Latest / Daniel and Kelly’s Extraordinary Universe / Could stars have black holes at their cores?

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Could stars have black holes at their cores? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: What mysteries lie inside the Earth, inside stars, or at
0:13
Speaker 1: the hearts of black holes? We always seem drawn to
0:16
Speaker 1: cracking things open and looking for the surprises inside. We've
0:20
Speaker 1: been walking around on this planet for hundreds of thousands
0:23
Speaker 1: of years until recently had no idea what was hidden within?
0:27
Speaker 1: Was it all just dirt? Is it hollow? Was Godzilla
0:30
Speaker 1: sleeping in his lair down there? What about in the
0:33
Speaker 1: hearts of stars? Science tells us that at their core
0:38
Speaker 1: matter is incredibly dense, the fusion furnaces that illuminate the
0:42
Speaker 1: universe and forge the heavy metals needed for life and podcasts.
0:46
Speaker 1: But what if there was something else, even more exotic
0:49
Speaker 1: in the hearts of stars? What if instead of iron
0:52
Speaker 1: or nickel or even nuclear pasta, stars hearts might contain
0:56
Speaker 1: the most mysterious objects in the universe holes? And what
1:01
Speaker 1: if that could solve another longstanding cosmic mystery. Today on
1:06
Speaker 1: the pod, we'll ask whether stars could have black holes
1:10
Speaker 1: at their cores. Welcome to Daniel and Kelly's extraordinarily dense
1:15
Speaker 1: but brilliant Universe.
1:30
Speaker 2: Hello, I'm Kelly Wadersmith. I study parasites and space and
1:33
Speaker 2: I love pizza. HM.
1:36
Speaker 1: My name is Daniel I'm a particle physicist, and I'm
1:38
Speaker 1: particularly particular about my pizza.
1:41
Speaker 2: I remember you and I had a discussion once about
1:43
Speaker 2: what we were like level twenty experts on, and you
1:46
Speaker 2: said that you were like a level twenty expert on pizza.
1:49
Speaker 2: And I'm embarrassed to say I couldn't figure out anything
1:51
Speaker 2: to say that I was a level twenty expert on.
1:53
Speaker 2: But anyway, you just visited Chicago, and so I have
1:57
Speaker 2: to ask you a very important question, which city makes
2:01
Speaker 2: the best pizza.
2:04
Speaker 1: It's easy. New York obviously near pizza, hands down.
2:10
Speaker 2: I'm so glad we can stay friends. I wasn't sure
2:12
Speaker 2: if there's gonna be like a white chocolate dark chocolate
2:15
Speaker 2: divide where I admit that I actually don't dislike white
2:17
Speaker 2: chocolate that much and then you get upset and then
2:19
Speaker 2: I pretend that I hate it. Moving forward, but yeah,
2:22
Speaker 2: New York does have the best pizza.
2:23
Speaker 1: It's similar to that, actually, because some people defend Chicago
2:27
Speaker 1: pizza and it's a tasty thing, but it's not pizza. Yeah,
2:30
Speaker 1: you know, it's like Mari Andara bathtub or something. I mean,
2:34
Speaker 1: it's delicious and greasy and it's good, but it's not pizza. Yeah,
2:38
Speaker 1: and when I gotta choose and I gotta make it myself,
2:40
Speaker 1: I'm definitely making thin crust pizza, though with a little
2:43
Speaker 1: bit more of a Neapolitan puffy crust around the edge.
2:47
Speaker 2: Yeah. I love that all. I mean, I love all
2:50
Speaker 2: kinds of pizza. But yeah, whenever I go to New York,
2:52
Speaker 2: I've got to get some pizza.
2:53
Speaker 1: And I don't know why they got to call it pizza,
2:54
Speaker 1: you know, like they don't call the Chicago hot dog
2:57
Speaker 1: like a taco, you know, like just call it its
2:59
Speaker 1: own thing. Why we use this word pizza for something
3:02
Speaker 1: which is to totally different from pizza.
3:04
Speaker 2: I mean, it's got the same ingredients, but just in
3:07
Speaker 2: different like depth. No you disagree, I don't know.
3:14
Speaker 1: I recently tried Detroit Pizza, also quite tasty, very weird, delicious,
3:19
Speaker 1: but still in my opinion, not pizza. But you know
3:22
Speaker 1: that's semantic. It's all delicious combination of excellent ingredients. My
3:26
Speaker 1: personal preference is the thin stuff. But you know, I
3:29
Speaker 1: get why people like Chicago pizza.
3:31
Speaker 2: We won't talk about pizza for that much longer because
3:33
Speaker 2: we have important sites to get to you. But I
3:34
Speaker 2: heard that Detroit Pizza is like in an like an
3:38
Speaker 2: automotive pan of some sort, or like what is the
3:42
Speaker 2: defining feature of Detroit pizza? Presumably you clean the pan first.
3:48
Speaker 1: Detroit is also a deep dish kind of pizza. But
3:51
Speaker 1: you have like sauce on the top in these rows
3:53
Speaker 1: on top of the cheese, and you get this crispy
3:56
Speaker 1: edge of cooks up if you do it right. Anyway,
3:58
Speaker 1: it's quite good.
3:58
Speaker 2: Okay, I should have eaten before we started recording this
4:01
Speaker 2: because now I'm hungry.
4:02
Speaker 1: But all right, but you know, if you eat too
4:03
Speaker 1: much Chicago pizza or too much Detroit pizza, you risk
4:06
Speaker 1: collapsing into a black hole.
4:08
Speaker 2: Ah, that's where it was going. You got there first.
4:11
Speaker 2: I was actually gonna like contribute a transition. But okay,
4:15
Speaker 2: so today we're talking about black holes, all right, and
4:18
Speaker 2: we are specifically talking about whether or not stars could
4:21
Speaker 2: have black holes at their core. And I will be honest.
4:25
Speaker 2: When you first sent this question to me, my thought was, well,
4:27
Speaker 2: could a star exist if it had a black hole
4:29
Speaker 2: in its core? It seems like the answer should be no.
4:32
Speaker 2: And so let's see if our audience's guts had the
4:35
Speaker 2: same response.
4:36
Speaker 1: No matter what pizza they happen to be digesting.
4:38
Speaker 2: We hope it's delicious no matter what it is.
4:40
Speaker 3: I guess stuff in the core of a star could
4:43
Speaker 3: get dance enough that it would turn into a black hole,
4:47
Speaker 3: but maybe that will eventually end up extinguishing the star,
4:51
Speaker 3: because I can see how the star could keep on
4:54
Speaker 3: burning only with its alter or shell. So I guess
4:58
Speaker 3: if that happens, it will be short lived and the
5:01
Speaker 3: star will die and turn into a black hole.
5:03
Speaker 4: I suspect a star can have a black hole for
5:05
Speaker 4: a core as long as the star is both big
5:07
Speaker 4: enough to survive then usual black hole formation and big
5:10
Speaker 4: enough that the black hole's gravity doesn't affect the outermost
5:14
Speaker 4: layers of the star.
5:15
Speaker 2: I suspect not it would collapse the whole star material,
5:19
Speaker 2: I think, into itself that's no longer being a star.
5:22
Speaker 5: I think it's possible to have a black hole inside
5:27
Speaker 5: the star in the core, because a black hole can
5:30
Speaker 5: be small enough even for you to have it in
5:34
Speaker 5: your hand, isn't it, And it would not.
5:35
Speaker 3: Affect the surrounded Because it's more.
5:38
Speaker 6: I don't believe a star could have a black hole core,
5:40
Speaker 6: mainly because for want to fall in the first place,
5:42
Speaker 6: a star would have to collapse, and if there was
5:44
Speaker 6: such a condition where it did have a black hole
5:47
Speaker 6: as its core, the gravitational force would pull in the
5:49
Speaker 6: surrounding matter that makes up the star anyway, so it
5:51
Speaker 6: could never be stable enough.
5:53
Speaker 7: It seems possible, but then you'd have to ask how
5:56
Speaker 7: did it get there and how does it stay there?
5:59
Speaker 7: And I don't know how it would form, but for
6:02
Speaker 7: it to stay there, the star around it would have
6:05
Speaker 7: to be spinning very very fast so it doesn't get
6:08
Speaker 7: pulled in, and I don't really know how that would
6:11
Speaker 7: ever start happening.
