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Can a planet be bigger than its star? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, are your kids taller than you? You know
0:11
Speaker 1: that day is not too far off. I've only got
0:14
Speaker 1: a few inches on my thirteen year old. Oh man,
0:17
Speaker 1: that's crazy. How about your parents? Are you taller than
0:19
Speaker 1: your parents? I'm like one quarter inch taller than my dad.
0:24
Speaker 1: I like how you've measured that precisely. It's like an
0:26
Speaker 1: important quarter inch to be taller than your dad. He's
0:28
Speaker 1: an engineer, so we pulled out the high precision measurement
0:32
Speaker 1: devices when that happened. I wonder if your dad was
0:35
Speaker 1: happy that he lost that measurement. But you know, it
0:37
Speaker 1: kind of makes me wonder. Do you think stars feel
0:39
Speaker 1: the same way new stars have children? Yeah? I mean
0:42
Speaker 1: like they have planets, right, Like, do you think they
0:44
Speaker 1: would feel proud if their planet was bigger than them?
0:47
Speaker 1: Or would they be jealous? I don't know. I just
0:49
Speaker 1: hope that one day my own kids escape my orbit
0:52
Speaker 1: and start their own solar systems. That's confusing, though, who
0:55
Speaker 1: would be the sun? You or your son? Hi am
1:12
Speaker 1: or handmade cartoonists and the creator of PhD comics. Hi,
1:16
Speaker 1: I'm Daniel. I'm a particle physicist, and I hope my
1:19
Speaker 1: kids never move out of the house, and do they
1:22
Speaker 1: wish that too? Even after this whole or deal we've
1:26
Speaker 1: been through, you still want them in the house. You know.
1:27
Speaker 1: It's pretty typical. When they were five or six and
1:30
Speaker 1: they learned that kids grow up and move out, they
1:32
Speaker 1: were like, what, No, we want to live at home forever.
1:34
Speaker 1: But now that they are teens and tweens, they are
1:38
Speaker 1: counting the days until they get to move out of
1:40
Speaker 1: the house. Wow. But welcome to our podcast Daniel and
1:43
Speaker 1: Jorge Explain the Universe, a production of I Heart Radio,
1:46
Speaker 1: in which we take you on a tour of everything
1:49
Speaker 1: that's amazing and crazy. The big things in the universe,
1:51
Speaker 1: the tiny things in the universe, the things that are
1:54
Speaker 1: so huge they blow your mind, and the tiny particles
1:57
Speaker 1: that are hard to wrap our minds around, and we
2:00
Speaker 1: app your mind around all of it. Yeah, a lot
2:02
Speaker 1: of wrapping. In this episode, we like to talk about
2:05
Speaker 1: all the amazing things out there that is wrapping us basically.
2:08
Speaker 1: I mean, we're surrounded by mystery and wonderful and incredible
2:14
Speaker 1: things happening in the universe, and we spend a lot
2:16
Speaker 1: of time as humans looking out there into the universe
2:19
Speaker 1: and trying to understand the way things work, And one
2:21
Speaker 1: deep question we have that we're asking all the time
2:24
Speaker 1: is whether what we see is typical, whether it's usual,
2:28
Speaker 1: or whether there are rule breaking examples out there, whether
2:31
Speaker 1: there are other ways the universe could be arranged. Yeah,
2:35
Speaker 1: because the universe is full of surprises. And so one
2:38
Speaker 1: thing that we've noticed that or that probably as kids
2:41
Speaker 1: we know it is about our Solar system, about planets
2:43
Speaker 1: and moons, is that there's sort of a like a
2:46
Speaker 1: size hierarchy, right, Like you know, suns and stars are
2:50
Speaker 1: bigger than planets, and planets are bigger than moons, and
2:53
Speaker 1: moons are generally bigger than like asteroids, right, and rocks, yeah, exactly,
2:58
Speaker 1: And it goes all the way down to space dust
3:01
Speaker 1: that we talked about on a recent episode. It's fascinating
3:04
Speaker 1: how our Solar system isn't actually filled with just these
3:06
Speaker 1: like different categories of objects, but this whole spectrum of
3:10
Speaker 1: objects from the tinies little particles out there all the
3:13
Speaker 1: way up to the Sun. But there does seem to
3:15
Speaker 1: be sort of an order their stars and planets and
3:18
Speaker 1: moons and then all these other little rocks, and so
3:21
Speaker 1: it's fun to wonder about whether that order could be
3:24
Speaker 1: inverted It'd be kind of weird to think that all
3:27
Speaker 1: kids are shorter than their parents, because how would it end.
3:30
Speaker 1: It would end with particle children, right, particle sized children, Yeah,
3:34
Speaker 1: cork size exactly. It actually seems to be going to
3:38
Speaker 1: the other way. A lot of people have kids that
3:40
Speaker 1: are taller than them, which means, you know, if you
3:42
Speaker 1: extrapolate that eventually children will be the size of stars.
3:45
Speaker 1: Oh wow, well my kids are already stars. Daniel in
3:49
Speaker 1: my twinkling eyes walked right into that. But I guess
3:52
Speaker 1: a big question about the universe and our Solar system
3:55
Speaker 1: is does it have to be that way? Do stars
3:58
Speaker 1: always have to be bigger than planets and through planets
4:00
Speaker 1: always have to be bigger than their moons? And one
4:03
Speaker 1: thing that inspired this question in my mind at least,
4:06
Speaker 1: was reading about a recent discovery of a really, really
4:10
Speaker 1: strange planetary system. There's a planet out there about four
4:13
Speaker 1: thousand light years from Earth that was recently discovered and
4:16
Speaker 1: confirmed by Hubble. And this planet is huge. It's three
4:20
Speaker 1: thousand times the size of the Earth. It's ten times
4:24
Speaker 1: the size of Jupiter. This thing is a monster. Wow,
4:27
Speaker 1: that is huge. I mean, Jupiter is like the biggest
4:30
Speaker 1: kid in our block. You know, now you're saying there's
4:32
Speaker 1: a planet that's ten times bigger. Yeah, and it's got
4:35
Speaker 1: a moon that's ten times the size of Neptune. So like,
4:39
Speaker 1: this moon in this other solar system is bigger than
4:43
Speaker 1: most of our planets, because than than us, much bigger
4:46
Speaker 1: than Earth. Yes, absolutely, so we are overshadowed by this moon.
4:49
Speaker 1: And that got me thinking about the question like, well,
4:52
Speaker 1: is it possible to have a planet so big that
4:55
Speaker 1: could even be bigger than its own star? Yeah, So
4:58
Speaker 1: to be on the program, we'll be asking the Russian
5:04
Speaker 1: can planets be bigger than stars? Well? Here about these
5:09
Speaker 1: huge planets kind of makes me a little house joke.
