story of exoplanets, this field that is in so much progress, that is connected to the quest for, but along the way has also revealed all kinds of other interesting surprises of planets around other stars. And what I want to be special about it, I want it to be very close to the evidence. I want to explain not just what we know, but how we obtain this knowledge and help the reader who really wants to know more about beyond the headline, about what we know now,

what we can expect to know based on simple geometry. based on some physics they may or may not remember from high school, but to help them connect it all to see this as a scientific feel. And so when I said that, the editor said, this will work really well in this series, these little books, they're kind of like briefings on a field of contemporary interest.

And so it didn't turn out to be as little as some of the other books in the series. I think it's like 350 pages. But I do think, I mean, my main goal was it to be exactly. that to be a complete briefing for the non-specialist about where we are in this field, deeply grounded in the evidence itself. Yes, it's truly wonderful. And the cover art is very sparse, but again, yes, it depicts, it actually depicts a planet bigger than the stars, which is interesting. That's right. We took a kind of minimalist approach to the cover, as you saw. You asked about a

subtitle. What would be a good subtitle? One of the themes that makes, this subject so much fun to work in is the shifting boundary between science and science fiction. So maybe that would have worked as a subtitle. This field is funny in that the field as a scientific subdiscipline is pretty new, right? Only got going in the mid-1990s. But people have been thinking about exoplanets and speculating about them for centuries before that. And in the most recent period, that's been in the form of science. science fiction. So a lot of my favorite papers, a lot of my favorite projects involve planets

that were known from science fiction and that, you know, we're just kind of catching up with that, planets that orbit around two stars at the same time. And it's like tattooy from Star Wars. All right, which makes it appearance in this book. As does the quote from Sir Arthur C. Clark that any sufficiently advanced technology is indistinguishable from magic. And of course, I am the associate co-director of the Arthur C. Clark's Interf Human Imagination, which is how we got the name of the podcast into The Impossible, another quote from Sir Arthur. I want to play on that theme of technology, which plays out somewhat in the book, but not as much as it might otherwise be portrayed. So I want to ask you, maybe it's not a simple question, but imagine, you know, what would it take for an alien telescope to spot, you know, Tokyo, the biggest city on Earth, from a distance of at least far enough that we haven't had

a chance to really tell them about our existence, say, more than a hundred light years away or something, the hundred light years being about the time when the first radio waves were being broadcast hither and yon from the earth. So how hard would it be to detect Tokyo from a distance of, you know, 100 light years, for example. So you're saying we want to see, not only we want to see the Earth in an image, we want to see the Earth and its continents and oceans, and we also want to see a point of light coming from Tokyo. Yeah, pale blue dot.

No, that sounds pretty, that's, you know, that's not going to take, we cannot do that today. We will not be able to do that with the next space telescope being planned, nor the one after that. So the next space telescope. So right now we have the James Webb Space Telescope, fantastic instruments doing all kinds of wonderful things. There's already another one that's planned for launch.

I think it's around 2027, the Roman Space Telescope. That one will likely be able to see planets that are same mass as Jupiter as points of light in an image around some nearby star. So it'll detect giant, planets, one that are easier to detect than Earth-like planets. The one after that, and this is really, you know, at the moment, it's not fair to call it a daydream, but it's just at the early stages of being planned, the habitable world's observatory. I hope it will be built in our lifetimes and launched and it will get to enjoy it, but it's, you know,

going to be decades away, and its main goal is to just see an Earth-like planet as a point of light in an image next to a sun-like star. You're asking about, okay, now can we zoom in on that Earth-like up planet and see evidence for civilizations on that planet? And my guess is that is, you know, maybe a century beyond this habitable world's observatory. What makes the habitable world's observatory unique? Does it have a sun's shade? Does it have a fleet of, you know, telescopes, the size of, uh, of, uh, of, uh, of, uh, of, uh, uh, of San Diego. What does it have exactly? The thing that makes this so difficult is the contrast

