Exploring Exoplanets, with Seth Shostak – StarTalk All-Stars

SETI Institute Senior Astronomer Seth Shostak, is back to host StarTalk All-Stars and go exploring exoplanets with guest Jason Wright, Associate Professor of Astronomy at Penn State, and co-host Chuck Nice. NOTE: StarTalk All-Access subscribers can watch or listen to this entire episode commercial-free. Find out more at https://www.startalkradio.net/startalk-all-access/

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

  This is StarTalk.

• 0:09Speaker 00

  Welcome one and all to StarTalk All-Stars and I'm your All-Star host of the evening, Seth Shostak. I'm Senior Astronomer at the SETI Institute, that's S-E-T-I, almost my name, but that's coincidence. SETI is an acronym and it stands for the Search for Extraterrestrial Intelligence. In other words, not just life in space, but life that's as clever as you are, or maybe even more so, not to take anything away from your cleverness. And joining me as co-host is the very funny Chuck Nice.

• 0:37Chuck Nice?

  Hey Seth, how are you?

• 0:38Speaker 00

  I'm okay. How are you doing over there?

• 0:40Chuck Nice?

  Doing well, man. Good to be here.

• 0:42Speaker 00

  Are you interested in planets?

• 0:43Chuck Nice?

  You know, I'm interested in this one planet that we're on. I'm definitely interested in that. But no, I think it's very exciting to actually talk about the planets that we know. The fact that there may be, I don't know, 600 million, was that the last figure that I heard? It could be 600 million Earth-like planets somewhere in the entire galaxy. I'm not sure if that's...

• 1:10Speaker 00

  Well, it may be more than that, but we're going to hear about that from our guest. And our guest is Jason Wright and he's an Associate Professor of Astronomy, a member of the Center for Exoplanets and Habitable Worlds, and he works at Penn State University in State College, Pennsylvania. Hey Jason, how are you doing?

• 1:28Speaker 02

  I'm doing really well. I'm actually coming to you from Aspen, Colorado, of all places at the moment.

• 1:34Speaker 00

  Really? Well, that's just a terrible place. I don't know why you want to be up there.

• 1:38Chuck Nice?

  No, it just sucks to be you, right?

• 1:40Speaker 00

  Well, you got your skis? A little early for skis.

• 1:43Speaker 02

  A little early for that. That's hiking.

• 1:45Speaker 00

  Hiking. Hiking is good. Well, what we want to know from you is what's the status of planets, not around our own sun, but around other suns. And, you know, one of the big news items recently was the discovery of a planet that may end up being the closest planet to us of any of them that aren't in our own solar system, Proxima B. Tell me a little bit about Proxima B.

• 2:06Speaker 02

  Right, that is big news. So there's no maybe about it. This planet is definitely the closest planet to the sun that's not orbiting the sun. So the star is called Proxima. We used to always call it Proxima Centauri, which is just Latin for the closest thing in the constellation of the Centaur. But now we know that it's actually the very closest star to the sun anywhere, so its planets really are the closest. So we've been finding planets around other stars in the galaxy for a little over 20 years now, and thanks to space missions like the Kepler Space Telescope, we now know of thousands of planets in the galaxy. And this one, though, is different. It's special because it's really our neighbor.

• 2:50Speaker 02

  And so we're going to be studying this one in particular because it's right there forever, basically, and we're going to be wondering about it and how to get there and what we can learn about it.

• 2:59Speaker 00

  Well, you say it's the closest one. I mean, maybe we ought to give them a number for that. How far away is it?

• 3:05Speaker 02

  So stars are really, really far away, to get technical about it. This one, being close, is a little over four light years away. So if you could ride on a light beam, then it would only take you four years to get there. So in cosmic terms, that's, they're our neighbors. They're right next door.

• 3:25Speaker 00

  Yeah, but I can't ride on a light beam.

• 3:26Chuck Nice?

  Yeah, I would love to ride on a light beam, as a matter of fact. That's going to be the name of my next album, Riding on a Light Beam with Chuck Nice.

• 3:33Speaker 02

  That's nice.

• 3:34Chuck Nice?

  So give us an idea of four light years. Let's break that down into human terms. How long would it take us to get there?

• 3:47Speaker 02

  Well, if we got our best rockets, launched a probe into interstellar space, and we've done this before, so you know, we know we could do that. Let's see, it would take something like, I don't know, 100,000 years to get there, maybe tens of thousands of years if we went really fast.

• 4:04Speaker 00

  Yeah, I figure about 100,000 is right. I mean, that's a long time to be eating peanuts off your lap in the middle seat, right? So 75,000 years to get there. Yeah, but I mean, it isn't to say that you couldn't get there faster. I mean, if you don't want to go yourself and you just want to send some sort of object, maybe the size of a silver dollar or something like that, to Proxima, you could do that faster, couldn't you?

• 4:26Speaker 02

  Well, in principle, right. I mean, this used to be all science fiction, but, you know, recently, people have thought hard about this. There's a project called Breakthrough Starshot, which is trying to figure out how to do exactly that. So there's this old idea that if you gave a spaceship a sail, a light sail, so just like a big parachute or something, and then you shot a really powerful laser beam at that parachute, you could accelerate something really fast. And it takes a really powerful laser beam to launch something that could have a person in it. But if you only wanted to launch, like, a tiny little microchip, or something like that, something that weighs less than a raisin, then you would only need a superpowered laser about a square kilometer across.

• 5:08Speaker 00

  Well, that's a very modest requirement, isn't it?

• 5:11Speaker 02

  I know, I know.

• 5:12Speaker 00

  Okay. Well, let's get back to those planets if we could, Jason, because, you know, Chuck over here figures that there are 600 million, kind of Earth-like worlds, cousins of the sun in our own galaxy. Now, obviously, we haven't found that number of planets.

• 5:25Speaker 02

  Right.

• 5:25Speaker 00

  But, but give them, give them the number. I mean, how many, how many planets out there are not just, you know, kind of worthless planets like Neptune, Uranus, those guys? But, you know, might be, might be the kind you'd want to build condos on, or, you know, the kind where you might have oceans, atmospheres, that kind of thing.

• 5:38Chuck Nice?

  Beachfront property is what we're talking about here, Jason.

• 5:41Speaker 02

  Right. You want to see, you want to see water on that thing.

• 5:43Chuck Nice?

  That's right.

• 5:44Speaker 02

  Someplace we would want to visit. Well, let's see, there's about 100,000, 100 billion stars in the Milky Way galaxy, and we now know that most or all of them have planets. And so, right away, we know that we've got many hundreds of billions of planets in the Milky Way galaxy. And some fraction of them, like 10 or 20%, probably have about the temperature that you would need for liquid water. And so, we're talking about tens of billions of planets in the Milky Way that could.