6:12
Speaker 2: Okay, so I'm feeling pretty good because a handful of
6:16
Speaker 2: our audience members had the same feeling as I did.
6:18
Speaker 2: And you know, I haven't gotten to the end of
6:20
Speaker 2: the outline yet, so I don't know if I'm right
6:21
Speaker 2: or if I'm wrong. It'll be an exciting journey that
6:24
Speaker 2: we'll take together.
6:25
Speaker 1: And these are great ideas. I like the way they're thinking.
6:28
Speaker 1: But you know, it strikes me that a lot of
6:30
Speaker 1: people think of black holes as like this infinitely powerful
6:33
Speaker 1: thing that will suck in anything. But you know, we've
6:35
Speaker 1: seen pictures of black holes, and we know what black
6:38
Speaker 1: holes should look like out there in nature and they're
6:40
Speaker 1: not totally by themselves. You can have stuff around the
6:43
Speaker 1: black hole, Like the famous picture of a black hole
6:45
Speaker 1: has a hot disk of gas right around it, because
6:49
Speaker 1: the environment around a black hole is quite complex and
6:51
Speaker 1: there's pressure out and gravitational attraction in, and so we're
6:55
Speaker 1: going to learn it's not quite so simple. Yeah.
6:57
Speaker 2: I was talking to Sarah Gallagher at Western University the
7:00
Speaker 2: other day and she studies the gases that like emit
7:03
Speaker 2: out of black holes, and I just kind of stared
7:05
Speaker 2: at her for a second because I was like, I
7:07
Speaker 2: didn't think anything could escape from black holes, and so
7:10
Speaker 2: we had a fascinating conversation about how I was wrong.
7:12
Speaker 1: Yeah, well, you're right that nothing can escape from a
7:14
Speaker 1: black hole, but things can escape from the vicinity of
7:17
Speaker 1: a black hole, right, And so it depends what you
7:19
Speaker 1: count as the black hole. If it's a black hole,
7:22
Speaker 1: plus it's accretion disk and all that stuff, then yeah,
7:24
Speaker 1: it can emit, and they certainly do. We see quasars
7:27
Speaker 1: from across the universe these incredibly bright emitters.
7:31
Speaker 2: Okay, but I think we can all agree that nothing
7:33
Speaker 2: escapes from the center of a black hole. So if
7:36
Speaker 2: you are a star that has a black hole, in
7:39
Speaker 2: your belly. It feels like that shouldn't work out. So
7:42
Speaker 2: where do we start. What do we think stars have
7:45
Speaker 2: at their center?
7:46
Speaker 1: Yeah? Stars already super fascinating objects even without the black hole. Right,
7:50
Speaker 1: It's incredible that these things exist. There are this delicate
7:54
Speaker 1: balance between gravity and fusion. But they're also stable. They
7:58
Speaker 1: can last for millions or billions, or we think sometimes
8:00
Speaker 1: trillions of years. It's really incredible, and understanding what's going
8:04
Speaker 1: on at their heart has taught us a lot about
8:06
Speaker 1: the nature of physics and even chemistry.
8:09
Speaker 6: Yeah.
8:09
Speaker 2: I also had the urge to sort of spit and costs,
8:12
Speaker 2: so I understand I'm.
8:15
Speaker 1: Going to wipe my face before we go on. Yeah,
8:17
Speaker 1: and also the distribution of stars that are out there,
8:20
Speaker 1: the sizes, the colors, the ages tell us a lot
8:22
Speaker 1: about the history of the universe. I love this about
8:25
Speaker 1: science that you can piece together a whole history from
8:28
Speaker 1: what you see around you. It's not just like does
8:30
Speaker 1: this work, but it's like, how did we end up here?
8:33
Speaker 1: Why do we have this arrangement of stuff? And that's
8:35
Speaker 1: some other arrangement. There's so much information just encoded in
8:38
Speaker 1: what's out there, So I love that we can dig
8:41
Speaker 1: into it, and from that we've put together a pretty
8:43
Speaker 1: good model for house stars form and what should be
8:46
Speaker 1: at their center before we get into exotic black hole stars.
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Speaker 2: Yeah, I also love that kind of detective work into
8:53
Speaker 2: the past, using science to understand things we couldn't have seen.
8:55
Speaker 2: But okay, let's jump into stars. What should be in
8:58
Speaker 2: the center of those stars.
9:00
Speaker 1: So stars are basically just a scoop of universe, you know,
9:03
Speaker 1: go all the way back to Big Bang, hot, dense
9:06
Speaker 1: soup of stuff. It expands and therefore it cools, and
9:10
Speaker 1: you get particles that form. You get electrons and quarks,
9:13
Speaker 1: and then the quarks bind into protons, and then you
9:16
Speaker 1: have protons and electrons in the universe. It keeps cooling,
9:19
Speaker 1: and those electrons then get captured by the protons, and
9:22
Speaker 1: so now you have hydrogen. And most of the universe
9:25
Speaker 1: at the very beginning is hydrogen. It's like overwhelmingly hydrogen.
9:29
Speaker 1: Tiny little bit of helium that forms because you can
9:32
Speaker 1: actually have hydrogen fusion during the first few moments of
9:35
Speaker 1: the universe to make a little bit of helium trace
9:39
Speaker 1: anything else. So the universe is hydrogen, but it's not
9:42
Speaker 1: perfectly smooth. The original quantum fluctuations in the early universe
9:46
Speaker 1: lead to over densities in some places and under densities
9:50
Speaker 1: in others, which gives gravity a handle to pull that
9:53
Speaker 1: stuff together to make stars. And so you have these
9:57
Speaker 1: big clouds of hydrogen. Some spots are little. They have
10:00
Speaker 1: more gravity, they pull on more hydrogen, gives them more gravity,
10:03
Speaker 1: gives them more hydrogen. You get this runaway effect, and
10:06
Speaker 1: then you get a collapse. So the first stars we
10:08
Speaker 1: think were mostly hydrogen and a little bit of helium.
10:12
Speaker 2: And if you were explaining how black holes are formed,
10:15
Speaker 2: would you have used all the same words or is
10:17
Speaker 2: that a totally different process?
10:21
Speaker 1: No, basically the same. But you need to get to
10:22
Speaker 1: a critical density to form a black hole. And what
10:25
Speaker 1: happens when a star is collapsing is that gravity isn't
10:28
Speaker 1: the only game in town. You get to a certain
10:30
Speaker 1: density at the core of the star and it ignites fusion.
10:33
Speaker 1: So it's hot enough and it's dense enough that the protons,
10:37
Speaker 1: which don't usually like to talk to each other because
10:39
Speaker 1: they're both positively charged, are squeezed together close enough that
10:42
Speaker 1: eventually they will fuse and they'll give you helium and
10:46
Speaker 1: release some energy. So this is fusion. You get protons
10:50
Speaker 1: fusing into helium and energy comes out, and that energy
10:54
Speaker 1: pushes back out on the star. It's effectively a pressure outwards,
10:57
Speaker 1: so you have gravity squeezing in and radiation pressure pushing out.
11:02
Speaker 1: That's what keeps the star from collapsing into a black hole.
11:05
Speaker 1: So you're right, black hole collapse very very similar, but
11:07
Speaker 1: you don't get there in a star because of fusion.
11:09
Speaker 1: Fusion keeps the universe from collapsing into black holes and
11:13
Speaker 1: keeps it bright. Right without fusion, we wouldn't have light,
11:16
Speaker 1: and the whole universe would be dark.
11:18
Speaker 2: Thank you fusion. If only we could use it to
11:20
Speaker 2: power our toasters, we'll get there one day.
11:23
Speaker 1: And this is not the primary topic of today's episode,
11:25
Speaker 1: but there is a theory that in the very very
11:28
Speaker 1: early universe, there might have been enough over density, maybe
11:31
Speaker 1: even before you formed all those protons to create primordial
11:35
Speaker 1: black holes, which exist like before there are quirks and
11:39
Speaker 1: protons and all sorts of stuff, so it's possible to
11:42
Speaker 1: form black holes in the very very early universe. A
11:45
Speaker 1: lot of people ask, like, if the universe was super dense,
11:47
Speaker 1: why didn't the whole thing collapse into a black hole?