between the star and the planet. So if aliens are trying to find the Earth and they're looking towards a solar system with their telescopes, they have to contend with the fact that the sun is about 10 billion times brighter than the Earth, which is just reflecting the tiniest fraction of sunlight. So how do you build a telescope and a camera that can both detect a star and a planet in the same image, even though one is 10 billion times brighter than the other. What happens is the glare from the star causes light to spill all over the image. So what the Habitable World's Observatory will have is a very fancy version of a technology that already exists called a coronagraph that is a telescope, but it includes some very,

telescopes involve collecting the light with some giant weirer, usually, and then concentrating it and bouncing it off various other mirrors before it hits a camera. And what's special about a coronagraph is that some very clever optical engineers have inserted some obstacles in the light path whose shapes are carefully designed so as to prevent the light from the star from ever reaching the camera, but allow the light from some nearby planet to get through. And so it takes a lot of precision engineering to get this just right. And this has been done for many years. In fact, the word coronagraph comes from the sun's corona,

this hot outer layer of the sun's atmosphere that is very difficult to see unless you block out the light from the main part of the sun. So coronagraphs have been used in the study of the sun for many, many years. They have also been used to try to detect exoplanets with some success with the telescopes we have now, but not for planets as small as the Earth. That will require another few orders of magnitude of improvement in our coronagraphs. And that is what the main goal of the habitable world's observatory is to be able to do that. Beat those few orders of magnitude and detect the earth as a pale blue dot.

Talk about how the various techniques compare. We talked about Doppler, occultation, transit methods. Compare and contrast them. If you only had one in your toolkit, what would you choose? One of the fun things about working in this field is we, we do. do have so many different methods for detecting exoplanets. When you talk to the public, depending on who you talk to, if I say that I'm exploring exoplanets, they probably think we're out there visiting them, you know, that we have rocket ships that we're exploring the solar system and visiting

different planets. That's totally out of the question, right? All we can do is trying, we're stuck here on the Earth. All we can do is use telescopes and cameras and our ingenuity to try to figure out whether planets do exist around nearby stars. So it's kind of amazing that there are five or six different ways that all work pretty well. The one that I work on the most, so my favorite, at least in the here and now, is the eclipse-based method, or as it's usually called, the transit method, where we wait for the planet to go in front of the star, and we can tell that's happening because the star gets a little fainter.

We can get a spectrum of the star during those events, and we can learn about the planet's atmosphere and all. kinds of other characteristics. So it's a very informative type of observation. The problem with transits is that transits aren't rare. It takes a special coincidence for the planet's orbit to be lined up just the right way so that it gets carried directly across the face of the star. Most planets don't transit. You said this place was steps from the water. We just haven't found the steps yet. How much did we save? Enough.

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It matters where you stay. Hilton for the stay. I keep coming back to this idea of aliens trying to find the Earth. Earth, that if aliens were viewing the solar system, all different directions, struggling to find the Earth, only one out of 200 of them would ever see the Earth transit. In most cases, the Earth never goes directly in front of the Sun. So that is the heartbreaking thing about the transit method, is that you miss most of the planets. The method that came even earlier, and that has also been extremely productive, is the Doppler method. And that's one that's a big part of my research

search group as well. That's the one that's based on the fact that we always say the planets are going around the sun, the planets orbit the sun, which is not exactly correct, right? Really, what's happening is that the planets and the sun, they're all going around the center of mass of the solar system, this point in space that represents the kind of mass weighted average of all the bodies consistent. And that means the sun is moving too. in response to the gravity from all the other planets. And that's what gives the Doppler method its power, because using the Doppler effect,

we can tell when a star is moving, and specifically when it's accelerating, when it's moving around in response to the gravity of some planet in the system. So by making Doppler speed measurements of the star, we can deduce the existence of planets, and we can measure their masses and all kinds of other, wonderful things. So that's another real workhorse of today's exoclite scientist. Another technique that's discussed, and I believe you call it the lazy method, which I'm very

partial to, which is to let little chunks of material come on by. And this is very important to me because I give away these little meteorites, and I'll bring you one next time I'm by Jadwin Hall or wherever you're hanging out these days. And I will look at. give you one and I give them to all my listeners and audience members who have a dot edu email address and that's if you go to brian keating.com slash edu and if you don't have an edu email address you can still try your luck and I give out one or two a month at bryankeating.com slash list that will get you into my mailing list where we talk about all sorts of cool stuff and we'll be talking about this very interview Josh so I hope you'll become a member and then I'll figure out the way to get

you one of these as well this came via you know the u.s. postal service and and we'll get there but gravity has brought other objects into our solar system that are fragments of extra, extra solar solar system. So talk about that method. And if it would be worth, instead of, you know, the generation that our great, great grandchildren will live to, you know, beyond the future habitable world observatory, should it be worth spending a lot more money to go after these objects as they come through the earth? I mean, they're not that rare and they're not that hard to catch up to. So talk about the lazy method and what that tells us about extra solar planets.

