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What are zombie stars? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey or heey? Do you think we should try to
0:10
Speaker 1: make physics cool? Isn't that an oxymoron? What do you mean,
0:15
Speaker 1: like connected to like the latest fat in the culture. Yeah,
0:19
Speaker 1: I was wondering if it might not be too late
0:21
Speaker 1: to ride the wave of the popularity of zombies. Well,
0:26
Speaker 1: zombies in popular culture just keep coming back like real zombies,
0:30
Speaker 1: So why not You don't think that they've like jumped
0:33
Speaker 1: the shark already. I mean, the Walking Dead came out
0:35
Speaker 1: like ten years ago. Well that that show definitely jumped
0:38
Speaker 1: the zombie shark. But no, it's it's had a little
0:41
Speaker 1: bit of a renaissance lately. Well, then maybe it's a
0:44
Speaker 1: perfect time for physics to get into the zombie game.
0:47
Speaker 1: I don't know if that's such a good idea. Man. Well,
0:49
Speaker 1: you know, we're experts at like giving new, confusing meetings
0:53
Speaker 1: to words that people already understand. You know, we did
0:55
Speaker 1: it for Color, for Spin, for Flavor. Now it's time
0:58
Speaker 1: to do it for zombies. Are you writing a movie
1:01
Speaker 1: called Quantum Zombies or Attack of the Zombie Courks? I
1:05
Speaker 1: am now dumb run Hi, I'm poor Handmay cartoonists and
1:25
Speaker 1: the creator of PhD comics. Hi I'm Daniel. I'm a
1:27
Speaker 1: particle physicist and a professor at UC Irvine, and I
1:31
Speaker 1: have never finished a zombie movie. What do you mean
1:34
Speaker 1: you've never finished making one or finished watching one? How
1:37
Speaker 1: many zombie movies have you try to make? I have
1:40
Speaker 1: made zero zombie movies. I have finished watching zero zombie movies.
1:44
Speaker 1: None of the above? Really? Why not? They just haven't
1:47
Speaker 1: been any good? Or you don't like the zombie genre.
1:49
Speaker 1: I haven't seen one yet that really clicks for me.
1:51
Speaker 1: You know, usually it's just ridiculous. The science isn't well explained,
1:55
Speaker 1: the zombies are slow and shuffling, or the action is
1:58
Speaker 1: all the same, like, boom, blow up a zombie's head, Boom,
2:01
Speaker 1: low zombie's head. It's just the same thing over and
2:03
Speaker 1: over again. Oh man, you just haven't been watching the
2:05
Speaker 1: right zombie movies. Tell me what are the right zombie
2:09
Speaker 1: Give me Orges top zombie movies. Well I have. I
2:11
Speaker 1: have a bit of an undead relationship with zombie the
2:14
Speaker 1: zombie Joe. What do you mean you're love for it
2:16
Speaker 1: died and then came back? Yes, kind of. I can't
2:19
Speaker 1: stand them. I hate them, and yet I can't stop
2:22
Speaker 1: watching them. I am fascinated by the whole genre. You're
2:26
Speaker 1: slowly shuffling towards even as you say no, no, Well,
2:31
Speaker 1: I can tell your zombie new because the sort of
2:34
Speaker 1: the latest flavor of zombies. They're fastened, they're lethal, ferocious. Yeah,
2:38
Speaker 1: can they hold a conversation? Some of them now they
2:40
Speaker 1: can yet? Watch Zombies got lines now it must be
2:43
Speaker 1: the Zombie Union has really done some negotia. Yeah, there's
2:46
Speaker 1: something I'll call half beat. If you're watching the latest
2:49
Speaker 1: Netflix zombie show, what did you say? A half beat?
2:52
Speaker 1: Have beat like a zombie, but a half zombie. That
2:55
Speaker 1: sounds like something in a quantum superposition of human and zombie.
2:58
Speaker 1: It does sound like something a physicism would come up
3:01
Speaker 1: with for a zombie show. But anyways, Welcome to our podcast.
3:05
Speaker 1: Daniel and Jorge explain the Zombie Universe, a production of
3:09
Speaker 1: Our Heart Radio in which we hope to infect your
3:11
Speaker 1: brain with the crazy virus that is reality. All of
3:15
Speaker 1: the amazing things that are out there in the universe
3:17
Speaker 1: that we understand, and all the incredible things that are
3:20
Speaker 1: out there in the universe that we do not yet understand,
3:22
Speaker 1: things that are blowing up and things that are blowing
3:25
Speaker 1: our minds we think about all of it, we talk
3:27
Speaker 1: about all of it, we joke about all of it,
3:29
Speaker 1: and we explain all of it to you. That's right.
3:31
Speaker 1: We want to bring back from the dead that fascination
3:33
Speaker 1: you had as a kid about the universe and everything
3:36
Speaker 1: in it, about how everything seemed amazing and wonderful and mysterious.
3:39
Speaker 1: We like to talk about all of those things that
3:41
Speaker 1: you can still see out there when you look out
3:43
Speaker 1: into the night. Kind And so, if I've never lost
3:46
Speaker 1: my love for the universe, does that mean that I'm
3:49
Speaker 1: still dead or I've always been a zombie? How does
3:51
Speaker 1: that work? It means you haven't turned into a zombie
3:54
Speaker 1: physic zombie. That's just in my future. Huh. If you
3:57
Speaker 1: get bitten by a physicist, although if you get bitten
3:59
Speaker 1: by a radio active physicists, maybe that's a whole different
4:01
Speaker 1: genre altogether. Then you get that physicist proportional intelligence or something. Well,
4:07
Speaker 1: it's hard to go down from where you Well, I'll
4:11
Speaker 1: try not to get bitten by a radioactive cartoonist. But
4:13
Speaker 1: you know, I'm not the first person to think about
4:16
Speaker 1: the idea of combining quantum mechanics and zombies. That's right. Yeah,
4:21
Speaker 1: it's a big part of the Marvel universe now, at
4:23
Speaker 1: least in the Marvel multi universe. Yeah, that's right. It's
4:26
Speaker 1: something called the quantum virus, virus that originated in the
4:30
Speaker 1: quantum realm and can turn his host into a quantum zombie.
4:34
Speaker 1: Whatever that is. Wow, I'm surprised you watched that episode
4:37
Speaker 1: of What If? I did say. I watched that episode
4:40
Speaker 1: internet googling. Oh I see, oh I see. You did
4:44
Speaker 1: no research for this episode today, minimal, minimal research, surface
4:50
Speaker 1: level zombie research. As much zombie research as I could stomach.
4:53
Speaker 1: That was a great episode. I think the original Adman
4:55
Speaker 1: went into the quantum realm and somehow got infected by
4:58
Speaker 1: a quantum virus and then turn into a zombie. And
5:01
Speaker 1: then when he came back, everyone turned into a zombie.
5:03
Speaker 1: All the superheroes turned into zombies. So where's the quantum mechanics?
5:06
Speaker 1: It just the virus came from the quantum realm. That's it.
5:09
Speaker 1: Do you need more? What more? Do you say the
5:13
Speaker 1: word quantum and it shuts down the conversation? You know?
5:15
Speaker 1: That's exactly how my son described it after we watched
5:18
Speaker 1: a Marvel movie together. He said, do people just say
5:20
Speaker 1: quantum when they mean you won't understand the science. Wow,
5:24
Speaker 1: and what did you say. I said, that's exactly what
5:27
Speaker 1: they usually. It means they don't understand the science, so
5:31
Speaker 1: they can't explain it to you. Well, it's kind of
5:33
Speaker 1: interesting because now the Marvel universe is all about the multiverse, right,
5:37
Speaker 1: which could be a quantum idea. Yeah. Well, there's millions
5:39
Speaker 1: more universes, so millions more ways to make money. And
5:42
Speaker 1: they mix it up with zombies, so you can see
5:44
Speaker 1: a zombie Captain America taking on a zombie Iron Man.
5:47
Speaker 1: Do zombies go to the movies? I wonder are these
5:49
Speaker 1: just for human audiences only if it's a brainy movie. Well,
5:54
Speaker 1: we are going to try to apply our brains to
5:57
Speaker 1: this universe and to understand whether things out there can
6:00
Speaker 1: die and maybe even come back to life, because there
6:04
Speaker 1: are so many strange things out there in the universe.
6:07
Speaker 1: Every time we look deeper in the universe, we find
6:09
Speaker 1: something weird, something bizarre, something strange, something we never expected
6:13
Speaker 1: to see. Yeah, it is a pretty bizarre universe, and
6:16
Speaker 1: sometimes things sort of come back to life, almost sort
6:19
Speaker 1: of like zombies. Everything in the universe has a second act.
