Factually! with Adam Conover - The Search for New Planets, Sun Blobs and Hot Jupiters w/ Sara Seager

Episode Date: September 25, 2019

Astrophysicist and planetary scientist at MIT, Prof. Sara Seager, joins Adam on earth this week to discuss the process of finding and looking for Earth cousins, the chance of discovering life on other planets, liquid lava lakes, "Star Shade" and so much more! This episode is brought to you by Acuity (www.acuityscheduling.com/factually). Learn more about your ad choices. Visit megaphone.fm/adchoices See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.

You know, I got to confess, I have always been a sucker for Japanese treats. I love going down a little Tokyo, heading to a convenience store, and grabbing all those brightly colored, fun-packaged boxes off of the shelf. But you know what? I don't get the chance to go down there as often as I would like to. And that is why I am so thrilled that Bokksu, a Japanese snack subscription box, chose to sponsor this episode. What's gotten me so excited about Bokksu is that these aren't just your run-of-the-mill grocery store finds. Each box comes packed with 20 unique snacks that you can only find in Japan itself.

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So if all of that sounds good, if you want a big box of delicious snacks like this for yourself, use the code factually for $15 off your first order at Bokksu.com. That's code factually for $15 off your first order on Bokksu.com. I don't know the way I don't know what to think I don't know what to say Yeah, but that's alright Yeah, that's okay I don't know anything Hello, welcome to Factually, I'm Adam Conover

And, you know, it's easy to forget But we live on a huge, watery, magnetic rock. That is to say, a planet. That's what a planet is. And this rock circles a slow-motion nuclear explosion. And since there are other slow-motion nuclear explosions out there, floating around in the void, it's logical to conclude that there are other water mag balls circling them, right? Other planets, just like ours. And that's an exciting thought

because planets are where life grows. So if there are alien planets, maybe there's alien life out there we can talk to or destroy. You know, maybe we're the bad guys in the movie. Hell, maybe we'll eat them. Maybe we'll just be giant alien farms. Alien ant farm, good band, underrated.

But just because it seems likely or intuitive that other stars have planets, that doesn't necessarily mean it's true, right? Science, as always, requires evidence to establish anything. And if you go back to the early 1990s even, we actually didn't have any evidence at all that other planets existed. Humans had advanced to the point where we'd created Microsoft Excel and Madonna's sex book, but we still had zero proof that there were any planets outside the solar system, let alone any that might support life. Within the astronomy community, the search for exoplanets,

as planets outside the solar system are called, was considered a little kooky. It was a weird topic, and it was even treated with some suspicion because there'd been decades of claims that exoplanets had been discovered, but all those claims had been proven wrong, which made the whole field seem a little scammy. You know, kind of like people who say they've discovered cold fusion or who describe themselves as influencers, right? You just have trouble trusting them. But in recent years, all of that has changed. There has been nothing short of an exoplanet revolution in

astronomy. The first breakthrough happened in 1992. Astronomers at the Arecibo Observatory in Puerto Rico actually discovered two actual planets about 2,300 light years away in the constellation Virgo. But importantly, this planetary system looked nothing like ours. These planets were four times the size of Earth, with orbits of only 98 and 65 days, and the system is tiny. The whole thing could fit inside the orbit of Mercury. But it was a start. Three years later, in 1995, there was another huge step forward.

Scientists discovered a planet circling a star like our own sun in the Pegasus constellation. It was a gas giant about half the mass of Jupiter, which circled its star once every four days. Not very Earth-like, but still, after that point, the floodgates opened and Jupiter-like planets were discovered on a monthly or sometimes even weekly basis. From then on, by 2002,

we'd confirmed almost 100 exoplanets. But look, I know, I know. Who cares about Jupiter-sized planets? Those big gassy guys are crappy candidates to find life. To find life, we would need to find Earth-sized planets. But Earth-sized planets are very, very difficult to find from the surface of Earth itself. To find smaller planets, you need to go into space.

And in 2009, NASA launched the Kepler mission to do just that. Part of Kepler's job was to find out how many planets exist in the habitable zone where life is possible in their solar systems, and it used what's called the transit method of exoplanet discovery to do that. Now, we're going to talk about the transit method a lot later in this episode, but what you need to know is that Kepler helped create a gold rush of exoplanetary discovery unlike anything else in scientific history. Think about it.

In 1990, we had no proof that there was a single planet outside of our solar system, and now over 4,000 exoplanets have been identified, more are on the way, and we are able to estimate that there are up to 10 billion habitable planets in our galaxy. Day by day, we are inching closer

to finding another Earth-like planet and to finding the telltale signs of life out there in the universe to finally find out that we are not alone. Well, our guest today is a leading figure in this effort to find another Earth. She's an astrophysicist and a planetary scientist at MIT and a MacArthur Fellow. Please welcome Sarah Seeger. Sarah, thank you so much for being on the show. Great to be here, Adam. So you search for exoplanets at MIT. Tell me about how that is done.

Like, what does that look like on a day-to-day? Well, the funny thing is finding planets, it's a lot like a lot of jobs. We sit in front of the computer a lot. We have a lot of meetings. The difference is, though, at the end of the day, we find lots and lots of what we call planet candidates. And the way we do this is we actually have a very fancy, very expensive space satellite. It's called TESS, like the girl's name. Transiting Exoplanet Survey Satellite.

