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Are there stars made of dark matter? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, I've got a really hard physics question for you.
0:11
Speaker 1: Oh yeah, bring it on. All right, it's gonna sound simple,
0:13
Speaker 1: but I think it's a tricky question. All right, now
0:16
Speaker 1: you're scaring me. Here's a question. How do you define
0:19
Speaker 1: a star? I guess i'd say a fusion burning ball
0:24
Speaker 1: of plasma in outer space. But what about a neutron
0:27
Speaker 1: star that's not burning? Um? Well, then I guess i'd
0:30
Speaker 1: say a star is a glowing ball of stuff in space. See,
0:35
Speaker 1: totally different. What about a cold white dwarf that's not
0:38
Speaker 1: technically glowing? Right? You? And there is no good definition
0:43
Speaker 1: for a star? All right? Do I get a star?
0:45
Speaker 1: Then a gold star? Hi am poor handmake cartoonists and
1:03
Speaker 1: the creator of PhD comics. I'm Daniel. I'm a particle physicist,
1:07
Speaker 1: and I never give out gold stars in my class.
1:10
Speaker 1: What you're one of those tough professors that are always
1:13
Speaker 1: marking things up with red ink. No. The reward for
1:16
Speaker 1: doing well in my classes you get to come do
1:17
Speaker 1: research with me more. I see, Oh, I see. It
1:23
Speaker 1: sounds like a great class. But you know that reminds
1:26
Speaker 1: me of what happened to me. This is a real
1:27
Speaker 1: story in undergrad I turned into physics assignment, and then
1:31
Speaker 1: the day they were to be returned, the professor gives
1:33
Speaker 1: a lengthy apology. He says, to the person whose assignment
1:36
Speaker 1: this was, I apologize, I misunderstood your answer and that's
1:40
Speaker 1: why I corrected it this way. And then he hands
1:42
Speaker 1: it to me and the page is covering in red
1:45
Speaker 1: ink all these insulting comments. What are you doing? This
1:47
Speaker 1: doesn't make any sense. And then at the very end
1:49
Speaker 1: of my solution, he says, oh, now I see where
1:51
Speaker 1: you were going. Good work, full credit. That sounds really familiar.
1:56
Speaker 1: That's how I feel every time we were recorded podcast Dane,
2:00
Speaker 1: I'm like, where are you going with this? What's oh? Now?
2:02
Speaker 1: I get it? Yeah, And that's why you don't use
2:04
Speaker 1: red inc the first time you read someone's designment. But
2:08
Speaker 1: we are the stars of the podcast. Daniel and Jorge
2:11
Speaker 1: explain the universe production of I Heart Radio, in which
2:14
Speaker 1: we mark up the whole universe and say, this doesn't
2:17
Speaker 1: make sense, how does that work? Where are you going
2:18
Speaker 1: with this anyway? Why do you have black holes? What's
2:21
Speaker 1: the plan? We try to unpack the entire universe, from
2:24
Speaker 1: the tiniest little particles to the spinning hurricanes on Earth,
2:28
Speaker 1: to the craziness inside neutron stars, to everything in between,
2:32
Speaker 1: and explain all of it to you. Yeah, the universe
2:35
Speaker 1: definitely gets stars for being awesome and mysterious and big
2:40
Speaker 1: and full of interesting ideas and things to discover. It
2:43
Speaker 1: gets a lot of stars, right, Daniel. I mean there
2:45
Speaker 1: are a lot of stars in the universe. There are
2:47
Speaker 1: a lot of stars in the universe, and there are
2:49
Speaker 1: a lot of different kinds of stars, and this is
2:52
Speaker 1: one of those really cool fields because the naming conventions
2:55
Speaker 1: for stars, what we call them pre dates, are like
2:59
Speaker 1: actual understand ending of stars. We started to call them this,
3:02
Speaker 1: We started to call them that, and then later we realized, oh,
3:04
Speaker 1: that's not actually a star, or this is really two
3:06
Speaker 1: stars or something. So it's fun when like the naming
3:09
Speaker 1: conventions pre date your actual understanding. Oh I see, is
3:12
Speaker 1: it like being a Twitter star or a YouTube star?
3:15
Speaker 1: Like that's not quite the same as being a movie star.
3:17
Speaker 1: You know, it turns out that's not exactly as bankable. Yeah. Yeah,
3:21
Speaker 1: but stars are something we've been studying for, you know,
3:23
Speaker 1: literally forever since we looked up at the sky and wondered, like,
3:26
Speaker 1: what are those things out there in the sky, and
3:29
Speaker 1: then later realizing they were like our sun, and then
3:31
Speaker 1: realizing there are lots of different kinds of stars, very
3:34
Speaker 1: very different from our son. Yeah, I guess you know,
3:36
Speaker 1: the definition probably started when we looked up at the
3:38
Speaker 1: night sky and saw you know, bright shiny things, and
3:42
Speaker 1: you know, that's what we thought were stars, like you know,
3:44
Speaker 1: the pinpoints in the night sky. Yeah, and it takes
3:47
Speaker 1: a real leap to understand that those are like actually
3:50
Speaker 1: super duper massive and far away, right, that they appear
3:54
Speaker 1: to be so tiny only because they are so distant,
3:57
Speaker 1: and the fact that they're so distant, yeah, we can
3:59
Speaker 1: still see them means they must be almost impossibly bright, right,
4:02
Speaker 1: And then we figured out that some of them are
4:04
Speaker 1: glowing in the nice guy are actually planet So those
4:07
Speaker 1: are definitely not stars. But there is sort of a
4:09
Speaker 1: wide variety of types of stars out there in the universe, right.