11:49
Speaker 1: And the reason is that for a black hole to form,
11:51
Speaker 1: you need density in one place relative to the density
11:54
Speaker 1: around it. If everything is super dense, then nothing is
11:57
Speaker 1: getting pulled. But if you happen to have once which
12:00
Speaker 1: is super overdense, potentially you can have direct collapse into
12:04
Speaker 1: a black hole in the early universe. But we're not
12:06
Speaker 1: talking about that today. We're imagining what happens to normal stars.
12:09
Speaker 1: So you get this collapse, you get fusion, and then
12:12
Speaker 1: you have a balance. Gravity and radiation are doing this
12:15
Speaker 1: delic balance and it can keep going for millions and
12:18
Speaker 1: millions of years. And at the core you're manufacturing new elements.
12:22
Speaker 1: So we're talking about what's at the core of stars. Well,
12:24
Speaker 1: it starts out with just hydrogen, and then you get helium,
12:27
Speaker 1: and if the star is big enough and massive enough,
12:29
Speaker 1: it could also fuse that helium into heavier stuff. You
12:33
Speaker 1: get carbon, you get neon, you get oxygen, and if
12:36
Speaker 1: it's big enough and massive enough, you can get silicon.
12:38
Speaker 1: You can get all the way up to nickel and
12:40
Speaker 1: then to iron. So that's how we manufacture these elements.
12:43
Speaker 1: They're made at the hearts of stars.
12:45
Speaker 2: All right, Let's see if I can pass the qualifying exam
12:47
Speaker 2: for my pod. If I remember correctly, the bigger the
12:51
Speaker 2: elements that you're getting, the more like heat you're losing,
12:55
Speaker 2: and over time that cools the star. Is that right?
12:58
Speaker 1: Almost? No, Definitely, the spirit of it is right. You know,
13:03
Speaker 1: up to a certain point, you are generating heat. So
13:06
Speaker 1: before iron fusion creates heat, like when you go from
13:11
Speaker 1: lighter elements to heavier elements, you release heat above iron
13:15
Speaker 1: fusion costs heat, right, it takes energy, So it can
13:19
Speaker 1: happen because there is energy there, but effectively cools the
13:22
Speaker 1: star when you fuse iron nuclei together to make something
13:25
Speaker 1: even heavier. And so that doesn't mean it doesn't happen,
13:28
Speaker 1: but it means it effectively kills the star because now
13:31
Speaker 1: the star is cooling down, and if it's cooling down,
13:34
Speaker 1: it can't push back against gravity. And what do you
13:36
Speaker 1: have is you start to have a gravitational collapse again,
13:39
Speaker 1: and then you can form like a normal vanilla black hole,
13:42
Speaker 1: like the kind that we have seen in our universe
13:44
Speaker 1: where the whole star becomes a black hole. And we
13:46
Speaker 1: talk about that a little bit more detail in a minute.
13:49
Speaker 1: But there's another thing that we need to understand first
13:51
Speaker 1: about normal stars, which is the limit on their size,
13:54
Speaker 1: and the connection between the size and the age of
13:56
Speaker 1: the star. You have the whole early universe, big cloud
14:00
Speaker 1: of hydrogen, some clumps of which collapse to make stars.
14:03
Speaker 1: And you might wonder, like, is there a limit to
14:05
Speaker 1: the size of the star, Like can you just get
14:07
Speaker 1: huge clouds that form together to make enormous mega stars?
14:12
Speaker 1: And the answer is that there is kind of a
14:13
Speaker 1: limit because the bigger the star, the higher the pressure
14:18
Speaker 1: and the density and the temperature of the core, and
14:20
Speaker 1: the faster fusion happens. Because fusion is very sensitive to
14:24
Speaker 1: the temperature and the pressure. Like you increase the pressure
14:26
Speaker 1: by a little bit, the rate of fusion increases very
14:29
Speaker 1: very quickly. And so what happens if you have a
14:31
Speaker 1: star that's too big is that the radiation pressure from
14:34
Speaker 1: the fusion is so intense that actually blows the star apart.
14:38
Speaker 1: It'll like rip apart the star and blow away its
14:41
Speaker 1: outer layers so effectively, you can't get a star that's
14:44
Speaker 1: like more than three hundred times the mass of our Sun.
14:48
Speaker 1: It'll tear itself apart.
14:49
Speaker 2: That would be a pretty epic way to go. I
14:51
Speaker 2: think my new goal is to become super massive towards
14:54
Speaker 2: the end of my life.
14:57
Speaker 1: Blow yourself apart from the fusion that you're That's what
15:00
Speaker 1: happens if you eat too much Chicago pizza.
15:03
Speaker 2: Yeah, yeah, you gotta be careful. You gotta be careful.
15:05
Speaker 1: And there's something else happening at the core of the star,
15:07
Speaker 1: which is really crucial. You've made those elements, right, you've
15:10
Speaker 1: made helium or iron or nickel or whatever. They're at
15:13
Speaker 1: the core of the star. But when the star dies,
15:15
Speaker 1: it goes supernova and it blows that material out into
15:18
Speaker 1: the universe, and then those heavy metals become the seeds
15:21
Speaker 1: of the next generation of stars. So when we start out,
15:25
Speaker 1: we have a universe mostly filled with gas that makes
15:27
Speaker 1: these really big stars, huge stars that don't last very long,
15:31
Speaker 1: maybe a few million years because they're so big. But
15:34
Speaker 1: the next generation it's different because now you have these
15:36
Speaker 1: heavy seeds to start stars. You don't just have to
15:39
Speaker 1: have a big hydrogen clump to start a big hydrogen star.
15:43
Speaker 1: You have like a blob of iron over here and
15:45
Speaker 1: some nickel over there, and those are excellent. It's seeding
15:48
Speaker 1: new stars. So then the next generation of stars are
15:51
Speaker 1: smaller because there's like more places to start, So the
15:54
Speaker 1: big clouds of hydrogen breakup into more chunks, and because
15:58
Speaker 1: they're smaller, they don't burn its hot and they ask longer.
16:01
Speaker 1: So the second generation of stars that have more metals
16:03
Speaker 1: in them last a lot longer than the first generation
16:06
Speaker 1: and are also smaller.
16:08
Speaker 2: That is beautiful, But my brain has gotten totally off
16:12
Speaker 2: on a tangent imagining Kelly at the bend of her
16:15
Speaker 2: life exploding into lots of little Kelly's, and that really
16:19
Speaker 2: would be a great way to go.
16:20
Speaker 1: Next generation of Kelly's will all be mini Kelly's. Yeah exactly,
16:23
Speaker 1: that's right, that's right.
16:24
Speaker 2: But at least there'll be more of them anyway. That
16:26
Speaker 2: is beautiful that a giant star produces more stars.
16:29
Speaker 1: Yeah, exactly. And in our universe we still have some
16:32
Speaker 1: big stars, Like if you look at the star mass distribution,
16:36
Speaker 1: mostly the stars in the universe are smaller, like our
16:39
Speaker 1: star is on the heavier, larger side compared to the
16:41
Speaker 1: average star. We may have yellow star, but most of
16:44
Speaker 1: the stars out there are red dwarfs. They're smaller and colder,
16:48
Speaker 1: and therefore they burn cooler than our star. So the
16:51
Speaker 1: smaller the star, the cooler, the redder it is. The
16:54
Speaker 1: bigger the star, the hotter and bluer.
16:56
Speaker 6: It is.
16:56
Speaker 1: So if you look out into the universe, you can
16:58
Speaker 1: actually tell the age distribute of stars because the blue
17:01
Speaker 1: stars disappear more quickly. So if you're like looking at
17:04
Speaker 1: a part of the universe and there's a bunch of
17:05
Speaker 1: blue stars, you know that stars have been formed there recently,
17:09
Speaker 1: Whereas if you look at some corner of the universe
17:10
Speaker 1: you're like, oh, it's all red stars, then you know
17:12
Speaker 1: there have been no stars born recently. It's like a
17:15
Speaker 1: retirement home versus a new subdivision or something.
17:18
Speaker 2: But like, could you make a reasonable guess at star siblings,
17:21
Speaker 2: Like this star exploded and produced these thirty stars in response.
