How big can a rocky planet get? Can a rocky planet turn into a gas giant? Why are some planets rocky and others gassy? I discuss these questions and more in today’s Ask a Spaceman!

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EPISODE TRANSCRIPTION (AUTO-GENERATED)

We're talking about the biggest possible planets today, and I decided to divide the episode into two parts, an easy mode and a hard mode. And we'll do the easy mode first and then obviously, do the hard mode. Second, because there's only two parts and the easy mode comes first anyway, the easy mode is asking the literal question. What is the biggest planet? And in order to get into this and this will be a recurring theme throughout the episode. When I say biggest or you say biggest or anyone says biggest, we need to define what that means because there's the difference between size and mass. We need to say or do you mean the most massive planet? Do you mean the largest planet? Because there can be large planets with low density and small planets with high density, and both of them have the equal amount of mass. So so which one is bigger? And we run into this issue? Because as we start looking at big planets both in terms of size and mass, uh, we start edging into brown dwarf territory, which itself is hard to define because it exists as a category between stars and planets, and now we're talking about the lower boundary of that category.

We're looking at what happens when planets become classified as brown dwarfs, which might just be a category in its own right. It gets complicated real quick because these these boundaries are fuzzy. Usually the bottom edge of a brown dwarf definition is around 20 times the mass of Jupiter, and the upper edge of the brown dwarf range is 80 times the mass of Jupiter. That upper end is when hydrogen fusion kicks in and you've entered the main sequence and you're powering yourself for millions or billions, or sometimes even trillions of years, that that's a star. You're just a definitely a star if you're at least 80 times the mass of Jupiter at the lower end of the usual lower boundary, and I did a whole episode on this, and you can dig into it if you want about. Brown Dwarfs is around 20 times the mass of Jupiter, and this is the critical threshold to allow deuterium fusion in your core for at least a brief period of time. Planets definitely don't fuse anything in their core.

Stars definitely do fuse things all the time in their core. Brown dwarfs fuse some things some of the time in their core, and it seems that boundary is around 20 times the mass of Jupiter. However, we only know this from modeling from computational modeling from our our understanding of physics, because we can't visit any planets that are 20 times the mass of Jupiter and crack them open and see what the goo is like on the inside. And it also depends on the density and the composition, exactly what it's made of its environment. It's complicated. This boundary is very fuzzy and not very well known. This boundary between planet and brown dwarf one planet may have the same mass as another. And that one planet may just be a small brown dwarf if it can sustain deuterium fusion while the other is definitely a planet. Because, like I said, it's complicated and very fuzzy and not very well known. It depends on all sorts of complicated factors, but it is safe to say that at some point if you start building a planet, you instead find yourself building a brown dwarf.

And then if you keep adding on stuff, you eventually find yourself building a star. If you start making a hill and you keep piling on dirt, eventually you're just going to have a mountain on your hands. But you can't exactly point to when you cross the line from Hill to Mountain. It's all fuzzy, and it depends on a lot of things. Like, for example, there's this object HD 100546 B. Sorry about the phone number names, which are gonna be all over this episode. These things just have catalog designations. They don't have cool names. You can substitute names for any of these phone numbers. As you wish. It's about 320 light years away. Could be around six times the width of Jupiter. That is a huge monster and with a mass of around 17 times that of Jupiter, Probably a brown dwarf. But we can't be sure. We do know it just started forming, so it will probably shrink with time. You know, if we could watch it for a million years, we get to see this play out real in real time, so that might be the largest planet ever known.

Uh, but it's right there in the brown dwarf territory. And since it's just started forming, we don't know if it's crossed over into that deter in fusion limit that marks the beginning of Well, now you're a brown dwarf and not a planet. The largest, almost certainly a planet planet is ROXS 42 BB or the first B is upper case, and the second B is lower case S. Sorry, it's about 440 light years away from us 2.5 times the width of Jupiter. Um, although keep in mind that all these numbers that I quote throughout this entire episode of pretty big uncertainties attached to them because that's astronomy for you and it has around 10 times the mass of Jupiter. And it's in this super big orbit 2000 year orbit around its star. That's in terms of radius. However, if instead we focus on mass, uh, then we already have known examples of giant planets that blur the lines between planet and brown dwarf. For example, the most massive planet is HR 2562 B.