• 6:12Chuck Nice?

  Wow.

• 6:13Speaker 02

  And we, we like those planets that might have liquid water, because we want to study them and figure out if they do have liquid water or whatever. So, yeah, there's, there's a lot of property out there to be, to be claimed.

• 6:24Chuck Nice?

  Look at that.

• 6:25Speaker 00

  So, so, I mean, what you're saying, if there are tens of billions of planets that are sort of like the Earth, the possibility that this is the only place where anything interesting is happening, if you think anything interesting is happening here.

• 6:36Speaker 02

  It's happening, right.

• 6:37Speaker 00

  Yeah, right. I mean, that, that, that would, that would make us pretty special, wouldn't it?

• 6:42Speaker 02

  Um, if they were right, if none of them had life like life on Earth, yeah, that would make Earth, you know, fantastically unique, you know, one in 10 billion or something like that. That would be, um, maybe very surprising.

• 6:54Chuck Nice?

  Yeah, and but but is it possible to, I mean, when you think about, I mean, if you were just to play Earth out to its logical conclusion, which is, uh, the sun will expand and burn us off to a crisp, uh, is it possible that that has already happened? So there's been life, but it's expired because, of course, that's what all life does at some point. So is it, it, it, it, how, how would we be able to find that signature? Or is that if, if the idea is to find life first and then you can draw those conclusions?

• 7:31Speaker 02

  Well, it's true. There's got to be a lot of planets out there that used to be able to have liquid water on it. And by the way, the, the term we use, we say that the planets in what's called the habitable zone. That just means it's far enough from its star, uh, so that it's not boiling all the water away. But it's, it's close enough to the star that it's not just an ice ball. So when planets are in that habitable zone, that's, that's where we think we'd see this liquid water. Um, and so certainly there are planets that used to be inhabitable zones of their stars, but something happened, like the star got big and blew up or, or burned out, or, you know, one of the things stars do, or something might have happened to the planet in its orbit. Um, so when we give that count, we're talking about the number of planets that are in their habitable zones today.

• 8:13Speaker 02

  But yeah, the history of the galaxies, 10 billion years. And so there's probably a lot of formerly habitable planets out there.

• 8:20Speaker 00

  It sounds to me like Chuck is more interested in, in life that's deceased than in the country. It's like going to New Jersey and looking for fossils instead of looking for New Jerseyites, right?

• 8:31Chuck Nice?

  Exactly.

• 8:31Speaker 00

  Yeah, there, there are plenty of fossils, but, yeah, and some of them are actually New Jerseyites.

• 8:36Chuck Nice?

  Most of them have been buried by, uh, irreputable.

• 8:40Speaker 00

  Forces, I'll just say. Jason, I've got to ask you because you're really responsible for this idea being promulgated about a star that has the lovely name K I six eight four six twenty eight fifty two. All right, never mind the name. Say that name again, please. K I C eight four six twenty eight fifty two, but I may have gotten it wrong.

• 8:56Speaker 02

  How can you remember that stuff? I can never remember that.

• 8:58Speaker 00

  It just falls off the tongue, actually, I find, but I call it Bob, whatever.

• 9:03Speaker 02

  That's very cool.

• 9:04Speaker 00

  So, this is a star, I mean, it's not very close to us, but it's very unusual. And there was a really interesting find about it, but you can tell me about that.

• 9:15Speaker 02

  Sure, well, the Kepler spacecraft was looking for planets around other stars. And to do that, it looked at 100,000 stars, and most of these aren't nearby. They're not like proxima, just four light years away or something. They're more like 400 light years away. And it was watching their brightnesses extremely carefully, just in case a planet, maybe like Earth, passed in front as it went around the star, passed in front of the star and made it a little bit dimmer. And so it found thousands of planets like that. It also found lots of stars misbehaving, getting brighter and dimmer for other reasons. But there was one that was just totally unlike all the other. It started to get dimmer, as if there was a planet going in front of it or something. But then instead of getting just maybe 1% dimmer, because there's a planet like Jupiter

• 10:00Speaker 02

  around it, it just kept getting dimmer. And over the course of days, it got like 20% dimmer than it had ever been before. And then all of a sudden, over a few more days, it got bright again and went back to normal. And stuff like this kept happening. It kept having these strange dimming events, as if very large amounts of stuff was between us and the star. And this stuff has to be much bigger than something like Jupiter. And whatever it was, it wasn't round like a planet or like another star. And so it just had all the astronomers completely baffled about what was going on.

• 10:35Speaker 00

  Well, we don't have too much time, but tell me, what are the possibilities? I mean, a star getting dim like that, that's unprecedented. Could it be alien handiwork?

• 10:44Speaker 02

  So, yeah, there's a lot of possibilities. We've been scratching our heads looking for lots of natural explanations. But one thing that I noticed is that there was a guy named Luke Arnold, who published a paper before Kepler launched. And he said, hey, if there are advanced civilizations, they might build giant things in space, maybe to collect lots of energy, like solar panels or something. If that's true, then those pass in front of the star, Kepler would see that happen. And it wouldn't look like a planet. It would look like something we totally didn't understand. So when this star was discovered, I said, hey, you know, this guy Luke Arnold, he said, we might see this. And if we do, that we should be on the lookout. It could be solar panels. So, could be. We're not out of all

• 11:29Speaker 02

  of our other ideas, but that that one's definitely out there now.

• 11:33Speaker 00

  Okay, I gotta ask you, this is just the last, the last question, really quick now, Jason. If you're sitting in the local diner there in State College, Pennsylvania, and the guy next to you says, okay, how much are you willing to bet that what we're seeing going on here is the result of a giant, alien astroengineering project? What do you say?

• 11:52Speaker 02

  Well, what odds are you giving me?

• 11:54Speaker 00

  No, that's...

• 11:55Speaker 02

  Not, not, not, not very much. You know, we see weird things in space all the time. We can talk about other bizarre signals that have come from space and turned out to be not aliens, but something really new and amazing and interesting in and of itself. So I think we've almost certainly found a new weird kind of way stars can get dimmer that we haven't seen before. But I don't know how to put odds on aliens. I presume it's very low.

• 12:19Speaker 00

  Great. We'll be getting back to you. But now it's time to go to Chuck and the Cosmic Queries. These have been culled from the best, the best questions on the internet about this subject and maybe others.

• 12:30Chuck Nice?

  Yes, exactly. You know, our listeners are extremely curious, as a lot. And they have all of, from Facebook and Twitter and every station where you find StarTalk, they have sent us some queries for you guys to tackle. So you don't know what they are, but it doesn't make a difference. It's, it's not about stumping you. It's just about, if there is an answer, I'm sure you'll have it.

• 12:55Speaker 00

  I'm glad you said that.

• 12:56Chuck Nice?

  Yeah.

