Rogue Planets & Exomoons with David Kipping

Welcome David Kipping

0:00So Chuck, love me some David Kippen. Yes. He gets on his skateboard, comes down from Columbia, catches us up on all the cool stars out there. And I gotta tell you, you're not supposed to say it, but he's very good looking. Coming up on StarTalk.

0:19Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

0:32This is StarTalk. Neil deGrasse Tyson, your personal astrophysicist. Got with me, Chuck Nice, baby. Yeah, what's up? What's up, Neil? Chuck, baby. Hey. All right. This is going to be a Cosmic Queries. Oh, okay. Good. One of our favorite people out there in the hood. That's right. The boy band of astrophysics. A boy band of one. A heart throb, no doubt. We have the one, the only. David Kipping. David, welcome back to StarTalk. I don't deserve the introduction, but I will take it. Thank you.

1:02Very kind. And I have to announce that you're based in Columbia University, which is up the street a couple of miles, and you skateboarded here. There wasn't even a skateboard. What do you call the thing with the single wheel? Oh, that's a unicycle. That's what it is. That's what it is. It is a unicycle. I hate this. Literally. Yes, yes. Hoverboard style. Yes. Yeah, yeah. So, you are Associate Professor of Astronomy up in Columbia.

1:35That's where I got my PhD, at Columbia University. And you are the host of Cool World's podcast. Cool World's YouTube show and a podcast. Yes. Yeah. Yes. Cool World. The same name. Cool World's. I always find people get confused. I say, even when I just had a YouTube channel, and I'd say, I'd describe to people, they're like, oh, so tell me about your podcast. I'm like, no, no, that's a different, a podcast is a different thing, at least in my mind. Yes, yes. So, we have a main, why do you like these kind of mini documentaries about space and universe and things I'm working on, and then we have the podcast.

2:07So, it's the Cool World podcast and YouTube channel. You got it. There you go. Yeah. So, David, you study exoplanet. That's right. Yeah. Last I checked, we were rising through 6,000 of these things. Wow. In the catalog, pushing 7,000. I've stopped counting at this point. Right, yeah, yeah. At this point. But I'm old enough to remember when there were none. Yeah. Okay. Right. Back in the day. Well, they were there.

2:30But we got to get right to it.

Discovering an exomoon

2:33We're a planet. We're presumably an exoplanet to aliens orbiting some other star. Right. Yeah, absolutely. But we have a moon. Hmm. So, what's this I hear that an exomoon was recently discovered? Yeah, there was, in the news recently, CD35, a load of letters, B. Just call it CD35B for short. CD, is that the name of the catalog it came from? That's the catalog. I have no idea what the CD is supposed to stand for, but that's the boilerplate name going around.

3:07And what's interesting about this object is it's a brown dwarf that orbits a M-dwarf star. And around that brown dwarf, they see evidence for a companion. And the question is, is that a moon or is that a planet? So, a brown dwarf, again, is not quite a star, a little too massive to be a planet. So, this is an object which is in between the mass of, say, 13 Jupiter masses to about 80. And 80 is the point where you have enough mass for hydrogen fusion to happen.

3:39So, you can shine like a star. But below that, you can actually still have enough mass for deuterium fusion to occur. But there's hardly any deuteriums. It's not a very efficient process. So, you're like a reality star. Yeah. You're on that C tier. Like, I was big on Bravo for a while. Right. So, you know that people who story brown dwarfs get kind of edgy about that kind of stuff because they're like, no, no, it's not a failed star. Yeah. It's an overachieving planet, right? So, it depends how you frame it.

4:09So, says the therapist. I was going to say, I'm going to tell you the truth. I'd rather be Jupiter.

4:16I'd rather be Jupiter. King of the planets. That's right. Just king of the planets instead of the overachieving not quite a star. You have a red-blooded star, a almost star, not quite a star, too much to be a planet thing. Right. And that's not weird to have a brown dwarf orbiting a star. No, that's right. So, this is the first time we found basically a triple system. An object orbiting an object orbiting the object where two of them are not stars. Well, not quite because we have binary stars.

4:47Right. No, I'm saying this is where two of them are not stars. He said two of them are not stars. Yes. So, it depends on how you think of the brown dwarf because some might say the brown dwarf and the star is kind of a binary star system. Yes. Yeah, but you can't, you just eliminated that possibility by degrading it to a not quite star overachieving planets. So, did it make the news because we don't really know what to call it? It's not that it was some major astrophysical bit of enlightenment.

5:19Is it just who ordered this kind of thing? I think it's a bit of both. I mean, first off, there is an object almost identical to this one that we discovered before. It's like HD 206 something, something or other. That's a very similar configuration. They use a different method to find it and they're not as confident. So, they say this is a candidate object around a brown dwarf around a star. The authors of this paper are much more confident. They're like, this is legit. This is definitely something there. And so, who's lead author on this? Kevin Hoy. So, it's a Chilean group who led this using the VLT, take observations.

5:50And they're able to measure the wobble, the Doppler wobble of this object. And that's where they get this evidence for. But, yeah, if you go, if you turn to the IAU definitions, they're actually pretty clear. And they say that this thing's a planet. Anything in orbit of a brown dwarf is a planet according to those definitions. Now, we can argue about those definitions, but it's... Oh, so it doesn't then say, suppose the brown dwarf is orbiting something else. It doesn't say anything about it. It says, no matter how, when it says, actually, specifically, no matter how it formed, what it's doing, what color it is, whatever it is, if it's between 1380 Jupiter masses, it's

6:23a brown dwarf and anything in orbit of that, again, doesn't really matter, is always a planet. Wait, but suppose I have a binary brown dwarf orbiting the main star. You can't call that a planet. No, then it's a binary brown dwarf. Yeah. Because they actually do have a, it's a footnote of if it's more than, less than 1 over 25 mass ratio, then it's a binary. So this object is 1 over 37 mass ratio. So that's in moon category right there. Planet category, I'd say. There is no moon category in the IAU definition. The IAU says there's no word moon or satellite anywhere in this document.