6:22
Speaker 1: And speaking of rebirth and birth, I want to take
6:25
Speaker 1: a moment to wish a very special thirty fifth birthday
6:28
Speaker 1: to one of our listeners, Agnish Sabulci, have a very
6:32
Speaker 1: happy birthday, Agnish, and a very nice week visiting your family.
6:36
Speaker 1: In fact, you are made out of stuff from a
6:38
Speaker 1: star that once exploded and sprayed those heavy elements out
6:42
Speaker 1: into the cosmos. So everything that you were made of
6:45
Speaker 1: was once part of a burning star. So in that sense,
6:48
Speaker 1: we are all cosmic zombies. Are you saying, Daniel, that
6:52
Speaker 1: our son like us? Right now? We're the sequel, We're
6:55
Speaker 1: not the original production. Yeah, we might not even be
6:58
Speaker 1: the sequel. We could be the third generation or the
7:00
Speaker 1: fourth generation. We did an episode about how many generations
7:03
Speaker 1: of stars there might be, and how many generations of
7:05
Speaker 1: stars there might have already been. We could be a mixture.
7:09
Speaker 1: Some of our elements could have been in two or
7:10
Speaker 1: three Stars already, and others could still be fresh from
7:13
Speaker 1: the Big Bang. So we are like a zombie casserole
7:17
Speaker 1: where the reboot, where the slightly warmed up remake exactly
7:22
Speaker 1: the unimaginative castion of intellectual property strip mining. I guess
7:29
Speaker 1: all of Hollywood is full of zombies. Kind of true
7:32
Speaker 1: shuffling about trying to eat your brain. Every canceled TV
7:36
Speaker 1: show eventually comes back to life with a younger cast,
7:41
Speaker 1: better looking casts. Usually sometimes I think there's a new
7:43
Speaker 1: Jurassic Park movie coming out that has the original cast
7:46
Speaker 1: from the first movie. I'm amazed those folks are still alive.
7:49
Speaker 1: Or maybe they're not. Maybe the cost their zombie versions.
7:52
Speaker 1: Maybe the dinosaurs are Oh my goodness, you just give
7:55
Speaker 1: me an idea, dino zombies. I'm sure somebody in Hollywood
7:59
Speaker 1: is it's that to somebody else already. Let me call
8:02
Speaker 1: the Discovery Channel. They we'll have a shared universe with
8:06
Speaker 1: the sharknadoes and alligator Hurricane. I'm already looking forward to
8:10
Speaker 1: the zombie dinosaur Tornado sequel crossover event. That's right, that
8:16
Speaker 1: those would be the quantum dinosaurs. No God, they'll be
8:23
Speaker 1: both brilliant and terrible at the same time. Don't collapse
8:27
Speaker 1: the wave function at your own peril. It's called the
8:30
Speaker 1: Heisenberg Hollywood principle. But anyways, it is a pretty interesting
8:34
Speaker 1: universe full of life cycles. Things that have come into
8:36
Speaker 1: being and then explode or fade away, but then they
8:39
Speaker 1: have a way sometimes of coming back. In this universe,
8:42
Speaker 1: and apparently it happens also with stars. That's right. Stars
8:46
Speaker 1: have lots of different ways to live out their life cycle.
8:49
Speaker 1: They can burn on for trillions of years if they're
8:51
Speaker 1: very small, or they may very rapidly burn up their
8:54
Speaker 1: fuel and end in a cataclysmic explosion, a supernova that
8:58
Speaker 1: tears it apart. And you I think that a super
9:00
Speaker 1: over will always kill a star, would shred it from
9:03
Speaker 1: the inside and destroy any chance of its future burning.
9:07
Speaker 1: But that might not always be the case. So to
9:09
Speaker 1: be on the podcast will be tackling the question what
9:17
Speaker 1: is a zombie star now, Daniel? Is this a star
9:20
Speaker 1: that's a zombie or like a zombie that's also like
9:23
Speaker 1: a Hollywood star? That's right, This is a zombie whose
9:27
Speaker 1: career is really on the rise, and a list zombie
9:32
Speaker 1: was that it's supposed to be a zombie punt? Yeah, exactly.
9:34
Speaker 1: You know, we resurrected their career from the dead. You know,
9:37
Speaker 1: for example John Travolta, he is a zombie career, right.
9:41
Speaker 1: You know these are after physical objects, not folks in Hollywood.
9:45
Speaker 1: This is not, after all, an entertainment podcast, as much
9:47
Speaker 1: as we'd like it to be sometimes, So Zombie Stars,
9:52
Speaker 1: is that the official physics term or is that just
9:54
Speaker 1: what you're calling them. I did not invent this term.
9:56
Speaker 1: This is a term that exists in science. Is the
9:59
Speaker 1: term of those co into by astrophysicists. And as you learn,
10:02
Speaker 1: I think it's actually a pretty good description. Interesting, and
10:05
Speaker 1: these are these related to z bosons? Is that what
10:08
Speaker 1: the z and the z boson is zombie boon? No,
10:13
Speaker 1: that's what zombies exchange when they meet each other. No,
10:15
Speaker 1: this has nothing to do with z bosons. Though. It
10:17
Speaker 1: would be awesome if you could form a star purely
10:20
Speaker 1: out of z boson, So that would be a very
10:22
Speaker 1: weird kind of matter. Interesting. And then it dies and
10:26
Speaker 1: becomes a zz boson star, or it maybe turns into
10:29
Speaker 1: a different kind of court, then it'll be the zz
10:31
Speaker 1: top cor And I don't even know where this is going,
10:35
Speaker 1: but anyways, we're wondering how many people out there had
10:38
Speaker 1: heard of this term zombie star and whether or not
10:41
Speaker 1: it's meet it out into the public like zombie virus.
10:44
Speaker 1: So Daniel went out there into the wilds of the
10:45
Speaker 1: internet to ask people what do they think is a
10:49
Speaker 1: zombie star? So thank you to everybody who volunteers to
10:52
Speaker 1: answer these questions. Whereas on the podcast. It's super helpful.
10:55
Speaker 1: If you're out there and you've been listening to the
10:57
Speaker 1: podcast for a while and you would like to hear
10:59
Speaker 1: your one voice in the podcast. Please don't be shy.
11:02
Speaker 1: Just write to me two questions at Daniel and Jorge
11:05
Speaker 1: dot com and I'll let you know how to participate.
11:07
Speaker 1: To think about it for a second, what comes to
11:09
Speaker 1: mind when you think of a zombie star. Here's what
11:12
Speaker 1: people have to say. I'm gonna take a wild guess
11:15
Speaker 1: and say that a zombie star is a star that
11:17
Speaker 1: continues to live by sucking material, sucking mass out of
11:23
Speaker 1: a nearby star. They can be killed with a neutron
11:26
Speaker 1: bullet to the head. The zombie stars, I think it's
11:31
Speaker 1: the type of remnant star after a supernova. Zombie stars,
11:38
Speaker 1: I suppose, are stars that have used up all of
11:42
Speaker 1: their stellar material but have stayed small enough to not
11:47
Speaker 1: explode or become black holes. And so they maybe are
11:50
Speaker 1: brown dwarf stars that perhaps crash into another star of
11:56
Speaker 1: enough mass that the whole thing will reignite away, reanimating
12:01
Speaker 1: a dead star like a zombie. Zombie stars are stars
12:06
Speaker 1: that blew up and went cold and then got it up.
12:10
Speaker 1: Some yeah, some new materials like new Maybe they went
12:15
Speaker 1: through a field of gas or something of hydrogen and
12:19
Speaker 1: reached critical mass again and fired up again, and yeah,
12:23
Speaker 1: now they're one stead but alive again, basically like rogue
12:29
Speaker 1: dead stars that didn't collapse into a black hole. I
12:32
Speaker 1: have no idea, but I'm going to guess that it
12:35
Speaker 1: has to do with a start dying and not exploding
12:39
Speaker 1: or turning into a black hole. Maybe it's mass is
12:42
Speaker 1: not massive enough to create a singularity, and so that
12:45
Speaker 1: star just burns out and just stays out there, dead,
12:50
Speaker 1: encircling a galaxy. Uh, stars just wandering the universe that
12:55
Speaker 1: don't have, you know, a stable place where they exist.