4:13
Speaker 1: There is a kind that are burning, and there's the
4:15
Speaker 1: kind that's just simmering there, and then there are the
4:17
Speaker 1: kinds that they're just sitting there right and glowing out
4:19
Speaker 1: of their own kind of restlessness. Right. Yeah, Well, we
4:22
Speaker 1: had a whole fun podcast episode about the weirdest kinds
4:25
Speaker 1: of stars, And in that episode, I define stars to
4:28
Speaker 1: be things that have fusion inside them that prevent them
4:31
Speaker 1: from collapsing. And you pointed out, well, a lot of
4:33
Speaker 1: the things we were calling stars, like neutron stars and
4:36
Speaker 1: white doors, don't have fusion going on inside. They're still
4:39
Speaker 1: just really hot because they are leftovers from something that
4:42
Speaker 1: used to be burning. But they're not actually burning anymore,
4:44
Speaker 1: even if they're still glowing right right, So then would
4:47
Speaker 1: you say maybe a better definition is just you know,
4:49
Speaker 1: things that glow out there in space above a certain
4:52
Speaker 1: you know, glowiness. I don't know, wouldn't you need a
4:55
Speaker 1: minimum size? Also, like would a rocket ship be a
4:58
Speaker 1: star because it's glowing out the back? Yeah? Why not?
5:01
Speaker 1: I mean to an alien seeing you, you know, burning
5:03
Speaker 1: in the sky, you'd be like, oh look there's another
5:05
Speaker 1: star and it's coming towards us. Yeah, I suppose. I
5:09
Speaker 1: mean you might wonder like, why do we even have
5:11
Speaker 1: this concept of a star. It's because we see this pattern.
5:13
Speaker 1: We see this thing out there in the universe. There's
5:15
Speaker 1: a lot of this sort of similar type of thing,
5:18
Speaker 1: and we do this categorization where we try to say, well,
5:21
Speaker 1: this and that are kind of related can we fit
5:23
Speaker 1: them into a larger scheme only because we're trying to simplify,
5:26
Speaker 1: because we're trying to get down to the root cause
5:28
Speaker 1: and understand why do we have stars at all? You know,
5:32
Speaker 1: why is this a thing that seemed to happen in
5:34
Speaker 1: the universe more than other shapes of matter. But there
5:37
Speaker 1: is sort of one thing that all of those stars
5:39
Speaker 1: have in common, you know, like nutron stars, regular star,
5:41
Speaker 1: fusion stars, white dwarves, brown dwarfs, they all have one
5:45
Speaker 1: thing in common, and that is that they're all made
5:47
Speaker 1: out of regular matter. They are, right, They're made out
5:49
Speaker 1: of quirks and leptons, just like you and I are,
5:52
Speaker 1: And just like all the ice cream in the world is,
5:54
Speaker 1: and just like all the planets out there and all
5:56
Speaker 1: the kind of normal stuff that we're familiar with are
5:58
Speaker 1: made out of the same fundamentutil building blocks, mostly up
6:01
Speaker 1: corks and down corks and electrons, sometimes a few strange
6:05
Speaker 1: quirks or whatever else thrown in. But yeah, it's the
6:07
Speaker 1: same basic building blocks that make all of those different
6:10
Speaker 1: kinds of stars. Yeah, they're all made out of the
6:11
Speaker 1: same kind of matter. But then it turns out that
6:14
Speaker 1: that kind of matter is not the only type of
6:17
Speaker 1: matter in the universe. In fact, there's a lot more
6:19
Speaker 1: of another kind of matter that makes up all the
6:22
Speaker 1: stuff in the universe. Yeah, the kind of matter we're
6:24
Speaker 1: made out of is actually unusual. We call it normal matter,
6:27
Speaker 1: but it's really kind of abnormal. It's only fifteen percent
6:31
Speaker 1: or so of all the matter in the universe is
6:34
Speaker 1: our kind of matter. Yet you always struck me as
6:36
Speaker 1: a little abnormal for a physicist. That's dark, Ben, No,
6:41
Speaker 1: that's a compliment, trying to compliment you're an abnormal physicist, Adnuel. Well,
6:45
Speaker 1: then your whole joke is kind of dark. Yeah, there
6:48
Speaker 1: is a whole slice of the pie of the universe's
6:51
Speaker 1: stuff that is not regular matter, and in fact it's
6:54
Speaker 1: there's still a big mystery. It is still a big mystery,
6:57
Speaker 1: and one mystery is what is it made out of
6:59
Speaker 1: and what is it doing? In fact, I was having
7:01
Speaker 1: dinner with my family the other day and my son
7:03
Speaker 1: was asking me about dark matter, and then he says
7:05
Speaker 1: to me, does dark matter form things the way normal
7:09
Speaker 1: matter does? Like? Can it make planets and stars and
7:12
Speaker 1: all sorts of crazy stuff? M interesting? So light dinner
7:15
Speaker 1: conversation in the whites and household is either sewage, which
7:19
Speaker 1: my wife studies, or dark matter, which I study. But
7:22
Speaker 1: they're both kind of dark. I wonder what you were
7:26
Speaker 1: eating to inspire these conversations. But yeah, there's a whole
7:29
Speaker 1: bunch of other matter in the universe that is not
7:31
Speaker 1: regular matter. It's dark matter. And so a pretty interesting
7:35
Speaker 1: and big question is what can you make with this
7:38
Speaker 1: dark matter? So to the on the program, we'll be
7:40
Speaker 1: asking the question, are there stars made out of dark matter? Now, Daniel,
7:50
Speaker 1: would those be called dark stars? Because that sounds like
7:52
Speaker 1: a pretty cool, like fantasy sci fi name. It does. Yeah,
7:56
Speaker 1: it sounds like a wizard with some special skills. Dark star.
8:00
Speaker 1: What's the matter with dark star? Yeah? Well, if we
8:02
Speaker 1: ever do discover one, I will definitely call you up
8:04
Speaker 1: and ask you to name it. I want bet on it.
8:07
Speaker 1: Neither the part where you discover something or the part
8:09
Speaker 1: where you can actually call me if you do discover something. Yeah,
8:12
Speaker 1: that's unlikely above them. Yeah, so this is a pretty
8:14
Speaker 1: interesting question. Can you make a star out of dark matter?
8:18
Speaker 1: I mean, you can make a star in many different
8:20
Speaker 1: ways at a regular batter, quirks and electrons and other
8:24
Speaker 1: kinds of particles, like that, but can you make it
8:26
Speaker 1: out of dark matter? And I guess the big question
8:29
Speaker 1: is would it glow like would a dark matter star
8:31
Speaker 1: glow or would it anti glow. Yeah, it's a super
8:34
Speaker 1: fun question because we see all these weird things that
8:38
Speaker 1: normal matter can do. Right, if you just were given
8:41
Speaker 1: like quarks and electrons, it would be really hard to predict,
8:44
Speaker 1: like all the kinds of things that those particles can do.