6:57So that's why there's an ambiguity here. Yeah, I think so. Yeah. We should bring the Pluto haters back because they know how to. They know how to get things done. Yeah. Without a doubt. Yeah. You know. Okay. So is it something to be excited about or is it just something to add to the catalog? I think it's definitely an exotic object. I look for exomoons, as you know, and for me, the reason why I do it is because I want to understand how common is the earth moon system, how common are the moons around Jupiter, like how common is us, like our backyard, you know, where do we come from? And this object, as cool as it is, doesn't really speak to anything familiar to that which

7:30we have in the solar system. So it's an exotic object. No, that's the rub right there. I love it. It doesn't fit. The way you originally described it, it's very exotic. Yes. And that's, yeah, that's what makes it. Which is cool. I like a bit of exotic. Which is what makes it exciting. Yeah. But I also want to understand our story. Right. Yeah. Right. How did this Chilean group discover this exomoon? I think this brown dwarf was already known and they were able to separate the light from the brown dwarf and the star using a chronograph. And then they were able to measure the Doppler shifts of the light from that brown dwarf.

8:01Wow. So it's kind of similar to how we discovered the first exoplanet around 51 Pegasi b. That was just a star by itself and we saw the Doppler lines. Here it's harder because you've got two sources of light. So you have to do that separation first. Disentangle that. Right. And then you can actually look for things around the brown dwarf. Wow. So, but they had to know to think to do that in the first place. Yeah. Yeah. Okay. It's not easy work. Yeah.

False starts in alien life

8:22So now you recently submitted for publication a paper that explores life on exoplanets, but that's quite the cottage industry. It's, you know, not a few months go by before another result. We found some chemistry in the atmosphere that means there's life on the surface because you can't see the surface. Right. It's too small, too distant, too dim. Right. But the chemistry pops out. So what are you, how are you adding to that conversation? You know, I was just frustrated as someone interested in the search for alien life that we keep seeing so many false starts, right?

8:53So you've had, you go all the way back when I was a kid, I remember Bill Clinton stood on the White House lawn talking about the Alan Hills meteor. Yes. As evidence for life. And of course that evaporated. We've had recently K-18B, this evidence of dimethyl sulfide that everyone got excited about could be life. And again, it's been challenged. Then we had Venusian phosphine. And so we just seem to have like time and time again. So dimethyl sulfide, and there's also dimethyl disulfide, right? I think there were two. Yes. Well, the original claim is just DMS, but now they think there's that as well. So on Earth, phytoplankton. Okay. The boys that do photosynthesis. The basis of everything here.

9:25The basis of everything. Right. They're the ones that give us these dimethyl sulfides. Yeah. And so if you're going to find that on another planet. It's possible. So then that's headline making. That's really cool, that. So has that been retracted, that discovery? It's not been retracted, but other authors have come up with other ways you could plausibly expect to have this atmosphere without necessarily life being involved. And you want a strong result. So this is kind of frustration we have that every, it seems like over and over again, someone sees something which looks like evidence of life.

9:56And then six months later, a theorist comes along and says, oh, by the way, I think of a way of doing that without life involved. But that doesn't make them right. Doesn't make them right. So have you found a way to make an airtight argument here? Well, I tried to point out two things. One is that as we plan these new observatories, like the Habitual Worlds Observatory, which will be the successor, hopefully, to James Webb, another multi-billion dollar telescope we're planning right now, we have to confront the reality of this epistemic problem that will

10:28be persistent, I think, for generations to come. And I suggest that one strategy could be kind of what we do in YouTube space of A-B testing. So instead of just looking at a bunch of things and saying, how often do I detect dimethyl sulfide? How often do I detect a biosignature? Split your group into two categories and accept that there will be some number of confounders in these two groups. But hopefully you can design these two groups such that the confounder rate is the same, but the life rate is somehow different.

10:59If you can do that, I'm not saying it's easy to do that, but if you can do that, you can solve this problem cleanly, statistically. And that's kind of the whole premise of my paper, that we need to think about the strategy, not just the technology, but really how we even approach this question. So is that similar to, because I remember back during the, was it the Challenger disaster? Any disaster, they bring in all the evidence and then come up with a conclusion. What I always think they should do is they should bring in only half the evidence

11:29and see what you conclude. Oh yeah, yeah. And then you add to it and see if the conclusion remains. Yeah, if the last bit of evidence is what tips it, then it means most of the evidence wasn't really pointing to that result. Yeah. And in science, you want the more evidence to align with what your thoughts were. Right. Otherwise, go home. Right. Yeah. Yeah. Right? Yeah. I mean, in statistics, we call that cross-validation. Cross-validation. Okay. I like that. When you block out some of the data, you do all your fits on the data you have,

11:59and then you uncover your hand and ask which one actually works. Yeah. And that's like the true discriminatory test of which one is working. Okay. That's cool, man. So this will be a way to keep people on notice. I think it's an important question. It's the question we all care about, right? Yes, of course. I think it's where there's life out there, and I just want to get an answer before I die, right? I hope that HWO succeeds. This is a major motivation of science. Yeah. I want to get it done before I die. Before I die. Right. Don't worry. When you die, Jesus will tell you all the answers. Okay? So you don't have to worry. He'll be right there. Bye.

12:29Bye. Bye. Bye. Bye. Bye. Space fact. If Earth rotated once in 90 minutes, rather than in 24 hours, the centrifugal force of that rotation would render everyone on the equator weightless. If you like that fact, you can find 4,999 more in Lost in Space.

13:075,000 facts to help navigate the universe. Latest collaboration between StarTalk and National Geographic Books. Lost in Space is now available for pre-order wherever books are sold. This is a Cosmic Queries.