5:12
Speaker 1: You know. It's like when you see somebody with a
5:14
Speaker 1: bigger house, you're like, I wish I had a pool.
5:16
Speaker 1: Is that what you think? I think? Man, cleaning that
5:18
Speaker 1: pool must be a pain in the butt. Well, it
5:21
Speaker 1: would take away time from your that's true, yeah, exactly,
5:25
Speaker 1: unless you have lots of couches and lots of different rooms.
5:27
Speaker 1: But then you know that feels like a chore, like,
5:29
Speaker 1: oh man, I have to sit on that couch and
5:30
Speaker 1: nobody's on a miscouch in a while. So did you
5:33
Speaker 1: just get a rolling couch. Then you can just scooch
5:36
Speaker 1: over to your pool lounge next to the pool while
5:38
Speaker 1: you clean it. There's always an engineering solution to you know.
5:41
Speaker 1: I'm a big believer in smaller houses actually, so I
5:44
Speaker 1: like our cozy little planet. I had some friends actually
5:47
Speaker 1: who were on track to getting divorced, and the reason
5:50
Speaker 1: was that their house was too big for real, for real,
5:54
Speaker 1: because they were always shouting each other from across the
5:56
Speaker 1: house and they didn't end up spending time together. And
5:58
Speaker 1: they moved into a smaller house where they have to
6:00
Speaker 1: share the space and get along, and they actually totally
6:02
Speaker 1: improved their marriage. So there's an equals of one study. Well, again,
6:07
Speaker 1: I think some engineering solus might have helped. You know,
6:09
Speaker 1: there's walking talkies intercoms that could have saved their marriage
6:14
Speaker 1: as well, and kept their big house that's too high
6:16
Speaker 1: tech and this is much cheaper anyway, Bigger is not
6:19
Speaker 1: always better, you know. I like our cozy little planet. Yeah,
6:22
Speaker 1: we don't have to shout at each other to talk.
6:25
Speaker 1: We have cell phones, dand he and podcasts. Yeah. Well,
6:28
Speaker 1: but it's a big question here about bigness and whether
6:32
Speaker 1: planets can be bigger than stars. Having a hard time
6:35
Speaker 1: wrapping my head around that question. I mean, how could
6:37
Speaker 1: have planet be bigger than its star? Or what does
6:40
Speaker 1: it even mean to be bigger like dancer size or
6:44
Speaker 1: or what? Yeah, lots of fun stuff we will dig
6:46
Speaker 1: into in this very episode of our podcast. All right, Well,
6:50
Speaker 1: as usual, Daniel went out there into the wild to
6:52
Speaker 1: the Internet to ask people if they thought that planets
6:55
Speaker 1: could be bigger than stars. And so, if you are
6:57
Speaker 1: a denizen of the wilds of the Internet and you
7:00
Speaker 1: are waiting for somebody to ask you tough physics questions
7:03
Speaker 1: for which you have no time to prepare an answer,
7:05
Speaker 1: please write to us two questions at Daniel and Jorge
7:09
Speaker 1: dot com and we will send you something. Yeah, I
7:11
Speaker 1: think about it for a second. Do you think planets
7:13
Speaker 1: can be bigger than stars? Here's what people have to say. Well,
7:17
Speaker 1: I would guess it couldn't be bigger, although I would
7:20
Speaker 1: also guess that it couldn't be more massive or more
7:24
Speaker 1: dense star. I'm thinking about the door star they discovered
7:28
Speaker 1: that has a planet. Some planets can be bigger than
7:31
Speaker 1: a growth star. So yeah, I think the size of
7:34
Speaker 1: stars changes over its lifetime and after it's gotten through
7:39
Speaker 1: its red giant phase. Um. There's a few things that
7:43
Speaker 1: could happen afterwards, but I think it can ultimately turn
7:47
Speaker 1: out to be a much smaller size than it was
7:50
Speaker 1: for the majority of his life, and some large gas
7:53
Speaker 1: giant far enough away. UM. I think as a chance
7:57
Speaker 1: of being larger than its star at a point in time.
8:01
Speaker 1: My guess is that if a planet was bigger than
8:03
Speaker 1: its star in the sense that its actual mass was
8:07
Speaker 1: larger than that of its star, the planet's gravity would
8:10
Speaker 1: be bigger than that of the star, and it wouldn't
8:14
Speaker 1: really rotate around the star, but would probably form a
8:19
Speaker 1: kind of binary system. I think that a planet could
8:23
Speaker 1: be bigger than it's sun, but it would have to
8:26
Speaker 1: be secluded so that wouldn't pick up other mass. But
8:31
Speaker 1: I would also wonder if there could be sustainable life
8:35
Speaker 1: on this planet, and also would there be no nighttime
8:39
Speaker 1: on this planet? If the Sun is in place of
8:41
Speaker 1: the Moon, but the Sun is also spitting around the Earth,
8:45
Speaker 1: would it be eternal daytime? All right? Pretty intelligent answers
8:50
Speaker 1: here A lot of people digging into the masses of
8:53
Speaker 1: things and different kinds of stars that people could orbit
8:57
Speaker 1: or that planets could orbit around. A lot of interesting
9:00
Speaker 1: answers here. Yeah, a lot of fun speculation. Thank you
9:02
Speaker 1: especially to Ryan, our nine year old listener for sharing
9:05
Speaker 1: his speculation about what would be like to live on
9:07
Speaker 1: such a planet. I love the breadth of ages we
9:10
Speaker 1: have in our listening group. Yeah, so I guess let's
9:14
Speaker 1: jump into it, Daniel, And let's start what I guess
9:17
Speaker 1: with the basic question, which is like, how big could
9:19
Speaker 1: planets get? Like, is there a size limited planets? Like?
9:23
Speaker 1: Doesn't does it at some point collapse into a star? Yeah?
9:26
Speaker 1: This one is not that satisfying because it turns out
9:28
Speaker 1: that the definition of a planet, the thing that distinguishes
9:31
Speaker 1: something from being a planet and a star, is really
9:34
Speaker 1: closely connected to the size, So it's a bit arbitrary.
9:37
Speaker 1: And what distinguishes a star from a planet is whether
9:40
Speaker 1: or not there is fusion happening inside. Like you've got
9:44
Speaker 1: a big blob of stuff but it's just sort of
9:46
Speaker 1: sitting there and not fusing. You call that a planet.