• 12:57Speaker 00

  Yeah.

• 12:59Chuck Nice?

  So, let's, uh, let's jump right into it. Let's start off with a Patreon patron question. And Patreon is a, uh, a, a place where people support StarTalk and, uh, monetarily. And if they do so, uh, we give them, uh, first crack at, uh, asking us a cosmic query. Just a little, just a little perk of buying our love and affection. So, um, this is from Keela Silves from Patreon, and she says, "I'm Keela Silves from Minnesota, and my aunt, Dr. Patty Boyd from Goddard, helped me with this, uh, particular question for Exo- Exoplanets." Do you guys know Dr. Patty Boyd, either one of you, uh, gentlemen? I don't think so. No?

• 13:42Speaker 00

  Well, yeah, she may be working under a pseudonym.

• 13:44Chuck Nice?

  A pseudonym? Yes, exactly. Uh, yes, it's like her, like, that's her stripper name. Dr. Patty Boyd. Um, she says, "Besides radio waves, what signs is humanity giving off to other stars that Earth possesses intelligent life?" So, aside from the actual signals that we are shooting out into space, is there any other indication from somebody who's looking at us from four light-years away to say, "Wow, there might be some intelligent life on this little rock from the, from the sun."

• 14:21Speaker 00

  I, I have to say, it hasn't impressed them enough for them to send their interstellar battle wagons to Earth, so there's at least that. I, I'll let Jason start. Uh, what, what do you think is the answer to that, Jason?

• 14:32Speaker 02

  Well, yeah, there's a few ways that you might notice that we were here. Um, one of my favorites is that our large telescopes often shoot big laser beams into space to try and correct for the Earth's atmosphere. We create little artificial stars in our atmosphere and then deform the mirrors of our telescopes to compensate for the blurring effects of the atmosphere. So what that means is we're always shooting these lasers off into space. And so if we shot one on one of, you know, another planet, they might notice the laser. It's pretty weak, but it's, it's conceivable.

• 15:02Speaker 00

  But it's only a couple of directions, right? They have to be in the right place.

• 15:05Speaker 02

  They'd have to be right along, we'd have to be intentionally pointing our telescopes. telescope at them presumably for some other reason.

• 15:12Chuck Nice?

  That would be kind of like, you know, the old movies where the person would use a mirror.

• 15:17Speaker 00

  Yeah.

• 15:17Chuck Nice?

  Where they're lost at sea and the plane says, what's, what's that down there? I think I see something.

• 15:23Speaker 00

  It was always cowboys trying to signal that the Indians were afoot. That's what I saw.

• 15:26Speaker 02

  Although, you know.

• 15:27Speaker 00

  That was back before they invented sound.

• 15:30Speaker 02

  In movies when you're standing there and suddenly that little laser beam appears on your, on your chest. It's usually not a good sign. So maybe we shouldn't be doing that.

• 15:37Speaker 00

  Well, I'll tell you, that, that's one way. There, there are other things, Chuck. I mean, for example, if you use hairspray, it doesn't look like you use hairspray, but if you wouldn't.

• 15:45Chuck Nice?

  I use mousse.

• 15:45Speaker 00

  Okay.

• 15:46Chuck Nice?

  Anyone, anyone knows me.

• 15:47Speaker 00

  Yeah, well, in the old days hairspray had these chlorofluorocarbon, you know, and that. They kind of changed the contents of the atmosphere, right? You remember the ozone hole and all that stuff.

• 15:55Chuck Nice?

  The big hole in the ozone.

• 15:56Speaker 00

  If they had a big enough telescope, it didn't have to be a really big telescope, but maybe they could find that in the atmosphere. Hey, that, what do you think, zork? That doesn't look natural. So maybe, maybe that would be a thing. And of course, if they had a really big telescope, maybe you're talking about telescopes the size of downtown Baltimore or something. If you had a telescope really big, maybe you could see things like freeway interchanges and so forth. Or, and you can work this out, actually, the lights from New York City. Uh, you know, you could pick up that light, you'd see, gee, it's awful, awfully close to this. It's a sodium based light, right? All that orange light.

• 16:28Chuck Nice?

  Right, right.

• 16:29Speaker 00

  We're getting rid of those now, but for a long time. And maybe you could do that. It would take really big instruments. The easiest thing, pick up the radars, the television, the FM radio.

• 16:37Chuck Nice?

  So really, it's, it's, it's, it's more the signals than anything else?

• 16:41Speaker 00

  I think so. I think that that's, that's a point because that means that since we've only been doing that since the Second World War, really.

• 16:46Chuck Nice?

  Right.

• 16:47Speaker 00

  Probably nobody knows we're here. So, you know, those people who feel they're being abducted, you gotta ask, how come they came now?

• 16:52Chuck Nice?

  Mm-hmm, right. So now, in addition to that, uh, does that mean that the signals that we have, however weak, like our just regular television and our regular radio? Does that escape and go out as well? I mean, would somebody, let's say if they had the right listening equipment, be able to pick up a broadcast from 1930? It's just like, you know, like, "Good evening, ladies and gentlemen, on a ship from sea." Would they pick that up as well?

• 17:21Speaker 00

  Well, I don't know how they'd feel about the content, but they wouldn't actually be able to pick it up. Because AM radio is refracted by the ionosphere. That sounds kind of techie. But what it means is it bounces around the earth. In fact, that's why you can pick up a Chicago station here on the east coast, or whatever. So it has advantages, but it means that all those early radio signals didn't make it. Do we have a really quick question?

• 17:40Chuck Nice?

  Yeah, well, you know, I'll give you the question, and then we'll maybe take a break and we'll make it a cliffhanger. Okay, well, cliffhanger. All right, this is from Nicholas Loving on Facebook. "Are there any types of planets that have been theorized to exist, but haven't been observed yet? If so, can you provide some examples?"

• 17:58Speaker 00

  Wow, do you have a need to know? All right, well, we're going to take a short break. But we'll be back shortly answering more of your cosmic queries right here on StarTalk.

• 18:09Speaker 00

  Welcome back to StarTalk once again. I'm your all-star host Seth Shostak from the SETI Institute. And here joining me as co-host is comedian extraordinaire Chuck Nice.

• 18:19Chuck Nice?

  Oh, you're too kind.

• 18:19Speaker 00

  Well, you're extraordinary. And Skyping in from Penn State University, more or less, Jason T. Wright.

• 18:26Chuck Nice?

  More or less. Aspen, Colorado.

• 18:29Speaker 00

  They're on the same planet.

• 18:30Chuck Nice?

  Exactly.

• 18:33Speaker 00

  You were just about to throw a cosmic query at us, so let's go back to that.

• 18:37Chuck Nice?