17:26
Speaker 1: You can understand stars siblings in the sense of like
17:29
Speaker 1: you can estimate the age of a star from its neighbors, right, Like,
17:33
Speaker 1: if there are no blue stars around, you can guess
17:35
Speaker 1: that it's probably older, and if there's lots of blue
17:37
Speaker 1: stars around, you can guess that it's probably younger. It's
17:39
Speaker 1: really hard to trace back an individual star and say
17:42
Speaker 1: this one was formed from the explosion of that earlier
17:45
Speaker 1: star which no longer exists, and the other ones that
17:48
Speaker 1: came from that star that's really tricky. And also it's
17:50
Speaker 1: complicated because like our sun was formed from the remnants
17:53
Speaker 1: of other stars, but not just one. Right, It's not
17:55
Speaker 1: like one chunk of some other star landed in a
17:59
Speaker 1: gas of high It's like a huge conglomeration of probably many,
18:02
Speaker 1: many stars that all came together. So yeah, the family
18:05
Speaker 1: tree gets pretty messy there. Yeah, it's like a big
18:08
Speaker 1: orgy that happened to make our star.
18:10
Speaker 2: Good. Good way to make this a non kid appropriate episode.
18:13
Speaker 1: You can have totally family friendly orgies. You can have
18:16
Speaker 1: like an orgy of pizza for example, right, sampling lots
18:19
Speaker 1: of different pizzas.
18:20
Speaker 2: Yeah, I'm not sure that you know what people usually
18:23
Speaker 2: mean when they use that word, Daniel.
18:25
Speaker 1: I know what people usually mean. I'm saying for folks
18:28
Speaker 1: that they're listening with your kids, there's an explanation for you.
18:31
Speaker 7: Yeah.
18:31
Speaker 2: I hope they don't repeat it at school. All right, So,
18:34
Speaker 2: should we talk about any other stars on our tour
18:38
Speaker 2: of local Stars?
18:39
Speaker 1: Yeah? So there are some really big stars in our universe,
18:42
Speaker 1: and they're really fun to think about because the sizes
18:45
Speaker 1: are just really incredible. A famous big star is Beetlejuice.
18:50
Speaker 2: Beetlejuice is Oh, that's two, don't say it a third time.
18:56
Speaker 1: That star is famous because it's in Orion and it
19:00
Speaker 1: has a radius a thousand times that of our Sun. Wow,
19:03
Speaker 1: Like the Sun is already enormous compared to Jupiter, which
19:07
Speaker 1: is gigantic compared to the Earth. And now Beetle Juice,
19:12
Speaker 1: it's showtime. It's a thousand times the radius, which means
19:16
Speaker 1: a billion times the volume.
19:18
Speaker 2: Holy cos it's just.
19:20
Speaker 1: Hard to really wrap your mind around. If you put
19:22
Speaker 1: it in our solar system, its edge would be at
19:24
Speaker 1: the orbit of Jupiter, right, we would be inside Beetlejuice. Also,
19:28
Speaker 1: it's a weird star because recently it's been seen to
19:31
Speaker 1: be dimming, so it's like quite variable in ways people
19:33
Speaker 1: don't understand, which some people think might mean it's about
19:36
Speaker 1: to go supernova and there's interesting stuff happening at its core.
19:40
Speaker 1: But again, we don't really understand the core of stars
19:42
Speaker 1: in detail. It's so chaotic and difficult to describe with
19:45
Speaker 1: simple equations and expensive to model with supercomputers. So it's
19:49
Speaker 1: really an active area of research. But that's a really cool,
19:52
Speaker 1: really big star.
19:53
Speaker 2: So my interest in a topic is directly proportional to
19:55
Speaker 2: how much it impacts me. So if beetlejuice explodes, is
20:00
Speaker 2: that going to be bad for me?
20:01
Speaker 1: If beetlejuice explodes, it'll be dramatic and exciting, but probably
20:05
Speaker 1: not super dangerous. It's six hundred and fifty light years away.
20:08
Speaker 1: It's not the time of travel that keeps us safe.
20:10
Speaker 1: It's not like, oh, it explodes, we have six hundred
20:12
Speaker 1: and fifty years to do something about it. We won't
20:14
Speaker 1: know it explodes until six hundred and fifty years after
20:17
Speaker 1: it explodes, because that's when the signal is going to
20:19
Speaker 1: arrive here on Earth. But because it's so far away,
20:22
Speaker 1: the radiation it produces will be quite diluted. That radiation
20:25
Speaker 1: is going to spread out in a huge sphere and
20:28
Speaker 1: cover the inside of that sphere, and the Earth is
20:30
Speaker 1: a tiny, tiny slice of that. So we're only in
20:33
Speaker 1: danger to supernovas that are much closer than that.
20:36
Speaker 2: Okay, that's good. I feel great. Now that I feel great,
20:39
Speaker 2: Let's take a break, have some pizza, and when we
20:41
Speaker 2: come back, we'll talk some more about some big stars
20:43
Speaker 2: in our galaxy. All right, so I hope you had
21:06
Speaker 2: some delicious New York style pizza. Let's go and talk
21:09
Speaker 2: about yet another star in our galaxy? Which one are
21:13
Speaker 2: we talking about next, Daniel?
21:14
Speaker 1: So the biggest star that we know about is a
21:16
Speaker 1: star called Stephenson to eighteen. This one has twice the
21:21
Speaker 1: radius of Beetlejuice. Right, Beetle Juice already a thousand times
21:24
Speaker 1: the radius of the Sun. This one's twenty one hundred.
21:27
Speaker 1: And it's so big that it's so hot. It's five
21:31
Speaker 1: hundred thousand times brighter than the sun. Wow, Like, imagine
21:35
Speaker 1: five hundred thousand suns in the sky. That's Stevenson two eighteen.
21:40
Speaker 1: It's not kidding around.
21:41
Speaker 2: So how is it that I have heard of Beetlejuice before,
21:43
Speaker 2: but I haven't heard of Stevenson to eighteen.
21:45
Speaker 1: Beetlejuice is a star in the sky, it's a constellation.
21:48
Speaker 1: Stevenson to eighteen is much much further away. It's like
21:52
Speaker 1: nineteen thousand light years away, so it's still in our galaxy,
21:56
Speaker 1: but it's like a completely different arm so you can't
21:59
Speaker 1: really see it with the naked eye. It's something we've discovered,
22:02
Speaker 1: and there's still a lot of uncertainty about what we
22:03
Speaker 1: know about it because it's so far away. But yeah,
22:06
Speaker 1: it's a pretty dramatic star. And this is one of
22:09
Speaker 1: the things I love about astrophysics and astronomy is like
22:12
Speaker 1: the more you look out into the universe, the more
22:14
Speaker 1: weird stuff you see that you can't explain, you know.
22:16
Speaker 1: It's just like always a surprise when you build something new,
22:20
Speaker 1: which is why I think we should have like ten
22:22
Speaker 1: times as many space telescopes as we do and ground
22:25
Speaker 1: telescopes and satellites, and like, wow, think about the things
22:28
Speaker 1: we're missing in the universe just because we're not looking.
22:31
Speaker 2: That's right, And we in more money for fish research too.
22:34
Speaker 2: We're missing things we could be looking all over the place, guys,
22:37
Speaker 2: and we're not looking. Enough more money for science.
22:40
Speaker 1: Let's build a space telescope that's excellent at finding alien
22:43
Speaker 1: fish on exoplanets. How about that? Is that a good compromise, Daniel?
22:46
Speaker 2: I am so glad we found something we can agree on. Yes, amazing.
22:50
Speaker 2: As long as those alien fish have alien parasites, I'm
22:53
Speaker 2: one hundred percent in and I bet they.
22:55
Speaker 1: Will, all right, excellent. I look forward to building that
22:58
Speaker 1: telescope with you. Okay, it's slam dunk funding case for sure.
23:02
Speaker 2: They can't turn us down, all right, So let's focus
23:05
Speaker 2: away from fish unfortunately onto black holes. All right, so
23:08
Speaker 2: let's go you. You told us that some of the
23:10
Speaker 2: process for starting a star is similar to the process
23:13
Speaker 2: for starting a black hole. Remind me where those processes diverge, please.
23:18
Speaker 1: Yeah, So a lot of stars end up as black
23:20
Speaker 1: holes because fusion can't last forever. Right, it's eating the
23:24
Speaker 1: stars using the star as fuel. It's converting the light
23:28
Speaker 1: stuff into heavy stuff, and eventually converts it into heavy
23:31
Speaker 1: stuff that it can no longer burn. Like our sun
23:34
Speaker 1: is hot enough to burn hydrogen, and near the end
23:37
Speaker 1: of its life, it's going to be hot enough to
23:38
Speaker 1: burn helium very very briefly. But anything heavier than that.