8:47
Speaker 1: They can make protons and neutrons, and those protons and
8:49
Speaker 1: neutrons can make all sorts of crazy stuff like hurricanes
8:52
Speaker 1: and water droplets and hamsters and bananas and ice cream
8:55
Speaker 1: and stars, and that's really complicated. We don't even know
8:58
Speaker 1: what dark matter is made out of, so it's hard
9:00
Speaker 1: to get your mind around, like what can those bits
9:02
Speaker 1: of dark matter do when they get together and dance?
9:05
Speaker 1: Can they make really complex emergent phenomena like our matter
9:08
Speaker 1: can or not? And so, as usually, we were wondering
9:11
Speaker 1: how many people out there had thought about this question,
9:13
Speaker 1: whether you can make a start out of dark matter.
9:15
Speaker 1: So Daniel went out there into the wilds of the
9:17
Speaker 1: Internet and asked a couple of people, well, Daniel, did
9:20
Speaker 1: you go into the internet for this one, or did
9:22
Speaker 1: you just walk down the hall? This is on the internet.
9:25
Speaker 1: Thanks for the volunteers. I have not recently asked my
9:27
Speaker 1: children these questions. They tend to run away when I
9:29
Speaker 1: show up with my phone on record. I guess the
9:31
Speaker 1: internet has halls sort of. And so you ask people
9:35
Speaker 1: if they thought that dark matter could make a start,
9:38
Speaker 1: and so think about it for a second. What would
9:40
Speaker 1: you answer. Here's what people had to say. Well, dark
9:42
Speaker 1: matter feels the force of gravity, so it definitely can
9:46
Speaker 1: clump together. I don't know if it can get dance enough,
9:49
Speaker 1: but even if it did, it doesn't feel the strong
9:52
Speaker 1: nuclear force. And in order to have a start you
9:54
Speaker 1: need to have a nuclear fusion reaction inside of it.
9:58
Speaker 1: So if it can't feel the strong nuclear force, I
10:01
Speaker 1: don't think it can make stars. About the definition between
10:04
Speaker 1: no stars today, As far as I understand its stores
10:08
Speaker 1: are bodies of burning gas um involving nuclear reactions. Since
10:18
Speaker 1: they are made of elements, and through nuclear actions they
10:24
Speaker 1: produce new elements, I don't see how that could happen
10:27
Speaker 1: through doc matters. So no, I don't think so all right.
10:30
Speaker 1: I like how they avoided the answer, like they said
10:33
Speaker 1: a lot of words, but not yes or no. It's complicated.
10:36
Speaker 1: You can hear that they were sort of thinking about
10:38
Speaker 1: it for the first time as they answer the question.
10:40
Speaker 1: They were like doing physics on the fly. I love
10:43
Speaker 1: hearing that. Hearing people like use the models they have
10:46
Speaker 1: in their minds to try to fit them together and
10:47
Speaker 1: think about how they can come up with an answer.
10:49
Speaker 1: That's the process they're doing physics. It's wonderful to hearing
10:52
Speaker 1: you don't always get to the answer right away. I see,
10:55
Speaker 1: but these are pretty cool answer. I mean, some people
10:57
Speaker 1: allude to the idea that maybe dark men it doesn't
11:00
Speaker 1: feel the strong force or therefore there's no fusion in
11:03
Speaker 1: a dark matter star, and also talking about what kind
11:07
Speaker 1: of reactions you would need to make a star. Yeah,
11:09
Speaker 1: it's super fascinating to think about, Like could there be
11:12
Speaker 1: dark strong force, like a different kind of strong force
11:15
Speaker 1: just for dark matter. That would be super cool. What
11:18
Speaker 1: a dark strong force? It sounds like another superhero villain name.
11:23
Speaker 1: It's the power that the dark Star is going to
11:24
Speaker 1: use to battle our star when it comes into our
11:27
Speaker 1: solicits to destroy us, right right right. It sounds like
11:30
Speaker 1: some muce. You make a movie about the dark side
11:32
Speaker 1: of the force. Or something, and how it has two
11:34
Speaker 1: sides and how there should be balanced. That sounds like
11:36
Speaker 1: a billion dollar idea, maybe a fifty billion dollar idea.
11:39
Speaker 1: He had three ego dark star Wars. We'll call it
11:43
Speaker 1: all right, Well, let's recap for maybe those listeners that
11:46
Speaker 1: don't know Daniel, what can we say about dark matter?
11:48
Speaker 1: Like how do you define it? And what do we
11:50
Speaker 1: know about what it could be made out of? So
11:52
Speaker 1: there's a lot we don't know about dark matter, but
11:54
Speaker 1: there is also a lot that we do know. Dark
11:57
Speaker 1: matter is just our word for this invisible source of
12:01
Speaker 1: gravity that we haven't been able to explain. Like when
12:04
Speaker 1: we look out at the night sky and we see
12:05
Speaker 1: things tugging on stars, we know that there's something they're
12:09
Speaker 1: providing gravity to tug on those stars. And so, for example,
12:12
Speaker 1: when we look at galaxies and how they spin, we
12:14
Speaker 1: see that galaxies are spinning really really fast and something
12:17
Speaker 1: is holding them together. But if you add up the
12:19
Speaker 1: mass of all the stars in the galaxy, there's not
12:22
Speaker 1: enough gravity to hold them together. And so we say
12:24
Speaker 1: there must be something else there, something weird and new,
12:28
Speaker 1: something invisible that's providing the gravity to hold the galaxy together.