And TESS is essentially like four glorified telephoto lenses, if you will, all attached to a platform. And it looks at lots and lots of stars over a very wide field of the sky. And that data comes down to earth through the deep space network. And we analyze that data looking for planets. And so what sort of analysis of the data shows you that a planet is there? Because my understanding is you're not actually able to see these optically, right? You're not like literally seeing a sphere against a black background and going, oh, I think I see some clouds and stuff. So what are you looking for? It's really a lot of detailed work. What we're looking for is we're looking for planets whose orbits are specially aligned. They're called transiting planets. And as seen from our

telescope, they happen to be fortuitously aligned so that the planet goes in front of the star, as seen from the telescope. And what that amounts to is just a tiny, tiny, tiny drop in brightness with a very characteristic shape. So we're monitoring all these stars, like tens of thousands,

hundreds of thousands of stars at a time. And our computer literally plunks a little circle down over each star and counts up how bright that star is. And it does that over and over again as a function of time. And then the computer is looking for that little tiny drop in brightness that repeats each time the planet goes in front of the star. That is so cool. So it's just looking for a little periodic flicker. Exactly. It's a periodic flicker. And it's funny, but this field is really quite mature now. I mean,

it seems crazy, right, to just say, hey, this type of planet finding, it's just mainstream routine. Wow. And I could even train you. Like, if you wanted to and you were here, I would invite you to one of our planet finding sessions. Because, you know, our computers do all the hard work. But at the end of the day, you know, we go from tens of thousands of these so-called light curves down to, like, 50 that we have to sort through as humans. And we have a team of experts, and we all sit around the table and the screens twice a week for a couple hours. And those are our planet-vetting sessions.

And we sort through them. And, yeah, if you were around here, I would actually invite you to see how that operates. Oh my gosh, I'm 100% going to take you up on that. That sounds amazing. All right. That'd be so fun. Yeah. And so once we find these so-called planet candidates, we release them to the community and they're publicly available if you know where to get them. And then they have to go to, yeah, it's on the internet. It's on an archive called MAST, and they host pretty much all astronomy public data. And you'd go on there, and you could download these light curves. And we also have a coordinated follow-up team. Because these little flickers of light, as you called them, there's a number of other things that could be causing them.

Specifically binary stars, two stars that happen to be orbiting each other and eclipsing each other. Which is the coolest arrangement for stars. Like, that's, I love thinking about it. But okay. Well, you know, some of these, yeah, the binaries are, okay, well, one person's trash is another person's treasure. So for us, the binary stars, we just don't want them. And so we have a team of follow-up observers, and they're somewhat self-organized to sort

through what these little dips in light are. Are they genuine planets, or are they false positives? And so there are binary star people out there who, if you find out it's a false positive, they're like, oh boy, a new binary star for me, binary star man. That's right. There are all the people out there. The binary stars, there's variable stars. Some stars just vary in brightness seemingly randomly. There's people who like that. There's very special types of variable stars. They have names like Delta Scuti.

They're named after their prototype star. And people specialize in individual types of variable stars. So there's all kinds of interest. So this is a very, like, crowdsourcing is not the right word, but this is a real group effort to sort through all this data, first with computers and then with humans pouring over it to find the planets. Right. Are we limited? So I'm interested when you say the transient planets, so they have to pass in front of the star from our perspective in order for us to detect them.

Does that mean we're only able to detect a very, because that must be a small subset of the number of planets that are out there. So are we limited to a really small subset of what we're able to see? For now, we are. I mean, there's a lot of other techniques to find planets. This particular one, transiting planets, it's actually just the most mature. And in terms of the detectors and the technology, it's just the easiest way to find planets right now. That's why it's right now the main game in town. But if we had this conversation, you know, 10 years ago or 10 years from now, we might be talking about a different planet-finding technique. I love charting the way that science changes in that way,

that the techniques change and the discoveries that we make as a result of the techniques change. Are discoveries that we make as a result of the techniques change. Where do you have, are there techniques that you foresee coming in the future that'll become mature, that'll allow us to see them in different ways? Yes, there are. There's a couple of them. I can describe both of them if you want or pick one, but... Pick your favorite and then we'll see if we're hungry for one after that. So the transiting planets, definitely it's limited. And it's really just the first part of a much longer journey in discovery.

What I really like, my favorite method that's still to mature is called direct imaging. And that doesn't mean we're going to get a picture like the beautiful Apollo images of Earth. It means that we will see the planet in its own reflected light. But to do that, we have to be able to block out the starlight to see the planet directly. So imagine like putting your hand up to the light or your hand up to the sun and blocking it out. We have to block out the starlight. And astronomers already do this for a special kind of really weird type of planet. But there's some very big, very hot, very young planets out there, and they shine from their own thermal energy, like heat. And we can block out the starlight,

and we can see those planets. They're typically quite far from the star. They're not like really anything that we call, that we're familiar with from our own solar system, but nonetheless, the technique works there. The only problem is we have to do way better to find planets like those in our solar system, particularly like Earth's. Like we'd have to make the technique maybe, I want to say, 100,000 times better than it is right now.

So that's a big number. I mean, imagine trying to make anything you do like 100 times better. Yeah. 100,000 times better. I mean, yeah, my goal for my own life as a comedian is to make, you know, maybe do things twice as good, three times as good. I think that would be the maximum I could hope to achieve. But doing the same thing 100,000 times better is wild. But that's, I mean, that happens in science, right?

I mean, our ability to, I don't know, look at data transmission and, you know, packet technology and stuff like that is orders of magnitude better than it was 100 years ago. It's not wild to think that that could happen. Right. Well, we're planning for it to happen. Oh, that's what I love. That's amazing. So let me describe it a little more to you because there's different ways to block out starlight. But one way is with a giant specially shaped screen.

And we call it Starshade. And Starshade is a screen. Great name. That's a great name. And you get to listen to these numbers, yeah? To listen to these numbers, but it would be tens of meters in diameter. So imagine if the Starshade is 30 meters in diameter, that's somewhat close to 100 feet. That's, wow, I mean, 100 feet wide. And this star shade would have its own spacecraft, and it would fly in outer space with a telescope. They're separated from each other by a vast distance of tens of thousands of kilometers. Wow. And this star shade has a very special shape. It's shaped like a flower. And it would block out the starlight completely so that only planet light would enter the telescope. That's, what a beautiful image. I'm just like astonished picturing what that would look like.

How is it able to separate the light from the star versus the light from the planet? I'm not quite clear on that mechanism. Well, it just, it's actually, I'm going to explain the complication from it, but the concept itself is really quite straightforward because it would be like you having, let's say, a dinner plate, like a circular kind of object, and putting it in front of the sun, and putting it in front of the sun's at arm's length. It would just block out the light. I see. So, like, the overall concept is literally just blocking it.