It's about 100 10 light years away from us, and it's 30 times the mass of Jupiter, but only 10% wider. See, unlike those other planets that I've mentioned that have this incredibly big Radius, Uh, it's actually relatively cool, and it's not inflated it. And maybe it has a different composition. Maybe it's made of different, heavier stuff. Maybe it has more rocks and ices and and less gas inside of it. And also, maybe it's a brown dwarf. There's a huge uncertainty here in the mass. Estimate it's 30. Get this. It's 30 times the mass of Jupiter, plus or minus 15 times the mass of Jupiter. So it could be as small as 15 or even just the size of Jupiter or, as big as you know, approaching something the size of a star. This is a massive, massive uncertainty, but that's just life. With these kinds of planetary measurements, they're really hard to come by. The largest planet with a precise mass estimate.

At least precise enough for government work is Kelt one B, which is 27.34 times the mass of Jupiter. Look at that precision and a two is only about 15% wider than Jupiter. So here, right off the bat, we get two examples at either extreme We have some planets that are truly, truly beefy in terms of mass, but are only slightly larger in width compared to Jupiter. And then we have other planets. These, as are especially known as the hot Jupiters that are really hot, Really inflated. Yes, they are more massive than Jupiter, but not ridiculously so. And they're inflated out in these. They have these incredibly large radii. That's just life. And if you want to say what's the biggest possible planet, you have to specify, and we can just spend the rest of the episode going down the list of these. Maybe they're a planet. Maybe they're a brown dwarf. Maybe they're big enough to have deuterium fusion. Maybe they're not. You know, we could do the rest of the episode on this, and we're not, because that was easy mode.

Just what is the biggest planet boom? Here's the largest planet that we know of that in terms of radius. And then here's the largest planet that we know of in terms of mass. Both of the examples stretch the boundaries and are possibly brown dwarfs because that's life. So let's switch to hard mode, where I'll spend the rest of the episode and in hard mode, I'm going to ask, what's the biggest habitable planet? Whoa, whoa, whoa, whoa, whoa. Why am I asking this? Because it's a lot of fun. And this is my show. And also, some of you asked that question, so I figured I would combine the topics. But in order to answer this, we again have to be very careful with our words. If there's one thing that scientists and lawyers and philosophers all have in common is that we insist on being precise with our words because the tiniest difference in word choice matters much to the annoyance of my family. But that's not today's subject, just like we saw before. When I say, Let's look at the biggest planet.

Wait, What do you mean? We have to be precise. Do you mean the most massive planet or the largest planet in terms of width or volume? And if I say what's the biggest habitable planet? Well, we have to define what habitable means and this is a giant issue. This is cutting edge astronomy. This is the latest stuff. No one really knows what habitable means. There are lots of ways to potentially define it like Europa, the moon of Jupiter covered in ice but with more liquid water than the Earth has, except except it's all cut off from sunlight. Is Europa habitable? I don't know. There's lots of liquid water, which makes it sound like a really fun place. But I don't know if there's anything swimming around in there. I hope there's something swimming around in there that'd be really fun Space whales on Europa and all that. So I can't tell you if Europa or any of the other frozen moons are habitable or not. But for purposes of this discussion, where we are investigating what is the biggest habitable plant?

And yes, we will explore both in terms of mass and Radius, we are going going to define habitable. We we need some sort of definition, So work with me here. My definition of habitable is going to be that it has liquid water on its surface. So this discounts worlds like Europa that have liquid water under their surface. Uh, because those tend to be small moons anyway, and we're not really interested in them because they're not gonna be big because they're they're small we want liquid water on the surface. We want it to look a lot like the Earth. OK, we want beaches. We want Caribbean resorts or Caribbean style resorts. You know, we want nice temperatures. We need just the right mix to have liquid water on the surface. We need a thick but not too thick atmosphere. We're gonna encounter some planets that are definitely potentially capable of hosting liquid water on their surface if it weren't for their thick, choking atmospheres. For example, Venus is in the habitable zone of the sun where the temperature, uh, the amount of light radiation coming off the sun is just right to potentially have liquid water on the surface of a planet.