Right. So, yeah, as you mentioned, the lazy method, if you want to call it that, is that let the exoplanets come to us. We're too busy here to build big spaceships and travel elsewhere, and that takes too long. The little kernel of reality underlying this idea is that there have now been two detections of big chunks of material, you know, objects that are more than 100 meters in size, flying through the solar system, that probably, you know,

used to belong to somebody else's planetary system. They were probably asteroids or comets or something like that that were ejected, some kind of close encounter occurred in a different planetary system. That sometimes causes material to get ejected and never come back. This material was just floating around in the galaxy for who knows how long, you know, a billion years before it happened to chance, by chance, to be directed towards our sun. and it came into the solar system, the sun's gravity deflected it in a different direction,

but had no way of slowing it down or bringing it into an orbit around the sun. So the sun's gravity simply deflected it, and then they went off in a different direction, never would be seen again. So this has now happened twice. You know, it was pretty recent. I think the first one, which went by the name of Omuamua, was discovered, I don't know, maybe seven or eight years ago at this point. And then it wasn't long after that, but in two years, I think. a second one was detected called Borisov.

And two is not very meant, right? But nevertheless, this could be, and probably is, the birth of a whole other field of astronomy, the study of these interstellar objects. Because even though there are only two of them that were found, the other thing that's important to know is that we hadn't been very good at looking for these objects for that long. we've only been kind of haphazardly searching for objects of this size and that are moving at these speeds.

We haven't had the technology or the motivation to be scanning the whole sky on the lookout for these things. So just the fact that two of them were found after a kind of incomplete search implies that when we do get serious about this, we should find could be as many as five to ten per year. And we are about to get serious about it. There is a new observatory coming online. It was built for completely different reasons of the Rubin Observatory, it's in northern Chile. And when it does come online, it will be especially good at finding these and all kinds

of other objects in the solar system. So I expect that if they really are as common as they appear to be based on the simple statistical calculations you can perform, based on the two that were discussed, up, or if they really are that common, it is going to become a very big deal. We're going to see how often these things occur, how many times planetary systems eject asteroids and comets. We're going to measure their sizes and colors and spectra. We're going to see what they're made of. And we'll probably find some surprises. You know, there've already been some surprises, as you might know. Yeah, I've had Avi Loeb on the podcast many times, and of course he's quite

convinced that this is not only from extra solar planet, but it's an extra solar technology. And I wonder how you react to that. You seem skeptical in the book, at least, but has your opinion changed since the COVID years? And there's been other findings, including interstellar media. First, let me try to explain the problem as I see it. So I mentioned there's, there are two of these interstellar objects were detected. One was called Omuamua. One was called Borissau. Borisov appears to have been just like a comet. In fact, if you didn't know that it was moving at extremely high speed, if you just looked at it into an image and looked at its color and its shape and all of that,

it would look just like a normal comet. So that was apparently a comet that was ejected from some other star system and ventured into our own by accident. Onuamua is more puzzling. The puzzle of Omuamua is that, first of all, it was smaller than Boris. love. It was more, and in some ways it looked like an asteroid rather than a comet. Comet is a big dirty snowball, and it's the feature that makes it famous is when it gets close to a star, some of that ice sublimates, it vaporizes, and makes a big, glorious tail that you can see

in an image, unmistakable. So, a moment it didn't do that. So that suggests it was just a piece of rock or rock and metal. It did not have any ices on it. And And that makes it more like an asteroid. However, unlike an asteroid, it didn't just follow the kind of ballistic trajectory that one would expect of an asteroid going around the sun. Instead, it appeared to shift in position relative to its expected trajectory. Now, comets do that all the time. That's because when they do vaporize partially, that pushes off gas in one direction and that