  So Nicholas Loving, right before we had to take a brief respite, said to us via Facebook, "Are there any types of planets that have been theorized to exist, but yet haven't been discovered or observed? If so, can you provide some examples?" It's actually a cool question.

• 18:56Speaker 00

  It is, it is. Yeah, cubicle planets or something. All right, Jason? That's a tough one, actually, I think.

• 19:02Speaker 02

  It is. Well, you know, we find these planets that are about the mass, about the radius of Earth, but we don't know if they have liquid water on them. So I think that's the easy one. We'd like to really find one that's like Earth with liquid water and ice atmosphere like ours. But more exotic things, you know, sometimes you see in science fiction or something like that that there might be a moon of a planet, a moon of another planet, like something like Jupiter, a moon like Earth. And so we haven't actually found any planet-sized moons around bigger planets yet. And that's something that people are looking for, and that would be really exciting to find. We haven't found any binary planets, so two planets orbiting each other. That's been theorized. It could happen, but we haven't seen any of those.

• 19:45Speaker 02

  And then there's also ways that you can put more than one planet in the same orbit, so they have the same time to go around the sun, they're just in different parts of the orbit. And that would also be really neat to find. So those are my top, at the top of my wish list.

• 19:59Speaker 00

  Let me just reverse that very briefly, because one of the most common sorts of planets that we are finding are what are called super-Earths. It sounds like they wear capes. Super-Earths. But we don't have one in our own solar system. No super-Earths here. We have ordinary Earths. What's a super-Earth and why is it so new? And why are they so common?

• 20:16Speaker 02

  Yeah, well, I'll take it one at a time. So in the solar system, we have what we call the terrestrial planets, that are mostly rocks and metals, like Mercury, Venus, Earth and Mars, and they're all pretty close to the sun. And then farther out, we have the giant planets, the gas giants Jupiter and Saturn, and then the ice giants Uranus and Neptune. So we always forget those are the three kinds of planets. And sure enough, we find lots of gas giants, we find lots of things that are presumably ice giants. But it turns out there's an in-between kind of planet that, and we're not really sure, is it a sub-Neptune? Is it just an ice not quite so giant? Or is it a super-Earth? Not meaning it's much better than we are, just that it's much larger and more massive than the Earth.

• 20:57Speaker 02

  And so one of the surprises that's come out of these searches is that there are a lot of them. In fact, there are a lot more super-Earth slash sub-Neptunes than there are ice giants and gas giants. So one of the most common kinds of planets in the galaxy, we don't have a single example that we know of in the solar system. And interestingly, Proxima B, just next door, is a little more massive than the Earth. So, the, the very closest exoplanet turns out to be exactly one of, uh, one of this class.

• 21:29Speaker 00

  Super Earth, alright.

• 21:30Chuck Nice?

  Earth?

• 21:31Speaker 00

  Yeah.

• 21:31Chuck Nice?

  Alright.

• 21:32Speaker 00

  Prepare yourself. Okay.

• 21:35Chuck Nice?

  Well, that's a great, great, great answer. Um, let's move on to Benjamin Bottoms, which, I, honestly, I just picked his name because his name is Benjamin Bottoms. I don't know why I find that very-

• 21:46Speaker 00

  Not Benjamin Buttons.

• 21:47Chuck Nice?

  Yeah, not Buttons, but Bottoms. And I don't know why I find that so incredibly entertaining, but I just wanna keep saying Benjamin Bottoms for some... I'm sorry. I'm so juvenile.

• 21:59Speaker 00

  So, what's the bottom line?

• 22:00Chuck Nice?

  Exactly, exactly. Here we go. Uh, Benjamin from Facebook says this. "I would still love to know what SETI and NASA have been doing about seeing what flora and fauna will adapt and what will change under the effects of hypergravity, including higher masses found with Proxima Centauri, uh, and other exoplanets. I hope to do my own research on this, uh, though doing with, doing it with minimal resources."

• 22:30Speaker 00

  Right.

• 22:30Chuck Nice?

  In other words-

• 22:31Speaker 00

  Uh, uh, he's no different from us, actually. In that regard, at least, but-

• 22:35Chuck Nice?

  So, anyway, how, how would the development of flora and fauna be affected by stronger gravity, uh, on exoplanets, uh, maybe a super Earth? So, you got a super-

• 22:43Speaker 00

  Well, well, let me just start, but I, uh, uh, obviously turn this to Jason. Uh, you know, the, the gravity of a planet doesn't change very rapidly when you, you make the planet a little bit bigger, a little bit smaller. If I remember my high school physics correctly, I think it scales as the radius, more or less. So, in fact, if you, you know, all the other things being equal, if you had a planet that's 50% larger in, in diameter than, than the Earth, and maybe the Proxima B planet is like that, or 20% or something like that, then the gravity, yeah, it's a little stronger. And instead of weighing 150 pounds, you know, you'd weigh 230 pounds or something like that. Uh, I don't know that that would change things terribly much. I mean, the range of weights that we have, even as it is, certainly encompasses those kinds of changes.

• 23:27Speaker 00

  So, uh, hypergravity, I mean, I don't know what you mean by that. A hundred times the gravity of Earth, you're, you're not gonna find that on a planet, but I, I think you'd keep low to the ground. Jason, what would you, what would you say?

• 23:38Speaker 02

  Um, no, I, I agree with you. We don't expect the gravity to be too much higher. Uh, it, uh, I suppose you could put plants and things in centrifuges and subject them to, to high G-forces and see how they do. Um, but the topic of how Earth life in particular, uh, might adapt to other situations is actually one of considerable research. Um, NASA funds a lot of research into, uh, what are called extremophiles. That's Earth life that really thrives or lives at all, in fact, uh, in very extreme environments. So very hot environments, very cold environments, um, water that's extremely saline, um, very acidic environments, uh, and the idea is to what degree can life as we know it exist on, in environments

• 24:24Speaker 02

  as we don't know it, like could we have algae that live on Mars, for instance? And that's hopefully going to give us an idea of what sorts of planets are amenable to life as we know it, so that we know where to point our telescopes and try and find it.

• 24:37Speaker 00

  So what you're saying is having increased gravity may be the least of your problems.

• 24:40Speaker 02

  Yeah, yeah.

• 24:41Speaker 00

  It may not be attractive, but of course it will be attractive.

• 24:45Speaker 00

  Chuck, you're on for another question here.

• 24:49Chuck Nice?

  Uh, okay, let's go to, uh,

• 24:55Chuck Nice?

  let's go to John Roberts, uh, who's coming to us from Denver, Colorado. And John says this, "Of all the known exoplanets that can support life as we know it, how thoroughly are they being observed or listened to for signs of intelligent life?"

• 25:11Speaker 00

  Yeah, well, let's start with the observed part because in, in general, this may not be known by everybody, uh, we don't actually see these planets. Jason, how, how, how carefully are they being observed, man? Maybe you have a secret project here.