9:48
Speaker 1: If it's got enough stuff so the collapses and causes
9:51
Speaker 1: fusion to happen inside of it, then you call it
9:54
Speaker 1: a star. And the thing that controls whether that happens
9:58
Speaker 1: is basically the mass of stuff you have, right, like
10:01
Speaker 1: the gravity the thing that's compressing all of that mass,
10:04
Speaker 1: it might trigger fusion or not. It's not dependent on
10:07
Speaker 1: the size of it, right, the physical volume. It only
10:10
Speaker 1: depends on the mass. And you do these calculations, and
10:13
Speaker 1: you can talk about things in terms of like the
10:15
Speaker 1: mass of Jupiter. So Jupiter, for example, doesn't have enough
10:19
Speaker 1: stuff to have enough gravity to collapse and cause fusion
10:23
Speaker 1: to happen at its core. You need like about ten
10:26
Speaker 1: or thirteen times the massive Jupiter to have a special
10:29
Speaker 1: kind of star called a brown dwarf, which is a
10:31
Speaker 1: special kind of fusion. And so anything up to about
10:34
Speaker 1: ten times the massive Jupiter is definitely a planet because
10:38
Speaker 1: it can't have fusion inside of it, right, But it doesn't.
10:41
Speaker 1: It also depends on what it's made out of. Like
10:44
Speaker 1: Jupiter is made mostly out of hydrogen, right, which would
10:48
Speaker 1: sort of fuse easily. But if you have something, you know,
10:50
Speaker 1: like a giant planet made out of iron, you would
10:53
Speaker 1: need a whole lot more to get anything going if
10:56
Speaker 1: if you can't all yeah, it does definitely depend on
10:58
Speaker 1: the material. But most the stuff in the universe is hydrogen, right,
11:01
Speaker 1: So if you're gonna get a blob of stuff and
11:03
Speaker 1: cold us it into an object. It's mostly going to
11:06
Speaker 1: be hydrogen, but you also are sensitive to the kinds
11:09
Speaker 1: of hydrogen you get, Like you can get a brown
11:11
Speaker 1: dwarf only under certain conditions. We have the right ratios
11:15
Speaker 1: of different isotopes of hydrogen to start a particular kind
11:17
Speaker 1: of fusion. To start the kind of fusion we have
11:19
Speaker 1: going on in our son, for example, you need basically
11:22
Speaker 1: pure hydrogen of the simplest isotope, and then you would
11:25
Speaker 1: even need more of it. So how much stuff you
11:27
Speaker 1: need to start fusion definitely depends on the amount of
11:30
Speaker 1: stuff you have. And you're right, if you just start
11:31
Speaker 1: with a blob of iron, the massive hydrogen, that wouldn't
11:34
Speaker 1: actually fuse, right, Yeah, because it can. You could have
11:37
Speaker 1: like a giant planet made out of iron that it
11:41
Speaker 1: could be. You know, the whole size of the galaxy?
11:43
Speaker 1: Is that? Is that crazy? Or would that just turn
11:45
Speaker 1: into like a neutron star at some point? Wow, the
11:47
Speaker 1: size of the galaxy. Oh my gosh, you took like
11:50
Speaker 1: all of the iron in the galaxy and blobbed it
11:52
Speaker 1: up together into a big planet. Would that start to
11:55
Speaker 1: fuse or do other crazy stuff? Yeah? I don't know.
11:58
Speaker 1: I don't know anybody's does that calculation. That's really fun.
12:00
Speaker 1: It definitely wouldn't fuse, right because, as you say, fusion above,
12:03
Speaker 1: iron actually absorbs energy and so it would cool the object,
12:06
Speaker 1: and so it wouldn't create fusion. If you get enough
12:09
Speaker 1: heavy metal in there, then gravity eventually wins. It'll just
12:13
Speaker 1: compress it further and further until it collapses into a
12:16
Speaker 1: new drawn star. And if it has even more mass,
12:18
Speaker 1: it will become a black hole. So a galaxy sized
12:22
Speaker 1: blob of iron would pretty likely turn into a big
12:25
Speaker 1: black hole. But in terms of the stuff that we
12:27
Speaker 1: actually see out there in the galaxy, the materials that
12:30
Speaker 1: are available, most of the stuff out there in the
12:32
Speaker 1: galaxy is still hydrogen. You know, we've been slowly cooking
12:36
Speaker 1: hydrogen into heavier elements and the inside of stars, but
12:39
Speaker 1: it's still a very tiny fraction of the hydrogen in
12:42
Speaker 1: the galaxy that's been turned into heavier metals. There's kind
12:45
Speaker 1: of an upper limit then, on the mass a planet
12:47
Speaker 1: could have, at least in the universe that we see
12:49
Speaker 1: not in his imaginary iron field universe. That's right up
12:53
Speaker 1: to about you know, ten or fifteen times the massive Jupiter.
12:56
Speaker 1: You can still call it a planet. You can arrange
12:59
Speaker 1: for other ways to work to get more massive without
13:01
Speaker 1: actually fusing, but that's the typical limit. I see anything
13:05
Speaker 1: more than fifteen times a massive Jupiter, if it's made
13:08
Speaker 1: out of hydrogen, then it's going to start to fuse
13:10
Speaker 1: and become a son and it would become a star exactly.
13:13
Speaker 1: All right, Well, that's like the mass limit. But we
13:15
Speaker 1: we kind of post a question as a bigger can
13:18
Speaker 1: a plan and be bigger than stars, in which case
13:21
Speaker 1: it can has more to do with the volume, right,
13:23
Speaker 1: like the measurement of it the size. Yeah, and this
13:26
Speaker 1: is really weird. Like if you took Jupiter and you
13:29
Speaker 1: started adding mass to it, you have like a hydrogen pump,
13:32
Speaker 1: and you just started dumping hydrogen into Jupiter, then it
13:34
Speaker 1: would get more massive, but it wouldn't actually get larger
13:38
Speaker 1: very quickly because it would mostly just get denser, Like
13:41
Speaker 1: the gravity would get more intense and it would hold
13:43
Speaker 1: itself together and it would get denser and denser. So
13:46
Speaker 1: as you pump hydrogen into it, you could actually get
13:49
Speaker 1: Jupiter up to like seventy times its mass without changing
13:53
Speaker 1: its volume very much. You're saying Jupiter right now is
13:56
Speaker 1: actually kind of fluffy. I mean a lot of it
13:58
Speaker 1: is just like gas right out it is just gas.
14:01
Speaker 1: And if you added seventy jupiters and put them all
14:03
Speaker 1: on top of each other, they would just like collapse
14:06
Speaker 1: to a denser object about the same size as Jupiter. Yeah,
14:10
Speaker 1: are there any examples of that? Have we seen? Yeah?