23:42
Speaker 1: Our sun doesn't create the temperatures and the pressures and
23:45
Speaker 1: the densities to fuse, and so anything else that it
23:48
Speaker 1: makes is inert. It interferes with the process of the star.
23:52
Speaker 1: And so that's why our sun, for example, is going
23:55
Speaker 1: to get a core that's basically dead. It's not participating
23:58
Speaker 1: in fusion anymore, and then fusions are going to move
24:00
Speaker 1: to outer layers of the star, and that's why the
24:03
Speaker 1: star puffs up near the end of its life. You hear,
24:04
Speaker 1: like the sun is getting hotter and bigger and in
24:07
Speaker 1: billion years it's going to be really big. And that's
24:09
Speaker 1: true because the fusion is moving to the outer layers
24:12
Speaker 1: where there still is hydrogen. But eventually the star accumulates
24:16
Speaker 1: so much heavy inert stuff, stuff that can't participate in fusion,
24:20
Speaker 1: that the star collapses. Gravity winds right, Eventually fusion just
24:24
Speaker 1: peters out, and this collapse is really spectacular. You get
24:27
Speaker 1: this pressure wave that goes into the star and then
24:30
Speaker 1: it bounces back and comes out and explodes the star.
24:33
Speaker 1: And that's where you get a supernova. Right, It's like
24:35
Speaker 1: this shock wave that goes in and then out that
24:37
Speaker 1: travels are like incredible velocities, really violent stuff, really amazing.
24:43
Speaker 2: You sound like my daughter. She's really into violent stuff
24:45
Speaker 2: right now. She also sounds very excited when she's fucking
24:48
Speaker 2: about explosions and stuff.
24:50
Speaker 1: Well, it's not that I want anybody start to blow up,
24:52
Speaker 1: it's just the energy is just incredible. The numbers here
24:56
Speaker 1: are just mind boggling. And then what happens at the
24:59
Speaker 1: core of the star depends on the amount of mass,
25:02
Speaker 1: So you get this really hot dense thing left over.
25:05
Speaker 1: If it's not quite dense enough, it can form a
25:07
Speaker 1: neutron star, which doesn't collapse into a black hole because
25:10
Speaker 1: there's something else pushing back. Now, it's not fusion pressure.
25:13
Speaker 1: Neutron star is a star, but there's no fusion happening.
25:16
Speaker 1: It's just electron degeneracy pressure. Like the particles that are
25:20
Speaker 1: in there, they're all fermions, which means they don't like
25:22
Speaker 1: to be on top of each other the way electrons don't,
25:25
Speaker 1: and that effectively creates a pressure. Like they can't squeeze
25:28
Speaker 1: down and cool down into the lowest energy levels because
25:32
Speaker 1: they can't be in the same energy levels, and so
25:34
Speaker 1: they have to be in higher energy levels, which means
25:36
Speaker 1: they keep some energy, they move around, they basically push back.
25:40
Speaker 1: That's what degeneracy pressure is. People write in sometimes and
25:42
Speaker 1: ask like what force is degeneracy pressure, or like why
25:46
Speaker 1: does the universe keep particles from entering the same state?
25:49
Speaker 1: You know, And there's no special force there. It's just
25:51
Speaker 1: that the particles cannot be in the same state, and
25:54
Speaker 1: so they stay in higher energy levels to avoid each other,
25:57
Speaker 1: and that creates pressure. Effectively. Start doesn't collapse because of
26:01
Speaker 1: quantum mechanics. But you know, eventually, if you have enough mass,
26:05
Speaker 1: it can overcome that. It can push these things together,
26:08
Speaker 1: so they're no longer really neutrons. Like they get smushed
26:11
Speaker 1: together and their neutron this sort of goes away as
26:14
Speaker 1: the quarks form this soup, and then the proto black
26:17
Speaker 1: hole can collapse. So if you have enough pressure to
26:19
Speaker 1: squeeze those neutrons out of their fermion states and form
26:23
Speaker 1: a soup, you can form a black hole. And that's
26:25
Speaker 1: when you get above this critical threshold.
26:27
Speaker 2: Okay, So when we first started talking about fermions and
26:29
Speaker 2: you said that they don't like to be near each
26:31
Speaker 2: other the same way that electrons don't, I have been
26:33
Speaker 2: thinking about fermions as something that was kind of electron adjacent,
26:38
Speaker 2: and I forgot that fermions are more like neutrons.
26:41
Speaker 1: Well, fermions are category particle. All matter are fermions, electrons, quarks, neutrons, protons,
26:46
Speaker 1: they're all fermions. And fermions have this particular property that
26:50
Speaker 1: you can't have two of them in the same quantum state,
26:52
Speaker 1: which is why electrons, for example, are not all in
26:54
Speaker 1: the lowest energy level around hydrogen. When the lowest energy
26:58
Speaker 1: levels filled, the next one can't be there. It's got
27:00
Speaker 1: to be in the next level, and then the next
27:02
Speaker 1: level and then the next level. That's why electrons spread
27:04
Speaker 1: out on the ladder of energy levels, one per level.
27:07
Speaker 1: You know, there's like different spins you can have or whatever,
27:09
Speaker 1: but they all have to be in a unique state,
27:12
Speaker 1: which keeps the electrons effectively hotter. Right, If the electrons
27:15
Speaker 1: could all collapse into the lowest energy level, they would
27:17
Speaker 1: be cooler, but they're not, which keeps some electrons at
27:20
Speaker 1: high energy. And that's the same thing that's happening in
27:23
Speaker 1: the neutron star. The neutrons have to stay at higher
27:26
Speaker 1: energy because they can't collapse all into the lowest energy state,
27:29
Speaker 1: and that keeps the star hot, and that keeps pressure going.
27:32
Speaker 2: Okay, and so when a big star collapses, presumably there's
27:36
Speaker 2: still fermions around. But what you said was that the
27:40
Speaker 2: black hole is so immense that it just squishes them
27:43
Speaker 2: down anyway and overcomes their desire to remain in happy
27:47
Speaker 2: states and push back out.
27:48
Speaker 1: Yeah, exactly, because neutrons are fermions because they're combinations of quarks,
27:52
Speaker 1: and so the rule still applies because you have fermions there.
27:55
Speaker 1: But if you squeeze those quarks together, you can get
27:58
Speaker 1: other states that are not fermions, and then it can
28:00
Speaker 1: collapse them exactly. And the crucial thing to know for
28:03
Speaker 1: our later discussion is that when this collapse happens, you
28:07
Speaker 1: get a black hole. You get an enormous shockwave that
28:09
Speaker 1: comes out right. This gravitational collapse produces an enormous shock wave,
28:13
Speaker 1: and a black hole heats up everything around it. The
28:16
Speaker 1: gravity the black hole is really intense. The accretion disc
28:19
Speaker 1: the stuff around the black hole gets heated up by
28:21
Speaker 1: the gravity of the black hole, and it radiates. This
28:24
Speaker 1: is why black holes are so hot, because they heat
28:27
Speaker 1: up everything around them, which then blows that stuff out.
28:30
Speaker 1: So like, black holes is a limit to how fast
28:32
Speaker 1: they can grow in the universe because they emit so
28:35
Speaker 1: much radiation. They're pushing their food away from them. Yeah,
28:38
Speaker 1: the more massive they get, the more they heat up
28:40
Speaker 1: the stuff near them, which then blows the food away
28:43
Speaker 1: from them. There's no theoretical limit to the size of
28:45
Speaker 1: a black hole, but there's an effective limit to how
28:47
Speaker 1: quickly they can grow because they push away their food.
28:51
Speaker 2: Baffling. This blows my mind. I can't understand that behavior.
28:54
Speaker 1: Yeah, and so these are normal stellar black holes, right,
28:58
Speaker 1: These are black holes that form the end of the
29:00
Speaker 1: life of a star. And so we call these small
29:03
Speaker 1: black holes, even though they can be up to like
29:05
Speaker 1: fifty or one hundred times the mass of the sun.
29:07
Speaker 1: But there's another category of black holes that we need
29:10
Speaker 1: to understand for today's episode, which are called super massive
29:13
Speaker 1: black holes.
29:15
Speaker 2: It's a great song.