13:00
Speaker 1: Maybe stars that are appeared to be dead but then
13:05
Speaker 1: they come to back to life or something to do
13:09
Speaker 1: with the cranberries. Of course, there are stars which were
13:13
Speaker 1: dead so after they were super nova they somehow start
13:20
Speaker 1: capturing material and comm alive again. But that would be
13:25
Speaker 1: close to what class hours are, but class ours are
13:29
Speaker 1: for black holes. No idea, stars that are dead but
13:34
Speaker 1: still produced light. All right, it seems pretty much everyone
13:38
Speaker 1: I knew exactly what you were talking about. That that's
13:42
Speaker 1: that's a very powerful thing about the word zombie it's
13:44
Speaker 1: like you you kind of everyone knows what that means. Yeah,
13:47
Speaker 1: I think it's actually a well named phenomena in after physics, right,
13:51
Speaker 1: I don't really believe that they actually call these zombie stars.
13:56
Speaker 1: Show me the paper, all right, will include a link
13:59
Speaker 1: to the paper in the show notes, so that everybody
14:01
Speaker 1: can verify for themselves that I have not fabricated this.
14:05
Speaker 1: But if I did fabricated, then I should get the
14:06
Speaker 1: credit for naming these things zombie stars. So in fact, yeah, sure,
14:09
Speaker 1: I'm happy to take the credit. This was my brilliant idea. Wow. Yeah,
14:14
Speaker 1: I feel like you're gaslighting me. Now you're both asserted
14:16
Speaker 1: that you came up with it and that you didn't
14:18
Speaker 1: come up with it. That's right, it's quantum credit. It's
14:21
Speaker 1: quite quantum plagiarism. No, but everyone seems to sort of
14:28
Speaker 1: kind of know what you're talking about, or at least
14:30
Speaker 1: how I think they have an idea what you're talking about,
14:32
Speaker 1: Like a star that dies and then comes back to life?
14:34
Speaker 1: Daniel stepp us through here. What is a zombie star?
14:37
Speaker 1: How do you define a star that dies and then
14:39
Speaker 1: comes back? Yeah, so a zombie star is exactly that.
14:42
Speaker 1: It's a star that sort of survives its own death.
14:45
Speaker 1: And you might be wondering, well, you know, how do
14:47
Speaker 1: stars die? What does that mean? Well, the most spectacular
14:50
Speaker 1: way for a star to end its life or to
14:53
Speaker 1: die is to blow up, is to go supernova. That's
14:56
Speaker 1: when it stars, gravity can no longer contain it, and
14:59
Speaker 1: it erupts and sprays its material out into space and
15:02
Speaker 1: is extraordinarily bright for a very brief amount of time. Right,
15:06
Speaker 1: But there, I think there are several kinds of supernova's. Right,
15:10
Speaker 1: then one of them it actually happens when it runs
15:12
Speaker 1: out of fuel and gravity takes over. Right, that's right.
15:16
Speaker 1: There's a couple of different varieties of supernova. Actually there's
15:19
Speaker 1: lots of different varieties, but sort of two major categories.
15:22
Speaker 1: The one that people typically think about it is called
15:24
Speaker 1: a core collapse supernova. That's when you have a star
15:27
Speaker 1: that's like ten to a hundred times the mass of
15:29
Speaker 1: the Sun, so a really big massive star. And at
15:32
Speaker 1: the heart of the star, remember what's happening is fusion.
15:35
Speaker 1: You squeeze together hydrogen to make helium, and then if
15:37
Speaker 1: it's a big enough star like these guys, that helium
15:40
Speaker 1: then gets fused to make something heavier, and the net
15:42
Speaker 1: gets fused to make something heavier, and if you keep
15:44
Speaker 1: going far enough, you get all the way up to iron.
15:47
Speaker 1: Problem is, when you fuse iron, it doesn't make any
15:50
Speaker 1: more heat, it doesn't fuel the star, doesn't continue the burning.
15:53
Speaker 1: It sucks up heat, so it cools the star down.
15:57
Speaker 1: So now all of a sudden, this balance between the
15:59
Speaker 1: energy of usuon pushing out on the star and gravity
16:02
Speaker 1: pushing in is disrupted and the star very suddenly collapses
16:06
Speaker 1: and then has this shock wave outwards. So that's a
16:09
Speaker 1: core collapse supernova. And these are really dramatic and they
16:12
Speaker 1: can like trigger the formations of new stars as the
16:15
Speaker 1: shock wave propagates through the universe. It's really pretty incredible.
16:19
Speaker 1: That's the core collapse type of supernova. That's one kind.
16:22
Speaker 1: The kind of we're interesting today is actually not that kind.
16:25
Speaker 1: It's from the star that didn't make it to supernova
16:28
Speaker 1: and then later on gets the material that it did.
16:30
Speaker 1: So that's called the type one A supernova, which is
16:34
Speaker 1: different from this core collapse kind of supernova. And I see,
16:38
Speaker 1: so we're talking today about the type one A. And
16:40
Speaker 1: sometimes that type one A can turn into a zombie.
16:43
Speaker 1: So step us through what's happening in a type one
16:44
Speaker 1: A supernova. So the type one A supernova is when
16:47
Speaker 1: you have a lower mass star, one that's on its own,
16:49
Speaker 1: could never become a supernova. So you have like less
16:52
Speaker 1: than eight times the mass of the Sun, and this
16:54
Speaker 1: thing goes through its normal life cycle, maybe becomes a
16:57
Speaker 1: red giant. It burns, the hydrogen burn is the heavier stuff,
17:01
Speaker 1: but it doesn't have enough mass, for example, to burn
17:03
Speaker 1: carbon inside of it. So the carbon that's inside of it,
17:07
Speaker 1: it just accumulates like ash. And what happens in these
17:10
Speaker 1: stars is that you get a gravitational collapse when it
17:13
Speaker 1: runs out of fuel, when it can no longer burn
17:15
Speaker 1: because now it's just like filled with carbon at its core.
17:18
Speaker 1: You get a gravitational collapse, but you don't get a supernova,
17:20
Speaker 1: and you don't get a black hole, and you know,
17:22
Speaker 1: you don't get a neutron star. What you end up
17:24
Speaker 1: with is a white dwarf. A white dwarf is something
17:28
Speaker 1: that's no longer fusing. It's just like a big hot
17:31
Speaker 1: lump of stuff sitting out there in space. It's like
17:34
Speaker 1: a mix of oxygen and carbon, but again it doesn't
17:37
Speaker 1: have enough mass to keep going, and so most white
17:40
Speaker 1: doors just sit out there, and they can sit in
17:42
Speaker 1: the universe for millions, billions some people think trillions of years,
17:47
Speaker 1: just sort of glowing and not fusing until eventually they
17:50
Speaker 1: become black dwarves. So that's a typical life cycle for
17:54
Speaker 1: a star like that. But sometimes something intervenes. If one
17:58
Speaker 1: of these white dwarfs is actually the member of a
18:00
Speaker 1: binary system, meaning there's another star nearby, then they can
18:04
Speaker 1: start to steal some of the material from that other
18:06
Speaker 1: star and that can trigger a supernova that can give
18:10
Speaker 1: it enough material to get it like over that hump
18:12
Speaker 1: to collapse into a supernova. All right, that was kind
18:15
Speaker 1: of a lot a lot there, but it sounds like
18:18
Speaker 1: it's sort of like a star not much bigger than
18:20
Speaker 1: our It's like only eight times bigger than our sun.
18:23
Speaker 1: And then that kind of happens in the same way
18:25
Speaker 1: that's the other stars that do supernova. It runs out
18:28
Speaker 1: of things to fuse together, it just doesn't have enough gravity,
18:32
Speaker 1: and so it collapses and then it just simmers there.
18:34
Speaker 1: You're saying, well, what happens is that it collapses, but
18:36
Speaker 1: not as a supernova. It just sort of like becomes
18:38
Speaker 1: a white dwarf and it just sits there hot, glowing
18:42
Speaker 1: into the universe until it's a neighbor this binary star.
18:46
Speaker 1: Maybe that one becomes a red giant or gets too close,
18:49
Speaker 1: and then the white dwarf can steal some of the
18:51
Speaker 1: mass from its neighbor, and now the white dwarf. Otherwise
18:54
Speaker 1: we just sit there happily. But when this new material
18:56
Speaker 1: accumulates to the surface of the white dwarf, then it
18:59
Speaker 1: pushes is it over the limit the gravitation limit for
19:02
Speaker 1: a stable white dwarf, and then it collapses. So it's
19:04
Speaker 1: like you didn't have enough mass to go for collapse
19:07
Speaker 1: from the beginning, like a typical core collapse supernova, but
19:10
Speaker 1: instead you've got like a late second helping and it's
19:13
Speaker 1: extra stuff you steal from your binary partner that lets
19:16
Speaker 1: you collapse to a supernova. And this is a type
19:19
Speaker 1: one a supernova, and it's famous because it's helped us
19:22
Speaker 1: understand like the shape and the acceleration of the universe.