14:12
Speaker 1: Actually there's a bunch of them. There's a star out there,
14:14
Speaker 1: trappist one A. It's eighty times the massive Jupiter and
14:18
Speaker 1: it's a star. Right, so this thing is burning, it's
14:21
Speaker 1: a star. It's the same size as Jupiter. Right, So
14:24
Speaker 1: right now out there there's a star which is the
14:26
Speaker 1: same size as a planet. It's just much much more dense, right,
14:30
Speaker 1: This thing is so dense. It's mostly hydrogen, but it's
14:32
Speaker 1: like twenty five times as dense as granite. That. Yeah,
14:36
Speaker 1: that's crazy to think that hydrogen can be that dense. Yeah,
14:39
Speaker 1: they're really weird phases of hydrogen. Als. So when he
14:41
Speaker 1: gets so dense, they are these things called like metallic hydrogen,
14:44
Speaker 1: and we can dig into that one time in some
14:46
Speaker 1: other episode. But there are a bunch of these things,
14:48
Speaker 1: Like there's another star out there that's a red dwarf
14:51
Speaker 1: and it's about the size of Saturn, and so it's
14:54
Speaker 1: actually a star that's smaller, smaller than Jupiter, right, And
14:58
Speaker 1: that's just because of these weird effects that as you
15:01
Speaker 1: add more volume, the gravity gets more intense, and so
15:04
Speaker 1: the planet doesn't actually grow in size. It only grows
15:07
Speaker 1: in mass. But it's still a star, meaning it has
15:10
Speaker 1: fusion at the center. It's just not exploding maybe like
15:13
Speaker 1: our star. And then there are some other examples. You know,
15:16
Speaker 1: we say that as you add more mass to the planet,
15:18
Speaker 1: it doesn't actually grow in size. That's what we expect
15:21
Speaker 1: and that's what we see most of the time, but
15:23
Speaker 1: there are some counterexamples that we don't yet understand. Like
15:26
Speaker 1: there's a planet out there they found called celt eleven B.
15:30
Speaker 1: This is the one they called the styrofoam planet because
15:33
Speaker 1: it's one fifth the mass of Jupiter, but it's actually
15:36
Speaker 1: like larger than Jupiter. So it's like a big fluffy planet,
15:40
Speaker 1: extra fluff. It's like Jupiter exactly. It's like the whipped
15:44
Speaker 1: up version. Right. Somebody put a mixer in there and
15:46
Speaker 1: set it on high and they're gonna fold it into
15:48
Speaker 1: their angel food cake. But this is not something that
15:50
Speaker 1: we understand, like it's thought in the models it shouldn't exist,
15:53
Speaker 1: and so it tells us that there's something about planetary
15:56
Speaker 1: formation we don't understand, or maybe it's some weird thing
15:59
Speaker 1: and it just explode, odored and still coalescing. You know,
16:02
Speaker 1: a lot of questions there, but mostly we expect that
16:06
Speaker 1: you can't get a planet much larger than Jupiter by volume.
16:10
Speaker 1: Oh I see, So there is kind of a size
16:13
Speaker 1: limit of two planets because if you keep adding more,
16:17
Speaker 1: at some point it will stay the same size, but
16:19
Speaker 1: at some point it will become a star. So you
16:21
Speaker 1: can't have a bigger planet. Yeah, exactly. Roughly, Jupiter is
16:25
Speaker 1: about the biggest planet you can make that we understand.
16:28
Speaker 1: There's one example out there that the king of planets
16:31
Speaker 1: currently is this planet out there h D zero five
16:35
Speaker 1: four six b N, which we think has seven times
16:38
Speaker 1: the diameter of Jupiter. So this is the largest known planet,
16:42
Speaker 1: but it still looks like it's forming, like it's in
16:44
Speaker 1: a young solar system, and so it may actually be
16:46
Speaker 1: like a brown dwarf that's still sort of coalescing. The
16:49
Speaker 1: biggest baby in the universe. It's a big, dangerous baby.
16:54
Speaker 1: So careful what you call it. But I guess the
16:58
Speaker 1: main point is there's a size limit and a mass
17:02
Speaker 1: limit to planets if we sort of stick to what
17:04
Speaker 1: we see in the universe, which is mostly hydrogen. But
17:08
Speaker 1: I guess the point is that there isn't large enough
17:10
Speaker 1: concentrations of the heavier elements to make biger planet. Is
17:13
Speaker 1: that kind of yeah? I mean, there might be some
17:15
Speaker 1: really big planets out there that fluctuate into having huge
17:19
Speaker 1: deposits of rock, but you know there'll be a lot
17:21
Speaker 1: of rock. Is a larger rocky core in the center
17:23
Speaker 1: of Jupiter than the volume of the Earth, right, So
17:27
Speaker 1: typically if you get that large a rocky planet, it's
17:30
Speaker 1: also going to have a huge amount of gas around it,
17:32
Speaker 1: as you'll end up with the gas planet. All right, well,
17:35
Speaker 1: let's get into how the other side of the equation,
17:39
Speaker 1: which are the stars? How small can a star get?
17:42
Speaker 1: And then we'll talk about the question can a planet
17:45
Speaker 1: get bigger than its star? First, let's take a quick break.
18:00
Speaker 1: All right, we're talking about planets and stars and their
18:03
Speaker 1: relative sizes. Can your kid be bigger than you depends
18:08
Speaker 1: on what you feed them. I suppose, yeah, who knows
18:11
Speaker 1: what they put in milk these days? But Yeah, we
18:14
Speaker 1: talked about planets, and now let's talk about stars, Like,
18:16
Speaker 1: what's the smallest size star can get? Because if you
18:18
Speaker 1: can have a tiny star but it's pretty heavy, then
18:21
Speaker 1: you could imagine it can have a much bigger planet
18:24
Speaker 1: orbiting around it. Yeah exactly, We're gonna talk about the
18:27
Speaker 1: biggest planet. Now we need to talk about the smallest
18:29
Speaker 1: possible star. The thing that's really fascinated about stars is
18:32
Speaker 1: that their size depends on where they are in their
18:35
Speaker 1: life cycle. Like a star isn't just born and then
18:38
Speaker 1: it fizzles out and it always stays the same size.
18:40
Speaker 1: It actually evolves a lot. So the size of a star,
18:43
Speaker 1: even like our sun, depends on where it is in
18:46
Speaker 1: its life cycle. Yeah, it changes size, like it's our
18:49
Speaker 1: son is going to get bigger, much bigger at some
18:51
Speaker 1: point in the future and then shrink. Yeah exactly. And
18:54
Speaker 1: so the way a star is formed is that you
18:56
Speaker 1: get a huge blob of gas like hydrogen gas, which
18:59
Speaker 1: move to the stuff when you're forming a solar system,
19:02
Speaker 1: goes to the Sun because gravity is a runaway process.