29:18
Speaker 1: And if I opened to Chicago Pizza doing, I would
29:20
Speaker 1: call it super massive pizza because these are definitely like
29:24
Speaker 1: a lot bigger. These are a few million to a
29:26
Speaker 1: few billion times the mass of the sun. Wow, right,
29:29
Speaker 1: like normal black holes, just one hundred times fifty times
29:32
Speaker 1: the mass of the sun. This is millions or billions
29:35
Speaker 1: of suns into a black hole. It's really incredible.
29:38
Speaker 2: So how do you go from an exploding star to
29:41
Speaker 2: something that's so much more massive than the star was initially?
29:45
Speaker 1: Yeah, it's a good question, and people have been wondering
29:48
Speaker 1: about this in particular for a long time, and they
29:51
Speaker 1: asked exactly your question, and they did a bunch of simulations.
29:54
Speaker 1: They thought, well, maybe you have early galaxies with early
29:57
Speaker 1: stars and some of them formed black holes, and then
29:59
Speaker 1: those black hole clump together and they just gather together
30:02
Speaker 1: at the center, which makes sort of sense. And they
30:05
Speaker 1: ran simulations, but those simulations do not describe what we
30:08
Speaker 1: see like in those simulations, you do not get super
30:11
Speaker 1: massive black holes. You get much smaller ones. But when
30:14
Speaker 1: we look out into the universe, we can look really
30:16
Speaker 1: far back in time at the formation of super massive
30:19
Speaker 1: black holes and ask how long did it take in
30:21
Speaker 1: the universe to form these black holes, And it didn't
30:24
Speaker 1: take very long. We see super massive black holes at
30:27
Speaker 1: the hearts of very very young galaxies much earlier than
30:31
Speaker 1: we expect. So they're like super massive black holes that
30:35
Speaker 1: are like thirteen billion years old, which is like about
30:38
Speaker 1: a billion years after the universe began. You already have
30:43
Speaker 1: black holes with like two billion solar masses. Nobody knows
30:46
Speaker 1: how they got so big so fast.
30:49
Speaker 2: So is that the answer, Like, we just we don't
30:51
Speaker 2: know full step.
30:54
Speaker 1: We don't know how super massive black holes have formed.
30:57
Speaker 1: That is definitely a huge open question in astrophysics. There
31:00
Speaker 1: are lots of crazy ideas out there. One of them
31:03
Speaker 1: is the one I mentioned earlier, primordial black holes. People
31:06
Speaker 1: thought maybe black holes formed in another special way, like
31:10
Speaker 1: in the early universe there were already black holes formed
31:13
Speaker 1: before even hydrogen, and so these guys were around to
31:17
Speaker 1: see the formation of super massive black holes in the
31:19
Speaker 1: universe perhaps, but nobody's ever seen a primordial black hole,
31:23
Speaker 1: and we should have seen one if they existed, so
31:26
Speaker 1: it's pretty hard to support that theory anymore. Although for
31:29
Speaker 1: a while they were an exciting candidate for dark matter
31:32
Speaker 1: because like, they're big, they're massive, they're dark. Maybe they
31:35
Speaker 1: explain the missing matter, but again, we haven't seen them
31:38
Speaker 1: and we should have. Another fun explanation for super massive
31:41
Speaker 1: black holes came recently when people noticed that the rate
31:44
Speaker 1: of super massive black hole formation, the rate of their growth,
31:48
Speaker 1: seemed to link weirdly with the dark energy in the universe.
31:52
Speaker 1: That like, the amount of dark energy in the universe
31:54
Speaker 1: is increasing because the universe expands, and as it expands
31:57
Speaker 1: makes more space than that space comes with more dark energy,
32:00
Speaker 1: so the dark energy fraction is increasing as time goes on,
32:04
Speaker 1: just like the super massive black hole mass is increasing.
32:07
Speaker 1: They noticed a very tight correlation and they came up
32:09
Speaker 1: with this theory, which went everywhere on social media when
32:12
Speaker 1: it came out like last year or so, that maybe
32:15
Speaker 1: super massive black holes are the source of dark energy.
32:18
Speaker 1: That like, weirdly they're creating dark energy or they are
32:21
Speaker 1: expanding the universe somehow. It's not a theory that's really
32:25
Speaker 1: become mainstream. There's some questions and uncertainties about it. There's
32:28
Speaker 1: a whole podcast episode about it. You should check it out.
32:30
Speaker 1: But the point is that this is an open mystery.
32:33
Speaker 1: How do you get black holes that are this big,
32:36
Speaker 1: this massive in the early universe?
32:38
Speaker 2: So how we how do? Real quick? Maybe you can
32:40
Speaker 2: just tell me? So how does it get bigger and
32:43
Speaker 2: more massive while also creating more dark energy?
32:46
Speaker 1: Like?
32:47
Speaker 2: Where is the energy for that coming from? You know what?
32:49
Speaker 2: I'll listen to the episode. You didn't do that episode
32:51
Speaker 2: with me? Right, and I've forgotten the answer? That was
32:53
Speaker 2: one with Orgey.
32:54
Speaker 1: Yeah, it's an episode I did with Jorgey quite a
32:56
Speaker 1: while ago. It's a really fun idea, And there's two
32:59
Speaker 1: things to understand that. One is that we do have
33:01
Speaker 1: a theoretical model for black holes, like we can solve
33:05
Speaker 1: the equations of general relativity for a black hole. But
33:08
Speaker 1: there's a detail that's often left out when people say that,
33:11
Speaker 1: which is that we only know how to solve these
33:13
Speaker 1: equations for a black hole in an empty universe, Like
33:16
Speaker 1: we can solve the equations for a super dense object
33:19
Speaker 1: and nothing else. All right, but that's not our universe,
33:23
Speaker 1: and more importantly, our universe is expanding, so we don't
33:26
Speaker 1: know how to solve the equations for a black hole
33:29
Speaker 1: in an expanding universe or a universe filled with stuff,
33:32
Speaker 1: and so theoretically there is a question mark there, like
33:36
Speaker 1: how do black holes form an expanding universe? What are
33:38
Speaker 1: those rules? We don't really know because we don't understand
33:41
Speaker 1: the solutions of general relativity. We basically only solved it
33:44
Speaker 1: for a very few simple cases, like a black hole
33:47
Speaker 1: in an empty universe or a universe filled with uniform dust.
33:50
Speaker 1: We can't even solve it for like the Earth going
33:52
Speaker 1: around the Sun. That's too hard.
33:54
Speaker 2: Wow, what is it? All models are wrong? But some
33:57
Speaker 2: models are useful? Are they are?
33:59
Speaker 1: These?
33:59
Speaker 2: These are still models, right?
34:02
Speaker 1: Gr is still usable and we can do in americal
34:04
Speaker 1: approximations a lot of times. But basically we don't understand
34:07
Speaker 1: how black holes form in an expanding universe in theory.
34:11
Speaker 1: And so these guys have an idea for what's inside
34:14
Speaker 1: the black hole that inside the black hole is not
34:16
Speaker 1: a singularity, but some weird vacuum energy that contributes to
34:20
Speaker 1: the expansion of the universe, and like, hey, that's possible.
34:25
Speaker 1: You know, it's a violation of general relativity, but we
34:27
Speaker 1: know general relativity has to be wrong at some point,
34:30
Speaker 1: and we don't understand how the expansion can be everywhere
34:33
Speaker 1: if it's sourced from the black holes, So there's a
34:36
Speaker 1: lot of open questions about that. You know, black holes
34:38
Speaker 1: also are really big and massive, but there are a
34:40
Speaker 1: tiny fraction of the mass of the universe, whereas dark
34:43
Speaker 1: energy is like seventy percent of the energy in the universe,
34:46
Speaker 1: So this doesn't really answer that. But the point is
34:49
Speaker 1: that we still don't understand how super massive black holes form,
34:53
Speaker 1: but they are out there in the universe. So there's
34:56
Speaker 1: another really crazy and exciting theory that we'll talk about
35:00
Speaker 1: after the break that might tell us what was inside
35:03
Speaker 1: even bigger stars than we can imagine.
35:26
Speaker 2: All Right, we're back and it's time for the big payoff.
35:29
Speaker 2: Could black holes be inside of a star? Daniel?