pushes the rest of the body in the other direction. But asteroids, at least they're not supposed to do that. So why did Omuamua deviate from its expected trajectory, even though by all other observations, it appears to have been an inert asteroid rather than a comet? So I completely agree with Avi and many other planetary scientists who have studied this problem, that there really is a problem here, that there is a puzzle of a muamua in that when we take the entirety of the data, we don't have a very compelling model that allows us to connect it all. There have been some proposals involving, for example, maybe it was a chunk of nitrogen ice, a big nitrogen iceberg. It has to be made of nitrogen for rather technical reasons that I won't get into just now. but, you know, and there are other ideas for what it might have been that would fit all the data,

but they're all kind of ad hoc. They're all just kind of made up to explain the data rather than being something we might have expected beforehand. Obie's hypothesis is also, in my view, like, the same category. It's kind of ad hoc that, well, maybe it is a piece of technology. Maybe it is a broken chunk of a spaceship, maybe a garbage barge. The great thing about Avi is that he's a brilliant physicist. His calculations are correct. It really could be made out of mylar or aluminum foil and it would fit all of the data in a sense.

But is that hypothesis any better than it's a big nitrogen iceberg or maybe just something we haven't thought of yet, something kind of complicated that mixes different part asteroid part comet or something like. part asteroid, part comet, or something like that. So I regarding it as a genuine scientific problem, but also a very frustrating one. Because we only had about a month to study it before it got so far away that it's out of reach, even with our biggest telescopes. So it makes it, in my mind, kind of a sterile problem. There's a genuine problem. There's a conflict between theory and observation.

It could be really interesting, but it's very hard to know how to make progress, because it's gone. It's not bring it back to the laboratory, you know. I mean, I suppose we could build a rocket ship and try to catch up with it. That's what I told Javi, actually, in our first interview that we ever had in 2021 when the book first came out and there's a whole splash on it. And I should say we're talking on the, you know, the day after Lou Elizando's book imminent, which details not only life in the universe, but terrestrial intelligence captured by the U.S. government and other agencies and witness by him and many other members of the military. But I told Avi, look, you're friends with this guy, Yuri Milner, and he's scheduled this $100 million project called Project Star Shot to shoot cell phone size cameras to Proxima Centurie B. Why not, you know, spend that money and catch up to Omoa and he said, oh, no, we'll see many of these things with Rubin.

And I said, that's true. But still, what if you don't? What if this is the only one? And you have to, you know, leave the, you know, possibility that that could actually occur. So I've actually said, yeah, you should save some money for actually going to these objects instead of just looking at them. Yeah, I guess I agree that if it were our highest priority as a species to figure out what Omuamua is, we could do it. Right. We really could.

But it probably makes more sense to wait a few years, see what Rubin shows. Maybe we'll see that Omuamua is just one of a new category. of objects that only really comes to light when we have a dozen of them and we can start to see what's going on. My guess is that that is how it will play out. I can't be sure, obviously. I want to jump to the nuts and bolts of what you do for a living. And don't be afraid to be tactical. My audience is the most brilliant in the known multiverse in this area of the multiverse. That is to dive deep into what I think we scientists get paid to do, which is not to measure something, but to to characterize how little we know about what we've measured.

And in other words, characterize our ignorance or uncertainty and ways that we could be biased into seeing something that's not really there. Talk about the different biases that tend to cause us to see certain exoplanets and not others. Talk about the nightmare scenario that keeps you up at night. If you were to see something, you know, you conclude the book with a discovery in the newspaper of life and technology. How do you guard against irrational, or maybe rational exuberance.