19:25
Speaker 1: M I see. So this only happens in binary star systems,
19:28
Speaker 1: like star systems with two stars in it or more.
19:32
Speaker 1: It almost only happens with binary star systems, probably not exclusively,
19:36
Speaker 1: but yeah, that's the best way to accumulate some extra material.
19:40
Speaker 1: So then you have this white dwarf which is just
19:42
Speaker 1: like a ball of oxygen and carbonages simmering, just glowing
19:46
Speaker 1: there from the heat. And then you're saying, like the
19:48
Speaker 1: other it's partner stars somehow falls in or get sucked
19:51
Speaker 1: in or or what happens to it. Yeah, these two
19:53
Speaker 1: things can be near each other, and remember a binary
19:55
Speaker 1: star system. Eventually they get closer and closer and even merge.
19:59
Speaker 1: Sometimes you can them even like one goes inside the
20:01
Speaker 1: other star. But eventually these two stars in the binary
20:05
Speaker 1: system get close enough that the white dwarf can steal
20:08
Speaker 1: some of the material from the other one. You've probably
20:10
Speaker 1: seen these like artistic renditions. You know, you have two stars,
20:13
Speaker 1: one much bigger than the other one and the smaller
20:16
Speaker 1: one having this like trail of material accumulating from the
20:19
Speaker 1: bigger star. And I see they're like rotating around each other.
20:22
Speaker 1: But eventually, over time they orbit collapses and it starts
20:25
Speaker 1: to suck suck it in to the bigger one, which
20:28
Speaker 1: is the white dwarf exactly. And if the white dwarf
20:30
Speaker 1: gets enough material, then it can actually go supernova, and
20:34
Speaker 1: it's really fascinating because these white dwarfs are very regular,
20:37
Speaker 1: like there's a very specific critical mass at which a
20:40
Speaker 1: white dwarf will get triggered to go into one of
20:42
Speaker 1: these type one A supernova, and that makes it very
20:45
Speaker 1: nice to study because that critical mass is like a
20:48
Speaker 1: basic feature of the physics. It's the same everywhere in
20:51
Speaker 1: the universe, and that means that these type one A
20:53
Speaker 1: supernova are very regular. They're sort of easy to standardize.
20:57
Speaker 1: There's a simple relationship between the light curve, like how
21:00
Speaker 1: much light is admitted per time and the true brightness,
21:04
Speaker 1: which is one of the things that allows us to
21:05
Speaker 1: calibrate them, to say, oh, we know how bright it
21:08
Speaker 1: was at its source, and so we can figure out
21:10
Speaker 1: how far away they are. And that's why they played
21:12
Speaker 1: such a crucial role in extending our distance ladder and
21:15
Speaker 1: helping us understand how far away some of these distant
21:18
Speaker 1: galaxies are. I think you're saying that this process for
21:22
Speaker 1: the supernova through the white dwarf is very repeatable, like
21:25
Speaker 1: it always kind of happens at the same time or
21:27
Speaker 1: at the same point in the life cycle of the
21:29
Speaker 1: star YEA. As soon as this white dowarf accumulates enough
21:32
Speaker 1: mass and gets over this threshold boom, that's when it
21:35
Speaker 1: goes supernova. And so that's very repeatable exactly. And so
21:38
Speaker 1: the supernova is really pretty incredible process. You know, it's
21:41
Speaker 1: a supersonic propagation of energy out of the heart of
21:45
Speaker 1: the star. You know, the explosion is happening faster than
21:49
Speaker 1: the speed of sound inside the star, and so it
21:52
Speaker 1: builds up this shock wave which propagates out at you know,
21:55
Speaker 1: some like significant fraction of the speed of light. It
21:58
Speaker 1: can be going like ten kilometers per second through this
22:01
Speaker 1: stellar material. That's like more than five of the speed
22:05
Speaker 1: of light. Wow. All right, well, let's get a little
22:07
Speaker 1: bit more into detail of what's happening when this thing collapses,
22:10
Speaker 1: and let's talk about how that gives rise to zombie stars.
22:14
Speaker 1: But first let's take a quick break. All right, we
22:29
Speaker 1: are back from the dad here talking about zombie stars,
22:32
Speaker 1: stars that come back from the dead, and we talked
22:35
Speaker 1: about how you said that these come usually in in
22:38
Speaker 1: binary star systems, where one of them turns into a
22:41
Speaker 1: white dwarf, meaning it runs out of fuel, it collapses,
22:44
Speaker 1: it's simmering there and then it sucks the mass from
22:46
Speaker 1: its partner star and somehow that gives it enough I
22:50
Speaker 1: don't know, juice to explode. What's happening there, Like it increases.
22:54
Speaker 1: It was nice and stable and simmering, but now it
22:56
Speaker 1: has extra mass. So what happens? Yeah, Well, the white
22:58
Speaker 1: dwarf is stable, and to understand how it becomes unstable
23:02
Speaker 1: and turns into a supernova, you have to understand what
23:04
Speaker 1: the forces are at play. So pushing it in, of
23:07
Speaker 1: course is gravity. Gravity is compressing it. It's very dense,
23:11
Speaker 1: it's very heavy, so there's a lot of force inwards.
23:14
Speaker 1: What's pushing out, what's keeping this thing from collapsing into
23:17
Speaker 1: a black hole or something else, is actually quantum mechanics.
23:21
Speaker 1: This thing is super dense, but the electrons that are
23:24
Speaker 1: inside the white dwarf they don't like to overlap with
23:26
Speaker 1: each other. Electrons are a special kind of particle. They're
23:29
Speaker 1: called fermions that don't like to be in the same
23:31
Speaker 1: quantum states as any other fermion. So they don't like
23:34
Speaker 1: to overlap and they resist, and that's what keeps white
23:37
Speaker 1: dwarfs from collapsing. But that's not infinite. If you put
23:40
Speaker 1: enough gravitational pressure on this thing, it will eventually collapse
23:43
Speaker 1: into a supernova and maybe leave you at the heart
23:46
Speaker 1: with a black hole or a neutron star. So what
23:49
Speaker 1: you need is more gravity. Which you need is more mass.
23:52
Speaker 1: So if you add extra helping of stuff to your
23:55
Speaker 1: white dwarf, then it will actually collapse and create a supernova.
23:59
Speaker 1: But I guess it's keeping the electrons from collapsing into
24:03
Speaker 1: each other. You're saying they don't like being together because
24:05
Speaker 1: of quantum gravity, But what's the actual force there? Is
24:07
Speaker 1: it like an electromagnetic forces kind of repelling each other apart. Yeah,
24:11
Speaker 1: that's a really fun question, like what force is actually
24:14
Speaker 1: at play keeping electrons apart? You know, and you don't
24:17
Speaker 1: have to think about everything in physics has happened as
24:19
Speaker 1: requiring a force. You know, this is just something that
24:22
Speaker 1: like quantum mechanically is suppressed. Electrons don't like to do this.
24:26
Speaker 1: You can overcome it by squeezing these things down and
24:29
Speaker 1: basically having the electrons being captured by the protons that
24:33
Speaker 1: are also inside the star, converting them into neutrons, and
24:36
Speaker 1: so then you can avoid the electron degeneracy pressure. But
24:39
Speaker 1: that takes a lot of energy, a lot of gravitational
24:41
Speaker 1: pressure to basically push the electron inside the nucleus, so
24:45
Speaker 1: it gets captured and gets converted into a neutron. That's
24:48
Speaker 1: not an easy thing to do. Takes a lot of
24:50
Speaker 1: gravitational pressure, all right, So then you had this white dwarf.
24:53
Speaker 1: It was sitting there. Happily it got more stuff, and
24:55
Speaker 1: now it's so heavy that it collapses, like the gravity
24:58
Speaker 1: kind of overcome is this propulsion and it collapses. And
25:02
Speaker 1: then how does that lead to an explosion? Well, it collapses,
25:04
Speaker 1: which is an implosion, right, which creates incredible density at
25:08
Speaker 1: the core, and that triggers basically a thermonuclear explosion. So
25:12
Speaker 1: it happens there is that all of a sudden, you
25:14
Speaker 1: do have the conditions you need to create carbon fusion.