The major complication is this, though. It turns out if you block out a point source of light, like a pinprick of light, guess what? You actually don't end up blocking it out because light can act like a wave. And instead of blocking it out, the light bends around the edges of if you had a giant circular screen, and you get ripples. Wow. Just like if you throw, yeah, just like if you throw a pebble in a pond. Right. You get ripples. Just like if you throw, yeah, just like if you throw a pebble in a pond, you get ripples. But these are light ripples, not water wave ripples. So what the star shade has is like a very clever solution is it's an incredibly special shape.

So that starlight that you're blocking out, it still diffracts, it still bends around the edges, but it cancels itself out in a very special way so that the image is incredibly dark. That would be like throwing a pebble in a pond. And instead of getting ripples, the pond would be perfectly smooth. Wow. All the waves, all the waves would be pushed to the outer edges. all the waves would be pushed to the outer edges. So you're controlling the shape of the pebble such that the waves that it generates

cancel themselves out perfectly so it ends up going into the pond with no ripple. That's a really interesting way to look at it. Yeah. Well, the ripples would be configured somewhere else. Right. Yes. That is so, so, so incredibly cool.

I'm sorry. For you to be doing this in your daily life and then to talk to someone like me who's thinking about it for the first time and having my mind blown by it must be a little... Right, right, right. I'm glad you... Well, it's great that you're so enthused about it, but this idea was first conceived in the 1960s. Really? Like as an idea kind of on paper and mathematically. It was conceived by a person named Lyman Spitzer, who was also one of the, literally the fathers of the Hubble Space Telescope.

And it wasn't like buildable or anything at the time, nor was it buildable each decade when people revisited it. nor was it buildable each decade when people revisited it. And in 2015, I got to lead a team of people, and our job was to either bring Starshade to life, showing the world that it's possible, or to show the world it's impossible, and it's an idea that should be kind of shelved forever. So fortunately, we showed it was possible,

and we continue to work on it today. Are there plans to actually launch it and put it up there? Well, that's why I said before, we're doing the easier things first, and easier usually means cheaper. Right. So the ideas out there, we're kind of competing to try to get it selected, but it's not a funded mission right now. It's just moving forward, developing technology. So we hope it will be real someday, but we're competing with a lot of other ideas. But you're working on it in order to make it real one day.

You're in that stage. Yes, we're working on it. That's right. We're working on it to make it real one day. And so if you do that, you will, if we have that star shade, we will be able to see exoplanets, not see them directly,

but just observe their light directly? Yes, we'll be able to observe their light directly, which is why we creatively call it direct imaging. Got it. And we'll be able to see solar system-like planets around the nearest sun-like stars. Like we'll be able to see like another Earth, another Jupiter, another Venus, maybe things like that. And those are the things that are hard to see now, like seeing an Earth-sized planet is specifically difficult, is my understanding. Seeing an Earth-sized planet around a sun-like star

in an Earth-like orbit hasn't been done, actually. It's still out of reach. Really? So, because I know that, you know, as I talked about in the intro, we've now seen many, many exoplanets, but we have not seen sort of an Earth twin in that way at all. No, no, but we're starting to think we have a bunch of, like, call them Earth cousins around.

We're not sure exactly what they are. But right now, many of the potential Earth cousins, they're around small stars, much smaller and much redder than our sun. Again, we're kind of doing the easy things first, but we have a phrase we call it, you could probably think of something more funny, but for astronomy, this is about as funny as we can get. We call it the race to the bottom because we're racing to like look at the smallest stars possible. The smallest stars, it's just easier to find planets around them because the signal is bigger. Like imagine the transiting planet going in front of the star. Right.

In front of a small star, it takes out a much bigger area than in front of a big star. So how do we, when you're actually trying to learn about those planets, if all we're seeing right now is a flicker in front of a star, or if, you know, in the future, if we get starshade going, and again, incredible name, I love to say it. If we get starshade going, and we're getting that direct light, that's still far from, you know, actually being able to, you know, like look and see, oh, yeah, I'm seeing an atmosphere here. Oh, look, I see some purple clouds or whatever. How do we learn about the planets from this sort of somewhat abstract sounding data? Yeah. And the funny thing is that hundreds of people around the world work on that, that very question. One way is that when the planet goes in front of the star, it blocks out

light in the ratio of the area of the planet to the area of the star. So if we know the area or the size of the star, we can get the size of the planet. Similarly, there's another technique we could follow up with to get the mass of the planet. And if you have the mass and the size of the star, we can get the size of the planet. Similarly, there's another technique we could follow up with to get the mass of the planet. And if you have the mass and the size, you can get the density of the planet. So you could know, is this like really heavy, like a rocky planet? Or is it very kind of light, like a giant exoplanet,

like a giant planet like Jupiter? So kind of we can tell approximately what the planet's made of if we can get a mass and a size. So that's the first thing to do. The second thing with these transiting planets, and I'm not sure if this will blow your mind or not, but when the planet goes in front of the star, I want you to imagine the starlight shining through the planet atmosphere. Just like shining a flashlight through a fog, some light might make it through and some light may not make it through. Right. And so because the starlight's shining through the atmosphere, we can pick up what part of that is from the planet atmosphere. And we're actually able to

measure very crudely, but what is in some exoplanet atmospheres and dozens of exoplanet atmospheres have been observed that way. Yeah, that does blow my mind. And you have a great track record for blowing my mind over the course of this episode so far. So you're saying that based on the quality of the light in that little flicker, you're able to detect, because some amount is being blocked by certain atmospheric qualities,

certain things in the atmosphere, you're able to tell what's in the atmosphere by what happens to the light passing around the planet as it crosses. Right, I can actually, yeah, I can explain it a little more specifically. So first of all, we can look at the star by itself, and then we look at the star when the planet's in front of the star. And we can subtract those, and then we're left with the atmosphere. But here's the thing.