19:05
Speaker 1: You know, the heaviest thing has the most gravity, so
19:07
Speaker 1: it attracts the most stuff, so you get most of
19:09
Speaker 1: the hydrogen sort of falling in towards the center of
19:12
Speaker 1: the Solar system, and that's how it gets big. Right,
19:14
Speaker 1: that's why it doesn't just turn into a planet. It
19:16
Speaker 1: turns into a star because it has much more than
19:19
Speaker 1: ten or a hundred or even a thousand times the
19:21
Speaker 1: mass of Jupiter. And so the early stages of the
19:24
Speaker 1: stars that it just gathers all that stuff and then
19:26
Speaker 1: fusion happens in the center of the star and that
19:28
Speaker 1: pushes back against the gravity. Right, you have gravity pulling
19:32
Speaker 1: everything in to form the star and then fusion shining
19:35
Speaker 1: energy out and keeping it from collapsing any further. Yeah,
19:39
Speaker 1: So then that does that put a limit then to
19:40
Speaker 1: how small or how large a star can be. Well,
19:43
Speaker 1: in the beginning, it just depends on the mass, Like
19:46
Speaker 1: as you add mass to a star, it gets bigger
19:49
Speaker 1: and bigger and bigger. And our Sun is actually unusually
19:51
Speaker 1: large on average, like most of the stars in the
19:54
Speaker 1: galaxy are smaller than our Sun. But there's no limit
19:57
Speaker 1: really on the size of a star in this phase,
20:00
Speaker 1: Like it can get really really big. And we're gonna
20:02
Speaker 1: do a fun podcast episode next week. I think about
20:05
Speaker 1: what is the biggest star in the universe. But we're
20:07
Speaker 1: interested in the smallest star, right, But what happens when
20:11
Speaker 1: a star burns is that fusion pushes all of this
20:14
Speaker 1: stuff out. So you get a big star, which causes
20:16
Speaker 1: this gravity, which collapses stuff in, and then it causes fusion,
20:20
Speaker 1: which works backwards. It's like a back reaction. It pushes
20:22
Speaker 1: all the stuff out. It tends to make the star bigger.
20:25
Speaker 1: So what happens in the life cycle of the stars
20:27
Speaker 1: that it burns for a long time, like billions of
20:29
Speaker 1: years depending on its size, and then it grows like,
20:32
Speaker 1: as you said, our star is gonna get much much bigger,
20:35
Speaker 1: and not like twice as big or three times as big.
20:38
Speaker 1: It's gonna be huge. It's gonna grow so much that
20:41
Speaker 1: it's radius is going to almost encapsulate the Earth. Yeah,
20:45
Speaker 1: there'll be a nice toasty time for Earth if we're
20:49
Speaker 1: still here. And this is important to understand in the
20:52
Speaker 1: question later about whether or not you're gonna have a
20:54
Speaker 1: planet surrounding a star, because before a star gets small,
20:57
Speaker 1: it gets really really big, right, And and what happens
21:00
Speaker 1: is that it collapses right as you say, what happens
21:03
Speaker 1: in fusion is that you're making these heavier metals, and
21:05
Speaker 1: so you start out with a blob of hydrogen, but
21:08
Speaker 1: soon you have a core of helium which is fused
21:10
Speaker 1: from the hydrogen, and then that helium, if the star
21:13
Speaker 1: is big enough, burns and the heavier stuff and you
21:15
Speaker 1: end up with neon and carbon and oxygen and all
21:18
Speaker 1: of this stuff. And so now you have increasing density
21:21
Speaker 1: in the center of the star and gravity is sort
21:24
Speaker 1: of pulling on it. Again. I love the dynamics of
21:26
Speaker 1: star formation and star life cycles because it's this like
21:28
Speaker 1: back and forth between fusion that's pushing out on the
21:31
Speaker 1: star and gravity that's like trying to collapse it, and
21:34
Speaker 1: each one sort of trips itself up, Like gravity causes fusion,
21:37
Speaker 1: which pushes stuff out, but then fusion creates denser stuff,
21:40
Speaker 1: which increases the gravity. And so eventually what happens is
21:44
Speaker 1: that the star collapses because you get so much heavy
21:47
Speaker 1: stuff in its center that it can no longer burn. Yeah,
21:49
Speaker 1: it's a big drama, like a bit of a dysfunctionnel
21:53
Speaker 1: relationship between fusion and gravity. Maybe they should just get
21:57
Speaker 1: a smaller house, you know, maybe that would work. A
21:59
Speaker 1: smaller universe. Hey, we would all be a lot cozier,
22:03
Speaker 1: be like living in the pandemic all the time, forever,
22:07
Speaker 1: all right, But I guess it seems like the inevitable
22:09
Speaker 1: fate of most stars is to shrink. Like theyll might
22:12
Speaker 1: have some heydays where they're huge, but then eventually they
22:15
Speaker 1: all shrink because they run out of field. Basically, yeah, exactly,
22:18
Speaker 1: they shrink, and what you are left with is some
22:21
Speaker 1: really really dense core. Like they blow out a lot
22:23
Speaker 1: of the stuff and you get some sort of like
22:25
Speaker 1: layers of fluff blown out into the Solar system. But
22:28
Speaker 1: at the core, which you're left with, it is a
22:30
Speaker 1: few different options. Depending on the mass you started with,
22:33
Speaker 1: you might end up with a white dwarf, or a
22:36
Speaker 1: neutron star, or actually a black hole. What's a white boar?
22:40
Speaker 1: A white dwarf is the future of our Sun. It's
22:43
Speaker 1: basically just a huge hot blob of heavy metals, and
22:47
Speaker 1: there's no more fusion happening anymore. It's like not big enough,
22:50
Speaker 1: there's not enough compression to cause fusion at its core.
22:54
Speaker 1: But it's still hot. Right. If you like took a
22:56
Speaker 1: scoop out of the center of the Sun and put
22:58
Speaker 1: it in space, it still be a big hot blob
23:01
Speaker 1: of heavy metals and that's what a white dwarf is.
23:04
Speaker 1: It's not glowing anymore because it's making fusion, but it's
23:06
Speaker 1: still hot. So they call it a white dwarf because
23:08
Speaker 1: it glows from its heat, right, But it's not technically
23:11
Speaker 1: a star anymore, right, because there's no fusion. Man, good question,
23:15
Speaker 1: is a white dwarf a star? You're right, there's no
23:17
Speaker 1: fusion happening anymore. It's like a stellar remnant. It's definitely
23:20
Speaker 1: not fusing. But I think you do still call a
23:22
Speaker 1: white dwarf a star. Really, but we just said earlier
23:25
Speaker 1: that we need a fusion. Daniel, you're confusing me. Oh
23:27
Speaker 1: my god, astronomical names are confusing. What news flash? Well,
23:32
Speaker 1: it's they call it a star because it's bright and
23:33
Speaker 1: it's giving of light right in the form of heat,
23:37
Speaker 1: but it's not fusing. It's kind of it's kind of
23:40
Speaker 1: somewhere in there. It's somewhere in there. Does it become
23:42
Speaker 1: a planet eventually? Eventually? Sort of? What happens is that
23:45
Speaker 1: these things eventually cool and they become a black dwarf.