25:17
Speaker 1: Remember the white dwarf died because it accumulated all of
25:20
Speaker 1: this carbon at its core, and it wasn't big enough
25:23
Speaker 1: and hot enough to create the temperature necessary to fuse carbon,
25:26
Speaker 1: so sort of stopped. And then all of a sudden, boom,
25:28
Speaker 1: you have incredible pressure from this implosion, this shock wave
25:32
Speaker 1: that's traveling inwards because the gravitational collapse, and that does
25:36
Speaker 1: create the conditions needed for carbon fusion, and all of
25:39
Speaker 1: a sudden, all that carbon goes up in just like
25:42
Speaker 1: you know, days, So instead of taking millions or billions
25:45
Speaker 1: of years to burn all of it, it's like a
25:47
Speaker 1: huge bomb goes off instead of a self sustaining reaction. Wow,
25:51
Speaker 1: it's like you brun the entire sun in like a
25:53
Speaker 1: matter of a few days. Yeah, it's so much energy
25:56
Speaker 1: that it basically unbinds the star. It just blows up
26:00
Speaker 1: out into space and disperses its material over a huge region.
26:05
Speaker 1: Sometimes it just blows everything out into space. So that's
26:08
Speaker 1: really like the death of a star, or at least
26:10
Speaker 1: one particular death of of this kind of binary star.
26:14
Speaker 1: And you say when it explodes, When this kind of
26:16
Speaker 1: star explodes, the type one A, that's the kind that
26:19
Speaker 1: we use as standard candles right as to kind of
26:22
Speaker 1: measure how far galaxies are. Yeah, because they do so
26:25
Speaker 1: in a very predictable way. The light curve has a
26:27
Speaker 1: very distinctive shape, and so we can spot it was like, oh,
26:30
Speaker 1: that one's a Type one A. We know what happened there.
26:32
Speaker 1: And because the shape of the light curve is easy
26:34
Speaker 1: to relate to the true luminosity, like the actual brightness.
26:38
Speaker 1: So if you look at the light curve, you can say, oh,
26:39
Speaker 1: it's one of these type one A. It's one of
26:41
Speaker 1: those type one A, so you can know exactly how
26:44
Speaker 1: bright it actually is. Sort of similar if you remember
26:47
Speaker 1: to how we first measured cosmic distances, which with these sephids,
26:51
Speaker 1: these variable stars, where their period was related to their brightness,
26:55
Speaker 1: so you can measure the period of their variability and
26:58
Speaker 1: you could use that to deduce how bright they were
27:00
Speaker 1: the source. That's always what you want to do to
27:02
Speaker 1: understand how far away something is is understand how bright
27:06
Speaker 1: is it really if you were right next to it,
27:08
Speaker 1: and then you can compare that to how bright it
27:10
Speaker 1: appears here on Earth and you can know how far
27:13
Speaker 1: away it is. Right. I think what you're saying is
27:15
Speaker 1: that this type of supernova, it almost always explodes with
27:18
Speaker 1: the same brightness, Like you don't have this kind of
27:20
Speaker 1: supernova for a small white dwarf. It only happens for
27:23
Speaker 1: very particular size of a white dwarf. And when it happens,
27:26
Speaker 1: it always happens at the same brightness, which means you
27:29
Speaker 1: can tell where it is. Almost is one little wrinkle there,
27:32
Speaker 1: which is they're not all exactly the same brightness, but
27:35
Speaker 1: you can tell how bright they are by how rapidly
27:37
Speaker 1: they emit light and then fade away. So the shape
27:39
Speaker 1: of that light curve over time tells you what the
27:42
Speaker 1: brightness is. So it's not exactly that they're all the
27:44
Speaker 1: same brightness, but you can figure out how bright they
27:46
Speaker 1: are by measuring this light curve. I see. All right,
27:50
Speaker 1: So that's one way for a start to die. And
27:52
Speaker 1: you're saying, this is the kind of explosion, this kind
27:55
Speaker 1: of death of a star that leads to a zombie star.
27:57
Speaker 1: So this kind of explosion destroys the star that's are dead,
28:00
Speaker 1: dead and never coming back. It's like a big with
28:03
Speaker 1: a big cloud of dust and gas. Yeah, exactly, But
28:06
Speaker 1: what we noticed about twenty years ago is that that's
28:08
Speaker 1: not always what happens. Sometimes, when you have a type
28:11
Speaker 1: one day supernova, it doesn't actually destroy the star. It
28:15
Speaker 1: explodes a little bit differently, and it leaves behind something
28:18
Speaker 1: that has enough stuff to keep glowing, so it can
28:21
Speaker 1: sort of like have a supernova and still survive. Wait what,
28:25
Speaker 1: So it collapses, it creates incredible fusion in the middle.
28:29
Speaker 1: It explodes from that, but not completely like it doesn't.
28:33
Speaker 1: It doesn't all disperse. It stays there and no black
28:36
Speaker 1: hole is for me, that's right, it's sort of like
28:38
Speaker 1: it tries to go supernova but doesn't quite make it.
28:41
Speaker 1: So this peculiar kind of supernova comes from the same
28:44
Speaker 1: sort of basic setup. You have a white dwarf in
28:46
Speaker 1: a binary star system. It accumulates some mass, but for
28:50
Speaker 1: reasons that are not fully well understood, it doesn't actually
28:54
Speaker 1: trigger the same kind of supernova trigger sort of like
28:57
Speaker 1: halfway supernova. It does definitely do a collapse, and there's
29:01
Speaker 1: some carbon fusion that's happening at the core, but not
29:04
Speaker 1: enough to like really ignite it. So it like blows
29:07
Speaker 1: up a little bit, sends out a huge amount of light,
29:09
Speaker 1: but not quite a full on type one A supernova,
29:12
Speaker 1: and it leaves behind something which can still burn. So
29:16
Speaker 1: basically it just collapses. It doesn't actually explode that much.
29:19
Speaker 1: It does create carbon fusion, and that does create a
29:23
Speaker 1: ripple through the star, but the key is that that
29:25
Speaker 1: ripple is not supersonic and so it doesn't create a
29:28
Speaker 1: shock wave. And that's key. I think about what happens
29:31
Speaker 1: as you row your boat through a lake, right you
29:33
Speaker 1: leave ripples, and those ripples passed through the lake. If
29:35
Speaker 1: you're driving a motor boat, for example, you're going super
29:38
Speaker 1: fast you're going faster than the speed of your ripples.
29:40
Speaker 1: Then you create a wig because all those ripples are
29:43
Speaker 1: catching up to each other, they're adding up at the
29:45
Speaker 1: same place. And so that's what happens in a Type
29:47
Speaker 1: one A supernova is the explosion is supersonic, so it
29:51
Speaker 1: creates this incredible shock wave which blows up the star.
29:53
Speaker 1: And a Type one A X supernova this weird version
29:58
Speaker 1: of a Type one A. It doesn't quite me. It
30:00
Speaker 1: doesn't go supersonic, and so it sort of heats up
30:03
Speaker 1: the star. It gets bright, but it doesn't actually blow
30:06
Speaker 1: it up. See now you're confusing me. Now you're saying
30:09
Speaker 1: it's called a one A X. Shouldn't have been like
30:11
Speaker 1: a one It should totally have been a one A Z.
30:16
Speaker 1: I think they must have labeled it one A X
30:18
Speaker 1: because when they saw these, they were like, hold on
30:19
Speaker 1: a second, this is really weird. Type one A supernova
30:22
Speaker 1: usually super regular and predictable. Here's a weird version. So
30:26
Speaker 1: they like X for like X files, So this is
30:30
Speaker 1: like the X file star. And so what's the difference,
30:32
Speaker 1: Like what made this one explode in a different way
30:35
Speaker 1: than the other one. They're not sure, but one theory
30:38
Speaker 1: is that it depends on the kind of stuff that
30:40
Speaker 1: the white dwarf is accumulating. Like if your binary star,
30:44
Speaker 1: the companion, the one that's feeding you this extra material
30:46
Speaker 1: that triggers you, that has a lot of helium instead
30:49
Speaker 1: of just a lot of hydrogen, and that might set
30:51
Speaker 1: off a different kind of reaction. It might only make
30:54
Speaker 1: carbon fusion happen within a specific bubble of the star.
30:58
Speaker 1: It doesn't trigger it well enough. But truth is, we
31:00
Speaker 1: don't really understand the process of a supernova well enough
31:03
Speaker 1: to predict it and to understand it and to disentangle it.
31:06
Speaker 1: So it's sort of like a puzzle. We need to
31:08
Speaker 1: figure this out. We don't know why it didn't blow
31:11
Speaker 1: up like the other ones. Yeah, we don't know. What
31:13
Speaker 1: we do know is that they look different, right, So
31:16
Speaker 1: these things are less bright. There's still really dramatic events,
31:19
Speaker 1: but they're not as bright as type one a supernova.