A lot of what I do has to do with the geometry of exoplanet systems. When you need to build up your team to handle the growing chaos at work, use Indeed sponsor jobs. It gives your job post the boost it needs to be seen and helps reach people with the right skills, certifications, and more. Spend less time searching and more time actually interviewing candidates who check all your boxes. Listeners of this shell will get a $75 sponsor job credit

at Indeed.com slash podcast. That's Indeed.com slash podcast. Terms and conditions apply. Need a hiring hero? This is a job for Indeed sponsored jobs. In the solar system, the geometric properties, but when we're children, we learn that the planets all move in nearly circular orbits around the sun, that the orbits are all aligned with each other. So that it's like they're all grooves in the same record, which was an analogy that made sense, you know, when I was a child, maybe not so much anymore. So I like to try to find planetary systems where those things are not true, where the planets are not moving on nearly circular orbits.

Maybe they're highly elliptical orbits. Or where the planets are spaced much more closely than they are in our solar system. That causes them to interact and have chaotic gravitational encounters with each other. Or to find systems where the planets' orbits are not aligned, where maybe they're, you know, gross. misaligned. Another fun thing about the solar system is that planets are all revolving the same way, and the sun is rotating in that same direction. And we actually have very good reason for that. We think that all of this rotation and revolution, all of that motion is inherited from the very conditions of formation of the solar system, from the gravitational collapse of a

cloud of material that was swirling around. But it turns out, that there are a lot of exoplanetary systems where that's not true, where you have a planet going this way, but the star is rotating in a tilted direction, or even a perpendicular direction, or there are even some wonderful cases where the planet's revolving this way, but the star is rotating backwards. And so I love performing those measurements and trying to figure out, what are they telling us? Like, what did we miss in our theories for planet formation? What happened here? basically, that apparently did not happen in the solar system. Now, you mentioned bias in our methods, and that's something that also is a big preoccupation, not just of me, but everybody

who works in this field, because we're in a field where the thing we're studying is extremely hard to study. Planets are so much smaller than the stars they orbit. They're very difficult to detect. And planets come in different sizes, some of which are very, very, very different. difficult, and some of which are merely difficult, right? So there's a range of difficulty levels. And so what that means is that the ones that we are successful in detecting are not necessarily representative of the planets that are actually out there. For example, my colleagues and I, we often study a type of planet called a hop Jupiter, very exotic kind of planet, just as big and massive as Jupiter is in our solar system, but very unlike Jupiter in that its orbit is something

like a hundred times smaller than the actual orbit of Jupiter around the Sun. That makes them very hot because they're so close to the central star. So hot Jupiters are this, with this big, shocking surprise when the first one was discovered in 1995, some large fraction of all papers about exoplanets are about hot Jupiters. I would guess, I don't know. 25% just to make up a number. And a lot of the observations being conducted with the Hubble Space telescope, with the Web Space Telescope, they're about hot Jupiter's. That's because they're so scientifically interesting, but it is also because they're very easy to detect compared to other types of planets. They're bigger. They don't take so long to go around the star. Both of those

things make them much easier for us to detect than, say, an Earth-like planet around the same star. And so there's like a near obsessive level of detail in our knowledge and our body of observations about hot Jupiters, even though they're, they're not that common. You know, if you pick a random star like the sun, there's only about half a percent of a chance that it would have a hot Jupiter. And yet they're way overrepresented in our planet catalogs and in our scientific journals for that reason. You know, I did a lot of, you know, diving into some of the surprising results. And you actually call them, you know, you have these three different surprises ranging from misplaced giants, which hot Jupiters represent, high orbital eccentricities, which is also a big surprise to you. And I mean, all this is a surprise to me, Josh, because I'm an ignoramus about planets other than the one I live on. And then surprise number three, that, you know, planetary systems can be much more tilted and misaligned.

right? Those are your three surprises. And then, you know, when I look up, you know, kind of the biases that we'll get into in a little bit more, the number one bias is that you're biased towards seeing, you know, kind of close in and large objects because they go around much faster via Kepler's Law. And they also can block more of the light because they're physically bigger. So does it worry you that the number one surprise thing is also the biggest sort of of potential, you know, not confirmation bias, but measurement bias, you know, sample bias. So how do you reconcile? It definitely is a big worry and it makes it hard to draw the right conclusions from our data. When we survey as as we have in the past, you know, say 10,000 stars and