Atmosphere of LHS 1140B

13:35You have a huge fan base out there among our followers. And so, Chuck, you got it lined up? I have them right here. Okay. And you haven't seen these questions, right? They're coming right out of the blue for you. Cool. Good for... Yeah, that makes three of us. I didn't call it. Okay. And these are our Patreon supporters who have given us $5 a month. Right. Which qualifies you to be able to submit your query. All right. Here we go. This is Andor Klomp, who says,

14:08Dear Dr. Kipling, Dr. Tyson, Lord Nice. Kipping. Kipping, sorry. Dear... I said Kipling. Oh. I made you quite literary, didn't I? Kipling and... Widger and... Widger and... Exactly. I say, oh boy. Anyway. Dear Dr. Kipling, Dr. Tyson, Lord Nice.

14:27LHS 1140B has a confirmed atmosphere. 48 light years away. If microbial life lives there under ice or in its ocean, what would be the very first sign we would detect from this distance? Greetings from Rotterdam, the Netherlands. And so if I remember from the news, 1140 is a rocky planet, right? Well, we're not sure. That's a good question. We're actually not sure.

14:58Oh, really? Yeah. So actually, it's probably almost certainly not rocky, to be honest with you. Really? Okay. It's about five and a half Earth masses. All right. But it's 1.7 Earth radii. Okay. So when you do the math, that gives you a density that is actually similar to that of the Earth. Sounds like it. Right. But... So that's why they... That's why all the news was, rocky planet found. Right. So you might think that's rocky. But the problem with that is, is that that's compressed density, right? There's 1.7 Earth radii squeezing all that self-gravity. So if you kind of relaxed it, it means that the stuff that it's made of must be lighter than rock.

15:30It can't just be pure rock. It can't have squeezed in that way. Correct. So it's probably some rock and then something on top, like a big envelope of gas or maybe an ocean or something in between, like ice or something. So something's confounding those blunt calculations and confusing how to interpret. I mean, it's a challenge because we have nothing in the solar system to point at and say, oh, that's what it must look like. Again, there's the problem. There you go. Right. The solar system is not a thing. It's in between Earth and Neptune. It's okay.

16:01And we just don't really know what those things are. Does that nullify the inquiry here? No, it's at the right distance from its star, potentially for liquid water, if it has water. Yeah. It's in the Goldilocks zone. And it's small, so it seems like it would be potentially possible that it could have had a water delivery. It's not a gas giant. So if it has life on it, which I think is possible, it's not an Earth-like planet. I want to be clear about that. It's not an Earth-like planet, but it could still have life nevertheless. And then maybe we could look for things like phytoplankton, like this dimethyl sulfide

16:34signature that we talked about earlier. We could look for oxygen. You could look for methane. You could look for some of these gases. But then it kind of comes back to that original question of like, well, then how are you sure that if you see methane, that really is life? So that's just an unsolved question. So here's what I want to know, all right, just has really nothing to do with this, just because you said something that triggered me. All right. When it's Goldilocks zone, right? Yeah. The star that creates the Goldilocks zone, you said the right distance.

17:05Does that distance change on the size of the star and the age of the star? And do stars burn cooler when they get older, increasing or decreasing the Zodiac? The Goldilocks zone. Yes, yes, and no is the short answer to those three questions. Wow. There you go.

17:24That was easy.

17:27Yeah, I wasn't tracking it to be that efficient in my reply. We're done. Next one. No. Yeah, all stars. This is actually an M-Dwarf, so it's a small star. I'm not sure if it's exact mass, but it's less than half the mass of the sun. So that's why it has this red dim light. That's why it's in the LHS catalog, because it's nearby, but it's not a visible star. It's not a naked eye star. You can't see it with a naked eye, so you have to take telescopes to detect it. But it is nearby. The star, because it's less luminous than the sun, means this Goldilocks zone is much closer.

17:57Much closer. Right. And, yeah, as it ages. And importantly, for these cooler stars, cooler, there's thousands of degrees, the Goldilocks zone is not only closer, it's narrower. Ah, okay. Okay. Okay. So the hotter stars get bigger Goldilocks zones. Right. So these are, in the statistics of Goldilocks planets, this matters. Okay. Yeah, of course. Yeah. Okay. And just to finish that point, as it ages, the Goldilocks zone will actually move out, usually, for main sequence stars. Right. So it should, as the sun is increasing luminosity, it was about 30% less luminous four billion years

18:27ago than it is today. I think that's roughly about right. Yeah, that feels right. So that means the Goldilocks zone is moving out. Right. We used to be on the outer edge of the Goldilocks zone, and now the Earth is on the inner edge, which is why we're so sensitive to CO2, right? If it wasn't, if we were two billion years ago, we could have probably polluted a lot more and not worried about it. But because we're on the inner edge of the Hadron zone now, we have to kind of worry about this a bit more. Yeah. A lot more. Yeah. Wow. We'll go back four billion years. Neither one. Yeah, exactly. All right. Yeah, let's go on. Here we go. This is Alejandro Guardado.

18:59He says, he says, hello, Dr. Tyson, Lord Nice, and Dr. Kipping, Alejandro here from Washington State. Hello. Or should I say, hola? That is not what's in there. I know it's not. That's what you said.

19:24Oh, God. Okay. He says this. Let me stop messing around. He says, I'm sorry. I got to agree. That's what Alejandro should sound like. If he don't sound like that, he should take some lessons. Exactly. I just see him sitting around drinking an espresso with Antonio Bandera. Yeah, exactly. That's what I'm about.

Searching for technological life

19:45Yeah.

Searching for technological life

19:46Okay. All right. Here we go. This is what he says. My question is, in our search for life in the universe, why does it matter if aliens are intelligent? Should the search for intelligent life be simplified to just life? Would the simplification lead to less fear in our society about aliens and lead to advances in the search? Thank you for always keeping me curious. NASA, in the day, used to have interest in the search for life.