But it doesn't because the giant atmosphere has choked itself to death. And we can't have no atmosphere because then we're like Mars. Mars is also in the habitable zone of the sun, but also not very habitable because it has no air. So we need a thick atmosphere like the Earth. Maybe a little thicker we could tolerate. We'll see, but definitely not too thick. Has has have a magnetic field because we want to protect that juicy, juicy atmosphere from any solar wind. We we want that to be at our backs. We need our force fields up. We need to protect our atmosphere. And I've already mentioned this obliquely. But let's say it out loud. It needs to sit in the habitable zone of its parent star. Can't be too close where all the water boils. Can't be too far away where all the water freezes. And that's it. Yeah, Before you stop me, I know that this doesn't guarantee habitability. Like I said, Venus and Mars are in the habitable zone of the sun. But, you know, they don't have liquid water on their surfaces.

They don't have just the right atmosphere. They don't have magnetic fields. So this stinks. And, yeah, you could totally have a planet that meets all four of these criteria and not a single creature is going to be alive on that world because there's a lot more to habitability than these four things. But I figured, let's stop here. We don't want the episode to be infinitely long, and we want to find an earth like planet. That's the goal. We we want to find an Earthlike planet, but we really want to push the boundary of what Earth like really means. We really wanna push this threshold. So if we take a picture of the earth, how big can I get a planet? And it still looks like a picture of the earth. Why again? Because it's fun. And because by pushing the boundaries here, we get a chance to explore what habitable really means and also scope out some new vacation spots because the beaches near me are getting way too crowded. So let's explore these four criteria. After all, with thousands of examples we know of like five or 6000 exoplanets that's known.

And there are billions, probably a trillion more with these thousands of examples to choose from, can we find one at least one that checks all four of these boxes and is still nice and big? Well, let's see the first criteria, which is a thick atmosphere but not too thick, and I know I'm doing this out of order, but because that's the way I wrote my notes, so we'll take as our first criteria. The thick atmosphere, but not too thick has to be just right. We're going to look at planets larger than the Earth. And it's a good thing I devoted so much time to the whole large planet versus brown dwarf, fuzzy and ambiguous boundary thing, because we're going to run into this kind of issue again. We're pretty lucky here in the solar system. We have basically two kinds of planets. We have small, rocky planets with either no atmosphere or a relatively thin one, and we have giant planets with super duper thick atmospheres. Earth is the largest of the rocky ones, and Neptune is the smallest of the gassy ones.

Yes, I know it's technically classified as an ice giant, but it still has a super thick atmosphere. So for these purposes, we're gonna call it a gassy planet. Neptune is about 17 times the mass of the Earth, and that's it. There's this big, distinct gap between these two kinds of planets. All the giant planets are relatively the same size, and all the rocky planets are relatively same the same size. And then there's this big gap between the two kinds of planets, and these two kinds of planets look and act and smell and feel very, very different. It turns out, though, that the kinds of planets that we experience in the solar system small, rocky worlds, big gassy ones are actually relatively rare. We found thousands of exoplanets, and the most common detected planet is somewhere between the mass of the Earth and the mass of Neptune, where we have none of those in the solar system. But it turns out when we do these surveys of exoplanets, that is the most common one we find. I should note that smaller planets are probably even more common, but they're much more difficult to detect.

But the point remains that planets larger than the Earth but smaller than Neptune are much more common than we had any reason to believe. In fact, the first exoplanets ever discovered back in 1992 had masses of around four times that of the earth. So we need to focus if we're gonna look at this pushing the boundary of earth like what can be habitable and how big can you be? We have to focus on these in betweeners and at the latest count, we have around 2000 of them. Now, I want you to imagine a line. Earth will be at one end of the line and Neptune will be at the other. Obviously, the earth is nothing like Neptune except well, maybe they're both round. I guess the biggest difference is in their atmospheres. Earth has a thick, but compared to the mass of the earth, it's pretty thin. Atmosphere it. It's not very large. It's not super dense. It's pretty nice. There are fluffy clouds out there. It's it's pretty great. Neptune, on the other hand, 17 times more mass than the Earth, has this giant, super thick, crushing atmosphere where you can plunge for, like, thousands of miles and and you get to, uh, pressures that are millions of times that of the Earth.