12:32
Speaker 1: So that's the basic hypothesis that there must be something
12:35
Speaker 1: else out there providing gravity but being invisible. And we
12:39
Speaker 1: have more evidence than just the rotation of galaxies. We
12:42
Speaker 1: can see the effect of dark matter all over the place,
12:44
Speaker 1: from the very early universe, how it affected the ripples
12:48
Speaker 1: in the plasma that gave us the cosmic microwave background,
12:51
Speaker 1: to then the evolution of the universe. The whole structure
12:53
Speaker 1: of the universe, from galaxies to clusters to superclusters, would
12:57
Speaker 1: look totally different if there wasn't dark matter. And we
13:00
Speaker 1: can also see blobs of dark matter in the sky
13:03
Speaker 1: bending the light from background galaxies. So we know that
13:06
Speaker 1: it's a thing. It's matter. It's out there, but it's
13:09
Speaker 1: invisible and we don't know what it's made out of. Right,
13:12
Speaker 1: it's the name we give something that we know it's there.
13:14
Speaker 1: You can see it in many different ways, or you
13:16
Speaker 1: can know that it's there in many different ways. You
13:18
Speaker 1: just can't like see it or touch it or somehow
13:21
Speaker 1: like shine a light on it. Right, because it's dark,
13:24
Speaker 1: it doesn't feel or interact with the magnetic force, that's right.
13:28
Speaker 1: That's the key thing is that it doesn't seem to
13:30
Speaker 1: have any interactions other than gravity, Like if you shoot
13:33
Speaker 1: photons at it, they passed right through. It doesn't feel
13:36
Speaker 1: photons because it has no electric charge, and only things
13:39
Speaker 1: with electric charge feel photons. We know that it doesn't
13:42
Speaker 1: feel the weak force, and it doesn't feel the strong
13:45
Speaker 1: nuclear force. None of the forces that we are familiar
13:47
Speaker 1: with affect these particles except for gravity, and that's the
13:51
Speaker 1: only way we know about its existence and the only
13:53
Speaker 1: way we have so far to interact with it. And
13:55
Speaker 1: that makes it really challenging because gravity is so weak.
13:59
Speaker 1: So it's really hard to use gravity to study, for example,
14:02
Speaker 1: a particle, because the particle has almost no gravity it's
14:05
Speaker 1: so tiny. Instead, we have to use it to study
14:07
Speaker 1: like enormous blobs of dark matter like at the center
14:10
Speaker 1: of the galaxy or huge halos that's surround the galaxy.
14:13
Speaker 1: Makes it hard to figure out exactly where the dark
14:15
Speaker 1: matter is and what it's doing because we have such
14:17
Speaker 1: a weak way to probe it, just gravity. Right, It's
14:20
Speaker 1: like the only way you can know it's there is
14:22
Speaker 1: if you have a lot of it, like you can
14:24
Speaker 1: like grab a little bit of it and look at
14:26
Speaker 1: it closely, because it's invisible. Because it's invisible and you
14:29
Speaker 1: can't grab it, you know, it's like grabbing something that
14:31
Speaker 1: your hand passes right through. And in fact, dark matter
14:34
Speaker 1: is here. It's all around us. It's everywhere. It's not
14:36
Speaker 1: just like out there in space. It's here on Earth.
14:39
Speaker 1: We think we don't know what it's made out of.
14:41
Speaker 1: It if it's made out of a particle or something else,
14:43
Speaker 1: or many particles, but it is all around us. We
14:45
Speaker 1: just have to figure out a way to interact with
14:48
Speaker 1: it other than gravity. If we're going to figure out
14:50
Speaker 1: what it's made out of. Right, that's a huge question.
14:52
Speaker 1: And it's not just like a little bit of stuff
14:54
Speaker 1: out there in space. It's a huge percentage of the
14:57
Speaker 1: mass and energy of the universe. Right, It's not like
15:00
Speaker 1: a rare thing out there. It's like most a thing. Yeah,
15:04
Speaker 1: if you just look at like the fraction of the
15:06
Speaker 1: mass in the universe, it's like eight percent. So the universe,
15:09
Speaker 1: the stuff in the universe, is mostly dark matter. So
15:12
Speaker 1: you can't pretend to like understand the universe at all
15:15
Speaker 1: if you don't understand anything about eighty percent of it
15:18
Speaker 1: for sure. And then if you look at the whole
15:20
Speaker 1: energy budget, mass and energy of the universe, dark matter
15:23
Speaker 1: makes up about twenty of all the energy in the universe,
15:27
Speaker 1: whereas our kind of matter is only like five percent.
15:29
Speaker 1: But that doesn't mean that we know like nothing about
15:31
Speaker 1: dark matter, because, as you say, we can study really
15:34
Speaker 1: big blobs of it. We actually do have some clues
15:37
Speaker 1: about dark matter. Like we can tell how quickly dark
15:39
Speaker 1: matter is moving around, because if it moves around really
15:42
Speaker 1: really quickly, if it's hot, then it changes how it's distributed.
15:46
Speaker 1: And if it's not moving around really really quickly, if
15:48
Speaker 1: it's cold, then it tends to like move more slowly
15:50
Speaker 1: and clump a little bit more. That changes how it's distributed,
15:53
Speaker 1: and that changes how it tugs on other matter. So
15:56
Speaker 1: we've been able to figure out, for example, that dark
15:58
Speaker 1: matter is around. It hangs out and need really big
16:01
Speaker 1: fluffy diffuse clouds that surround the whole galaxy. Yeah, I
16:05
Speaker 1: guess you could say it's pretty cool, totally chill, it's
16:08
Speaker 1: cool and dark exactly just likes to hang around. Yeah,
16:12
Speaker 1: we know it's all around this. It basically forms like
16:15
Speaker 1: a big blob in our galaxy, right, Yeah, and most
16:17
Speaker 1: of it is concentrated at the center of the galaxy.
16:19
Speaker 1: That's where the strongest gravitational pull is that it gets
16:22
Speaker 1: sucked in like other things. But because it's cold and
16:25
Speaker 1: slow moving and it doesn't feel a lot of other forces,
16:28
Speaker 1: it tends to mostly stay in a big fluffy cloud
16:30
Speaker 1: and swirl around the galaxy. So the galaxy is actually
16:32
Speaker 1: much bigger than you can see. The dark matter halo
16:35
Speaker 1: extends out like twice as far as the visible stars,
16:39
Speaker 1: So we're hanging out in a huge cloud of dark matter, right,
16:42
Speaker 1: and it it sort of makes up most of the
16:44
Speaker 1: galaxy in a way. Right, Like the stars are just
16:46
Speaker 1: like the sprinkles on the ice cream exactly. If you
16:49
Speaker 1: want to visualize the whole universe as a cupcake, then
16:52
Speaker 1: like the cake part is dark energy, the frosting is
16:55
Speaker 1: dark matter, and then the stars are the little sprinkles
16:57
Speaker 1: on top, right, and then we are the cherry on top.