20:16Okay. Which included the search for intelligent life. Okay. And then it ended up in the sites of William Proxmire for the Golden Fleece Award, which was given to agencies who do research on public money for things that he judges is a waste of money. Golden Fleece. Okay. And so NASA, in the search for intelligent life, he viewed that exercise as completely beyond the pale. And so NASA, in response, separated the search for life, which is of interest to everyone,

20:51biologists and everybody, from the search for intelligent life. And in that separation, they forfeited the search for intelligent life, and that was picked up by SETI. Right. SETI is talking about that. Okay, so there's a whole SETI institute, which is privately supported. Yes. And so, kind of in response to this, they are two separately funded activities. Now, if someone on your exoplanet waves to you, you don't have any problem with that, but that's not what you're after. You're looking for any kind of life at all. I think, I mean, I would especially be interested in life that was technological.

21:24I try to avoid the word intelligent, because we may not even have intelligent life here. Yeah, that's been established. Yeah. But technological life, I think, is something we could look for, and it's pretty interesting if that's out there. It does answer a different question, because it's one thing to say, okay, a planet has some kind of life, microbial life, but what if in the evolutionary chain that gets from there to something like us, there is what we call a great filter, some point, which is a bottleneck, which makes it incredibly unlikely that the animals ever develop past a certain

21:54point or something. So, if we discover technological life, then it would prove that, oh, there is no great filter. It's just a smooth track all the way, and it would make the so-called Fermi paradox even more puzzling. So, what you're suggesting is just one other example, which show that however narrow that bottleneck is, it's not so narrow it would have only produced one example of technology in the universe. Right. So, if you have another example, that- One independent example of either life or technology would be enough to say, look, hey,

22:25universe has done it twice, completely independently. And life has been on Earth for three and a half billion years. Right. For two and a half of those three and a half billion, it was just single-celled organisms. Right. So, if you're throwing a dart at planets with life, and if Earth is any measure of that, you're probably going to hit a planet with microorganisms. Right. More likely to do that. There's some of the dart statistics on this. But, okay. And would one sign of technology be smog?

22:57It could be. I mean, that'd be depressing, wouldn't it? I think the advantage, the beauty of a techno signature is that some of them, not all of them, not smog, could be unambiguous. Right? If you get, like in the film, Contact, where Jodie Foster has the headphones on and gets the transmission, and you can unpack it, and there's this engineering plan of how to build a machine, there's no way that's random chance that someone's engineered that. Exactly. Whereas if we detect a gas, so that would be slam dunk.

23:30There's definitely aliens. If you detect dimethyl sulfide in an exoplanet atmosphere, people are going to argue about that for years and decades to come. So that's the advantage of techno signatures. It can be clear cut. They're not going to argue over engineering. Exactly. Like, if they send you IKEA directions, it's a done deal. How to put together your table. Exactly. Right. And then at the end of the directions, it says, don't worry if there are pieces left over.

24:00Oh, wow. That's really cool. And I love that. Technical thing. Technical life. That's the way to go. Yeah, yeah.

Naming new exoplanets

24:06All right. Here we go.

Naming new exoplanets

24:07Larry Chan says, I'm Larry Chan from NYC, and I'm a science fiction writer. Once humanity travels to other star systems, planets will most likely be named after the gods of ancient times. For example, Tyrua and Cataquil were Native American gods. After the list of gods reaches its limit, how would we name exoplanets? I suggest naming them after characters of classical literature.

24:37For example, Ahab, the Mad Hatter, Tom Sawyer, Alice Liddell, et cetera. I love that. And there's no shortage of those. No, there isn't. Of those names. Right. You know, we had a similar challenge when asteroids were discovered. Yeah. How many are there? Well, there's at least 10. All right. And they were initially named. Well, the first asteroids we thought were planets. So they're named after Roman gods, as are the other planets. And then we discovered there's some other category of object.

25:08But there was an urge to name them after feminized versions of people. So there's an asteroid, not called Mozart, but Mozartia. Oh, okay. So that was a little weird. Because it was the, feminine would be the diminutive variant of a planet name. Gotcha. Okay, because they're asteroids, right? So then you quickly run out of names, although there's still a lot of names. I mean, there's a lot of names. People name me after their pet. There's an asteroid Santa.

25:39Okay. People love observing that on New Year's Eve. Right. Okay. A friend of mine did that, and he showed me the data. Okay. Just kind of. That's cool. When you have nerd friends, that's the kind of stuff you do. Yeah, this is up there, Joe. All right. I kind of think we should just call them GPS coordinates, you know? Just like, you give me a number, and then I know exactly where to go and look at it. Because if you gave me a name like, go to Aurelius or something, I'm like, well, I don't know anything about that star just from that name. I'd like to get some information about the star from the name. As you may know, the moons of Uranus, that are all named for Shakespearean, fictional characters in Shakespearean literature.

26:12Okay. Of which there are plenty enough to get you going there. So another thing, they wanted to name, largely successfully initially, all of the asteroids whose orbit cross Earth's orbit, which puts us at risk. They're named after evil gods. That's awesome. Yes. Now, that makes sense. Yeah. So one of them is Apophis. Right. The Egyptian god of death and darkness. And there are plenty of, you know, in the polyseistic realms, there's no shortage of these.

26:43Well, there is a shortage because there's hundreds of thousands of asteroids that'll do this. So that's the problem. But you go to Lyft Street, you've got Sauron. You've got Sauron. That's what I'd be doing. That's all right. Cool. Yeah, man. Yeah. I love that. Well, hey, hey, there you go. Yeah. But I think David is right. At some point, the coordinate on the sky is uniquely identifies it. Right. And you know what we can do? Because were you an amateur astronomer at all? As a kid, not at a high level. Yeah, yeah.