It's very, very different composition, diff different arrangement. So, obviously, if you start building a planet, if you have enough mass to build something like the Earth, you'll end up with something like the earth, probably rocky, with some water and a little bit of air. And the same goes for Neptune. If you have enough mass, if you have 17 earth masses worth of stuff to crime together, you're probably going to build something that looks a lot like Neptune. That's very, very gassy. with this super thick atmosphere. But what if you have something in between? Well, there's this fuzzy transition. You can imagine that planets only slightly bigger than the Earth will still look a lot like the Earth. Just a little bit bigger in planets, a tiny, bit less massive. The Neptune will be a lot like Neptune, just a little bit smaller. What we call the first group Super Earths. These are planets that are a little bit bigger than the Earth, but probably still pretty Earthlike, Rocky et cetera. And then we call the second group Mini Neptunes, because why not? When we're looking at habitability? Neptune is definitely off the list.

It's no fun to go there. There are no parties, no good restaurants. And so it's probably safe to guess that many Neptunes, these planets that are just a little bit smaller than Neptune, are also not very habitable because they're just like Neptune, only smaller. If, on the other hand, I gave you a planet that was, I don't know, 10% more massive than the Earth. You could probably reasonably guess that it has a good shot at being habitable as any other earth sized planet. That's not a big enough difference to to, well, make a difference in terms of habitability. But what about 50% more massive than the Earth, or 100% more massive or five times the mass of the Earth or 10 times the mass of the earth? At some point, you're going to start crossing over into mini Neptune territory, just like when we looked at the big planets. If you look at bigger and bigger if you start piling on mass on Jupiter at first you just have bigger versions of Jupiter. But then, at some point you cross over into brown dwarf territory. And here, if we take a planet the size of the Earth and start piling on more material, we're gonna have super Earths.

But at some point, we're gonna cross over into mini Neptune territory and mini Neptune territory is definitely not habitable. But where does that line exist? And is it one simple line? Is it nine times the mass of the Earth that we're cool and at 9.5 times the mass of the earth we're not? Is it more complicated? Well, the answer is it's complicated, because why should the universe Be simple. If you want to simplify the universe, you need to contribute to patreon patreon dot com slash PM Sutter P MS U TT ER It is how you you keep this show going and it's how I attempt to simplify the universe. No, the universe is complicated. Generally we call anything between one and 10 times the mass of the earth, a super earth, and anything above that is a mini Neptune. And then you get into Neptune proper, and then you get into the mini Saturn and then Jupiter, blah, blah, blah. But we don't care about those. But that doesn't help us when it comes to habitability. That's the astronomer's definition. Yeah, yeah, yeah, If you're if you're 10 times the mass of the earth and you're a super earth, if you're 11 times the mass of the Earth, you're a mini Neptune.

But that doesn't tell us about habitability because two planets of the same mass aren't always going to look the same, just like when we're looking at those giant planets that are bigger than Jupiter. Two planets with the exact same mass. One might actually be a brown dwarf because it has the right density and composition and confused deuterium, and the other may just be a planet. I can have one planet that's, I don't know, three times the mass of the earth. Small, rocky, dense and then the other. That's the exact same mass, but big and gassy and fluffy. And and they'll have the exact same mass down to the kilogram. But if I were to show you a picture of these, even though they have the same mass, one would look a lot like the Earth. You would call it a super Earth because you would see rocks and water, maybe an atmosphere. And if you were to see the picture of the other, even though it has the exact same mass, you would call them and mini Neptune because it looks super gassy regardless of what the official dividing line is.