35:33
Speaker 1: So we talked about how stars form, and the crucial
35:36
Speaker 1: things to remember there is that stars can't get too
35:38
Speaker 1: big because they blow out their stuff, and if a
35:40
Speaker 1: black hole forms, it blows stuff away from it also,
35:44
Speaker 1: And then we talked about how we don't understand how
35:46
Speaker 1: super massive black holes formed in the universe. So The
35:49
Speaker 1: idea is bring these two things together and say, what
35:51
Speaker 1: if there was a special kind of star in the
35:54
Speaker 1: early universe that was so big, so massive that it
35:59
Speaker 1: formed a black hole at its core, which ended up
36:02
Speaker 1: being the seed for a super massive black hole, and
36:05
Speaker 1: so big that it was protected against that shock wave
36:08
Speaker 1: of blowing stuff out, so.
36:11
Speaker 2: It would just be a star until the black hole
36:14
Speaker 2: took over.
36:14
Speaker 1: So let's walk through the life cycle of it, because
36:16
Speaker 1: it's kind of crazy and kind of a fun theory.
36:19
Speaker 1: So you start in the very early universe. Just like
36:21
Speaker 1: we talked about before, everything is very dense, everything is
36:23
Speaker 1: very hot, and you know, we have areas of over
36:26
Speaker 1: density that are pulling stuff in. Something I should have
36:28
Speaker 1: mentioned before, which I think is super cool, is that
36:31
Speaker 1: it's not just over densities in the normal matter, not
36:34
Speaker 1: just like, oh, here's a little bit more hydrogen. It's
36:36
Speaker 1: actually over densities in the dark matter that are really important.
36:40
Speaker 1: Because remember, dark matter is the dominant source of matter
36:42
Speaker 1: in the universe. That's most of the matter. So if
36:45
Speaker 1: you happen to have a clump of dark matter, then
36:47
Speaker 1: the normal matter is going to get pulled towards that.
36:49
Speaker 1: So dark matter actually controls where normal matter forms structure,
36:54
Speaker 1: or you can think of it that way or the
36:56
Speaker 1: other way, which is like normal matter tells us where
36:59
Speaker 1: the dark matter is. It's like tracers. So if you
37:01
Speaker 1: look at in the night sky and see a bunch
37:03
Speaker 1: of stars, you know, oh, there's probably a big blob
37:05
Speaker 1: of dark matter there. That's why stars formed there. Anyway,
37:08
Speaker 1: that's super cool, But in the very early universe, we
37:11
Speaker 1: didn't have metals to form these stars, right, So you
37:13
Speaker 1: have either an over density of hydrogen or an overdensity
37:16
Speaker 1: of dark matter. Pulls this stuff together. You get super massive,
37:19
Speaker 1: short lived stars. And in the standard theory, remember that
37:22
Speaker 1: if it gets too big, it gets too hot and
37:24
Speaker 1: it blows that stuff away. But if the star is
37:27
Speaker 1: big enough, like really enormous, not three hundred times the
37:31
Speaker 1: mass of the sun, not a thousand times the mass
37:33
Speaker 1: of the sun, We're talking millions of times of the
37:36
Speaker 1: mass of the sun. If you happen to get a
37:38
Speaker 1: blob of stuff together from a dark matter over density
37:42
Speaker 1: and then try to collapse that gravitationally, the idea is
37:44
Speaker 1: maybe something special happens at the core of the star,
37:47
Speaker 1: and the star's mass protects it against the radiation. That's
37:51
Speaker 1: coming out because gravity is just so overwhelming.
37:54
Speaker 2: And it becomes black hole.
37:56
Speaker 1: Yes, And so what happens is you have this huge
37:58
Speaker 1: blob of stuff. We're talking about like a million times
38:01
Speaker 1: the radius of the Sun, right, so like blow your
38:04
Speaker 1: mind trying to hold this thing in your head. The
38:06
Speaker 1: core gets hotter and gets denser, just like we talked
38:09
Speaker 1: about before. But now there's enough gravitational pressure to turn
38:12
Speaker 1: the core into a black hole. So you have this
38:15
Speaker 1: enormous star and at the heart is this tiny but
38:18
Speaker 1: very very dense black hole, like a few tens of
38:20
Speaker 1: a kilometers across. How cute, How cute, but terrifying that's right. Now. Normally,
38:27
Speaker 1: when you form a black hole or you have this
38:29
Speaker 1: gravitational collapse of the core, you would get a shockwave
38:32
Speaker 1: that would like tear the star apart, right, That's what
38:34
Speaker 1: supernovas are in general. But this one is so massive
38:38
Speaker 1: that the shockwave just like it just gets absorbed, right,
38:41
Speaker 1: It doesn't get all the way to the outside. The
38:43
Speaker 1: outside layers are squeezing back in. It's like you know,
38:47
Speaker 1: a violent crowd or an English football game or something,
38:49
Speaker 1: you know, squeezing back in. And so something else happens.
38:52
Speaker 1: The outer layers of the star that are squeezing the
38:54
Speaker 1: gas are forcing it into the black hole. Usually black
38:58
Speaker 1: holes can grow only slowly because they're pushing their food away. Right, Well,
39:03
Speaker 1: what if there's like a huge blob of gas on
39:05
Speaker 1: the outside forcing it back. So now it's being force
39:08
Speaker 1: fed gas even though the radiation pressure is pushing it away.
39:12
Speaker 1: So now your black hole is growing pretty quickly as
39:14
Speaker 1: it's like being force fed gas at the heart of
39:17
Speaker 1: this star. So, yes, it is a star and there's
39:21
Speaker 1: a black hole at its core, and the thing that
39:23
Speaker 1: keeps it from blowing apart is its sheer mass. It's
39:26
Speaker 1: too big to collapse.
39:28
Speaker 2: Holy cow, I'm impressed. Okay, so it seems to me
39:31
Speaker 2: that this process should pretty quickly result in the star
39:35
Speaker 2: becoming a giant black hole. Is that the point you
39:37
Speaker 2: can get black holes forming in the center of stars
39:41
Speaker 2: before they're at their end of their life, and it
39:44
Speaker 2: hastens the end of the life of the star.
39:46
Speaker 1: Yeah, so eventually this thing will collapse. It can't last forever.
39:49
Speaker 1: It's got a pretty good run though for the few
39:52
Speaker 1: moments in the universe's history that it glows like it's
39:55
Speaker 1: super duper bright. You know, we talked about fusion happening
39:57
Speaker 1: more rapidly at high temperatures and pressures. So this one
40:01
Speaker 1: single massive star with the black hole core would have
40:04
Speaker 1: been about as bright as the entire galaxy. Wow, so
40:07
Speaker 1: like really incredible. Essentially as bright as a supernova. A
40:10
Speaker 1: supernova is also as bright as a galaxy. And so
40:13
Speaker 1: the black hole is growing, the star is expanding, right,
40:16
Speaker 1: Eventually the whole thing becomes thirty times the width of
40:19
Speaker 1: our solar system.
40:20
Speaker 4: Wow.
40:21
Speaker 1: So we were talking beetle juice is like orbit and jube,
40:23
Speaker 1: but wow, that's big. Yeah, this thing is monster as
40:26
Speaker 1: compared to that, right, and then you get magnetic fields
40:29
Speaker 1: which create radiation and quasar. It's just like we talk about.
40:32
Speaker 1: But eventually the black hole grows so much that it
40:35
Speaker 1: will tear the star apart because their radiation pressure from
40:38
Speaker 1: the black hole is pushing out and that will eventually
40:41
Speaker 1: take over because there's only so much star to eat.
40:44
Speaker 1: And the thing that was keeping this stable was the
40:46
Speaker 1: outer layers of the star. The more you eat the star,
40:49
Speaker 1: the less protection you have. It's like you're eating your
40:52
Speaker 1: own spaceship. Right, So it only lasts like ten million
40:55
Speaker 1: years or so in the early universe. But what's left
40:58
Speaker 1: over is a very massive black hole, much more massive
41:02
Speaker 1: than you would expect from the death of a normal star.
41:05
Speaker 1: And if you have a very massive black hole around
41:07
Speaker 1: and other stars are forming nearby, you could imagine that
41:10
Speaker 1: they would start orbiting that really massive black hole and
41:13
Speaker 1: it could end up being the center of a galaxy.
41:16
Speaker 2: Okay, so we've seen super massive black holes. Yeah, but
41:19
Speaker 2: we have not seen this in the process of happening
41:22
Speaker 2: because this would have happened so long ago. Exactly could
41:26
Speaker 2: we still see this happening super far away, or this
41:28
Speaker 2: happened so long ago that that light would have already
41:30
Speaker 2: passed us or something.
41:34
Speaker 1: Great question, we're going to.