27:13I was a pretty high level amateur astronomer. So we, there are a lot of objects discovered by an amateur would later get a catalog designation. But then you would carry both names. Right. I was going to say, you have the coordinate as the name and then in parentheses underneath. Or in quotes, there's Tabby Star, there's Barnard Star. Barnard Star is another one of these stars that's nearby. And Barnard first studied it, but it's got a catalog name. Okay. So I think that's how you do it. If there's a reason to have a name because of its properties or because of who discovered it, you do it.

27:48But you still need the unambiguous identifier. Okay. Yeah. All right. All right. Hey, well, thanks a lot there, Larry.

Diversity of solar systems

27:55That was a good question. Okay, let's go to Mary Rose. Mary Rose says, hello to all at StarTalk. This question is coming to you from the tiny island of Malta in the Mediterranean. Ooh, I want to be there. Yes, we are. Invite us. What's your name again? Mary Rose. Mary, invite us all. Yes, we'll be right there. Hope you got room for a sleepover. Okay. She says, David, what has been the most surprising find for you so far in the study of exoplanets?

28:26Thank you, Mary Rose. I love that. Yeah, that's a great question. There are many things we've discovered which blew our minds. I think what we kind of expected, I mean, this is a little bit before my time, is that we'd find other solar systems which looked like our solar system. This is the template. Everything would look the same. Of course. And I think the greatest... Oh, the hubris. Yeah. We are the default. But it turns out we're actually kind of weird. And most solar systems look very different. So I think, you know, it's a very kind of vague answer, but to give some examples, mini

28:57Neptunes, which we talked about with this LHS 1140. That's the most common type of planet in the universe. What? And we do not have one. And we don't have one. We don't have one of these. That ain't right. That ain't right. Yeah. That's weird. That ain't right. That's kind of strange. Well, how many is a mini Neptune? It's in between about... What fraction of Neptune's mass would that be? Well, it's in between about two and four times the size of the Earth. So that's about half the size of Neptune. Yeah. So, super Earths. Yeah. Super Earth. Super Earth. Is that the same as a mini Neptune?

29:28We don't know. The other thing, because people argue about the name. Some of them say, you can't call it super Earth. We don't know it's rocky. You shouldn't call it mini Neptune. David, I invite you to show for you to say that you don't know. You're the expert here. We don't know. That's how you know he's good. That's it. That's right. That's it. That's it. Exactly. Okay. But I think that diversity is surprising. There are circumbinary planets, like the Tatooine, like you heard in Star Wars. Like George Lucas imagined that. Everyone just thought he was crazy. But we now know that that's a very common thing. It's a very common thing. Yeah. Do you think he really knew or did he just think it was cool?

29:59No. No. No. No. No. But I do. It's the only science in all of Star Wars. That's as good as it gets. Oh my God. It's downhill from there. That's it. It is downhill. Oh, that's just awful. It is totally downhill from there. Um, that only worked because of the distance to the planet relative to the distance between the stars. Mm-hmm. So that the planet sees two stars. Right. That's the double sunset.

30:30Right. The famous scene is double sunset. Those have to be so close together that the planet thinks they're one source of gravity because if they were more separated and the planet is trying to figure out where to go. Out of orbit, you get a chaotic trajectory. That's the three-body thing, right? It's a three-body problem. That's a three-body problem. You lose the stability, either falls into one of the planets or escapes. Yeah. So that one was correctly shown with the two stars setting together. Mm-hmm. And we can judge what that distance, that planet was.

31:01So that you can create stable orbits that way. So that's the only way that works. So that's good science. And just to add, we call that a P-type orbit. A P-type orbit. Because you can have a binary star where they're close together, like Tatooine, that goes around the two close together on the outside. That's a P-type orbit, planet type. Or you can have the binary stars widely separated and the planet goes around the one of them. Oh, that's also a stable orbit. That's an S-type. That was the S-type. Satellite. Oh, okay. Yeah. That's cool. There you go. That's very cool. But then you don't get two sunsets. No. Yeah, yeah, yeah. That was cool. Okay. So here's what I want to know.

Rogue planets in space

31:31I read that one of the most common things that we never consider with planets are rogue planets, that in the formation of solar systems, so many planets are flung out of the solar system, so stable orbits can be achieved by the rest of the planets, right? Yeah, they just got out of dodge. Just get out of here. Yeah. So how common would it be if we were able to see them, would we just see planets wandering around like they lost from the home? Homeless planets. Homeless planets.

32:01They were homeless, and then they became rogue planets. Oh. Well, that sounds a lot more badass. It's a little bit more badass. Yeah, yeah. So only none of y'all. So David, the numbers I remember are that our solar system might have started with as many as 30 planets, coming down to the eight that we now have. Yeah. So that tells us that maybe there are more rogue planets than there are planets with homes. Right, yeah. This is a really hot area in astrophysics right now, rogue planets. So you could get a PhD right now doing this.

32:32It's a hot topic. Right on. But you're right. It's thought the solar system had more planets. Some of them merged together. It's really thought there was a fifth giant planet. There's a lot of evidence for that. It's actually really difficult to keep Neptune stable unless there was another Neptune-like planet in the solar system in the past. So it's not canonical, but it's widely accepted that it's likely true there was a fifth giant planet in the solar system in the past that got ejected out into space. And that's how you keep the outer solar system stable. So there should be a ton of those. And the Roman Space Telescope, which is coming up, is going to be-

33:05Nancy Grace Roman Telescope. Yeah, it's going to be the perfect machine using microlensing to detect a whole host of those. So we're expecting thousands of those to be found with the Roman Telescope. So this is where you have a star in the background. Ideally, it's a dense star field, like the center of the galaxy. Of course. And you just watch for any starlight that- That- That- No, no. That- Oh. Gets brighter. Gets- It's not an eclipse. Okay? Oh. Gets brighter. Why? Because light going on either side of the planet, you can't see the rogue planet, of

33:35course, because nothing's illuminating it. Right. It's in the middle of frickin' nowhere. Right. And there's a planet behind it. Pathways of that star's light- Star's light. Going around the planet. Come back and join, magnifying the brightness of the star itself. Because a sight line would have gone and missed you. Right. This light line would have missed you. Right. To get bent into your view, adding to the brightness of the object. It is gravitational lensing. So it's gravitational lensing for rogue planets. But it's only a tiny amount, and that's what we call it, microlensing. Yes. Yeah, yeah. Yeah. There's enough of a variation in the travel of the light for you to determine that?