So even though the dividing line is at 10 times the mass of the Earth, it's not gonna be a useful gauge for us. What matters to building a habitable super Earth isn't just mass but density. For example, TO I 2 70 C orbits its star every 5.7 days. Uh, but it orbits a red dwarf star. So it's not molten has about seven times the mass of the earth, about 2.4 times the radius of the earth, which should classify it as a super earth. Right? That's definitely not 10 times the mass of the Earth, but really, it looks more like a small mini Neptune, like a like a micro Neptune. If I showed you a picture of it, you'd say, and I didn't give you a scale, you'd say That's a gas giant. Well, it's not. It's just super fluffy. So your super Earth has to be the right kind of super Earth, which there are, like 55 KE, which is 41 light years away. It's eight times the mass of the Earth, almost two times the radius. Notice how it's even more massive than the last plant TO I 2 70 C.

But it it's smaller in terms of radius because it's more dense and it's definitely rocky. But when it comes to habitability, the orbit matters. And this is the second criteria that we're going to examine again out of order, because that's how I wrote down my notes. The habitable zone of the Star 55. Kinky E is definitely a rocky planet, definitely pretty chunky. Eight times the mass of the Earth definitely has the right mass and density to be a rocky super Earth. Definitely not a mini Neptune or a micro Neptune or a nano Neptune. It's also so close to its parent star that its orbit is 17 hours long and its surface temperature is so high that it's permanently molten. So that's right out. Yes, that 55 K is a giant giant super earth that is definitely rocky. And it's good luck living on Lava World and now a word from our sponsor. Better help. Burnout can be tough. Sometimes you're just putting in way more into life than you realize.

And then out of nowhere, you're tired and unmotivated, and you just wanna sit around listening to mind blowing science. Podcasts Well, better help. Online therapy wants to remind you to prioritize yourself. Therapy is powerful. Therapy is useful. It's just like going to a doctor for your body. But it's for your mind. I can't say it enough. Better help is customized online therapy that offers video, phone and even live chat sessions with your therapist so you don't have to see anyone on camera if you don't want to. It's much more affordable than in person therapy, and you can be matched with a therapist in under 48 hours. Our listeners, uh, my listeners get 10% off their first month at better. Help dot com slash spaceman. That's better. HE LP dot com slash spaceman OK, third criteria. We need some liquid water. This is a tricky one. It gets into the habitable zone. That habit habitable zone is the minimum condition you need in order to have liquid water on the surface.

But you definitely need more. Because again, Venus and Mars are in the habitable zone of the sun. They could potentially have liquid water based on the amount of energy they receive from our star, and yet they don't. Water itself is super common in the universe. In fact, it's the most common molecule it's made of hydrogen and oxygen. Hydrogen formed in their earliest minutes of the Big Bang and the most abundant element in the universe. Oxygen is formed in the most one of the most common kinds of stars in the universe, and the most common kind of star to churn itself inside out and spew its guts all over the place. They like to get together. Water is the most common molecule, but it usually only comes in one of two flavors. Gas or solid. It's either frozen or vaporized liquid water, especially surface liquid water. Again, we're not talking about Europa like worlds with hidden locked oceans. We want Earthlike. Planets need stable, moderate temperatures, as in the habitable zone of their star, and they need an atmospheric lid to keep things on.

55 KE failed that test. It was too close to its star. But that atmosphere has to be just right, like Venus and Mars again. Not great places for life. And the trouble here is that super Earths like to hold onto their atmospheres. It's because they're so big in the planetary formation phase when they're just getting started. They acquire so much mass. If you if you build a rocky planet that's like five times the mass of the earth, that's a lot of mass. And in the protoplanetary disc where planets are just getting started, there's a lot of gas hanging around, and they will just suck it all down because they've got a lot of mass. They tend to gobble up a lot of gas, and they tend to have two thick atmospheres. They're really, really, really good at holding onto their atmospheres because they are so big. They're so massive, they're so grabby and greedy. And so when we look at Super Earths, they tend to be super venuses. We actually have the wrong word for them.