23:48
Speaker 1: And a black dwarf is just a white dwarf that's
23:50
Speaker 1: had enough time to radiate away its heat into the
23:53
Speaker 1: universe and cool from being white hot to be you know, cooler.
23:58
Speaker 1: The interesting thing is that there aren't any black dwarks
24:01
Speaker 1: in the universe yet because they think it would take
24:04
Speaker 1: like trillions of years for a white dwarf to cool off,
24:08
Speaker 1: and so there just hasn't been enough time yet to
24:10
Speaker 1: form any of these things. I guess they sort of
24:12
Speaker 1: become planets, but everyone's too polite to tell them that
24:14
Speaker 1: they're no longer a star. You know, it's kind of
24:16
Speaker 1: like a professor emeritus. You know, they're not really professors anymore,
24:20
Speaker 1: but you know, you don't want to striper way their title,
24:23
Speaker 1: yeah exactly, or last decades a list celebrity. They don't
24:26
Speaker 1: get invited to the parties anymore, but you know, people's
24:28
Speaker 1: last for their autograph. But the amazing thing is that
24:30
Speaker 1: you get like six of the mass of the original star,
24:33
Speaker 1: but now compacted into an area that's about the volume
24:37
Speaker 1: of the Earth. Our sun will be about the size
24:40
Speaker 1: of the Earth after all this happens, even though it
24:42
Speaker 1: will be much much more dense than the is. It
24:45
Speaker 1: sounds tiny, But then there are other possible fates for
24:47
Speaker 1: a star, right, not just a wordwarf. That's right, If
24:50
Speaker 1: the amount of stuff that you end up in the
24:51
Speaker 1: core is large enough that you still have a lot
24:53
Speaker 1: of gravitational pressure. You can collapse those heavy metals even
24:57
Speaker 1: further and you don't get fusion. What you do is
24:59
Speaker 1: you sort of force the electrons and protons together and
25:02
Speaker 1: you end up with forming neutrons. It's called electron capture.
25:06
Speaker 1: You're like push the electron into the proton and you
25:09
Speaker 1: get this interaction in the core that turns all the
25:12
Speaker 1: protons and electrons into neutrons, and then you get a
25:15
Speaker 1: neutron star. Now, but technically that's also not a star
25:19
Speaker 1: because there's no fusion going on anymore. Hold on, I'm
25:22
Speaker 1: gonna make sure I have a comprehensive list of your
25:24
Speaker 1: objections to astronomical categories so we could submit it to
25:27
Speaker 1: the committee. Let's get this straight out, because you're confusing.
25:30
Speaker 1: At least one cartoon is here anyway. That's right, Well,
25:33
Speaker 1: I have the official form here, so I'll make sure
25:35
Speaker 1: to fill it out and submit it after we'dune. But
25:37
Speaker 1: you're right, it's a neutron star. It's not fusing, right.
25:40
Speaker 1: It's probably still hot like we see neutron stars, but
25:43
Speaker 1: they don't emit light in the same way. Mostly we
25:46
Speaker 1: see them in the X ray. But these things are
25:49
Speaker 1: tiny because they're super duper dense. So you have like
25:53
Speaker 1: one and a half times the mass of the Sun,
25:55
Speaker 1: and the radius of these things is like ten kilometers.
25:58
Speaker 1: It's like a whole star in Los Angeles. Wow. But
26:01
Speaker 1: it's amitting light just from its heat or from from
26:04
Speaker 1: some kind of process or why are we still giving
26:06
Speaker 1: it the honorary title of the star. It's definitely not fusing,
26:10
Speaker 1: and so it's giving off light the same way everything
26:12
Speaker 1: gives off light that everything with a temperature radiates. It's
26:15
Speaker 1: called black body radiation. And all matter that has electromagnetic
26:19
Speaker 1: interactions will give off light at some frequency that's connected
26:23
Speaker 1: to its temperature. And that's why you know things that
26:25
Speaker 1: get hot glow, even things that you don't see glowing
26:28
Speaker 1: or are actually glowing just at wavelength that you cannot tell.
26:33
Speaker 1: All right, And then a star can also end up
26:35
Speaker 1: as a black hole, right, Like if you compress you
26:38
Speaker 1: have more mass, even like stronger gravity, it can collapse
26:42
Speaker 1: into a black hole. Yeah, exactly. The neutron stars prevented
26:45
Speaker 1: from collapsing into a black hole because these neutrons don't
26:48
Speaker 1: want to press against each other even further there like
26:50
Speaker 1: pushing back. There's some pressure pushing back, but if you
26:53
Speaker 1: have enough mass, you can also overcome that. And then
26:55
Speaker 1: you get a total gravitational collapse into a black hole.
26:59
Speaker 1: And because the things are collapsing right there, even more dense.
27:02
Speaker 1: And so from white dwarf to neutron star to black hole,
27:06
Speaker 1: the density of matter at the core at least is increasing,
27:09
Speaker 1: and so the radius is decreasing, and so these things
27:12
Speaker 1: get pretty small. And now you're gonna tell me that
27:14
Speaker 1: the black holes also star, Daniel, it's a black hole star?
27:17
Speaker 1: Is that the technical term? It's a star of science?
27:21
Speaker 1: At least, it's a star of mystery. It's a tell
27:24
Speaker 1: our performer out there in space. But yeah, then at
27:27
Speaker 1: that point it's no longer star. I mean, come on,
27:29
Speaker 1: it's a black hole. A black hole is not a star.
27:31
Speaker 1: I think we can definitely rule on that one here today.
27:33
Speaker 1: All right, well, let's get into now whether or not
27:37
Speaker 1: you could have a planet that's bigger than its star.
27:40
Speaker 1: We talked about how big planets get and how small
27:43
Speaker 1: stars can get, and how to push the limits of
27:47
Speaker 1: what astronomers call things in space. But first let's take
27:51
Speaker 1: a quick break. All right, we've set up these two
28:06
Speaker 1: topics Daniel, stars and planets, and now we're gonna ask
28:09
Speaker 1: can a planet be bigger than its star? I guess
28:11
Speaker 1: the question I just remember what we talked about is
28:14
Speaker 1: is yes, right. I mean, you can get tiny stars
28:16
Speaker 1: and you can get big planets. So there must be
28:19
Speaker 1: some point, someplace in the universe where the two are together.