34:10I mean, in terms of the magnification? The magnification, yeah. It's very small, but Roman's a very precise telescope. Holy crap. The real trick is that these are very rare events. So you'd have to observe millions and millions, even billions of stars simultaneously to have a chance of detecting one per day or so, right? And that's kind of the rate they want to get to. One per day, yeah. That's the power of Roman. It's, I mean, you probably know the numbers better than I do, but the field of view is like 10 times Hubble or something, or 20 times Hubble. That can boost your statistics. Well, if the star gets brighter and dimmer, how do we know it's not the star doing that?

34:40Because usually the star repeats that, whereas a microlensing event is singular in time. Plus it has an exact profile. Oh, it would be singular because the planet is on the move. It's on the move. The planet's on the move. It's on the move. It's on the move. Oh, crap. And the profile of the brightness and the dimming is, you know that in advance because of Einstein's general relativity. So let me ask you, David. That's wild. David, Earth retains some of its heat of formation. Yeah. And it's got heat from radioactive decay within the crust.

35:13If Earth left the solar system, there would still be a source of energy within it. Some life would not care that we no longer have the sun to sustain it. How many of these rogue planets still have energy within them and therefore might still have life making no reference to the sun? Because life in the bottom of the ocean never seen the sun ever. Yeah. Anyway, they're all blind. It's possible. I mean, people have speculated about that recently. If you have moons, it's even better, right? Because moons can have tidal heating.

35:43Think about Io. Right. Io is a volcanic world. Lots of energy there. Europa 2 probably has a liquid ocean. And by tidal heating, you mean like a subtle stretching and contracting of the... Yeah. So as multiple moons interact with each other, it causes sometimes the moons to plunge a little bit deeper into Jupiter's gravitational field, sometimes a little bit further out. And so it's like a squash ball. It kind of gets stretched and squeezed like a piece of dough. So that's probably what happened to these moons. And so you could have, for billions of years, life just thriving in between the stars.

36:17That is dope. Yes, totally dope. That is unbelievable, man. Well, it's totally believable. That's what makes it dope. Wow. Yeah, and in fact, look at the bias thrust upon us by biologists. Right. Saying, the sun is the source of all life in the world. It's the source of most life. Right. But there's life doing the backstroke at the bottom of the ocean. That never gets a chance to encounter. That never gets a chance to encounter. Geothermal energy. Right. And so it's not that life needs the sun, it's that life needs energy. Right. And if you find another way to get the energy. That's why we're looking for life on Europa. Yeah. Another tidally heated moon of Jupiter.

36:50Right. Yeah. Interesting. Okay. Wow, that's so cool, man. Wait, so what's the difference between Europa and Io in their tidal heating? In terms of the amount of energy? Yeah. Well, Io is on the inside. It's close to Jupiter, so it gets the real brunt of it. There you go. Europa is, I think, number two, right? So it still gets heated, but not as much as Io. Okay. But Io is so significant that there's volcanoes on it. Yes. Yeah. Right. It's liquefied the rocks. Oh, you can see it coming out into space. Yeah. It's crazy. Yeah, it's cool.

37:27I'm Nicholas Costella, and I'm a proud supporter of StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

Radiation near galactic centers

37:44All right, this is Peter Jacobs, and Peter Jacobs says, G'day to David, Neil, and the applaudable, laudable, audible, oh, my lordy, lordy, lord nice. What? Yeah. Peter Jacobs here from Mooloolaba in sunny Queensland, Australia. Okay. I'd like to get me some dimmies. Okay. All right. He says, thinking of the Fermi... That's quite the intro to the... Did you make that up or did you write that? No, this is written. I don't know sometimes.

38:15I was just doing a terrible Australian accent. That's all I added to that. Sometimes I don't know what it is. Okay, okay, go on. Okay. He says, thinking of the Fermi paradox, how close can we get to SAG-A before ambient radiation from surrounding stars would make life impossible and would pulsars, quasars, and colliding black holes sterilize their galaxies? Oh, wow. Wow. So, the amount of radiation coming out of a pulsar or a collision...

38:48Sagittarius A is the supermassive black hole in the center of the galaxy. Right. And it is a rockin', rockin', sockin' place. Yeah. And other galaxies, it's even more severe than ours in terms of just the flux of high-energy radiation. So... So, do you guys think about... That's wild. Let's soften this just a little bit. Okay. Some stars give off a lot of UV, but like the blue stars, the bluer stars, and UV is hostile to life. Yeah, it's to everything. So, are you thinking about life on planets that orbit high-temperature stars?

39:21Yeah. So, I think... But it's a great question, and I think it touched on an idea called the galactic haptical zone. So, you can have a haptical zone around a star, but there might also be a haptical zone in our own galaxy. Okay. And that would be a radiation problem for you if you're a little too close to the center. Not necessarily just radiation. It could be metallicity. The metallicity of the galaxy changes in different locations. I don't know what metallicity is. So, the... It's jargon, and he's now got to explain the jargon. Okay. Okay. So, it's the heavy atomic elements. Basically, in astronomy, anything heavier than hydrogen and helium, the two things came

39:54out of the Big Bang, are a metal. And that's what you're made out of primarily. Chemists hate that. Yeah. Because we call everything metal. Is it metal rich? Yeah. If it has, you know, carbon, it's considered a metal. Right. And chemists hate that. So, the whole universe is one big headbanger's ball. A metal ball. A metal man! Okay. So, you have the radiation in the center. Yeah. And you need enough heavy elements... To make planets. To make planets and people. Yeah. And you need... I mean, when you really look around Sagittarius A star, you've seen some of these animations

40:26they've reconstructed of the star paths. They're on top of each other. So, planets wouldn't even be stable. Yeah. Okay. Right? So, these stars... Yeah, there's like these loop orbits and it's what won the Nobel Prize. Right. That the observations confirming the black hole in the center of the galaxy by tracking these orbits... Okay. ...shared the Nobel Prize with our guy, our physics guy, Roger Penrose, who showed early the mathematical rigor of why you would get a black hole in the first place. Interesting. A perfect combination of theory and observation there.