17:00
Speaker 1: Obviously we are a piece of dust on one of
17:02
Speaker 1: those sprinkles. So that's dark matter. And so let's get
17:07
Speaker 1: into the big unknown question, which is can you make
17:10
Speaker 1: a star out of dark matter? So we'll get into that,
17:13
Speaker 1: and also you would go around doing that. But first
17:16
Speaker 1: let's take a quick break. All right, we're talking about
17:30
Speaker 1: dark matter and whether or not you can make a
17:32
Speaker 1: star out of it, or as I might call it,
17:35
Speaker 1: a dark star, which, Daniel, I just looked it up
17:38
Speaker 1: on the internet. It is a Marvel superhero or villain.
17:40
Speaker 1: It's a Marvel character for sure, called dark Star. You know,
17:43
Speaker 1: I really appreciate the deep research you do for this podcast.
17:46
Speaker 1: Thank you. You're right, I should have looked it up
17:48
Speaker 1: on Wikipedia, like like you do for physics. Oh, so
17:52
Speaker 1: what are the powers that dark Star and the superhero has.
17:55
Speaker 1: I don't know. You know, if it was scientifically accurate,
17:57
Speaker 1: I guess she would be invisible, but still the way
18:01
Speaker 1: something right, Yes, she could gradually influence motion of stars
18:05
Speaker 1: in the universe. Like well, I guess we all do that.
18:08
Speaker 1: That's not that special. But she is a superhero, and
18:11
Speaker 1: I guess. But that's what we're talking about today, is
18:13
Speaker 1: that if you made a star out of dark matter,
18:16
Speaker 1: if you could, we don't know that. What kind of
18:18
Speaker 1: powers would it have, what would it be like? And
18:20
Speaker 1: is it even possible? So I guess let's talk first
18:23
Speaker 1: about how to make a regular star and then we'll
18:25
Speaker 1: see if that applies to dark matter or if it
18:27
Speaker 1: can apply to dark matter. So, Daniel, how do you
18:29
Speaker 1: make a star besides putting it up on the Internet
18:32
Speaker 1: and hoping it goes viral. A star has a few ingredients.
18:35
Speaker 1: One is the raw materials, right. You start with like
18:38
Speaker 1: a big cloud of gas or dust left over from
18:41
Speaker 1: the explosion of a previous generation, or left over from
18:43
Speaker 1: the Big Bang, and you have it hanging out there
18:45
Speaker 1: in space, So that's ingredient Number one is the stuff
18:48
Speaker 1: you need to make the star. But of course a
18:50
Speaker 1: star is much more compact than a big cloud of
18:53
Speaker 1: gas and dust, so you need something to pull it together,
18:55
Speaker 1: and that, of course is gravity. So eventually, if you
18:59
Speaker 1: have a big cloud of of out there, gravity will
19:01
Speaker 1: tug on all the little particles, the little atoms hanging
19:03
Speaker 1: out there in space and pull them together. And as
19:06
Speaker 1: that happens, it'll get faster and faster, because you'll get
19:08
Speaker 1: a clump of stuff near the middle that has stronger gravity,
19:11
Speaker 1: and it'll pull on stuff more and more, and it's
19:13
Speaker 1: gravity will get stronger as it gets more massive, and
19:15
Speaker 1: then it'll get more massive as it gets dur under gravity, etcetera, etcetera.
19:19
Speaker 1: But there's one more critical thing you have to do
19:21
Speaker 1: to make that gas actually collapse into something that's really
19:25
Speaker 1: dense that can actually start to burn. What do you mean, Well,
19:28
Speaker 1: not everything that feels gravity's tug eventually falls into the center.
19:32
Speaker 1: For example, the Earth is feeling the tug of our star,
19:36
Speaker 1: but we're not plummeting into the Sun helping to contribute
19:39
Speaker 1: to its mass, right, and the same with Jupiter. For example,
19:42
Speaker 1: Jupiter is being tugged by the Sun, but it doesn't
19:44
Speaker 1: fall into the Sun. And the same is true of everything.
19:48
Speaker 1: If you have a big swiling cloud of gas and dust,
19:51
Speaker 1: stuff can start to fall in, but it'll just move
19:53
Speaker 1: faster and faster and end up in an orbit. It
19:55
Speaker 1: won't necessarily fall into the center. And that's because of
19:58
Speaker 1: angular momentum. If it's spinning at all around that point,
20:02
Speaker 1: it's going to keep spinning, and it's got to keep spinning.
20:05
Speaker 1: And that angular momentum is what, for example, keeps the
20:07
Speaker 1: Earth from falling into the Sun or Jupiter from falling
20:10
Speaker 1: into the Sun. So in order to form a really
20:12
Speaker 1: dense object, you have to find a way to get
20:15
Speaker 1: rid of that angular momentum, right. You needed to compress,
20:17
Speaker 1: otherwise it'll just be like a swirling cloud forever. It'll
20:20
Speaker 1: just be a swirling cloud exactly. The way. For example,
20:23
Speaker 1: stuff around a black hole doesn't instantaneously and automatically fall
20:27
Speaker 1: into the black hole. Right. The reason a black hole
20:29
Speaker 1: has an accretion disk around it is that that stuff
20:32
Speaker 1: is swirling around really fast, too fast to fall into
20:35
Speaker 1: the black hole. What makes it fall into the black hole,
20:37
Speaker 1: It's got to lose some of its angular momentum. The
20:39
Speaker 1: way it does that is by bumping into other stuff
20:42
Speaker 1: in the disc. Right, it's a big, jostling, hot mess.
20:44
Speaker 1: That's why these things are glowing, and they bump into
20:47
Speaker 1: each other and then one of them falls towards the center.
20:49
Speaker 1: Another way you can do it is you can radiate
20:52
Speaker 1: off some energy, like shoot off a photon, and then
20:54
Speaker 1: lose some energy and fall towards the center. The same
20:57
Speaker 1: thing is true if you're trying to make a star.