trying to find all the planets we can around those 10,000 stars, the planets that we find are so biased in their properties compared to the planets that surely exist around those stars. We only detect the giant planets. We only detect the close-in planets. So, for example, there's kind of a factoid that I hear a lot that exoplanet scientists have discovered that actually the solar system is the weird one and that all of the exoplanetary systems have revealed that the earth is very rare and unusual and that the architecture of the solar system is quite extreme. I don't think that's actually true. I think, I mean, it might be, but we're not. there yet. We cannot yet make that conclusion because we actually would have great difficulty

detecting an exact copy of our solar system, even around a nearby star. Our methods don't work very well. The inner planets like Mercury and Venus, they're a little too small to be easily detectable by our methods. And the outer planets are simply too far from the sun for the transit method and the Doppler method, the real workhorses for today, for them to work very well. well. So what we do know is that something like maybe a third of sun-like stars have detectable planets that make them kind of unlike the solar system, mostly in that they have a lot of close orbiting planets. But as for those other two-thirds, we just don't know. They don't have any readily detectable planets, but they might all have systems that are very similar to the solar

system. So it's still an open question in my view, whether what we see here in the solar system is really unusual or not. And that's exactly because of the bias that's inherent in our detection methods. The other thing that, you know, kind of strikes me about this research is the, you know, kind of outsized influence of the Kepler satellite. It seems to have just, you know, been the unlock, you know, for you and your colleagues, as, you know, Kobe was for mine or WMAP, you know, I I can't resist a satellite named after my PhD grandfather, David Wilkinson, at your fine institution. Talk about the importance of that and how many, you know, low-hanging fruit have been picked versus what might remain. So Kepler really was in that same league as Kobe and WMAP. I agree with that. It really opened our eyes to whole new categories of planets that we didn't know existed before.

and it gave us our first glimpse at truly earth-sized planets, which had not been detected before. And it gave us a lot of planets, gave us thousands of exoplanets. Even to this day, most of the planets in our kind of official catalog of exoplanets come from the Kepler mission. There was something really frustrating, though, about the Kepler mission. And there's a reason why it didn't solve everything, which is that for partly historical, partly practical reasons, reasons, Kepler spent most of the time looking at a particular star field, happened to be in the summer triangle, and it stared there for four years straight. And so it found thousands of exoplanets that happened to lie in that direction in the galaxy. And in order to build up a big sample of stars, it had to look pretty far away, thousands of light years away, in that direction, so that it had a lot of stars to base these conclusions on. What that means is that very often we found some weird, wild Kepa planet. First thing we want to do is obtain more data.

We want to do spectroscopy. We want to take the light from the star, spread it into 100,000 colors, and analyze the intensity at each color in order to perform measurements of the mass of the planet and figure out what kind of star it's orbiting, all kinds of other reasons. And that usually ended in tears because the stars are too faint. thousands of light years away, you know, it's too far away. But that makes the star so faint that by the time you do divide up the light into 100,000 different colors, you hardly have any light to work with.

So the Kepler stars were just too far away. So what we really want to do is something like the Kepler survey, but we want to explore the immediate neighborhood of the sun in all directions, not just the one direction where Kepler looked. And that is the mission of the successor. to NASA's Kepler mission, which is called Tess. It's the transiting exoplanet survey satellite. It is up there right now. So the Kepler mission ended, I think it was around 2018, 2019, right around the time Tess was launched. So Tess is up there right now, scanning the sky

every few years, looking for transiting planets, but it's looking for them around stars that are typically 30 or 50 times brighter than the typical Kepler star. So it's like suddenly having a telescope that's 30 to 50 times bigger. No, it's, you get to learn so much more when the star hosting your planet is close by than when it is, you know, thousands of light years away. So that's the fun right now, is that Tess is, we already learned a ton about what types of planets exist from the Kepler mission, and Tess is bringing them closer to us, allowing them to, to study them in greater detail with telescopes like the web telescope and large telescopes that

exist at observatories all over the world. Yeah, I was curious about web and how it's impacted your research in particular, especially since, you know, getting time on it is like, you know, winning the lottery, you know, twice in a row. How, how is it impacting your, your research? Yeah, what's not bad is that? Like, so you get, it's a good time on the web telescope. I think the odds are about one in ten. You know, if you have some good ideas, if you keep out of, you'll get, you'll get your web time. So web is, is most famous. for spectroscopy, this technique of dicing up light according to wavelength or color, and learning about the composition of objects and all kinds of other physical properties