If you could ever look at a rainbow, so everyone hopefully has got to see a rainbow at some point. This summer, I saw even a double rainbow. has got to see a rainbow at some point. This summer, I got to see, I saw even a double rainbow. But what you probably don't know is that if you could look at a rainbow very, very, very closely, you would actually see that some parts of the rainbow are missing. Like little tiny colors, little tiny strips of colors would be missing,

like a tiny bit of really dark red and a little more of maybe light red and some of orange. In fact, it's because of molecules in our atmosphere. Well, in the sun's atmosphere and in our atmosphere, they absorb radiation. The molecule, the way I explain it to my students, is like the molecule kind of like takes a bite out of the rainbow. And there are all these lines called spectroscopic lines, and people work hard to match up like a fingerprint, if you will.

Like each atom and molecule has a somewhat unique fingerprint of which colors it takes away. And so effectively, we look at this transit at different wavelengths or in different colors, and we see how those different differ from each other. So there's so the atmosphere has a because of the elements that are in the atmosphere has like a fingerprint that causes some of the light that goes through it to not travel all the way through. Exactly, yeah. That's exactly. You said it way better than I did.

So yes, that's what it is. No, I love it. Actually, I want to take that one step further, though. I want to take it one step further to what it really is. Yeah. Imagine now we're looking at a color or a wavelength where the atmosphere is transparent. There's no molecule or atom or anything absorbing at that particular wavelength. Then the planet is a certain size.

It's just, you know, the size of what it is. Now imagine an adjacent wavelength or a color where there's gases like molecules or atoms that are absorbing incredibly strongly. The light is not making it through, as you said. And the planet actually appears a tiny, tiny, tiny bit bigger. Because that atmosphere is like adding another layer to the planet. And so we're specifically looking for transits that are different sizes at different wavelengths. Oh, wow. Okay, I follow.

Yeah, if you look at different wavelengths of light, the planet would appear different sizes because more of it's getting blocked at different wavelengths. Exactly, yes. That's what it is, actually. Wow. That is so cool. And I also, by the way, I had no idea that that happened with rainbows on Earth, that we're seeing, in a way, Earth's own fingerprint. Every time we look at a rainbow, we're seeing its own spectrographic fingerprint. You're seeing Earth's, but mostly what you're seeing in Earth's rainbow, if you could do what I said, was most of what you're seeing is the sun's actually, so-called photosphere. It's called a photosphere, not an atmosphere, but mostly what you're seeing is coming from the sun. But yes, you could actually see Earth's

imprinted on that. And what you, you know, we have these instruments, we call them spectrographs, and they split the sunlight up so much. So it's like a rainbow spread out hugely over your detector, and that's where you can really see those lines. Amazing. And you can also get these little slides. We use them in the classroom. And you hold it up to the light, and you can see what I'm talking about. How so?

Like you hold it up, and what do you see? Like it's a little slide. That's what's called a diffraction grating. It sort of makes a fake rainbow for you. So it creates a rainbow for you. And you literally can see these little black lines where mostly things in the sun are absorbing. I see. Just to demonstrate that effect. Demonstrate, yeah, just to demonstrate it, yes.

That is so cool. So by using all these techniques, and by the way, this is incredible that you're able to get all of this from, again, what seems like the tiniest amount of data, just a little flicker in front of a star. You're able to- You know, we've been working on it. Right. It sounds incredible, but we've been working on this for a long time. In fact, I know this will sound like very arrogant, but I actually invented that technique almost 20 years ago. And at the time, 20 years ago, people thought it was just never going to go anywhere. They thought that,

you know, we can barely find planets. We don't even really know if they're real planets. And when the first transiting planet was found, I actually wrote this paper and I worked super hard to get it out because it's a highly competitive field. And people use that technique a couple of years later and saw the first gas in the first exoplanet atmosphere then. And today it's become so standard. It's standard in the field and there's dozens, if not like over 100 people around the world or more working on this. First of all, that is not arrogant at all for you to say.

I'm so happy that you said it. And if that were me, I would be shouting it from the rooftops because that's incredible. So you're saying that the technique that you invented was later used to find the first gas exoplanets? Is that the case? Well, the technique was used to find the first atmosphere on an exoplanet. I have to ask, what does that feel like, you know, as a scientist, but also as a person to, you know, have made a contribution that has really enlarged our understanding of the universe in like such a concrete way? Well, I haven't really thought of it that way.

That's, I'll have to think about it. I mean, there's several things I could say, but one is like, of course, I'm very proud of it. Secondly, honestly, there's a huge comfort just knowing that the laws of physics and chemistry not only apply everywhere, but they're reliable. Yeah. You can use them to, you know, say something and that can really be reality. That's amazing, too. The third common is, you know, we're always onto the next thing. You know, ambitious people, like there's never any rest.

Like I'm sure it's the same with you. Like you do something that people think is great, but now it's the next thing. You've got to focus on the next thing. Certainly, that's 100% true. And I'm always, yeah, I'm never able to, you have to try to find those moments of pride in your work and say, okay, that actually

was, that actually was really cool that, that that happened. But, um, yeah, I relate to that feeling of, uh, you know, I've, I've only gotten little glimpses of it myself when, uh, often like working with computers or, or video games or things like that, where I think I, I come up with a theory about like, oh, I think, I think it works this way. And then I think this is how this system operates. Let me come up with a theory and see if I'm right if I test it somewhere else. And when it does, there's like a huge pleasure in knowing that you understood the laws and you were able to use them to make a valid inference, but also that the laws are like universal in whatever sphere you're working in. There is a real comfort in that. That must be an incredibly powerful feeling as a scientist.

It is. It's very gratifying. Wow. Well, let's talk about what everyone wants to talk about the most is, again, Earth-like planets and finding life on planets. Because to some extent, that often seems like our goal. That's certainly how the press reports on it is whenever an exoplanet makes the news, it's when it is most similar to Earth or more related to life in some way.

First of all, I want to know, do you share that desire? Is that your goal as well, or are you interested in any old planet? I definitely share the desire and make it my life's goal to find another Earth, like a true Earth twin orbiting a sun-like star, and hopefully one that shows signs of life on it. And can you... So that's my main goal. But as the... There's a but there, right?