• 25:24Speaker 02

  No, um, no, that's a good point. A lot of the planets that we've discovered, we haven't actually taken a picture that shows a little dot and says, "There's the planet next to the star going around." Um, we often infer the planet's existence because as the planet orbits the star, in a, in a small way, the star also kind of orbits the planet. They orbit each other center of mass and we can detect that, that small wobble of the- Star and say, oh, there must be a planet there. So in those cases, we can't actually study the planet itself at all. And certainly not any planets that are cold enough that they might have liquid water on the surface. Might have, might have life now. The exception is when one of those planets passes between us and their star.

• 26:07Speaker 02

  And in that case, we can use the star's light to backlight the planet. And some of the light will pass through those planets atmosphere. And then we can study what the atmosphere is made of. And that, that's a subject of intense research. It's something that the new James Webb Space Telescope will do once it's launched to try and do exactly that. But for the moment, we haven't actually identified any planets that have atmospheres like ours. That we think do have liquid water on the surface like ours. So we have to find them first. But once we find them and can study them, then absolutely we'll, we'll, we'll observe them a lot.

• 26:42Speaker 00

  Could, could we find things like maybe some oxygen in their atmosphere and say, you know, I don't know what's there, but there's some plant.

• 26:49Speaker 02

  Well, that's right. So there's a lot of talk about what are called biosignatures. So what would you have to see on a planet to know that there's any kind of life on it? And if it's life as we know it, then absolutely oxygen would be a, a, a great signature. That there's some kind of photosynthetic life, although for almost any biosignature you can think of. There's some clever geochemist that can think of some natural process that, that would have created it without life. So, so it's, it's not necessarily going to be a slam dunk.

• 27:16Chuck Nice?

  Geochemists always the haters.

• 27:18Speaker 00

  Well, no, they're too clever.

• 27:22Speaker 00

  By the way, a part of that question was, are we actually pointing our radio telescopes in the directions of these worlds? To see if we get any signals. And the answer to that is yes, generally speaking, we do. But I mean, I have to point out the obvious, you, you know, the Klingons could have pointed their antennas in the direction of earth. For four and a half billion years and not picked up, I love Lucy, right? So the fact that you don't pick up a signal doesn't mean there isn't anybody at home.

• 27:42Chuck Nice?

  Right. And so, and, and the other thing is they have to be able to build something that would allow us to pick up a signal, right? That's what we're listening for.

• 27:51Speaker 00

  Yeah, yeah, they, they must have the technology as they said about this six million dollar guy. Yeah, yeah. All right, let's go to another question.

• 27:58Chuck Nice?

  All right, here we go.

• 28:01Chuck Nice?

  Here we go, Matthew, Matthew Mellorin, okay, Matthew, I think I got your name right. Matthew Mellorin says this, if an alien signal is detected by SETI, how much time would it take before SETI, as a team, can confidently determine that the signal is legitimate? And sorry, that's from Eric Coronado.

• 28:25Speaker 00

  Oh.

• 28:26Chuck Nice?

  Sorry.

• 28:26Speaker 00

  I guess Matthew wasn't actually.

• 28:28Chuck Nice?

  Matthew, Matthew, I'm sorry. I'm not gonna read your question.

• 28:32Speaker 00

  You just lost a listener there.

• 28:33Chuck Nice?

  Sorry, Matthew. Now, I'm gonna get to your question next, Matthew. So, that's a great question, though. What is the protocol?

• 28:38Speaker 00

  Yeah.

• 28:39Chuck Nice?

  What exactly is the?

• 28:40Speaker 00

  Well, there is a protocol. Everybody asks about the protocol. It sounds kinda evil to me, frankly, but there is a protocol, and it's like three typewritten pages or something. It's just a gentleman's agreement. It has no force of law, nobody stands behind it, nobody's gonna, you know, men in black are gonna show up and enforce it. They're not gonna do that, right? It would be maybe better if they did, because that means.

• 28:59Chuck Nice?

  I'm a little disappointed now.

• 29:00Speaker 00

  Yeah, there will be some budget somewhere for this work, right?

• 29:03Chuck Nice?

  I was totally waiting for Agent J to show up and give us the scoop.

• 29:06Speaker 00

  I keep waiting to see Will Smith walking in the office, but he hadn't done that. No, what it says is this, if you find a signal that looks like it's the real deal, the first thing you do is confirm it, to make sure that it's real, and that's, of course, the basis of this question, how long does that take? The second thing you do is you tell everybody, and the third thing you do is you refrain from sending anything back, aye, where the earthlings, you know, something like that, without sort of international consultation, so nobody feels that that's a bad idea. Okay, that's the protocol. It's apple pie and motherhood, I mean, nobody can argue with that. But, in fact, I can tell you what really happens, because we've had false alarms, and more than one, in which we've gotten a signal in which we thought, well, maybe this is it, right? And so, some people are reading the protocol, but it's irrelevant to read that, because

• 29:50Speaker 00

  what really happens is that as soon as you get a signal, there's no policy of secrecy. Everybody's, you know, tweeting and blogging and whatever, right?

• 29:58Chuck Nice?

  Exactly.

• 29:58Speaker 00

  And the media are going nuts, and your phone is, you know, melting down, because the, because the media wanna know, well, what about that signal?

• 30:05Chuck Nice?

  Right.

• 30:06Speaker 00

  And that's what really happens. Now, the amount of time it would take to get to the point where you'd say, okay, it's time for a press conference, all of which is, of course, you know, water under the bridge by that point.

• 30:16Chuck Nice?

  When does Jodie Foster get into this?

• 30:18Speaker 00

  Yeah, yeah. Well, I wish she would get into it, but, no, it would take, you know, on the order of five days a week, something like that, because you would have to get somebody at another. Uh, radio observatory to check the signal, because if, if you were the only one to get it, you know, it could be a Stanford undergraduate prank or something. So you've got to rule that out.

• 30:36Chuck Nice?

  You know how those Stanford undergrads are?

• 30:39Speaker 00

  Yeah, well, I pick on them, but they're nearby.

• 30:41Chuck Nice?

  Okay. So basically, the, the, the, the most important thing is confirmation.

• 30:47Speaker 00

  Yes.

• 30:48Chuck Nice?

  That's the most important.

• 30:49Speaker 00

  Yes, yes, because you, you know, it's a, it's going to be a big story. We know that. We've seen it happen. And because the public is interested. They see aliens every night on television, you know, in the movies, whatever. And they fully expect that they're out there, most of them. So it would be a very big story. And you don't want to say, hey, we found them. And then a week later say, well, actually, we didn't find them. That would, that would be a bummer.

• 31:08Chuck Nice?