41:35
Speaker 2: Take away my pod in physics.
41:36
Speaker 1: No, PD and physics come from asking sincere and curious
41:40
Speaker 1: questions about the universe, not about being right. Okay, so
41:43
Speaker 1: I never want to discourage somebody from thinking. And that's physics, right.
41:46
Speaker 1: What you're doing right there is physics. You're like, this
41:47
Speaker 1: is what I understand, this is what you're telling me.
41:49
Speaker 1: How do I fit it together into a model in
41:51
Speaker 1: my head? That's the essential step of doing science. And
41:55
Speaker 1: so yeah, absolutely, you earn your PhD twice over ya.
41:58
Speaker 1: The answer is if it happen in the early universe,
42:01
Speaker 1: we should be able to see it because we could
42:03
Speaker 1: just look further and further away. Because if it happened
42:06
Speaker 1: a long time ago, we just need to look at
42:08
Speaker 1: light that's been traveling since then, which means it's been
42:11
Speaker 1: a really long distance and we can see pretty far back.
42:14
Speaker 1: We can't see all the way back to that far
42:16
Speaker 1: in the universe. The James Web space telescope can see
42:19
Speaker 1: like formation of young galaxies, and that's helping us understand
42:22
Speaker 1: the super massive black hole question. But we can't with
42:25
Speaker 1: the James Web see that far back yet. But in
42:28
Speaker 1: principle we could be able to write these things would
42:31
Speaker 1: have been very bright even though they're super far away.
42:33
Speaker 1: We might be able to make them out. The other
42:36
Speaker 1: comment is like with the light from them have passed us,
42:39
Speaker 1: that's true for some of them. Like if there was
42:41
Speaker 1: one of these things at the heart of our galaxy
42:43
Speaker 1: and it admitted a bunch of light, its light would
42:45
Speaker 1: not be too far away for us to see. But
42:47
Speaker 1: the universe just goes on and on and on, and
42:49
Speaker 1: so there's always some more universe to send us light
42:53
Speaker 1: that's just arriving now. So that's why we can see
42:55
Speaker 1: the whole history of the universe from here if we
42:57
Speaker 1: look further and further.
42:58
Speaker 2: Away of today is fund more telescopes.
43:02
Speaker 1: Yes, exactly, it's fun more telescopes because there are deep
43:06
Speaker 1: mysteries here about how stars form and how matter works.
43:09
Speaker 1: And you know, this is a fun theory because it
43:12
Speaker 1: makes you think about huge stars and stars with exotic
43:15
Speaker 1: cores in them and maybe something else is happening at
43:17
Speaker 1: the hearts of stars or whatever, and because it solves
43:20
Speaker 1: a mystery, but probably the answer is something else, something
43:23
Speaker 1: even weirder than we have imagined. And so you know,
43:26
Speaker 1: it's a useful exercise in physics to be like, what
43:29
Speaker 1: about this? What about that? Could this even work? Very valuable,
43:32
Speaker 1: but it's also just a useful exercise to go out
43:35
Speaker 1: and look, you know, to ask the universe tell us,
43:37
Speaker 1: show us what's going on out there. And then we
43:40
Speaker 1: got to piece that together into our puzzle how the
43:42
Speaker 1: universe works and maybe have one of those moments of
43:45
Speaker 1: insight where we're like, oh, I get it, and it
43:48
Speaker 1: clicks into place and you're like, yeah, Universe, you make
43:51
Speaker 1: sense to me.
43:51
Speaker 2: Oh. It's so nice to have those moments with your partner.
43:54
Speaker 2: It's nice to have those moments with your universe as well.
43:57
Speaker 1: Do you have a similar relationship with the universe as
43:59
Speaker 1: you do with Zach.
44:00
Speaker 2: Both of them surprise me from time to time. You know,
44:04
Speaker 2: life should keep you on your toes.
44:07
Speaker 1: I hope you keep building a husband telescope so you
44:09
Speaker 1: can keep observing new surprises in your relationships.
44:13
Speaker 2: Well, my training was an animal behavior, so I'm always
44:15
Speaker 2: collecting data. I mess with him every once in a while.
44:18
Speaker 2: I'll do things like see how close I have to
44:21
Speaker 2: put the laundry bin to, like where he always throws
44:24
Speaker 2: the clothes on the floor before they'll actually end up
44:27
Speaker 2: in the bin? Like will he throw it if it's
44:29
Speaker 2: just an inch out of where he usually throw it? Anyway,
44:31
Speaker 2: I digress.
44:32
Speaker 1: Do you need an IRB to do experiments on your husband?
44:34
Speaker 2: Like, well, you know, I'm not really in academia right now,
44:37
Speaker 2: and so don't tell Rice.
44:39
Speaker 1: Okay, So was I gonna ask we were talking about
44:44
Speaker 1: the black hole of Zack's laundry.
44:46
Speaker 2: Oh God, that's actually a different topic. But okay, so.
44:51
Speaker 1: We're supposed to keep this family friendly, all.
44:53
Speaker 2: Right, all right, I'm back on track. I'm back on track. Okay,
44:56
Speaker 2: so you hear this theory that you've just presented to us.
45:00
Speaker 2: Do all the steps in this theory sound good to you?
45:02
Speaker 2: Does this sound plausible? You said that it's probably something
45:05
Speaker 2: else just because the universe is hard to figure out.
45:07
Speaker 2: But is there any step in this process that makes
45:10
Speaker 2: you feel like, I don't know, maybe not.
45:12
Speaker 1: There's nothing about this that's obviously wrong, there's no red flags,
45:16
Speaker 1: but there is a lot of speculation here, you know,
45:18
Speaker 1: there's like, well, maybe this can survive that, and maybe
45:21
Speaker 1: this happens and it gets force fed. But it's complicated,
45:24
Speaker 1: Like what you would really need to do is to
45:26
Speaker 1: model this, yeah, and not just be like more my
45:28
Speaker 1: intuition says it's probably correct. You need to see what
45:31
Speaker 1: it actually happened and put this thing into a computer.
45:34
Speaker 1: But that's hard. You know, we have trouble modeling individual
45:38
Speaker 1: stars turning into black holes and going supernova because you
45:41
Speaker 1: need to keep track of so many particles and they're
45:43
Speaker 1: very sensitive to the details we don't really understand, like
45:46
Speaker 1: why does this star go supernova and that one doesn't.
45:48
Speaker 1: It's not just a function of the mass, like it
45:51
Speaker 1: requires some special circumstance to happen or to not happen,
45:54
Speaker 1: and so there's probably just a lot of that, a
45:56
Speaker 1: lot of details that need to be filled in, and
45:59
Speaker 1: it's a lot of work. We should not only build
46:01
Speaker 1: new telescopes, we should hire more scientists and give them
46:04
Speaker 1: lots of computers.
46:05
Speaker 2: Yes, amen, because you got to start somewhere, and ideas
46:07
Speaker 2: like this help you identify the assumptions that you need
46:10
Speaker 2: to be testing in order to move forward. So yeah,
46:13
Speaker 2: very cool idea.
46:13
Speaker 1: And if you discover, oh, this doesn't work, it's going
46:15
Speaker 1: to give you another idea. And that's how we make progress. Yep. Right,
46:18
Speaker 1: start out with terrible ideas that inspire less terrible ideas. Yeah,
46:22
Speaker 1: dot dot dot science.
46:23
Speaker 2: Yeah, I think the answer to my PhD work was no,
46:26
Speaker 2: Kelly was wrong. But here's some other interesting stuff you
46:30
Speaker 2: could ask exactly.
46:31
Speaker 1: It's always fun follow up questions, that's right. And on
46:34
Speaker 1: that note, if you have follow up questions from today's
46:36
Speaker 1: episode or anything else you've heard about in physics, please
46:40
Speaker 1: write to us. We would love to answer your questions physics, biology,
46:44
Speaker 1: maybe even chemistry once in a while.
46:47
Speaker 2: Pizza related questions.
46:48
Speaker 1: Definitely, absolutely pizza related, especially the physics of pizza. No,
46:52
Speaker 1: I guess pizza's mostly chemistry, isn't it anyway? Write to
46:55
Speaker 1: us Questions at danieland Kelly dot org. We love hearing
46:59
Speaker 1: from you, really do, and we really will write you back.
47:02
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47:14
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47:17
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47:20
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47:22
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47:29
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47:35
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