20:59
Speaker 1: You know, this big swart in the cloud of gas
21:01
Speaker 1: and dust. It's got to somehow lose some of that
21:03
Speaker 1: energy so it falls together. But that only works if
21:06
Speaker 1: you can bump into stuff, or if you can radiate
21:09
Speaker 1: away energy, and that requires using electromagnetic forces. Right, it
21:13
Speaker 1: needs some kind of like I guess, stickiness. It's kind
21:15
Speaker 1: of what I think what you're saying, like It can't
21:17
Speaker 1: just be like out there swirling around. It has to
21:19
Speaker 1: somehow have a little bit of like a molasses to
21:22
Speaker 1: it so that it groups together in the middle. Yeah,
21:24
Speaker 1: you need more than just gravity. You need another force
21:27
Speaker 1: to make really compact stuff. You know. Another way you
21:30
Speaker 1: can think about it is as you just describe goopiness,
21:32
Speaker 1: Like imagine stuff out there in the cloud banging together
21:36
Speaker 1: and sticking together, right, holding themselves together with electromagnetic forces,
21:40
Speaker 1: chemical bonds, so that when they touch, they like hang
21:43
Speaker 1: out together, and then they touch another one and another one,
21:46
Speaker 1: and it gradually accumulates into something that likes to hang
21:49
Speaker 1: out together. You know. The thing that's holding the Earth together,
21:51
Speaker 1: for example, is not gravity, right, it's the bonds of
21:55
Speaker 1: in the rocks for example, that are holding those pieces together.
21:58
Speaker 1: The Earth wouldn't have come to other if the bits
22:01
Speaker 1: of the Earth didn't have those forces, those ways to
22:03
Speaker 1: hang onto each other. Yeah. I guess that's one sort
22:06
Speaker 1: of like definition maybe or requirement of a star is
22:08
Speaker 1: that things have to be really compact, right, Like do
22:11
Speaker 1: you have to like they have to be squeezed in
22:13
Speaker 1: together a lot and not just like flying around like
22:16
Speaker 1: a cloud of dust. Yeah, a huge cloud of gas
22:19
Speaker 1: is not a star, right. We don't have a great
22:21
Speaker 1: definition of the star, as we talked about earlier, but
22:23
Speaker 1: we know that it has to be something which collapses
22:26
Speaker 1: so that you can start fusion, so you can get
22:28
Speaker 1: it to somehow glow, because a big cloud of gas
22:30
Speaker 1: and dust and space doesn't glow, doesn't give off any light.
22:33
Speaker 1: It just sits there. It can reflect light, it can
22:35
Speaker 1: hang out, but it doesn't glow. So in order to
22:38
Speaker 1: have glowing happening, you have to have some sort of
22:40
Speaker 1: release of energy from fusion at the heart of it.
22:43
Speaker 1: And fusion doesn't start unless you make that star compact enough.
22:46
Speaker 1: You need to squeeze the stuff down, and that's what
22:49
Speaker 1: gravity and then some sort of inelastic force that can
22:52
Speaker 1: clump the stuff together can do together. Right, And so
22:55
Speaker 1: then that's the problem, kind of like trying to make
22:57
Speaker 1: a dark matter star. Is a dark matter doesn't feel
23:00
Speaker 1: the electromagnetic forces and so it can bump into it
23:04
Speaker 1: itself and so therefore it can't really you know, stick together. Yeah, exactly.
23:08
Speaker 1: That's why we think that dark matter stays in these
23:11
Speaker 1: really big fluffy clouds. We don't know what dark matter
23:14
Speaker 1: is made out of, but we've never seen it have
23:15
Speaker 1: any kind of interaction other than gravity. So if it
23:18
Speaker 1: doesn't feel anything else, it's really hard for it to
23:21
Speaker 1: slow down. Like it just passes through normal matter without clumping.
23:25
Speaker 1: It passes through itself, right dark matter bouncing into dark matter,
23:28
Speaker 1: it just passes right through. It's like invisible even to itself,
23:32
Speaker 1: and so that makes it really hard to slow down.
23:34
Speaker 1: So it's just gonna like swirl around the galaxy forever.
23:36
Speaker 1: It's not sticky, I guess, right, because it's transparent to itself.
23:39
Speaker 1: To like, if we have a particle of dark matter
23:41
Speaker 1: and another particle of dark matter flying towards each other,
23:43
Speaker 1: they'll just pass right through each other and keep going. Yeah,
23:46
Speaker 1: it's transparent and also intangible. Right, if you're talking about superheroes,
23:51
Speaker 1: like somebody who's invisible, you can still push against them
23:53
Speaker 1: and feel them there. But dark matter is not just invisible.
23:57
Speaker 1: It's also intangible. If you have like an enormous lab
24:00
Speaker 1: of dark matter, somebody had like a cube of dark
24:02
Speaker 1: matter they put right in front of you, you could
24:04
Speaker 1: push your hand right through it and not even feel it,
24:07
Speaker 1: just the same way. New trinos are almost intangible. They
24:10
Speaker 1: can pass right through you. Without noticing you, because they
24:12
Speaker 1: don't have an interaction that's strong enough for them to
24:14
Speaker 1: feel you. That's why newtrinos can pass through the entire
24:17
Speaker 1: Earth without even noticing. And so dark matter can do
24:20
Speaker 1: that to itself, right, it just passes right through itself.
24:23
Speaker 1: It's a dark matter that's swirling around has a hard
24:26
Speaker 1: time collapsing into any kind of compact object a star,
24:29
Speaker 1: a planet, even a dark rock or anything like that.
24:32
Speaker 1: So that's one big problem with trying to make a
24:34
Speaker 1: dark matter star. There's also the other problem, which is
24:36
Speaker 1: that stars also have another ingredient that's important, which is
24:40
Speaker 1: some sort of something that has to make it glow
24:43
Speaker 1: as well. Yes, stars are an amazing balance actually between
24:46
Speaker 1: gravity and something fighting back. Right, if we just had
24:50
Speaker 1: gravity and then these other forces to get things to clump,
24:52
Speaker 1: then everything would go straight to a black hole. Right.