  Never mind. All right. Hey, that's, that's pretty cool. Eric, thanks a lot. Um, let's now go to Matthew Mellorin, who I, I said I would get here, and I will, uh, from Facebook wants to know this. Will there ever be a way to detect exoplanets quickly without the need for long periods of observation? In other words, will there be a, uh, will there be a, uh, kind of like quick and easy snap to it like, hey, another exoplanet, there we go.

• 31:38Speaker 00

  Yeah, yeah. Well, they might put Jason out of a job. Jason, what do you think?

• 31:42Speaker 02

  Well, normally we have to wait for it to go all the way around the star. So whatever the planet's orbital period is, you want to have two or three of those. And so if it's a star, if it's a planet like the earth, that's going to take something like three years. But the other way is if you have a really, really good camera, something that can, uh, so, so just take a picture of the planet. And then it's just point and click. You point, you take a picture of the star. Oh, look, the dot there, that's the planet. And if you have the right kind of camera, it can tell you right away if it's the planet or not. Now, so that's the dream. It's called coronography. And, uh, there are chronographs that exist and, and they look for a long time. But if they look at the right star, in a matter of minutes, they know that they've found something that looks like a planet

• 32:25Speaker 02

  right next to it. So, yeah, hopefully we'll at some point get some space-based coronographic telescopes that can just point and click and find them pretty quickly.

• 32:34Speaker 00

  Yeah, that sounds like-

• 32:35Speaker 02

  Practically speaking, it'll take a while.

• 32:37Speaker 00

  That that sounds like Tom Hanks, right? Uh, in, in, in, what is it, the right stuff, whatever. That Tom Hanks puts his thumb up and blocks the moon.

• 32:44Speaker 02

  Blocks the moon, right.

• 32:45Speaker 00

  I mean, that's sort of what you're doing. You're, you're trying to block the light from the star, because that's drowning out the light from the planet, right?

• 32:52Speaker 02

  That's right.

• 32:53Speaker 00

  And you just want to hold a nickel in front of, in front of the star and see if you can see the planet, kind of thing.

• 32:57Speaker 02

  And it's a really hard problem. People talk about trying to, you know, find a firefly next to a searchlight in New York, but you're doing it from Los Angeles or something. I mean, it's a very difficult technical problem, and that's why, that's why we don't do it all the time right now.

• 33:10Speaker 00

  Terrific. All right, guys, we have to take another break. We'll be back right after this. We're back with StarTalk All-Stars. I'm Seth Schostak, your All-Star host. Chuck Nice, my comedic co-host, is sitting right over here.

• 33:24Chuck Nice?

  That's right, Seth.

• 33:25Speaker 00

  And sitting somewhat farther away is Jason Wright from Penn State University, where he studies stars, their atmospheres, their activity, and, for today's show, most importantly, their planets. All right, let's jump right back into talking about exoplanets, but we go to Chuck for another.

• 33:41Chuck Nice?

  Another cosmic query, this one coming from Jason Cook. Jason says this, "I've been hearing about the potential planet X that's being hunted. Could be a captured exoplanet. Would this mean that it was a rogue planet? Or could it have been caught from Schultz's star?"

• 33:58Speaker 00

  Schultz's star?

• 34:00Chuck Nice?

  Schultz's star, yeah.

• 34:01Speaker 00

  Yeah, that, that, that, yeah. I've never heard Schultz's star, but Schultz has presumably heard about it. Have, have you heard about Schultz's star, Jason? But you certainly know about Planet 9, but...

• 34:10Speaker 02

  Sure, yeah, I, I, I haven't heard of Schultz's star. If, if there is another planet in the solar system, way out in outer solar system, it's very weakly attached to the solar system. And so, in principle, I suppose, it, it could have been captured by the Sun, which would make it, yeah, a rogue planet, which is one that used to orbit another star, but had some sort of gravitational tussle with another star or planet and got ejected and was floating around in space. So, I'm not an expert on it, but that, that sounds like a distant possibility.

• 34:42Speaker 00

  Yeah, well, there are probably a lot of rogue planets out there, right? I mean, people have done sort of theoretical modeling of all this, so they do it in the computer. And, you know, you build a whole bunch of planets, and maybe a third or a half or something like that of them get kicked out of the nest in the very early days, and they just wander in space, eh, eh, eh. So, you know, you never see them again. Maybe this was one.

• 35:03Chuck Nice?

  So that's, so it's a possibility.

• 35:05Speaker 00

  Possibility.

• 35:05Chuck Nice?

  So the answer to your question is yes. Okay.

• 35:09Speaker 00

  Concise.

• 35:12Chuck Nice?

  Uh, here we go. This one from, um, Tom Donovan says this. Of all the stars we can see with the naked eye, which are stars in our galaxy and which are galaxies outside of the Milky Way? What percentage of the stars we see are individual stars? And what percentage are actual galaxies?

• 35:33Speaker 00

  Right. I think that that's a fairly easy one. At least if you're in the northern hemisphere, even if you're in the southern hemisphere. Jason, you want to take that?

• 35:39Chuck Nice?

  Go ahead.

• 35:39Speaker 02

  Sure. Yeah, they're all stars in the Milky Way galaxy. Anything you can see with the naked eye. There are a couple of examples of other galaxies, but they, they don't look like stars. They look like these fuzzy blobs.

• 35:50Chuck Nice?

  Right.

• 35:51Speaker 02

  So in the northern hemisphere, you can see, uh, the Great Galaxy in Andromeda. And from the southern hemisphere with your naked eye, you can see the large and small Magellanic clouds. And those are other galaxies near, near the Milky Way.

• 36:03Speaker 00

  Yeah. So, so everything you see is a star.

• 36:04Chuck Nice?

  Everything is a star.

• 36:06Speaker 00

  It's like Hollywood, right? So, and, and, and by the way, this is something, uh, I, I found interesting when I first learned about it. Most of those stars are what are called giant stars. They're really big, bright stars. You're not seeing the typical stars because they're too dim. You're seeing the brightest ones, right? It's like looking at only the front row of your classroom. You're only seeing the brightest students. That still works that way, right? Okay.

• 36:29Chuck Nice?

  Very cool. All right. Um, oh, I want to read this question because it sounds like this person might have a little bit of an issue with you, Seth.

• 36:43Speaker 00

  Not the first.

• 36:47Chuck Nice?

  God, I'm going to find out who it is, but I, I, I lost the actual question. But here's what she wanted to know. Aren't we overstating the importance of intelligent life?

• 36:58Chuck Nice?

  I mean, isn't the idea just to find life? So, is that, is that an argument to be made?