40:57So, there's other parameters. Yeah. So, you've got to form a planet, you've got to... With the right ingredients. Yeah. You've got to have a stable orbit. Stable on those planets. And then the radiation environment has to not sterilize you. All right. And obviously, if there's lots of stars around, and say one in a thousand stars go supernova, then the chances are, if you're in a busy neighborhood, if you're in Manhattan, you're likely to have one of these guys go off at you. So, you don't even want to be around another star that blows up. Right. Yeah. Okay. Yeah. Cool. That's funny because I read that one of the reasons for life here, where

41:29is the fact that we're in a suburb of the Milky Way galaxy. Yeah. Yeah. I think that's true. And we also don't... You know, our orbit is more or less circular. It doesn't like have an eccentric, but we plunge towards the center and come back out. So, we're in a nice neighborhood. We're about two-thirds of the way out.

41:49We didn't have to commute into the center. It's been red-lined from early on.

41:58We're in the Carroll Gardens. Milky Way.

42:04So, we're about two-thirds of the way out. And I hadn't appreciated, yes, we're in a basically circular orbit. Yeah. So, we don't risk changing neighborhoods and surviving the consequences of it. Gotcha. Yeah. And one full orbit is a couple hundred million years. So, that's at our distance. That's plenty of time. Well, no, but evolutionarily, it works for us. That's pretty stable. Yeah. Yeah. Gotcha. All right. Wow, that's all cool stuff, man. Damn. Yeah, you do some cool stuff, man.

42:35I think it's called the Cool Laboratory. Oh, that's right. Cool World. Cool Laboratory.

Extinct civilizations and relics

42:41All right. There we go. This is Mike Landers. He says, hi, Dr. Taising. Dr. Kipping, Lord Nice. This question comes from San Francisco. If we eventually detect an unambiguous technosignature or biosignature, do you think it might belong to a civilization that is already extinct by the time the signal reaches us, making our first contact essentially an archaeological dig? Oh, I like that. Ooh. So how far away are your stars? For SETI, for technosignatures, we can search across huge spans of the galaxy.

43:12I mean, you can span tens of thousands, even 100,000 light years in some extreme cases. So they could easily have gone extinct. But your stars, your cool stars, they're not that far away. For biosignatures, there's things that James Webb are observing and trying to get signs of atmospheres. Those are nearby. So those are tens, 20 light years, 30 light years away. Okay, so if presumably civilization takes so much longer than 30 years to establish, that a 30-year delay is not some major... It's not prohibitive of you getting some...

43:43Right, but the technosignature doesn't have to be like an active beacon. It could be... One of the coolest ideas I've ever heard for a technosignature is the idea of putting shades in space that orbit the sun and they would be artificial transits. So like put a giant triangle in space, like a sheet of aluminium. And as it transits the sun, it would create a very strange eclipse to alien observers. They'd be like, hold on, someone's put a triangle around that thing. That doesn't occur in nature. That's a space Dorito. You'd be like, that's weird.

44:13That shouldn't be there. And that thing would be stable for millions, billions of years, long after we're gone. So we could leave a relic that would betray our presence. And you could even have interesting signals there. These are the Easter Island heads. Oh. Yeah. The civilization left them there. Right. And it's been argued that you come upon the island and they're looking at you still. Right. Yeah. If you leave some purposeful relic. A monument. I mean, the pyramids are a communication

44:46from another civilization to us through time. Mm-hmm. And we too have the opportunity, with a time capsule of some kind, to communicate to future civilizations, perhaps even future, I think the most likely contact. Wait, just to be clear, he's not saying the pyramids were left by aliens. No. Just, I just want to. A human civilization. Yeah. Left by basically an extinct human civilization. Yes. Ancient Egypt. Yeah, yeah. Is no longer with us. Correct. It's like, they're descendants. Yeah. But they're not building pyramids anymore. My provocative claim is that the most likely alien contact

45:18we will ever have, not really a contact, but a way of knowing that we're here, is that we could leave something, like the voyage, like the golden record, like the pioneer plaques, we could leave something like that, perhaps on the moon, and maybe in 500 million years from now, another advanced civilization will emerge and discover that on the earth. So it will be a non-human intelligence, not alien, but still non-human that evolves after us, and they pick this up, and they realize, oh, we are not the only ones to ever develop. But that would imply that there isn't a continual awareness

45:52of a previous civilization. Are you referring to an apocalyptic earth? We all die, civilization disappears, and then some other intelligence evolves later, and discovers that earth used to have... It doesn't have to be an apocalypse, but yeah, we fade out maybe, just gradually. There's evolution, you know, species very rarely last longer than a million years, so eventually we change into something else, and some other future civilization emerges. I think there's mammal species around a million. Other species, I'm not sure. Yeah. Unless it's all species. It's rare. There are some, but it's unusual for a species to last that long.

46:23Believe me, we're not going to make it. We don't even have to worry about whether or not we're going to make it to a million years. Come on. So, I think... All right, that's cool. Velics are a cool way. There's a whole thing called Artifact SETI, which is the question askers should definitely look into. Yeah. All right, here we go.