31:22
Speaker 1: The stuff that flies out of the star as much
31:25
Speaker 1: lower velocity, so you're still like exploding part of the star.
31:28
Speaker 1: You can stand out like half the mass of the star.
31:31
Speaker 1: Or this thing is not just like a little burp, right,
31:33
Speaker 1: it is a big explosion. And they also look different,
31:35
Speaker 1: like there's more helium lines in these stars than in
31:39
Speaker 1: typical type one A supernova, So there's definitely something different happening,
31:42
Speaker 1: is something different going on, but we don't understand the
31:45
Speaker 1: process of a supernova well enough to really pint it down.
31:49
Speaker 1: But you're saying, then that doesn't explode is violently than
31:52
Speaker 1: as a regular type one A supernova, which means it
31:55
Speaker 1: leaves behind some stuff, at least stuff that can still burn.
31:59
Speaker 1: It leaves stuff that can still burn. And this is
32:01
Speaker 1: an incredible object, this zombie star, because it's very small,
32:05
Speaker 1: it's very hot. It might be like only the size
32:08
Speaker 1: of our moon. You know, this is a tiny, little
32:11
Speaker 1: astrophysical object. It's blown away a huge amount of its
32:13
Speaker 1: stuff in this sort of like half formed supernova, but
32:17
Speaker 1: it can still burn because it's dense enough and it's
32:19
Speaker 1: hot enough to glow. So they think that carbon fusion
32:23
Speaker 1: still happens on the inside, but in a more sustainable way,
32:26
Speaker 1: in a way that doesn't explode the star. Wait what
32:29
Speaker 1: so it's not just like a hot thing that glows
32:32
Speaker 1: from being hot it it's actually doing fusion in the middle,
32:35
Speaker 1: and it's only the size of the moon. You can
32:36
Speaker 1: have a sun the size of the moon. Yeah, it's
32:39
Speaker 1: come back to life. Man. It was fusing and it
32:41
Speaker 1: collapsed into a white dwarf and then it's fusing again.
32:44
Speaker 1: It can't do it forever, right, because it's a pretty
32:47
Speaker 1: small lump of stuff relative to other things in the universe.
32:50
Speaker 1: But the conditions that forced it to collapse can get
32:53
Speaker 1: carbon fusing. And what you need is temperature. So if
32:56
Speaker 1: it gets hot enough inside there to fuse carbon, that
32:58
Speaker 1: generates this heat that you need to keep it going, right,
33:01
Speaker 1: But I guess what keeps the star burning if it's not,
33:04
Speaker 1: if it's only the size of the moon, whereas all
33:06
Speaker 1: the gravity coming from to keep the fusion going, well,
33:10
Speaker 1: it's sort of ignited. Right. In order to have that
33:12
Speaker 1: kind of carbon fusion, you just need really high temperatures,
33:15
Speaker 1: and that temperature is now coming from the carbon fusion itself.
33:18
Speaker 1: So it's a kind of thing like once you've gotten
33:19
Speaker 1: it's started, it's easier for it to keep going. In
33:22
Speaker 1: many stars you just can't get carbon fusion started because
33:25
Speaker 1: you never reach that temperature. But in these zombie stars,
33:28
Speaker 1: you like across that threshold because of this collapse, and
33:30
Speaker 1: that ignites the star and then it can burn its carbon,
33:34
Speaker 1: even if there wasn't originally enough carbon to trigger that
33:37
Speaker 1: temperature just from gravitational pressure. Oh, I see, So it's
33:41
Speaker 1: like a self sustaining fusion reaction. No gravity need Well,
33:45
Speaker 1: gravity is still holding it together, but it didn't need
33:47
Speaker 1: the gravity to trigger the carbon fusion. But once that's happening,
33:51
Speaker 1: then it can keep going exactly. So these are really
33:53
Speaker 1: fascinating objects because they're weird, right, because they're different from
33:57
Speaker 1: the kind of tape one a supernova that you typically see. Well,
34:00
Speaker 1: it's kind of weird that you're calling it a zombie
34:02
Speaker 1: star because it's sort of not undead. It's like it's
34:04
Speaker 1: a lively star. It's burning. You know, I might might
34:08
Speaker 1: be even insulted if you call it a zombie, right.
34:09
Speaker 1: I see, you're saying zombies are not back to life,
34:12
Speaker 1: they're undead. That's the distinction. I'm not sure what I'm saying.
34:16
Speaker 1: I'm saying, like, like our son also came from a
34:19
Speaker 1: dead star maybe, but we don't call it a zombie star.
34:21
Speaker 1: It's just a new star, that's true. I guess this
34:24
Speaker 1: is more closely connected to its progenitor than the Sun is.
34:28
Speaker 1: The Sun came from just like a big cloud of
34:30
Speaker 1: gas and dust that swirled together to form the solar system.
34:33
Speaker 1: This is like a white dwarf that's pretty closely connected
34:36
Speaker 1: to the original I mean, in the same sense we're
34:38
Speaker 1: all zombies because we're all made out of organic material
34:41
Speaker 1: that's definitely been used in other beings. But you call
34:43
Speaker 1: a zombie zombie because it's like the same body. So
34:46
Speaker 1: this is like the same body of the original star
34:49
Speaker 1: that was fusing. That's sun corpse, he's saying. It's the same.
34:52
Speaker 1: It's a reanimated corpse, and therefore that's a zombie. Exactly.
34:56
Speaker 1: It's lost some of its mass, you know, part of
34:57
Speaker 1: its face has fallen off, but it's still ca double
35:00
Speaker 1: of shuffling around and entertaining you and and eating sun brains.
35:04
Speaker 1: What does it mean? Carbon? Yeah, well I guess so.
35:08
Speaker 1: Carbon is the brain of the sun, you know, and
35:10
Speaker 1: carbon is the basis of organic life here on Earth,
35:13
Speaker 1: and it's also at the heart of the brains. Yeah, exactly,
35:16
Speaker 1: eat star brains. All right, Well, let's get into how
35:19
Speaker 1: common they are in the universe and where we've seen
35:22
Speaker 1: that and what does it all mean. But first let's
35:24
Speaker 1: take another quick break. All right, we're talking about zombie
35:40
Speaker 1: star stars to have come back from the dead, and
35:42
Speaker 1: so we talked about how some stars sort of try
35:44
Speaker 1: to explode, but they sort of only half explode, I
35:47
Speaker 1: guess because they don't have to write ingredients to explode
35:49
Speaker 1: into a supernova, and so they you just kind of
35:52
Speaker 1: get a little bit of a dead corpse of a star.
35:55
Speaker 1: But it's still burnie. Still, it's shuffling about exactly. It's
35:58
Speaker 1: like a quantum star because it's both exploded and it survived.
36:03
Speaker 1: Oh wait, now you're just confusing whether there's no quantum
36:08
Speaker 1: superposition going on here. No, there's no quantum superposition. Now,
36:11
Speaker 1: it's like half of the stars blown up and the
36:13
Speaker 1: other half decided not to So it's more like a
36:16
Speaker 1: divorce star because you know, the different halves couldn't agree
36:18
Speaker 1: on what to do. That's a different kind of Netflix show.
36:22
Speaker 1: I feel we should maybe stick to one genre before
36:25
Speaker 1: we refuse people. It's a zombie star. It's not a
36:28
Speaker 1: divorce zombie star. It's not a zombie relationship. It's just
36:32
Speaker 1: a star. Isn't there a Netflix show about Mary zombies?