by studying those spectra. And so web is spending a lot of time. I would guess 15, 20%, all the observing time on web is being spent looking at the atmospheres of exoplanets using these tricks related to transits, that when a planet goes directly in front of the star, some of the starlight filters through the planet's upper atmosphere, which is partially transparent. And so the molecules in the planet's atmosphere absorb their favorite wavelengths as the starlight passes through it. And we can see that in a spectrum with the web telescope, at least in some cases. So there's a lot of work going on now, not only to know that

an exoplanet exists and to measure its size and its mass, but to see which molecules are. in its atmosphere and what the local conditions are, what is the pressure, what is the temperature, and things like that. In addition, so that's actually not what I do personally. I am a fan of that work, but it is not my own kind of first-person research. I'm not much of an atmospheric scientist. What really excites me about what, in addition to that, is that it's just a big telescope, much bigger than the Hubble telescope, and it's in space, so we get very, very precise measurements.

And so we might be able to see things that we just couldn't quite see with Hubble or any previous telescope. For example, one thing I'm working on actually at the moment with the graduate student here at Princeton. Your summer starts now with Memorial Day deals at the Home Depot. It's time to fire up summer cookouts with the next grill, four-burner gas grill, on special buy for only $199. And entertain all season with the Hampton Bay West Grove seven-piece outdoor outdoor diners. dining set for only $499. This Memorial Day, get low prices guaranteed at the Home Depot. While supplies last, price invalid May 14th or May 27th, U.S. Only Exclusions apply.

See Home Depot.com slash price match for details. One of the cool things about Saturn, if you look at a picture of Saturn, you see the rings, obviously, that's just dazzling. But then after you get over that, you look at the planet itself, you see it's not a circle. It's actually squashed a little bit. That's because it's rotating pretty fast. I think it takes like nine hours to go around. And that causes it to be distorted from a sphere into an oblite spheroid, you know, a squashed sphere. Wouldn't it be cool if we could see that same shape change for an exoplanet

and get a fix on how quickly it's rotating? So with Webb, we might be able to do that. Again, realize on this trick of transit. These planets are so far away. We can't see them even as a point of light in an image. no hope of actually seeing a silhouette like that. But when the planet goes in front of the star, it blocks some of the light, and we see the brightness of the star goes down. The signal looks slightly different if the planet is a sphere compared to if the planet is a squashed sphere. So especially

if that squashed sphere is tilted, like Saturn is tilted 20 degrees or something like that. So with Webb, we actually have a chance at being able to measure the shape of an exoplanet that's induced by its own rapid rotation. Hasn't happened yet, and in fact, this project I'm working on with this graduate student is a null result. We did not detect it. But we're not so far, I think, from being able to do it, and Web is just getting going. And furthermore, there's a host of other things that might pop out by applying Web just

as a very, very precise photometer as a device for measuring brightness variations of stars. For example, if planets have big rings like Saturn does, and if those rings, are opaque. We might be able to use the same trick to see them. If a planet has moons, then maybe we'll see the transits of those moons as they go ahead of the planet or behind the planet as both of them across and front. There's a group at Columbia led by David Kipping, and he has, I believe, an approved program with Webb to go looking for moons and this rotational effect and other effects for one of the best possible. targets that's currently known. So it could be that within months, maybe as long as years,

we'll be able to see some of these really subtle things thanks to the ultra-high precision of web. As we wrap up, I want to get your impression of why a young person might be attracted to this field. We have a lot of high school science enthusiasts all the way up through Nobel Prize winners that listen to this podcast. But what is so appealing about this field that you've chosen to dedicate not only this phenomenal new, or a year old book now, but really just a breeze to read. I listened to the audiobook. You narrated it.

It was lovely. Why should a young person be interested in this field? What are some of the perks of being a member of it? When you're thinking about what field to get into as a young person, it is not necessarily the best idea to ask senior people. And I have sort of regrettably become a senior person myself. You want to trust your own instincts. You want to see.