• 37:06Speaker 00

  There is, there is. Actually, where I work, at the SETI Institute, ninety-five percent of the scientists there are not looking for intelligent life. They're looking for life. And, and they're looking nearby, where you can get some, you know, media data by sending a rocket somewhere. Mars. Or, but there's six other places besides Mars where there might be life, you know, essentially next door. There are three moons of Jupiter, there are several moons of Saturn. These are all places where you might have some liquids, right? Most cases, liquid water. And if you have liquids, then you get chemistry, and if you have chemistry, maybe you'll cook up something alive. So, yeah, if you want to find life, that's maybe the way to do it. And that's where all the big money is. That's what NASA is doing, right? Uh, but intelligent life, you know, most people, if, if you say, hey, we're gonna use your tax dollars to find pond scum on Mars. And they'll say, yeah, okay, that sounds okay.

• 37:50Speaker 00

  But if you say, how about looking for the kind of life that could hold up its side of the conversation? Intelligent life? I think they're more interested in that, that's my bias, but I think they're more interested in, because those are the kinds of aliens they see in the movies.

• 38:01Chuck Nice?

  That's so true. There you go. Oh, that's excellent. Um, let's look, let's listen to Joe Cumming. He says, "Life as we know it is carbon-based, with a lot of hydrogen, oxygen, and nitrogen mixed in. Is it possible that life could have a different elemental makeup in a world where other elements may be more suitable for reactions to that lead to life?"

• 38:24Speaker 00

  Sounds like a perfect question for our astrochemist, astrochemist Jason Wright.

• 38:27Chuck Nice?

  Yes, Jason.

• 38:29Speaker 02

  All right, well, I'm a little weak on the astrochemistry, but yeah, absolutely. I mean, this goes back to the science fiction on Star Trek. They had the Horta, the silicon-based creature that they encountered. Um, so, we definitely try to keep an open mind about what life could be like. That it doesn't have to be carbon-based. Maybe it doesn't even have to be on the surface of a planet. I mean, there's old stories about, you know, the dark cloud, the black cloud in space that is self-intelligent. So, um, it's good to keep an open mind. Um, on the other hand, we also have to tell the engineers that build our telescopes and instruments what it is we think we're looking for. And we can't just say, "Look for anything out of the ordinary."

• 39:08Chuck Nice?

  So we generally start with looking for carbon-based life. But it's true that, for instance, silicon is really common on a lot of planets. And so absolutely, we should, we should think about that, too.

• 39:20Speaker 00

  Yeah, actually, Isaac Asimov, the famous writer.

• 39:23Chuck Nice?

  Yeah.

• 39:23Speaker 00

  He was a chemist by training, and he actually wrote a paper in which he investigated what other elements in the periodic table, right, could, could be, form the basis for life, and silicon is the best. Uh, but really, none of them work as well as carbon. The fact that we're carbon-based isn't so much an accident, I think.

• 39:39Chuck Nice?

  Right, it's, yeah, it's because it, it works. And most likely, I mean, nature does what, what works best, right?

• 39:45Speaker 00

  Yeah, well, it'll do that sooner, and then there's.

• 39:47Chuck Nice?

  Right.

• 39:48Speaker 00

  As soon as you have one kind of life on a planet, probably it beats all comers.

• 39:51Chuck Nice?

  There you go. All right, good question, though. Um, here's one from Gabrielle Keegan, who wants to know this. Gabrielle says, uh, this is basically for you, Seth. What kind of signal is SETI searching for?

• 40:08Speaker 00

  Yeah.

• 40:08Chuck Nice?

  Do you, do you know what you're looking for when you're listening?

• 40:10Speaker 00

  Well, we, we, we have to guess. I mean, it's, it's very analogous to what we just heard about, you know, how do you build a telescope to look for the signs of life? We look for simply a lot of energy at one spot on the radio dial. Okay, so it's what's called a narrowband signal. And all that means is, i- it's a signal sort of like you would pick up on your car radio. You know, you're turning the dial, trying to get that country and western, uh, station. I know that's what you listen to, Chuck.

• 40:33Chuck Nice?

  Oh, you know it is.

• 40:34Speaker 00

  Right, and, and, you know, you just hear static, static, static, and then you hear this squeal, and then there's the station. And it's the fact that that station's at one spot on the dial, eight, 10 kilohertz, or whatever it is, that you know that's a transmitter. So we're not worried about the, whether they're sending us the value of pi, or the Fibonacci series, or prime numbers, or any of the things that they do in the movies. We just want to find a signal that's at one spot on the dial. That turns out to be a lot easier than worrying about what the message may be. So that's what we look for. If you find that. You can be sure that somebody will have the capability of building a much bigger instrument and going back and saying, "Well, are they saying anything? Is there a message?" That sort of thing.

• 41:10Chuck Nice?

  Gotcha, gotcha. So it really is just a signal?

• 41:13Speaker 00

  Right. You just want to see the "on the air" sign is lit.

• 41:15Chuck Nice?

  Exactly. Cool!

• 41:17Speaker 00

  Now it's time for the lightning round. It sounds dangerous.

• 41:21Chuck Nice?

  Yes.

• 41:22Speaker 00

  So, so, lay it on us there, Chuck, and let's, let's...

• 41:26Chuck Nice?

  Yeah, this is where we'll move and try to answer as many questions as quickly as possible, and you will let us know when you are finished answering by hitting a little bell.

• 41:37Speaker 00

  All right.

• 41:38Chuck Nice?

  Okay, so here we go. From Chaz Murray. Chaz Murray wants to know this, not necessarily about SETI or XOPs, but what is being done to detect and avoid incoming objects that could really hurt us? So, does SETI do anything with that in terms of...

• 41:54Speaker 00

  Yeah, we, we have some asteroid experts, so they worry about it. There are two problems. One, you gotta find them, and if you find one that has your name on it, it's headed our way, you gotta deflect it. And there has been research on both of these. I can tell you if this will make you sleep better at night, that you don't have to worry about really big ones hitting. There's something that could take out, you know, downtown Manhattan, but those we don't know about yet, but we're working on it.

• 42:15Chuck Nice?

  Okay, all right. And no, I'm not gonna sleep better.

• 42:17Speaker 00

  Oh.

• 42:18Chuck Nice?

  Sorry to let you know, that didn't comfort me at all.

• 42:21Speaker 00

  Maybe medication.

• 42:22Chuck Nice?

  Thinking of the destruction of downtown Manhattan.

• 42:24Speaker 00

  All right.

• 42:25Chuck Nice?

  And goodnight, Chuck. All right. Jason Watson wants to know this. "Once you go alien, do you go back?"

• 42:32Speaker 00

  All right, that's cool, 'cause I think I'll leave that for the other Jason.

• 42:39Speaker 02

  Well, you know, I do most of my research on, on stars and exoplanets and stuff, but I've, I've started to do a lot of, of work with, with, with SETI and, and thinking about these projects. So, uh, yeah, you could go back and, and, and work on the other stuff.

• 42:53Chuck Nice?