36:36
Speaker 1: There have been movies. Yes, as you can see, I'm
36:38
Speaker 1: an expert on are Apparently you know there have been
36:42
Speaker 1: a movie about zombie romances. Well, anyway, I love zombie stars,
36:47
Speaker 1: even if I don't love zombie movies. Well, that's because
36:51
Speaker 1: you haven't seen one up close or in the middle
36:53
Speaker 1: of the night. I'll consider it. All right. Well, let's
36:56
Speaker 1: talk about how common they are. How often do we
36:58
Speaker 1: see these zombie stars. Are we like surrounded by zombie
37:01
Speaker 1: stars everywhere or is this kind of a rare thing. Well,
37:03
Speaker 1: it's sort of an interesting paradox because we know two
37:06
Speaker 1: things about them. On one hand, we haven't seen very
37:09
Speaker 1: many of these things. Only like a hundred type one
37:12
Speaker 1: A X supernova which leads to zombie stars, have ever
37:16
Speaker 1: been seen. The first one was spotted about twenty years ago,
37:19
Speaker 1: so that's not a whole lot. You know, we've seen
37:21
Speaker 1: a lot more Type one A supernova than that. On
37:24
Speaker 1: the other hand, based on you know, frankly speculative models
37:27
Speaker 1: for how this happens, if we understand what's going on
37:30
Speaker 1: inside supernova and we don't, then these calculations suggest that
37:35
Speaker 1: this should happen more often than you imagine that, like
37:37
Speaker 1: the full Type one A supernova should fail to trigger
37:40
Speaker 1: in like of the cases. But I guess it's all
37:44
Speaker 1: based on whether or not the companion star has the
37:47
Speaker 1: right ingredients. So how do we know what these companions
37:51
Speaker 1: have out there? We don't know for sure, but you know,
37:53
Speaker 1: we do know a lot about what is out there
37:55
Speaker 1: in the universe based on how stars glow. You can
37:59
Speaker 1: look at the light that comes from a star and
38:00
Speaker 1: you can tell mostly what's made out of what it's
38:03
Speaker 1: hydrogen helium mix, because remember that different kinds of materials,
38:07
Speaker 1: different elements like to glow at different frequencies because they
38:10
Speaker 1: can absorb and amid photons that match the various vibrational
38:14
Speaker 1: and rotational and orbital energy levels of that element. So
38:18
Speaker 1: you can tell how much helium and how much hydrogen
38:20
Speaker 1: there is in a star based on how it glows.
38:22
Speaker 1: And so we have some idea for how common it
38:25
Speaker 1: is to have like a very helium ish star, and
38:28
Speaker 1: that lets people do these calculations, but you know, it's
38:30
Speaker 1: totally speculative, and its conflicts with some of the data.
38:34
Speaker 1: The data says, look, we haven't seen that many of
38:36
Speaker 1: these things. Either there's a lot of them out there
38:38
Speaker 1: we haven't spotted, or maybe something's wrong with the calculation
38:41
Speaker 1: I see, because we've only seen kind of a few
38:43
Speaker 1: tents of these, right, like a hundred of these zombies stars.
38:46
Speaker 1: We've only that's how many we've seen. But you're saying
38:48
Speaker 1: there should we should see more. Exactly, we should see more.
38:51
Speaker 1: There should be more of them. Again, if our theory
38:53
Speaker 1: about how this happens is correct, or maybe it's not.
38:57
Speaker 1: And you know, this is the process of science. We
38:59
Speaker 1: see something new, we go what how does that work?
39:01
Speaker 1: They put together a model from maybe what makes it,
39:03
Speaker 1: and then we look at the consequences of that. We say, well,
39:05
Speaker 1: if this model is true, what does it predict about
39:08
Speaker 1: how many more we should see and where we should
39:10
Speaker 1: be able to find them? So let's go look. If
39:12
Speaker 1: we don't find them, that means we've got to go
39:14
Speaker 1: back to the drawing board and come up with a
39:15
Speaker 1: different model for how this happens. I think what you're
39:18
Speaker 1: saying is that we might be surrounded by zombie stars,
39:21
Speaker 1: but maybe they're hiding. Is that what you're saying. It
39:23
Speaker 1: sounds terrifying. They're waiting for nighttime, right, isn't that waiting
39:28
Speaker 1: for you to go to sleep for them to shine
39:31
Speaker 1: their zombie light on me. We should be careful about
39:33
Speaker 1: talking about scary things because I think some people listen
39:35
Speaker 1: to this podcast as they're falling asleep, and we don't
39:37
Speaker 1: want to give them bad dreams unless they're fans of
39:39
Speaker 1: zombie movies, in which case they will sleep very happily.
39:43
Speaker 1: Maybe you could be a fan of zombie movies without
39:46
Speaker 1: being a fan of having zombies in your dreams. I think,
39:49
Speaker 1: do you want to start a zombie movie now? I
39:53
Speaker 1: just want to dream about zombie stars? But that is
39:57
Speaker 1: kind of what might be happening right. There might be
39:59
Speaker 1: a lot of them and they but they might be
40:01
Speaker 1: hiding somehow. Or maybe this failed collapse happens a lot,
40:04
Speaker 1: but maybe just we just don't see it, like maybe
40:07
Speaker 1: it collapses in mud blows up exactly. It might be
40:10
Speaker 1: that happens in a different way that we imagine. And
40:12
Speaker 1: when challenge is that we haven't ever seen one of
40:15
Speaker 1: these in our own galaxy. Remember the Type one A
40:18
Speaker 1: supernova are so bright that we can see them in
40:20
Speaker 1: distant galaxies. In fact, that's why they're so powerful and
40:24
Speaker 1: so useful, because they can shine a light about how
40:26
Speaker 1: far away, really really distant galaxies are. Interesting thing is
40:31
Speaker 1: that we've never seen one of these Type one A
40:33
Speaker 1: X supernova we've never seen a zombie star in our
40:36
Speaker 1: own galaxy until very very recently. I guess you just
40:39
Speaker 1: made me think of a question, which is like, if
40:41
Speaker 1: we haven't seen one in our galaxy, then how do
40:44
Speaker 1: we actually know they happen? Like you see a bright
40:48
Speaker 1: flash in a distant galaxy, and then but then you
40:50
Speaker 1: can't see the zombie star, can you. It's too small? Yeah,
40:53
Speaker 1: the zombies are itself is too small to really see
40:55
Speaker 1: to make out in detail. But you can see that
40:57
Speaker 1: the type one A X supernova has happened. You can
41:00
Speaker 1: see the light curve that's really bright. It's not as
41:02
Speaker 1: bright as a type one A supernova, like ten times
41:05
Speaker 1: less luminous, but it's bright enough to see in other galaxies.
41:08
Speaker 1: And actually one time they caught a type one A
41:12
Speaker 1: X supernova happening accidentally. They were looking for type one
41:16
Speaker 1: A supernova, of course, as they usually do, and so
41:19
Speaker 1: they were using hubble to take pictures of one that
41:21
Speaker 1: had recently happened. And then shortly afterwards there was a
41:25
Speaker 1: type one A X supernova that happened in the same
41:28
Speaker 1: region of space in this distance galaxy. So they were
41:31
Speaker 1: able to go back because they happened to take pictures
41:33
Speaker 1: of it before it exploded, and to see the progenitor,
41:37
Speaker 1: the thing that created this Type one a X supernova.
41:40
Speaker 1: So it helped give them a clue about how this happens.
41:44
Speaker 1: But I guess you haven't actually seen these zombie stars, right,
41:48
Speaker 1: You've only seen like a failed flash, but you're sort
41:50
Speaker 1: of speculating that it leaves behind a zombie star exactly.
41:53
Speaker 1: These zombie stars are not bright enough to see directly.
41:56
Speaker 1: But in this case, it's cool because you can see
41:58
Speaker 1: the binary star system and you can see that the
42:01
Speaker 1: other star in that system is actually a bright blue
42:04
Speaker 1: helium star right next to a white dwarf. And then
42:07
Speaker 1: we see a Type one A X supernova has this
42:10
Speaker 1: characteristic shape. It's different from a Type one A supernova,
42:14
Speaker 1: and so it doesn't have enough energy to like totally
42:16
Speaker 1: destroy that star. But we see that the progenitor, this
42:19
Speaker 1: white dwarf, is no longer there. So it's fascinating because
42:21
Speaker 1: they could see it like before it happened. That's not
42:24
Speaker 1: something we've ever seen for a Type one A supernova.
42:27
Speaker 1: We've never taken a picture of a star system before
42:29
Speaker 1: it went Type one A, which is one of the
42:31
Speaker 1: challenges for understanding how these things happen. Wait, so you're saying,
42:35
Speaker 1: we've never seen a zombie star in our galaxy, isn't
42:38
Speaker 1: that weird? Yeah, it is kind of weird, And again
42:40
Speaker 1: it goes to our lack of knowledge about what forms
42:44
Speaker 1: these things. Some people speculate that it might depend on
42:47
Speaker 1: the age of the galaxy, that only in galaxies of
42:50
Speaker 1: a certain age does this kind of thing happen, because
42:53
Speaker 1: maybe you get more helium stars. But there's all just
42:56
Speaker 1: a lot of speculation in the literature about why this
42:58
Speaker 1: might happen. Recently, people saw something that they think might
43:02
Speaker 1: be a type one A X supernova, and that's very
43:06
Speaker 1: close to the center of the galaxy. There's this thing
43:09
Speaker 1: they're called supernova remnant Sagittarius A East. So it's very
43:13
Speaker 1: close to the black hole of the center of our galaxy,
43:16
Speaker 1: and the light that's coming from it looks consistent with
43:20
Speaker 1: what you would expect from a type one A X supernova.