Gravity on alien worlds

46:43This is... Here we go. This is Aiden Rodriguez, who says, hello, Dr. Tyson, Lord Nice, and Dr. Kipping. Greetings from Panama City. Panama, the country that gave the world the Panama Canal. I've been a fan of you guys for many years, and I'm a Patreon supporter now. My question is, could life exist on a planet with much stronger gravity than Earth? Say, two or three times stronger. If so, it also would it evolve in an atmosphere with much higher pressure than ours? Thanks so much. Keep up the amazing work.

47:15Yeah, that's pretty wild. That's a great question. I think the immediate challenge is, how would you engineer a planet to have two or three times Earth's gravity? Because as you increase the gravity, a planet will naturally accumulate gas around it as it's forming. So you're going to turn into a gas giant, basically. Even only three times the gravity? I think by three times, yeah. Really? I don't think there's any super-Earths that are more than like 1.7, 1.8. Oh, so super-Earths are just slightly more muscular, but not multiples. I did not know that.

47:45I don't think you can get that extreme. Oh. Yeah. And at that point, all the fluid that has accreted puts a pressure on the surface, and so the pressure would be super-huge too. Right. Yeah, so the pressure would be high. I mean, it is cool. You could probably have 1.5 times Earth's gravity, no problem. And what's interesting, I think, about these things... Everyone would weigh 50% more. Unfortunately. Just so you know. Everyone would be on a Zempick. Oh, I hate to go on a Zempick. Just here's the thing. Most of us already weigh 50% more, so if you want to know what it feels like

48:16to be on such a planet, there you are. Yeah. Wow. Now, you want to feel like it's back on Earth, lose that one-third your body weight, and then you're back to what it is on Earth. But let me tell you something cool about weight, though. Look at what's behind you, the Saturn V. Yes. Now, if you made the gravity 1.5 times heavier, that thing's not getting up. Yeah. And so, if you think about the rocket equation, the size that thing would have to be... Which one does all the time, you think about the rocket equation. Of course, yes. That thing would have to be the size of a pyramid to get up into... That's how... You'd have to lose 99.99999% of your mass as fuel.

48:48So, it's thought that super-Earth might be a prison, that civilization... Damn! ...might be trapped there. They can never get off them because the gravity is so strong, they can't have a space age. No, they'll invent wormholes. Don't be so... They have to go... Right, but there's no natural progression the same way that we've enjoyed... Maybe this is so much smarter... Dude, little Timmy in preschool just designed a new wormhole. Right. Yeah, let's use that one instead of the other. So, know that it isn't interesting. Given our engineering flight technologies,

49:20we would not be able to launch... We'd be stuck. ...from an Earth that's one and a half... Yeah, look at that. You know what else I think about? If we were Venus... Mm-hmm. ...you would never know there was a night sky with stars in it. Right. Because Venus is a thick, dense, opaque atmosphere. There's a tarp over Venus. Right, it's a tarp. There's a whole tarp. So, let me end on something that I wanted to even start with. This notion of unknown unknowns. Yeah. Because on Venus, like I'm saying,

49:50I know that tarp will prevent anybody from seeing anything about the universe. There'd be no astronomy. No one would have ever thought it up because when you look up, you just see clouds. Okay? So, to them, an unknown unknown is... Because it could be a universe beyond your planet. We don't have that problem here. Is there some unknown unknown that we don't even know we don't know that puts us in a prison that another planet freely escapes from? That is a truly frightening thought, Neil.

50:22And it reminds me of how in cosmology, cosmologists often take for granted the fact we live now, but were we to emerge 10, maybe 100 billion years in the future, when the universe has expanded so much, you would not see the galaxies at a certain point. The galaxies would have expanded beyond our horizon. And so, you'd think the Milky Way was the universe, and you would never know all of that which is out there. I think that's an amazing coincidence. In the time of Einstein's relativity,

50:53that's what anybody thought. To him, the universe was all the stars and the night sky of our Milky Way galaxy. So, have you thought about a missing chapter in our book of the universe that we don't even know is not there? How can you think about that which you do not know? You know, it's impossible, but it's certainly possible. But we just, we can't imagine what that might be. Wow. Okay. That we're just blithering idiots. I was going to say, one thing is for sure, we're stupid. Thank you, Chuck. So, David, how can we find you?

51:24Remind us. You can find me on the Cool World's YouTube channel. It's just called Cool World? Yeah, Cool World's. It's just called Cool World's. And I've also got a pod so you can go to the Cool World's podcast. And revenue from that drives your lab, isn't that correct? Yeah, yeah, yeah. We have donors, like you have your startup patrons, we have patrons, but all of that money is just used for research, actually. So, that's kind of fun that you can pledge your money to go to real discovering, hopefully new planets. And as more and more research money is evaporating, God, yes.

51:54that funding model becomes more and more significant. I think so. Thank you, Doge. Yeah. Until the day you get the phone call from somewhere else saying, we got a lab for you here. Which is probably, yeah. And, you know, with that accent, he's like, see ya, bitches. No, I'm joking. So, yeah. We already know, we already have colleagues who have been cherry-picked. Yeah, this is a real problem. You guys better write, you know, reach out to your Congress people, reach out to your senators,

52:24and let them know that you want science funded in this country. Chuck for president. And that the power of the purse still resides in the Congress and not the executive branch, and that you won't stand by and allow for science to be defunded. Okay? So, that's it. Thank you, Chuck. No worries. Are you just smart enough?

52:45So true. Funny you should say that, Neil. That's the name of my special. Which can be right here on the StarTalk YouTube channel. Check it out. Chuck, it's just smart enough. It's easy to find. It's right there. All right. So, thanks, David. My pleasure. Thank you. For skateboarding. Anytime. Anytime. For one-wheeling over here. And saving the planet with your water bottle and your one-wheel. That's right. He's still exhaling CO2, though. Well, yes. Still working on that.

53:15This has been StarTalk at Cosmic Queries Cool Worlds Edition. Ooh. Yeah. Until next time, we bid you to keep looking up.