As the kind of days and years and decades go by, I'm still doing my best to like make the foundation for it so that even if it can't, I mean, this sounds terrible. I shouldn't be saying this, but you know, if it doesn't get to happen for me, I've got to make sure it can happen. Yeah. I don't think that sounds terrible at all.

I think that sounds absolutely correct. Like, I mean, the, what about that sounds terrible at all. I think that sounds absolutely correct. I mean, what about it sounds terrible to you, that it feels that it shouldn't be such a self-driven desire that I want to find it? Is that your concern? It's not so much that. It's just that I'm really big on having concrete goals and realizing them, right? So it's sort of depressing if you can't reach your goal. I think that's the way to see it. So when I started working on Earths and Earth twins around Sun-like stars, I got to be involved with like these big NASA concept projects,

precursors to the star shade, if you will. But I was always the youngest person. Like I'm sure you had that as well. There's some point when you're like, you look around, you're always the youngest. We're young is like 30. So yeah, back then. So you're always the youngest person. It's like, oh, this, I have so much time, this field will always happen. Things will always go. And now, let's say 20 years later or more,

I'm now, I don't think I'm one of the older people, but I'm one of the leaders now, you know? So we went from that to that, but then what happens 20 years from now, then I roll off and then the other people roll on. So instead of like finding that perfect earth twin with all the signs of life and water and all the other wonderful things, now my goal is to get Starshade launched, even if it's a small version, to find planets that are like earth, that show water in the atmosphere, water vapor, which on a small rocky planet is signs of liquid water oceans needed for all life as we know it, and hopefully one even with oxygen, where we may not be 100% certain. So you'll be interviewing me or someone else down the road, and we can't say, oh, yeah, we're definitely there. No, we'll say, hey, this is great. This is like the planet

candidates I told you about. This is like a life potential, but we need more work. Because once we can anchor it with like an amazing discovery that now people are going to want to do more, then more things will follow, and then the next generations can continue the search. And why do you feel that the search for an earth twin is, like, why is that the goal for you? Maybe that's an easy question. Maybe it's a hard one. I think it's a hard one. I mean, oftentimes it's hard to say why we're doing what we're doing. You know, like, you can't ask a child, oh, why did you learn to walk? I mean, you know, they just, sometimes you're just driven on the inside for some reason. But one of the reasons I think is so we do just kind of want to know where did we come from? You know, why are we here? And this is just a more kind of concrete

scientific way of trying to address that question. Like how did our earth come to be is it unique is it is it rare or are there more like it out there do you feel that in your if you if you had to give it a probability of in your lifetime us finding that earth twin what would you give it i do have a number it's going to be funny but it's like 85 you give it 85 yeah i Mm-hmm. Yeah, I do. That makes me so happy because also I'm a little younger than you, I think, so I think my number will be a little higher. Maybe. I mean, this is the thing is that we know planets are incredibly common. It appears that all stars, as far as we can tell, seem to have planets.

Really? Except maybe some extreme, really big, hot stars, yes. Except maybe some extreme, really big, hot stars, yes. And with the Kepler Space Telescope, although we didn't reach down to the true Earth twin, Kepler has shown that small rocky planets are also very, very common. And so, you know, it's likely that they're out there. I feel, I do believe that, I mean, all the evidence points towards that small rocky planets are very common. And that's why I believe that the nearest sun-like stars have rocky planets just waiting to be found. And then how far does that go to, you know, being an Earth-like planet, right?

A small rocky planet around a sun-like star, does that fit Earth Twin for you? Or do you also want to see water? Do you also want to see green stuff? Or do you also want to see water? Do you also want to see green stuff? You know, how many colors that exist on Earth need to exist on this planet for us to say this is, you know, we found what we're looking for? I think we definitely want to see water. We definitely want a planet that has liquid water, which we'll see by seeing water vapor if we know it's a small rocky world.

Think about it. Like Venus is also a rocky planet. But Venus is like our sister planet, but it's incredibly hostile to life. It's so hot at the surface, hot enough to melt lead. Yeah. And maybe this is not even your field because I think astrobiology is something else, but if we were to find that small rocky planet with water on it, you know, life just being a chemical reaction that exists under the right circumstances, as I on it, you know, life just being a chemical reaction that exists under the right circumstances, as I understand it, if we've gotten that far down the, you know, probability curve to finding all those elements, what are the chances that such a planet could have life on it?

Yeah, we definitely don't, like, that's, I don't know how to say, we don't have a scientific answer to that. I would love to say that I think if the ingredients are there, I like to think life will find a way to form. But that's partly what we're trying to address. The funny thing is there's people here on Earth who are trying to create artificial life in the lab. Like they're literally just trying to start with basic ingredients and create a cell, a living cell. Of course. And they always tell me, well, yeah, they always tell me, you know, if we find signs of life elsewhere, that's fantastic because they'll know that their job is, let's say, easy, right? If life can happen all the time.

But I tell them the other way around, no, no, no, I need you to prove that you can figure out how to make life because if you can do that, it tells me that life should be everywhere because it's easy to get it started. Right. Right. So based on that sort of assumption that I laid out, which I assume would be shared by you and these folks, that life is a chemical reaction, that given the right substances and the right conditions, life is going to sort of spontaneously form. Is that correct? You're correct. I'm correct in not sharing that assumption. I share that assumption, although I don't know if all biologists share that assumption. Got it. But so there are folks out there who are saying, all right, let's try to get the conditions together and see if we can do it. Let's see if we can get some molecules replicating themselves with variations. Right. That's, man, well, you know, after the show, I'll hit you up. Maybe you can connect me to one of those folks because now I want to talk to them too.