43:23
Speaker 1: The supernova itself was actually seen on Earth like nine
43:27
Speaker 1: hundred years ago, and it's recorded in history. At the time,
43:30
Speaker 1: of course, they couldn't tell that it was the type
43:32
Speaker 1: one A X supernova. But now by looking at like
43:35
Speaker 1: what's around it, and how it affected the stuff nearby it.
43:38
Speaker 1: They're speculating that that might have been a type one
43:40
Speaker 1: A X supernova and it might have left behind a
43:43
Speaker 1: zombie star. Whoa wait, wait, we saw it here from Earth.
43:46
Speaker 1: There's records of it exactly in one a d for
43:51
Speaker 1: a hundred and eighty five nights. This supernova lit up
43:54
Speaker 1: the sky and Japanese and Chinese astronomers recorded it in history.
43:58
Speaker 1: So something we know half and we can look at
44:00
Speaker 1: the remnant it's very close to the center of the galaxy,
44:03
Speaker 1: and then we can look at stuff nearby it and say, like,
44:05
Speaker 1: what shock wave has impacted on that stuff nearby? What's
44:08
Speaker 1: the velocity of the stuff moving through space? And when
44:11
Speaker 1: they do the calculations, it looks like it's consistent with
44:14
Speaker 1: a type one A X supernova having exploded there like
44:18
Speaker 1: nine hundred years ago. I guess maybe it's a good
44:21
Speaker 1: thing that we haven't seen a supernova in our galaxy, right, Like,
44:25
Speaker 1: if there was a supernova nearby, we we did fried. Yes,
44:28
Speaker 1: supernova release a huge amount of energy, a huge amount
44:31
Speaker 1: of radiation, and so if one of them was too close,
44:34
Speaker 1: absolutely it could sterilize half of the planet. Fascinatingly, though,
44:37
Speaker 1: most of the energy of a supernova is actually carried
44:40
Speaker 1: out in new trinos, Like of the energy released in
44:44
Speaker 1: a supernova comes as new trinos, which of course hardly
44:47
Speaker 1: interact with us. Even that one percent, though that's left
44:50
Speaker 1: over if the supernova is close enough, is enough to
44:53
Speaker 1: sterilize an entire planet. So are we lucky then that
44:56
Speaker 1: the one near the center of the galaxy was a
44:58
Speaker 1: failed supernova? You know, like if it had been a
45:01
Speaker 1: real supernova, would it have affected us. It would have
45:03
Speaker 1: been brighter and so it would have been more dramatic.
45:05
Speaker 1: But even that one is still pretty far away the
45:07
Speaker 1: center of the galaxies, like twenty thousand light years away,
45:10
Speaker 1: so not close enough to really cause any damage, your honor,
45:13
Speaker 1: and I guess also too far for the zombie to
45:15
Speaker 1: come edith, I don't know, it's had nine years. Well,
45:19
Speaker 1: in a way, it's kind of funny because these zombie
45:21
Speaker 1: stars happen because one star eats another star. Oh that's true. Yes,
45:25
Speaker 1: one star is feasting off of the brains of another star,
45:28
Speaker 1: and that's what it brings it back to life. Yeah,
45:29
Speaker 1: that's the lesson. I think, do not eat brains like
45:33
Speaker 1: turn into a zombie or if that's your aspiration in life,
45:37
Speaker 1: eat away. That's right. If you if you endeavor to
45:40
Speaker 1: be a zombie star, that would make you an zalist star.
45:44
Speaker 1: I guess, all right, well, what what does it all mean.
45:46
Speaker 1: I guess it means that we still don't quite understand
45:49
Speaker 1: Supernovaz that will. I thought it was something that was
45:51
Speaker 1: pretty well understood and modeled, but it sounds like there
45:53
Speaker 1: are still a lot of questions about how it happens
45:55
Speaker 1: and in which way it can happen. It's a rapidly
45:58
Speaker 1: moving field, and we're always developing better and better models,
46:01
Speaker 1: which have gone from like two D to three D
46:03
Speaker 1: two much more realistic, and now with our impressive computational power,
46:06
Speaker 1: we're making more and more detailed models. But it's very
46:09
Speaker 1: tricky because we're talking about something that's happening very fast,
46:12
Speaker 1: very high density, and very high intensity, and so the
46:16
Speaker 1: modeling is difficult to get right. We're talking about the
46:18
Speaker 1: strong nuclear force, we're talking about incredible gravitational forces, and
46:23
Speaker 1: so it's difficult, and you know, our measurements are limited.
46:26
Speaker 1: We can see a few things about them here from Earth,
46:28
Speaker 1: but it's not easy to understand, like what's going on
46:31
Speaker 1: inside the supernova. And actually a lot of that information
46:34
Speaker 1: is carried by neutrinos, which can reveal what happened on
46:37
Speaker 1: the inside of the supernova. But neutrinos are so difficult
46:40
Speaker 1: to observe, so it's a real challenge for us to
46:43
Speaker 1: model and for us to understand, right. And it's also
46:46
Speaker 1: I think it's sort of this difficult intersection for physics
46:48
Speaker 1: of quantum mechanics and gravity, right, Like it's it's almost
46:52
Speaker 1: like you're looking at the heart of a black hole.
46:55
Speaker 1: It's like when these supernova happened, the pressure and the gravity,
46:59
Speaker 1: it's all sort of makes us together. So that's something
47:02
Speaker 1: we don't understand. Yeah, and it's very short lived and
47:05
Speaker 1: kind of rare, and even easier problems we still don't understand,
47:08
Speaker 1: like what's going on inside a neutron star. Neutron stars
47:12
Speaker 1: are everywhere, and they last forever and they glow steadily
47:15
Speaker 1: in the X ray, and still we don't understand sort
47:18
Speaker 1: of the equation of state, like what's going on in
47:20
Speaker 1: terms of the pressure and the density and the speed
47:22
Speaker 1: of sound and the inside of a neutron star. So
47:24
Speaker 1: supernova is harder because it's short lived, it's higher intensity,
47:28
Speaker 1: and there are fewer of them, and so we have
47:30
Speaker 1: a lot of work to do to understand what's going
47:32
Speaker 1: on at the heart of these things. But seeing the
47:35
Speaker 1: weird ones, the extremes are really helpful because they help
47:38
Speaker 1: you understand the boundary conditions, like why didn't this one
47:41
Speaker 1: go Type one A supernova? Why didn't that one? Is
47:43
Speaker 1: like examples of ones that survived and came back to
47:46
Speaker 1: tell us a story. So they're really useful clues, and
47:50
Speaker 1: it tells what triggers the type one day supernova and
47:52
Speaker 1: what doesn't. Yeah, that's pretty cool, and I guess also
47:56
Speaker 1: the problem is there are a lot of physicists who
47:57
Speaker 1: hate zombies, and so they won't even touched this stuff, right, Like,
48:01
Speaker 1: I'm surprised to you even finish that paper, Daniel. Anything
48:03
Speaker 1: for the podcast, and anything for the podcast except actually
48:06
Speaker 1: watching zombie movies that I can send you a long
48:10
Speaker 1: list of required zombie genre thanks to watch if you
48:14
Speaker 1: want to catch up. If not, you can just run faster. Alright,
48:18
Speaker 1: and listeners out there, tell us what is your favorite
48:20
Speaker 1: physics zombie movie. That's a that's a sub genre. I guess,
48:24
Speaker 1: I hope, so, I mean, apparently would watch those then yes,
48:28
Speaker 1: there's a physicist involved, you would watch it exactly. Maybe
48:32
Speaker 1: the physicist becomes a zombie and then she has her
48:34
Speaker 1: best ideas and that's when her career really takes off. Yeah,
48:37
Speaker 1: she becomes a zombie star in the physics community. All right, Well,
48:41
Speaker 1: we hope you enjoyed that thinking about what happens out
48:43
Speaker 1: there in the cosmos, and what doesn't happen in the cosmos,
48:47
Speaker 1: and what kinds of interesting new types of stars there
48:50
Speaker 1: can be and are being born every day. Thanks for
48:53
Speaker 1: joining us, See you next time. Yeah, thanks for listening,
49:03
Speaker 1: and remember that Daniel and Jorge explained. The Universe is
49:06
Speaker 1: a production of I Heart Radio. For more podcast For
49:10
Speaker 1: my Heart Radio, visit the I heart Radio app, Apple Podcasts,
49:14
Speaker 1: or wherever you listen to your favorite shows. H