28:22
Speaker 1: It certainly seems possible, right, But the key thing is
28:25
Speaker 1: can the planet survive? Because the stars tend to be
28:28
Speaker 1: large when they're young, then get even larger before they
28:32
Speaker 1: get smaller, and so for a planet to outsize its star,
28:36
Speaker 1: it has to survive that transition. And that transition is
28:39
Speaker 1: not an easy one to survive, right, Like going to
28:41
Speaker 1: this red super giant is going to be pretty toasty
28:44
Speaker 1: for any inner planets, and the collapse to like a
28:47
Speaker 1: black hole or a neutron star can involve a super nova.
28:50
Speaker 1: So even if the remnant is smaller than the planet
28:55
Speaker 1: originally was, to satisfy sort of say, technically you have
28:58
Speaker 1: to survive that transition. You have to make it to
29:02
Speaker 1: be bigger than your parents. I guess, I guess you
29:04
Speaker 1: have to make it through your parents middle age or something.
29:08
Speaker 1: You have to wait it out, wait for them to shrink,
29:10
Speaker 1: and then you're taller than your parents. Right exactly when
29:13
Speaker 1: their life explodes, if you can somehow hold on, then
29:18
Speaker 1: stay away from them. To Jupiter. Yeah, Jupiter, you should go,
29:25
Speaker 1: like you know, on a backpacking trip through Europe and
29:27
Speaker 1: come back when the Sun has become a white spread.
29:29
Speaker 1: Take that job in Asia for sure, and then come back.
29:33
Speaker 1: I think that is good parenting advice and good astronomical advice.
29:36
Speaker 1: Become a rogue planet at some point in your life,
29:39
Speaker 1: you get that tattoo, you know, maybe that's what the
29:42
Speaker 1: red spot is on Jupiter. Maybe it's already done his
29:45
Speaker 1: traveling man it. Maybe it's a tattoo of the sun.
29:48
Speaker 1: You know how some people get like a mom tattoo.
29:50
Speaker 1: Maybe that thought it's red, you know, that makes sense.
29:55
Speaker 1: We are solving deep, deep questions. An old, old, ancient
29:59
Speaker 1: miss the three is about the universe today on the
30:01
Speaker 1: podcast Physics and Parenting Podcast. All right, well, um, yeah,
30:06
Speaker 1: it's tricky to survive, but it's totally possible, right Like
30:09
Speaker 1: Jupiter in our solar system is going to survive our
30:12
Speaker 1: sun exploding and becoming a white dwarf right, because it's
30:15
Speaker 1: so far away. It is, but you know, it's going
30:17
Speaker 1: to be pretty crazy and we're gona lose some of
30:20
Speaker 1: the planets, and so it might be that Jupiter doesn't survive.
30:23
Speaker 1: Like Jupiter itself won't be disintegrated, but it will be disturbed.
30:27
Speaker 1: And so, for example, if Neptune takes off or Saturn
30:30
Speaker 1: takes off after the Sun goes white dwarf, and maybe
30:33
Speaker 1: that it perturbs the orbit of Jupiter so that it
30:35
Speaker 1: also gets flung out into space. Or you need like
30:38
Speaker 1: a new stable configuration and things have changed, and some
30:41
Speaker 1: of these things are a bit fragile, but it's technically possible, though,
30:45
Speaker 1: write like, isn't it kind of hard to kick a
30:46
Speaker 1: planet out of Sun's orbit? It's not that easy. But
30:49
Speaker 1: one thing that can do it is having your star
30:52
Speaker 1: grow to red super giant and push off outer layers,
30:56
Speaker 1: and so it totally can happen. And that's because what's
30:58
Speaker 1: left of the star when it's shed its layers is
31:01
Speaker 1: much smaller than the original star, so it just doesn't
31:04
Speaker 1: have the gravity to hold onto the big planets in
31:07
Speaker 1: the same orbit. So those planets sort of relax and
31:10
Speaker 1: get bigger orbits, and now those orbits are a little
31:12
Speaker 1: bit looser and more chaotic, and so they're more susceptible
31:16
Speaker 1: to tugs from passing stars that can pull them out
31:19
Speaker 1: of their orbits and even out of the Solar system.
31:21
Speaker 1: All right, well, it might happen in our Solar system.
31:23
Speaker 1: But we have examples of this configuration of a bigger
31:26
Speaker 1: planet than its star that we seem like, do we
31:29
Speaker 1: have evidence we actually have seen one. Yeah, NASA's telescope tests,
31:33
Speaker 1: which is excellent at looking for these things, that has
31:36
Speaker 1: spotted this solar system in the constellation Cancer. It's about
31:40
Speaker 1: fifteen hundred light years away, and at the center is
31:44
Speaker 1: a white dwarf, right, And a white dwarf is something
31:47
Speaker 1: which is a stellar remnant, which means that there used
31:49
Speaker 1: to be a big, powerful star there which like our Sun,
31:52
Speaker 1: burned for a long time billions of years and then
31:55
Speaker 1: collapsed into a white dwarf. And around this white dwarf
31:58
Speaker 1: they see a planet which is bigger than the white dwarf.
32:02
Speaker 1: It is. It's about the size of Neptune. And these
32:05
Speaker 1: white dwarfs, you know, they're about the size of a
32:07
Speaker 1: small rocky planet like the white dwarf that's in the
32:10
Speaker 1: future of our star will be about the volume of Earth,
32:13
Speaker 1: and so this one we think is about the same size.