You want to learn as much as you can. You want to eavesdrop on conversations that are happening in various scientific fields and get a sense for yourself. Like, where is the excitement? Where are things changing the fastest? Where might I be able to make a contribution? That's a much better strategy than just kind of asking around. I mean, that might give you some leads, but you should never trust senior people completely because we freeze out.

You know, we get comfortable. And we're not paying attention necessarily to what are really the next hot upcoming fields. The second part of your question, which is maybe more direct answer is, what is about exoplanets? That's exciting. I was in this situation. So when I was in the midst, let's see, when did I make this change? I guess it was when I was a postdoc. I was working in cosmology.

Basically, I was working in a very similar field that you work in. I was working in gravitational lensing. I was trying to find lensed quasars and use them to measure the humble constant and this trick that I'm sure you're familiar with. And the senior people I was working with seemed to think I was making good progress. And I would go to conferences and I would give my talk and, you know, things seemed okay. But I got a sense the field was stuck, at least some field I was in was stuck. Certainly I felt stuck. And when I went to the conference the next year, like my talk wasn't that different.

and neither was anybody else's. You know, I felt like nothing much was happening. And yet at the same time, the first few exoplanets had been discovered. I think the first transiting exoplanet had just been discovered. And there was just so much excitement. And I was in a place where there were a lot of people who were interested in this area. And I could tell that from one year to the next, the talks were all totally different. You know, it was a completely different feeling.

So the sense of being. part of something that had just begun but was clearly going to be very big. That made a big impression on me and convinced me myself that it was time to switch. Yet this was a time of opportunity. The field is still growing. You know, there is a lot of life left in the field of exoplanes. It is not an old, mature, you know, field just for senior people. Far from it. It doesn't have that same kind of exponential growth that I felt. Beginning of the field, you know, naturally, fields kind of have their own kind of trajectories. It's a little more sedate now, but it's still growing.

But what's great about it is that, first of all, the barriers to entry, I think, are quite low compared to some other fields, like cosmology, for example. To get to the frontier in cosmology is quite difficult compared to what it takes to get to the frontier in exoplanets. Not only in terms of knowledge, you know, you have to learn general relativity and perturbation theory, and maybe you have to learn some new technology. You have to be part of a big thousand person collaboration. There's a lot that's involved.

Whereas exoplanets, you need to know classical mechanics. You need to know about orbits. Obviously, you can go a lot deeper than that, but you can start making progress from a much smaller knowledge base. And there's a lot of public data sets that are out there that allow small groups to make interesting contributions. So that's another thing I still like about this field is that. that the barriers to entry from new people are pretty low. It's all technology driven, and technology is getting better and better. So that helps to set our agenda.

You know, we can foresee technological advances, and we know that whenever we can figure out how to measure starlight better than we have before, we're going to find more interesting exoplanets. History has prepared us in that way. Josh, you can tell from the neon glowing sign behind me. I'm a fan of science fiction, especially Arthur C. Clark, who gave us the name of the podcast, after all. I'm not sure you are that familiar with that particular. I have a big fan, but I don't recognize the quote. I may not remember. So, 2001, a Space Odyssey.

Dave wants to get into the Pod Bay, and he says, open the Pod Bay doors to Hal, and Hal refuses to open the Pod Bay doors, leading to great hijinks at the end of the film. But the pod was the motivation for an engineer working at Apple for the name iPod. And then that as a storage protective unit that you couldn't get into, I guess. And then that led them to create the concept of the podcast, which is what we're doing right now. And as a fan of science fiction, you might also recognize her Arthur's famous rendezvous with Rama, which has to do with a spacecraft, which is initially thought to be an asteroid, like this little chunk that you'll get. Brian Gehne.com or a comet and the crew is encountering it and learning about it and throughout the series. At one point, they say something very fitting, which I think is perfectly apt for our

conversation. They said, the more we learned about Rama, the more we realized how little we knew about the universe. And Josh, I want to thank you for illuminating a great deal of excitement in your field and in astrophysics in general and being so generous with your time. Thank you so much. Yamava Resort and Casino at San Manuel is California's number one entertainment destination for today's superstars. Catch the Jonas Brothers return to the Yamava Theater stage

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