But I have so many more questions, but we have to take a quick break. We'll be right back with more Sarah Seeger. All right, Sarah, so we've been talking about why we want to find an Earth-like planet. Let's talk about what we, you know, how we go about finding one and what we need to do in order to find one. You said you were, in your race to the bottom, looking for, you know, those smallest stars in order to find those. Is that, did I understand you right, that very small stars are where we might find an Earth twin? Well, very small stars, I'd say we'd find an Earth cousin. So we might find a planet that could support life around a red dwarf star,

but it would be very different from what we have here on our planet. Let me explain that to you, though. Please. Because just for a moment, I want to take you on a virtual trip to a rocky planet around a small star, a rocky planet in the so-called habitable zone of that star. So first of all, the small stars, they give out very little energy. So for a planet to be the right temperature for life, it has to be pretty close to the star. That's like the fire at campfire. If it's a small fire, you have to huddle pretty close to it to stay warm. And that's what the habitable zone means, right?

That there's a distance from the star where you're going to get the right temperatures you would need in order for water and life to form. Right. That's the habitable zone, yes. And there are, like everything in science, there's the simple picture and then it's always more complicated than that. Of course. Because you know what? It's the greenhouse effect of the atmosphere that really controls the surface temperature. Like here on our planet, we're worried about adding parts per million of carbon dioxide. But imagine if these planets had way more carbon dioxide.

You know, they'd be way hotter. But anyway, so imagine we could go to this planet. First of all, the star might be a bit bigger in the sky depending on the system. So you're, you know, because you're closer, so the star might be bigger. What's interesting about these planets is because they're so close to the star, due to tidal interactions, just like our moon and the earth have raised tides on each other, you know, we have the ocean tides. Because of these interactions over long periods of time, the planet gets into an interesting configuration. It would rotate one time for

every time it orbits. That's like the moon. Our moon is so-called tidally locked. It shows the same face to Earth at all times. It's actually rotating one time for every time it orbits. So this would mean if we could visit the planet, is that one side of the planet is always in daylight and the other side is always in night. So which side would you go? Where would you go? Which side would you go to? The light side, I think, so I could see stuff.

Okay, well, the astronomers would probably go to the dark side, but for what it's worth. Fair enough. The honeymooners might go to where the sun is always setting. Wow. That would be bizarre. Because the sun is always in the same spot in the sky depending on where you are on the planet's surface. That's right.

The planet's always in the same part of the sky at all times. Wow. It's crazy. So this world is a little different. Also, because the planet is so close to the star, by Kepler's third law, planets closer to the star also orbit more quickly. So on some of these so-called Earth cousins around small stars, a year would only be about 10 days. Yeah, so every year would go by pretty quick. Although, who knows, maybe they'll celebrate centuries rather than years.

But how would you even mark a year going by because there are no days? Because the planet's not rotating. Yeah, there are no days, but don't forget it's orbiting. And so the stars in the night sky, they change over time. Just like here on Earth, you know, sometimes if you look out at night, Orion, we only see Orion around here in the wintertime, actually. So, you know, whenever I see Orion setting, like it's this giant constellation, the western sky, I'm so happy because it means spring and summer's coming. And then now in fall, you start to see it,

and it's like, oh, great, that means we're in for a cold winter. That means, you know, our long cold winter is about to arrive. So, yeah, just like that, the stars would be different. That's the only way you could tell. But I guess you'd have to go to the night side to tell that. Yeah, so the sun is stationary, but meanwhile the stars are like whipping around, basically, because you're orbiting so quickly. Yes, so the sun is stationary, but meanwhile, the stars are like whipping around, basically, because you're orbiting so quickly. Yes, that's right. Yeah, that's right. Yes,

that's right. Yeah. Wild. So going to this planet sounds wild. I mean, it does. It sounds wild. It'd be cool to go on vacation there just for, you know, a difference. But on the other hand, it could be a terrible planet to visit because most of these, like nearly all of these red dwarf stars have flares, giant bursts of energy that would hit the planet and cause, you know, huge UV index, like what kind of sunscreen would you bring? I mean, it could, you couldn't, you know, you know how we're addicted to our cell phones? Well, the high energy particles from these flares would knock out the electronics, and your phone wouldn't work. Wow. So these flares are pretty crazy, and maybe it wouldn't be such a great place to visit after all.

The flares and these high-energy particles would cause mutations and cancer. So we kind of go back and forth about these Earth cousins. Do the planets even have atmospheres? Do these flares and other activity from the star blow the atmosphere away? Could there be life there? Maybe it has to live on the dark side or under the surface to be protected from these flares. We're not really sure. Wow. That is such a wild vision. Is it possible for life to arise or water to exist in that kind of situation? Or is there like too crazy of a temperature differential or anything like that?

exist in that kind of situation? Or is there like too crazy of a temperature differential or anything like that? Well, so people have been working on, you know, we always have an answer for almost any question. So that's the good news. And people have worked out that if there's an atmosphere, and as long as the atmosphere is, let's say, like Mars's atmosphere, which is a pretty thin atmosphere, then the energy will circulate around the planet and it should have somewhat of an even temperature. Do you know our planet Venus rotates very slowly? It has a few hundred day rotation period. I want to say it's like 200 and something. And so Venus has the same temperature all around because it's got this heavy atmosphere that moves energy around. Just like for people who

live somewhere where it's still hot out now, but winter is always approaching. Like on a winter's day, if you open your door to your house or your building, then the hot air rushes out and the cold air rushes in. So it's like that. The hot air wants to move around where it's cold. So that probably wouldn't be your biggest problem. It's probably these flares. You know, on Earth, we had, on Earth, this is digressing a little, but on Earth, in the, around, I want to say it was about 1850, we had a giant flare event. And it has a name. It's called the Carrington event, after Carrington, a British astronomer who was studying the sun, studying sunspots, and he noticed the sunspot whiten a little bit. And a day and a half later, a day and a half later,

sunspot whiten a little bit. And a day and a half later, a day and a half later, our Earth became electrified. And people didn't really understand at the time that Maxwell's equations weren't articulated. They didn't really understand magnetic fields or relationship to sunspots. But in this giant event, a flare and a corona, like a part of the sun, came off the sun. And it had a magnetic field embedded in it. And it came hurtling towards Earth. And it hit our magnetic field and induced a current and this current lit up our earth people could see the northern lights almost down to the equator in the northeast there are reports of the northern lights like lighting up the sky so you could read a paper at nighttime and telegraph operators some of them caught some of these telegraphs actually caught fire, and some of them could take the

batteries out of their end telegraph, and it still worked, actually. So some of these flares can be pretty intense. And on some of these M dwarf stars, they're called M dwarfs, these red dwarf stars, people have observed flares and seen that some of the flares are as powerful as that Carrington event. Amazing. I know'm really scared. I'm really scaring you off these planets. I mean, no, no, no. You know, we're not sure how crazy they are, but they're pretty crazy. The incredible. So so the Carrington event, like essentially what just created electrical activity just in stationary wires like, you know, you're you're holding a light bulb and a light bulb turns on in a way?