32:16
Speaker 1: And so this Earth size star has a planet around
32:19
Speaker 1: it that's the size of Neptune. Wow. So that's the
32:22
Speaker 1: situation that we're asking about the star with the planet
32:25
Speaker 1: that's bigger than flying around. And we've seen these, or
32:28
Speaker 1: at least we've detected them using gravity, right, Yeah, exactly,
32:31
Speaker 1: we have detected this one. It's sort of weird. We
32:33
Speaker 1: don't really understand it. Like the Neptune size planet. It's
32:36
Speaker 1: pretty close to the star. It's much closer to the
32:40
Speaker 1: star than you would expect because that star must have
32:43
Speaker 1: been like a red super giant at some point toasting
32:45
Speaker 1: any planet that was near it. And so this planet
32:48
Speaker 1: is like inside the radius of where the star should
32:51
Speaker 1: have been, and so there must have been some crazy
32:53
Speaker 1: gymnastics changing orbital radii after that happened. Oh, I see,
32:59
Speaker 1: it's like us surviving the flare up of our sun, Like,
33:02
Speaker 1: how could we still be there? Yeah, exactly, And so
33:05
Speaker 1: probably this planet was somewhere further out and then something
33:09
Speaker 1: crazy happened and it migrated closer. After the planet became
33:13
Speaker 1: a white dwarf. So that's sort of like one survival
33:15
Speaker 1: strategy is like maybe you don't go all the way
33:17
Speaker 1: to Asia, but you just have like a really distant
33:19
Speaker 1: orbit and then you come back in closer after then
33:23
Speaker 1: you reconnect with your parents after life, move into the city,
33:27
Speaker 1: and then you come back to the suburbs, you know,
33:29
Speaker 1: when they're ready to retire. All right. So that's one
33:32
Speaker 1: example that we've seen. Are there more? That's the only
33:34
Speaker 1: one that we've seen. But you know, the fact that
33:37
Speaker 1: we've seen this one means that it is possible to
33:40
Speaker 1: survive your stars transition to white dwarf for neutron star
33:45
Speaker 1: or even black hole, and so it's possible that there
33:48
Speaker 1: are a lot of these things out there. It's probably
33:50
Speaker 1: pretty common. Yeah. Cool. Well, I feel like we kind
33:54
Speaker 1: of cheated a little bit, though, Daniel, because if I
33:57
Speaker 1: hold you to the technical definition of a star to
33:59
Speaker 1: say that they're as to be fusion in it, it
34:01
Speaker 1: sort of becomes a very different question, right, Like, it
34:03
Speaker 1: is possible for a white dwarf to have planets that
34:06
Speaker 1: are bigger than it, but a white twarf doesn't have
34:09
Speaker 1: fusion in it, that's right. A white dwarf doesn't have
34:11
Speaker 1: fusion in it, and either does a neutron star. So
34:13
Speaker 1: if I hold you to the definition of that we
34:16
Speaker 1: post earlier about a star that it has to have
34:18
Speaker 1: fusion in it, do you think it's possible still for
34:21
Speaker 1: a fusing star to have a planet that's bigger than it. No,
34:24
Speaker 1: I don't think so, because a fusing star would have
34:26
Speaker 1: to be pretty big, right. You need to be like
34:28
Speaker 1: a hundred times the massive Jupiter to get that fusion going,
34:32
Speaker 1: and that would eventually be larger than Jupiter. And if
34:35
Speaker 1: you had a planet in orbit that was that same size,
34:39
Speaker 1: it would also turn into a star. And so what
34:41
Speaker 1: you would get then is a binary star system. And
34:44
Speaker 1: so it sort of comes just out of this definition
34:46
Speaker 1: of what we call a star or a planet. If
34:48
Speaker 1: you're gonna have something that's not fusing orbiting around someone
34:51
Speaker 1: that is fusing, then the thing that's fusing has got
34:53
Speaker 1: to have more mass otherwise it wouldn't be fusing. You
34:56
Speaker 1: just confuse me on that last state. So it doesn't
35:01
Speaker 1: sound possible, right, because if the star has to be fusing,
35:03
Speaker 1: they're usually bigger than the largest planet that you can
35:06
Speaker 1: have without fusion. That's what you're saying. You just defused
35:11
Speaker 1: the suggestion I diffused this whole podcast apparently, but I
35:16
Speaker 1: guess I mean, it's still possible. You just have to
35:19
Speaker 1: invert what you call who's orbiting who? Like, you could
35:23
Speaker 1: technically have a really heavy planet like it's it's it's
35:27
Speaker 1: mostly iron or there's a lot of iron in it,
35:29
Speaker 1: so it's very heavy. You could have a star maybe
35:33
Speaker 1: that's bigger than it, but it could be that the
35:36
Speaker 1: star is orbiting the planet. If the planet had more mass,
35:39
Speaker 1: then you could say the star is orbiting the planet.
35:41
Speaker 1: You know, in reality, it's not the case that the
35:43
Speaker 1: planet is orbiting the star. The two things are sort
35:45
Speaker 1: of orbiting each other, and the point that they orbit
35:48
Speaker 1: is their center of mass. And typically a star is
35:50
Speaker 1: much much heavier than the planet, and so the center
35:52
Speaker 1: of mass is close to the center of the star.
35:55
Speaker 1: But in a binary star system, the center of masses
35:58
Speaker 1: between them, and so they're both orbiting this point that's
36:00
Speaker 1: between the two of them. So where that point is
36:03
Speaker 1: that their orbiting depends on the relative mass the two objects.
36:06
Speaker 1: So yeah, in your fantasy system where you get to
36:08
Speaker 1: build up whatever you like, you could make an enormous
36:11
Speaker 1: iron planet that has more mass than the star it's using.
36:14
Speaker 1: Of course, they would collapse into a black hole, but
36:17
Speaker 1: the star would mostly be in orbit around Jorge's black
36:21
Speaker 1: hole world. Alright, Well, it sounds like a lot of
36:25
Speaker 1: this depends on the definition of a star. If we
36:29
Speaker 1: let stars keep their honorific even after they stopped using,
36:32
Speaker 1: then it's totally possible for a planet to be bigger
36:34
Speaker 1: than a star, because then the star kind of shrinks
36:37
Speaker 1: and becomes a door for a neutron star. Yeah, if
36:39
Speaker 1: you think professor emeritus are still professors, then a white
36:43
Speaker 1: divorf is still a star. But if not, then it's
36:47
Speaker 1: technically possible but not likely. Yeah, but sort of just
36:50
Speaker 1: by definition, because that's what we call a planet, and
36:52
Speaker 1: that's what we call a star. Boy all right, well cool,
36:56
Speaker 1: It sounds like the universe still has a lot of
36:58
Speaker 1: surprises in store for us, maybe new and interesting configurations
37:03
Speaker 1: that we didn't think we're possible. Yeah, and there are
37:04
Speaker 1: lots of solar systems out there that we don't understand,
37:07
Speaker 1: weird planets made out of styrofoam, and strange stars doing
37:11
Speaker 1: things that we don't understand. So this is all based
37:13
Speaker 1: on our current understanding of how planets and stars form
37:16
Speaker 1: and what's going on inside them. But there are lots
37:19
Speaker 1: of surprises out there in the universe, and the only
37:22
Speaker 1: way to learn them is to look. And so we
37:24
Speaker 1: should all be supporting astronomy and building more space telescopes
37:27
Speaker 1: so that we can just sort of buy our way
37:30
Speaker 1: into answers to these questions to revealing what's out there
37:33
Speaker 1: in the universe. The only way is to look or
37:35
Speaker 1: to go out there, which you should tell your kids
37:38
Speaker 1: that's an option if they want to become astronauts and
37:41
Speaker 1: they can get as far away from you as possible.
37:43
Speaker 1: But nobody out there should take this podcast as advice
37:46
Speaker 1: that you should get a red spot tattoo by yourself.
37:49
Speaker 1: Sure there are people already out there, all right. Well,
37:54
Speaker 1: thanks for joining us. We hope you enjoyed that. See
37:56
Speaker 1: you next time. Yea, thanks for listening, and remember that
38:06
Speaker 1: Daniel and Jorge Explain the Universe is a production of
38:09
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38:13
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Speaker 1: you listen to your favorite shows.