24:55
Speaker 1: You have a huge cloud of gas and dust and
24:57
Speaker 1: it would start to collapse and it would get stickier
24:59
Speaker 1: and stickier and eventually boom, black hole. You wouldn't have
25:01
Speaker 1: a star at all. A star only exists and burns
25:04
Speaker 1: for so many billions of years because it overcomes gravity.
25:08
Speaker 1: The fusion at the core that gives us the light
25:10
Speaker 1: that makes the stars twinkle also pushes back against the
25:12
Speaker 1: stuff inside the star so that it doesn't collapse. So
25:16
Speaker 1: the star is this incredible balance of gravity squeezing in
25:19
Speaker 1: and then fusion pushing out, right, Because without the fusion,
25:22
Speaker 1: like you said, it would just turn into a black hole.
25:26
Speaker 1: And so even if dark matter was sticky and could
25:29
Speaker 1: collapse and what could compress if it did that, it
25:31
Speaker 1: would just become a dark matter black hole, right, yeah,
25:34
Speaker 1: exactly the darkest of black holes right now. Dark black
25:38
Speaker 1: That sounds like an oxymron definition. And there are some
25:42
Speaker 1: other ways to avoid collapsing to do a black hole,
25:44
Speaker 1: Like many stars use fusion to avoid gravity. But some
25:48
Speaker 1: of the things we talked about earlier, which people argue
25:50
Speaker 1: about whether or not they're a star, like a neutron
25:53
Speaker 1: star or a white dwarf, those don't have fusion inside
25:55
Speaker 1: of them, but they're also not collapsing into a black hole.
25:59
Speaker 1: That's because there are other ways to prevent a collapse
26:01
Speaker 1: into a black hole, like a white dwarf does it
26:03
Speaker 1: by electrons and not wanting to overlap with each other.
26:05
Speaker 1: You know, Electrons are these weird particles that don't like
26:07
Speaker 1: to be in the same state as any other electron,
26:09
Speaker 1: so they resist being in the same place, and that's
26:12
Speaker 1: enough to prevent a white dwarf from collapsing into a
26:15
Speaker 1: black hole. And similar things are going on inside neutron stars.
26:18
Speaker 1: They don't have enough mass to overcome those barriers, so
26:21
Speaker 1: they don't turn into a black hole. Mostly it's fusion
26:23
Speaker 1: for stars, but for some of these other objects, there
26:26
Speaker 1: are other ways to overcome gravity and prevent collapsing into
26:29
Speaker 1: a black hole. And some people would say a neutron
26:31
Speaker 1: star is a star, and some people would say it's
26:33
Speaker 1: just a bunch of neutrons in space. It's just a
26:36
Speaker 1: neutron ball, all right. Well, it's just sort of sounds
26:39
Speaker 1: like maybe you define star as something that would go
26:42
Speaker 1: into a black hole, or like something on the edge
26:44
Speaker 1: of being a black hole. But something's keeping it alive,
26:47
Speaker 1: something's keeping it from collapsing, and somehow in that sort
26:51
Speaker 1: of tugger war, it generates a lot of light. Yes,
26:53
Speaker 1: like balance there on a nice edge, two totally different
26:56
Speaker 1: forces tugging in each other. And it's always been incredible
26:59
Speaker 1: to me that it's so stable. You know that this
27:01
Speaker 1: thing can last for millions or billions of years. In
27:05
Speaker 1: this incredible tug of war between these powerful forces. Whenever
27:09
Speaker 1: you have these two things battling against each other, I
27:11
Speaker 1: feel like any instability is going to slide off one
27:14
Speaker 1: way or the other. So I'm amazed that stars last
27:16
Speaker 1: for longer than, like, you know, a minute. That would
27:18
Speaker 1: be a pretty quick lifespander for the star. All right,
27:22
Speaker 1: So then dark matter would need to have something sticky
27:25
Speaker 1: about It's something that makes it collapse and not just
27:28
Speaker 1: fly or swirl around. And it also would need something
27:30
Speaker 1: to prevent it from becoming a black hole, because I
27:33
Speaker 1: guess you could make a black hole out of dark matter,
27:34
Speaker 1: Like if you put enough dark matter in one place,
27:36
Speaker 1: you would get a black hole. Right in theory, you
27:38
Speaker 1: could make a black hole out of dark matter. But
27:41
Speaker 1: for the same reason, it's hard to imagine that any
27:44
Speaker 1: of those exist because dark matter doesn't have a way
27:46
Speaker 1: to slow down. Like we have a huge amount of
27:48
Speaker 1: dark matter in our galaxy and we have a huge
27:51
Speaker 1: black hole at the center of it. How much of
27:53
Speaker 1: the stuff in that supermassive black hole came from dark matter,
27:56
Speaker 1: Probably not very much. It's probably mostly normal matter because
28:00
Speaker 1: normal matter is better at falling into black holes and
28:03
Speaker 1: losing its angular momentum. So probably there's very little dark
28:06
Speaker 1: matter in those black holes. But in theory, if you
28:09
Speaker 1: had some way to get dark matter to lose its
28:12
Speaker 1: angular momentum, where some other way to manipulate it, in theory,
28:15
Speaker 1: it could form black holes. It's just gravity, and dark
28:18
Speaker 1: matter definitely feels gravity. And then by the same talking,
28:20
Speaker 1: it could have something that prevents it from collapsing to right, Like,
28:24
Speaker 1: we just don't know because dark matter doesn't is not
28:26
Speaker 1: to thinky, so it never collapses that much, and so
28:29
Speaker 1: we don't know if it would become a black hole
28:31
Speaker 1: or if it would become some sort of stark. Yeah,
28:33
Speaker 1: let's be clear about what we don't know about dark matter.
28:35
Speaker 1: Like we know it feels gravity. We know it doesn't
28:38
Speaker 1: feel electromagnetism or the weak force or the strong force,
28:41
Speaker 1: and we've never seen it have another kind of interaction.
28:44
Speaker 1: That doesn't mean it doesn't, Right, It's very hard to
28:47
Speaker 1: study dark matter because you can't like take one particle
28:50
Speaker 1: in the other particle. We've never even seen a particle
28:52
Speaker 1: of dark matter, and so we don't know if there
28:55
Speaker 1: aren't other weird forces that dark matter does feel with itself.