Exactly, yes. And so, by the way, it's a separate topic, but we are kind of worried that if that event happened today, we're in big trouble, right? That was my next question. Because you have power grids. Yeah. It's actually a real concern. You can look this up later and maybe for another show do an interview on this

because there are sort of a set of people worried that if this happens, we're not really prepared for it. Right. And that was the last, that was the most recent one we had was over a hundred years ago, right? Right. That's right. And, but, you know, don't, I don't know if I would hit panic right now, because if the sun gives off one of these blobs, it has to be coming in our direction, you know, at the right time. It could give off one of these another time and send it off in another direction that wouldn't hit Earth. I see. But just to say that the planets close to the star, they're more in the line of fire than we are to our sun. Everyone's always worried about asteroids coming and hitting the Earth, but we don't worry about what's coming at us from the sun.

Right, right. Man, I love thinking about these red dwarf stars. Are there any other sort of strange planetary configurations that you've come across? There are. And the crazy thing is that we haven't yet found any solar system copies, although our solar system is hard to find. any solar system copies, although our solar system is hard to find. So, you know, nearly every type of planet I could construct a, like, like a picture or a visit to. So I could mention a couple of other ones. One of them is, and again, we can, and it turns out we can find planets close to the star more easily than we can find planets further away. But there are some planets so close to the star,

way closer to the star than anything we've been talking about, that the surfaces should be hot enough to melt rock. So these planets may have liquid lava lakes. That is not from volcanic activity, but they're just so heated by the star that there's just molten rock covering the surface. Another type of planet I just love because it's so mysterious are planets that are two to three times the size of Earth. These planets, the Kepler Space Telescope showed that planets two to three times the size of Earth are the most common type of planet in our galaxy as far as like the Kepler parameter space or the Kepler range of planet periods orbits can tell. range of planet periods, orbits, can tell. And it's just astonishing because we expected that Jupiters, Jupiter-sized big planets, would be the most common type of planet out there because it's the end member of planet formation. Like, imagine that planet's form. It starts out kind of like those dust bunnies under your bed. That dust and junk kind of starts collecting in the

material surrounding a star as the star is being born. And this material grows kind of like a dirty snowball. And eventually, this dirty snowball will, like a cosmic vacuum cleaner, suck in everything around it and keep growing until it exhausts its food supply, if you will. And that should be a giant planet. Yet these two planets that are a couple times the size of Earth appear to be like 10 times more common than Jupiter-sized planets. And so we don't, yeah, and you know what else is, our solar system does not have one of those.

We don't have a planet that is two to three times the size of Earth at all. We don't. We have Neptune and Uranus, and they're four times the size of Earth. We have Jupiter, that's 11 times, and Saturn's also very big. So it's so baffling, right, that the most common, what might be the most common type of planet out there,

like we don't have one, we don't know what it is, we don't know where it came from. And yeah, so we have ideas about what it could be, but we can't sort through those ideas until we get a lot more information. So that means, for instance, if the most common kind was the size of Jupiter, then we could say, okay, well, then anytime we see one of those, that's probably a Jupiter-like planet. But since we don't have, are you saying one that's two to three times the size of Earth, when you detect those, you say, well, we actually don't know what those planets are like? It is that, but it's one more thing I forgot to say. That is, you know, when you have an extreme end member, you can tell what it is.

Like if I gave you a box and it was so heavy that you could barely lift it, like you could guess what's in it, right? It has to be like iron or whatever the heaviest thing you can think of, right? It has to be. Or if I gave you a box that felt like nothing was in it, you know what? It might be that nothing was in it, just air. Yeah. So we can tell if things are at the extreme ends, but these planets two to three times the size of Earth,

they just happen to be like intermediate. Like, you know, if I gave you like a medium weight box that was kind of in between air and iron, like you might not know because it could be so many things. So it just turned out that these planets happen to fall in this in-between range, and they could be a number of different things, and we just don't know what they are.

We don't even know why would they have formed and started to become big and then not continue to grow? It's like meeting, yeah, why would they have stopped growing? So we have a lot of questions about them. I see. You know, just thinking about the way that, you know, these astronomical bodies form is one of the most mind-blowing things to me because, and I overuse the word mind-blowing, but I have trouble thinking of what other word to use in this sense because, you know, the way you describe it is, you know, my understanding is there was, you know, at one point there's just stuff floating around in the galaxy and then eventually what, that stuff just sort of comes together because of gravity. It just sort of coalesces, um, into a blobby ball that happens to be a sphere in most,

in most cases, cause that's how gravity works. Um, and that's just happening randomly. We've just got, we've just got random assortments of, of planets, uh, just sort of forming in that way. Um, it's, I don't know, there's something very disorienting to think that everything, of planets just sort of forming in that way. It's, I don't know, there's something very disorienting to think that everything, you know, every planet that exists in the universe is because of that just sort of random collection process. Does that make sense? Yes, I haven't thought of it that way before, but it does. It does seem a little disheartening in a way.

Things are just, you know, you don't like to think that you existing or your life or whatever happens is due to random chance. But the fact that our planets are just some huge accumulation of random chance does make it look that way. Well, it's not, I want to be clear. It's, it doesn't, I don't think it's negative. I do find it somewhat disorienting. But what it throws into relief for me is that sort of what's happening on Earth is the end of matter coalesced at the right distance with the right properties. And then all the conditions that are necessary for life to form were on this planet and happened to be stable enough for life to develop to a level where it created this entire new level of complexity of culture, which is what we're doing right now. You and I are operating on the level of culture.