They tend to have in this catalog of 2000 Super Earths or planets somewhere between the mass of Earth and Neptune. They tend to have really thick extended atmospheres. We should be calling them super Venuses. But we're all biased here with our our earth bias. The limit here appears to be around 1.5 to 2 times the radius of the earth. Now, notice I didn't say mass. I said radius. When we look at a planet and we can measure its mass or we measure its radius, the mass can be big if it's bigger than the Earth and it's a super Earth. But if the radius is a more than around 1.5 to 2 times the radius of the earth, then almost certainly it has. Most of that radius is taken up by a thick, extended atmosphere that's too thick to support life. So we've introduced a new criteria here. We need a planet bigger than the Earth in in Mass, and it's gonna be bigger than the Earth in terms of radius, too.

But it can't go over this 1.5 to 2 times the radius of the earth threshold. Otherwise, every time we've looked at one of these planets and we also understand this through computational modeling of the formation of planets, it most of that radius is just super thick atmosphere, and that's no good. It's possible to build a super earth, and for a while everyone debated. If habitable, super Earths were even possible because super Earths, like I said, like to hang on to their atmospheres. They like to have large radii, where most of that radius is in the form of thick atmosphere and not anything useful, like rocks and dirt and water. You can thin that radius out, so if you if you can imagine like OK, I built a super earth as like eight times the mass of the earth and then three times the radius. It's definitely not habitable. If I could just get rid of some of this atmosphere, I might might be able to get going. One way to do that is through photo evaporation, which is not what happens when an old Polaroid starts to fade.

It's when radiation from a star just just heats up gad and atmosphere and makes it go away. It just blows away. It's also not a new Instagram filter, Uh, but it is a tiktok filter. Ironically enough, this does happen. In fact, some super Earths are thought to be the leftover core from a giant planet that got too close, like 55 KE, we think started out much larger and did have a thick atmosphere. Then it got too close to its parent star, and the parent star heated up its atmosphere and blew it away. But of course, if you do that, you tend to not just thin out the atmosphere but completely blow it away, which again is not good for habitability. And so that's why, for a long time, astronomers debated if habitable super Earths were even possible, because the super Earths tend to have giant atmospheres, and the only known way to get rid of the giant atmosphere is to stick it right up against the fire of the sun. But then, when that happens, you get rid of all the atmosphere. Ultimately, it's pretty complicated, and we just don't know for sure again. Part of the problem is that we actually have very little data on these thousands of exoplanets.

You might get the radius very easily from the transit method. That's when a planet crosses in front of the face of a star. This method is really good for determining the radius of the planet, because you can see that transit event happen, and you can figure out the width of that little planet. But it's hard to get the mass, Uh, other techniques, like the radial velocity method where you watch the star wobble back and forth, gives you a good handle on the mass of the planet, but not its radius, because you you can't get a picture of it, and we need both. If we want to determine habitability, it's not just gonna be a matter of only mass or only radius. You need both so that you can get a sense of the density, and it needs to be in the habitable zone of the star. Uh, there's this one. Planet Gle 581 C. It's about 20 light years away, 5.5 times the mass of the Earth, and it's in the habitable zone of its star. But we don't know its radius, so depending on its radius, it could be a rocky planet.

Could be a mini Neptune, sometimes also known as a gas dwarf, could be made of solid iron. Could be made of diamond for all we know or some exotic form of ice or just completely carbon dioxide. Until we know the radius. We simply don't know only once. You have both the mass and the radius. Can you really start cooking? That's how you get the density. If the density is too low, then you definitely have a mini Neptune, your mostly gas. If it's too high, then you know that there's very little if any water, let alone an atmosphere. And there are some interesting mental cases where the densities do line up roughly with yours and are consistent with liquid water. I use that word consistent very carefully. Remember, precision counts because of a lot of this comes down to modeling. We don't have a lot of data on these planets. We don't have a lot of direct observations. We don't have pictures. We don't have samples. We don't have flybys or orbiters of these worlds.