  Okay, all right. Leon Gold from Twitter says this. "How could we detect the presence of intelligent life on an exoplanet?" So, uh, I mean, it's, yeah.

• 43:09Speaker 02

  Well, I would, I would, I would point one of Seth's radio telescopes at it and, and look for their signals. And I think earlier we talked about, you know, you might find something weird in the atmosphere, like a chlorofluorocarbon that could only be created artificially.

• 43:22Speaker 00

  Yeah, that, that's the thing. I mean, you know, maybe they'll send a rocket with their encyclopedia in it, and it just lands in a field somewhere. Doubtful, but...

• 43:29Chuck Nice?

  Alrighty, Neil Califf from Twitter says this: "One year on Proxima Centauri is 11 days. How could this impact our everyday lives if we lived on the planet?"

• 43:43Speaker 00

  Yeah, I'd get into the birthday candle business.

• 43:45Speaker 02

  This is a good question, because we didn't mention before that Proxima B is in the habitable zone. It's got the right distance to have liquid water, so this isn't a pure hypothetical. Maybe someday we'll be there. It means that the seasons only take 11 days, you cycle through all of them. And in fact, it's so close, it could also mean that the star is what we call tidally locked, which means the sun never rises and the sun never sets. So that's a big deal. Either it's daytime, or it's nighttime. There's just one time zone where you are, and the time never changes.

• 44:16Speaker 00

  Yeah, that'd be easier for plants, wouldn't it? They don't have to rotate around to follow the sun. I mean, they can always be pointed in the same direction. Yeah?

• 44:22Speaker 02

  Could be.

• 44:23Speaker 00

  Could be, could be. Alright, that was so tentative.

• 44:26Chuck Nice?

  Alright, AnythingForSalinas, that's the actual handle, AnythingForSalinas wants to know this: "Is there an estimate on how old KIC 8462852 is? And how does a system's age affect SETI?"

• 44:44Speaker 00

  Yeah, well...

• 44:46Speaker 02

  Alright, so the estimate for the age of that star is pretty poor. We know it's not super young, it's not like an infant star, and we know it's not about to blow up, but it's a couple billion years off.

• 44:56Speaker 00

  Adolescent star.

• 44:57Speaker 02

  That is what we can do. It could be youngish, it could be oldish, that kind of star is very hard to know.

• 45:03Speaker 00

  It could be youngish, it could be oldish, like the parties you go to, right? Yeah, okay, but at least a few billion years is long enough to cook up something interesting. It took four billion years to cook up Homo sapiens here, but, you know, maybe if a rocket wiped out the dinos 100 million years earlier, we would have had a, you know, we'd have the cure for death by now. I don't know. Okay, next question.

• 45:23Chuck Nice?

  Alright, here we go. Bob, oh, Ben Harb, Ben Harb wants to know this: "Do you think we will be able to mine resources from exoplanets in the future?" I mean...

• 45:36Speaker 00

  Yeah, transport costs are gonna be something, but, Jason, what do you think? Are you investing in this?

• 45:41Speaker 02

  Yeah, sure. If we're, uh, I mean, you gotta get there first. That's the problem. But sure, you give us, give us a million years. We've got settlements on those exoplanets. Yeah, they'll certainly have, uh, they'll certainly have things to mine and presumably we will have to mine them to build our settlements and our rocket ships and supercomputers and whatever else we're doing a million years from now.

• 46:01Speaker 00

  Yeah, but we're gonna mine stuff that's a lot closer to us.

• 46:04Speaker 02

  Oh, sure. We've got asteroids out there.

• 46:06Chuck Nice?

  Yeah.

• 46:06Speaker 02

  We've got asteroids on our solar system.

• 46:08Chuck Nice?

  It'd probably be, it'd probably be more feasible to mine an asteroid before we get to a, a, a planet that's more like years away.

• 46:15Speaker 00

  There are companies that are putting money into that. I mean, it's for real. You could, I don't know if you wanna sink your life savings into it, but you could.

• 46:20Chuck Nice?

  (laughing) All right. Um, hm, hm, hm. I like this. Uh, Getano Marrone. I, I, I think that's your name, Getano. I'm sorry. Uh, Getano Marrone says this. "Which conditions would create a stable or visibly non-spherical planet, such as a disk or a donut?"

• 46:44Speaker 00

  Yeah, donut planet.

• 46:45Chuck Nice?

  A donut planet.

• 46:46Speaker 02

  Yeah. So the thing with planets is the, the gravity is always gonna pull them into a spherical shape.

• 46:52Chuck Nice?

  Right.

• 46:53Speaker 02

  And so if you wanna get something that's not a sphere, you basically have to put it around it. So you could do one of these binary planets. You could have a ring of material like Saturn. But if you took the Earth and you made it into a donut, it would just squish itself back into a sphere under its own gravity.

• 47:06Speaker 00

  Yeah, yeah. Well, of course, you know, you could, could create an artificial planet, of course. If you're really in advanced society, you know, sort of a super duper space station, and then maybe the donut shape is, uh, not so crazy.

• 47:17Chuck Nice?

  There you go.

• 47:18Speaker 00

  Yeah.

• 47:18Chuck Nice?

  I don't know why, but...

• 47:19Speaker 00

  Make your eyes glaze over.

• 47:20Chuck Nice?

  I'm very, very hungry.

• 47:21Speaker 00

  Are ya? All right. Well, we, we have, uh, one more minute here. I don't know if you can get another, uh, another question in there real quickly.

• 47:28Chuck Nice?

  Here we go. Uh, "What is the biggest, uh, uh, for humans? What is the..."

• 47:35Chuck Nice?

  Biggest a habitable planet could be, or really the smallest for us to be there.

• 47:41Speaker 00

  Yeah, real quick.

• 47:42Speaker 02

  So if you've got a planet like the Earth, it's going to be a little smaller than the Earth, or a little bit bigger than the Earth. But if you get too much bigger, it's probably not made of rocks, it's probably made of gas and ice, and that wouldn't be very habitable.

• 47:53Chuck Nice?

  All right. Our planet is pretty much the size that we...

• 47:57Speaker 00

  This is the size.

• 47:59Chuck Nice?

  This is the size.

• 48:00Speaker 00

  All right. Thanks so much to all of our wonderful listeners for those truly amazing questions. Unfortunately, we're out of time here on StarTalk All-Stars. Thanks to Chuck Nice for co-hosting tonight. It's a pleasure. And reading all those great questions. And to Jason Wright for sharing his wisdom with us. Thank you, Jason. Pleasure. I'm Seth Shostak. I suggest to you that you might want to check out Big Picture Science. You can find it on all the usual podcast locations, and it may be on your local radio station as well. This is Seth Shostak. I've been your StarTalk All-Stars host, and as always... We'll be watching the skies. This is StarTalk.