It's like happenstance after happenstance after happenstance after happenstance. And that makes what's going on on this planet seem all the more remarkable to me. I've never agreed with people who feel that that devalues life or devalues human life. I think it makes it more valuable because we're the most remarkable thing happening in the universe. But it does make it seem maybe less likely that we're going to encounter another instance of ourselves out there? It might, actually. Well, our universe is so vast, and our galaxy alone has hundreds of billions of stars, and our universe has hundreds of billions of galaxies.

So it's probably out there somewhere, but our immediate question is, is it out there around one of the nearest stars that we can actually start to probe? Yeah. So I have, I have here that some of your early work was on hot Jupiters. What are those and how do, like, how, how, how are those surprising things? Well, hot Jupiters are Jupiter size or Jupiter mass planets, but instead of being like five times the earth sun distance and taking 12 years to go around the sun, these planets are so close to the star, the time it takes them to go around the star is only a few

days. And having these hot Jupiters like right up against their star is pretty crazy because we're confident that there's not enough material for Jupiter to form right close to the star. So the thinking is that these big hot Jupiters must have formed much further away from their current position, and that early on, after formation, they migrated, they interacted with the disk material and moved inwards, stopping right close to their star. Wow. So they moved from one spot in the solar system to another, which is not something I normally think of planets as doing. system to another, which is not something I normally think of planets as doing. Right, right. And these hot Jupiters, the reason I studied them early on is because they were the only thing to study. They're easy to find because they're so big and hot and they're right close to the star. And so that's why I studied them initially. Well, that's some of your old work. I want to talk about some brand new work on this topic that's just been done. As we're recording this, this episode won't come out until a little bit later, but on the day that we're recording this, there was a report just put out that a team believes they found a planet that has water vapor and possibly even rain. You were quoted in the article I read about this.

I'm just curious for your take on this potential discovery, because I know it's very early yet. Yes, well, this is one of those mysterious planets that's between two and three times the size of Earth that we were talking about. That's one of the most common types of planets in our galaxy. So it's a big step, a milestone, to be able to study its atmosphere.

Because the hope is that eventually the atmosphere will help us know what the planet is made of. Is the planet like a giant water world, like a scaled-up version of one of Jupiter's icy moons? Is it a planet that has like a deep rocky core surrounded by a giant envelope of hydrogen? We'd like to eventually be able to discriminate between those. So while this new measurement didn't discriminate between them, it's the first time that we've been able to, the community, the astronomers, have been able to observe the atmosphere

of such a small and one of these mysterious objects. So, yeah, it has water vapor in the atmosphere. And the authors of one of the two competing papers made an argument that the temperature in the atmosphere crosses over, that the temperature in the atmosphere crosses over, that the temperature in the atmosphere might also be suitable for liquid water, postulating that there could be water clouds in the atmosphere with water droplets. So it's pretty interesting.

It's interesting. But my understanding is it's very early yet, and we're not entirely sure about the liquid water particularly, but the rest of it you feel confident about? I do. Well, it's definitely a robust detection of water vapor. And it's tough, and this field is tough because planets are so small, and the atmospheres are even smaller.

So just to get any data at all is really a triumph for us. And it definitely has water vapor, and there's indication that, you know, so we make models to fit the data, and we ask, what's the best fit model? And in this case, the best fit model shows water, but also clouds must be present. And if they're clouds, they're likely water clouds. And so you sort of use reasoning to infer what could be there, including the possibility of liquid water droplets. Yeah. This is such an incredible field because it seems like so much is happening almost on a daily basis. And, you know, so many – it often feels that, you know, the parts of science where it's really, really big or really, really small are the ones that take the longest.

the parts of science where it's really, really big or really, really small are the ones that take the longest. And yet this is one where it feels like we're making progress so quickly. Do you share that feeling? Well, yes and no. Like, so as I mentioned, I first wrote down about this technique about 20 years ago. Right. A few years after that, people studied the atmosphere. This particular data set took three years to accumulate. So someone would have proposed for it. Actually, one of the lead authors of the papers is one of my former PhD students that I trained. And he must have proposed for the data four years ago, and it took three years to get the data, probably like another year to analyze it. So from the behind the scenes view, it took quite a long time, but I guess it does.

It's one of those phrases, this is what they use for kids. They say the days go by slowly, but the years go by fast. So while we tediously work on it all, it just seems to occur in a hurry. Well, it's, yeah, I'm not trying to minimize the labor that goes into it either or make it sound easy in any way. But, you know, our understanding of the universe around us is being rewritten here. It is. It really is. But it's also fair to say that really bright people who are extremely hard workers and ambitious, like there's a lot of people funneling into the field to make things happen. And so that's partly why you're seeing so many great results. Amazing. So what is your hope for the future of the field? I mean, you've talked about it a little

bit, but what do you hope that new discoveries in this field will bring to humanity at large? Well, my biggest hope, more practically, is that we can study the very nearest stars, like our very nearest neighbors, so we can see the planets around them and understand their entire planetary systems and find Earths if they're there and study the planet atmospheres to look for water and signs of life. That's my immediate goal. I hope finding another Earth would help us realize we're not alone, like in this universal sense, and that'll give us some understanding of where we've come from and where we might be going.

Well, I couldn't be more fascinated by the work that you're doing. And I thank you for bringing us that perspective, both as a scientist and on the show today. Yeah, thank you so much for being here. It's been incredible. Thanks for having me. It's been a fun conversation. All right, folks, that is it for this week's episode of Factually. I want to thank Sarah Seeger again for coming on the show,

and thank you for listening. Also, our wonderful producer, Dana Wickens, our researcher, Sam Roudman. I'd like to thank Andrew WK for letting us use his song, I Don't Know Anything, as our theme song. And you can follow me on Twitter at Adam Conover. You can follow me at Twitch at twitch.tv slash adamconover. If you want to watch me play some video games every now and again, you can sign up for my mailing list where

I will send you regular fascinating facts at adamconover.net. And until then, we'll see you next week on Factually. Thanks for listening. That was a hate gum podcast.