We just have a little scratch of data in the plot. We don't know. For the vast majority of these worlds, these exoplanets what they're made of, we might have their mass, their orbital distance, their density, their radius. So we have to rely on our understanding of physics. We have to do computer simulations. Uh, we have to do modeling atmospheric modeling, uh, models of the formation mechanisms trying to account for all the nagging little variables. It's hard to tell if a planet really, really does have liquid water on its surface. Yes, it might have the right density compatible, consistent with the presence of liquid water. But we can't know for sure, because until we get a close up look, we just don't know. So these are all educated guesses, so we have to switch from habitable to potentially habitable. Ultimately, the, uh, the ultimate resolution to this question is going to have to wait for follow up observations with the James Webb Space Telescope.

But one of its missions, Primary Science Goals, is to identify exoplanets and characterize them in better detail. But we have one more definition to get through the magnetic field. This one we straight up don't know. We know how the earth generates a magnetic field. We think we know why Mars doesn't have a magnetic field. We think its core cooled off long ago, shutting off the magnetic field. We think we know why. Venus, that magnetic field shut off again. We think the core locked up, but again, we don't really know. It depends on what the planet is made of how it formed, how quickly or slowly it cooled off, how quickly it's rotating. Venus is barely rotating, which is why we think its magnetic field shut off. The challenge is we don't have any nearby super earths that we can poke inside of, so we don't know how the conditions would be different. If you take a planet and make it 10 times more massive than the Earth, will it have a magnetic field? We we don't know if you take a planet and make it 10% higher than the mass of the Earth, will it have a magnetic field?

We don't know. My personal call is that it's perfectly possible for super Earths to have magnetic fields and probably likely probably the same amount of random chance and all the interesting factors that go into earth size planets or Venus sized planets or Mars sized planets. Giving them magnetic fields or not giving them magnetic fields are probably the same stuff that happens with super Earths. But we know even less about this than we know about liquid water. So after all this, after all this hemming and hawing and making definitions and strict criteria and ruling out this and ruling out that Oh, you're outside the habitable zone so you're out. Uh, you have too thick of an atmosphere. So you're ruled out. Are there any planets any super earths that are potentially habitable? And if so, what is the biggest one? Well, my money is on LHs 1140 B LHs 1140. B orbits a red dwarf star about 49 light years away. We have both the mass and the radius of this planet.

It's about 60% wider than the Earth, about 6.5 times more massive than the Earth. Definitely definitely a super earth right there on the edge in terms of radius of of straddling that line between Super Earth and mini Neptune. We do have the density, and it looks like it looks like the atmosphere isn't too thick. Orbit is very close to its star, less than 1/10 of an astronomical unit. Its orbit is just 25 days, which would normally blast it to kingdom come. But it's a red dwarf star, so it's actually on the outermost edge of the habitable zone of that star. And there's been some work to develop models of this planet of different thicknesses of atmosphere, one of the benefits of being a super earth, even though it's on the outermost edge of the habitable zone. And you might be afraid this planet would lock up into a shell of ice. Well, if it is a super earth and it is, it probably has a thicker than average atmosphere, which means it has a much stronger greenhouse effect in the earth, which might make it pretty pleasant.

Its densities are compatible with the presence of liquid water. On the surface. It it it doesn't appear to be a mini Neptune. As far as we know, this is the largest potentially habitable planet. So let's go there and find out. Thank you to Dan W on email at Al McClintock on Twitter at V G7. 10 on Twitter at Campbell D on email. Alien on email. Laurie S on YouTube and at V one T four L Statistics on Twitter For the questions that led to today's episode and, of course, thank you to all my patreon contributors. That's patreon dot com slash PM Sutter. I'd like to personally thank my top contributors this month. Justin G, Chris Barbeque, Duncan M Coy D, Justin Z, Nate H and F NAIA Aaron Scott M Rob H Loyalty. Justin Lewis, Paul G, John W Alexis Aaron J, Jennifer M, Gilbert M, Tom B, Joshua M and Bob H. Thank you again. Hey, send me some questions. Hashtag ask us Spaceman.

Ask us spaceman at gmail dot com. Ask us spaceman dot com for all the episodes, show notes and archives. Follow me on social media at Paul, Matt Sutter on all social channels and I will see you next time for more complete knowledge of time and space.

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