28:59
Speaker 1: We just have a note. It's totally possible. Yeah, it
29:01
Speaker 1: needs a better publicist maybe. All right, let's get into
29:04
Speaker 1: the question of can you make a star at a
29:06
Speaker 1: dark matter and what would that take and would we
29:09
Speaker 1: ever find them? But first let's take another quick break.
29:25
Speaker 1: All right, Daniel, we're talking about dark matter stars dark stars,
29:30
Speaker 1: and we talked about all the things dark matter would
29:32
Speaker 1: need to have in order for them to become stars.
29:35
Speaker 1: But we know that dark matter at least doesn't have
29:38
Speaker 1: one of those things. It's not sticky. We don't know
29:40
Speaker 1: that it has any way to be sticky. But we
29:42
Speaker 1: have some guesses, and you know, the best theory of
29:44
Speaker 1: dark matter we have right now the sort of leading
29:46
Speaker 1: candidate something called the WHIMP, the Weekly Interacting Massive Particle,
29:51
Speaker 1: And this says, well, maybe dark matter is made out
29:52
Speaker 1: of one kind of particle, and maybe it does have
29:55
Speaker 1: another interaction. It's just really really weak. And when they
29:59
Speaker 1: say weakly interacting, they don't mean the weak force with
30:02
Speaker 1: a capital W, the one we know and love the
30:04
Speaker 1: neutrinos interact with. They mean a not very powerful force,
30:07
Speaker 1: like a feeble force. So maybe there is some other
30:10
Speaker 1: kind of force out there we've never discovered before. That
30:14
Speaker 1: lets dark matter interact with normal matter in some very
30:17
Speaker 1: very gentle way we just haven't seen yet, all right,
30:19
Speaker 1: So then the question I guess is could you make
30:22
Speaker 1: a star out of dark matter? Or what kinds of
30:24
Speaker 1: stars would you be able to make? Well, there's sort
30:26
Speaker 1: of a variety of answers, you know, there's like maybe
30:29
Speaker 1: plausible stuff to less plausible to totally bonkers and crazy
30:34
Speaker 1: my favorite kind go on. So the most plausible, like
30:38
Speaker 1: best worked out scenario for dark stars is something which
30:41
Speaker 1: is a bit or a cop out because it's not
30:44
Speaker 1: just dark matter stars. It's like a combination. It's an
30:47
Speaker 1: object that's made of both normal matter and dark matter
30:50
Speaker 1: together acting in a weird way that you might call
30:53
Speaker 1: a star. But it's an interesting idea, like interacting with
30:56
Speaker 1: each other or just hanging out in the same place.
30:59
Speaker 1: Because I met like even our sun probably has dark
31:02
Speaker 1: matter in it, or it has dark matter floating around
31:04
Speaker 1: inside of it. It definitely has dark matter floating around
31:07
Speaker 1: inside of it, but that dark matter isn't very dense,
31:10
Speaker 1: like dark matter is everywhere and there's a lot of it,
31:12
Speaker 1: but it's sort of spread out evenly through the universe
31:14
Speaker 1: we think, And so in any particular volume, there's not
31:17
Speaker 1: that much dark matter, so the dark matter in the
31:19
Speaker 1: Sun doesn't really affect it. Like inside the volume of
31:22
Speaker 1: the Earth, there's about one squirrel's worth of dark matter,
31:26
Speaker 1: so it doesn't really have much gravitational effect on anything
31:28
Speaker 1: on Earth. Right, But it's a really big squirrel the
31:31
Speaker 1: side of the Earth. It's got some superpowers. I'm sure
31:34
Speaker 1: that's the side of dark star. It's dark squirrel. To
31:37
Speaker 1: the idea for these combination stars is that maybe they
31:40
Speaker 1: were the first kind of stars in the universe. So
31:43
Speaker 1: take your mind back to the very very early universe
31:46
Speaker 1: when there's gas and dust and all sorts of stuff
31:49
Speaker 1: left over from the Big Bang, but we haven't had
31:51
Speaker 1: a chance yet to form those into the first generation
31:54
Speaker 1: of stars and what we call population three stars. But
31:57
Speaker 1: there's also a bunch of dark matter, and so this
31:59
Speaker 1: idea is as well, maybe dark matter does have some
32:02
Speaker 1: kind of interaction, some way to get sticky that we
32:05
Speaker 1: just haven't seen yet. We haven't noticed yet because we
32:07
Speaker 1: haven't been studying it for long enough. And if that happens,
32:09
Speaker 1: then maybe sometimes dark matter bumps into itself and explodes
32:14
Speaker 1: and like turns into radiation, like giving off light or
32:18
Speaker 1: other kinds of particles, And this would be a rare
32:20
Speaker 1: thing to happen, because if it happened a lot, we
32:22
Speaker 1: would have seen it already. But according to their calculations,
32:25
Speaker 1: it's not something we can rule out. So then the
32:28
Speaker 1: ideas you have this like blob of dark matter sitting
32:30
Speaker 1: inside a cloud of normal matter, and the blob of
32:33
Speaker 1: dark matter is bumping into itself, annihilating, producing this radiation
32:37
Speaker 1: not from fusion, but from this other kind of interaction,
32:40
Speaker 1: and that radiation prevents the cloud from collapsing. So this cloud,
32:43
Speaker 1: which might eventually otherwise turn into a normal star, is
32:46
Speaker 1: now this big, huge blob of stuff gently warmed by
32:50
Speaker 1: the radiation from this annihilating dark matter. I see now,
32:54
Speaker 1: what makes us think that dark matter would annihilate with itself? Like,
32:57
Speaker 1: is there anti dark matter as well? There could be.
33:00
Speaker 1: There are various theories of dark matter. Remember that there
33:03
Speaker 1: are two kinds of particles. There are direct particles like
33:05
Speaker 1: the ones we're made out of, that have an antiparticle,
33:08
Speaker 1: and then there are myrona particles that are their own antiparticle.
33:12
Speaker 1: And we don't know if dark matter is direct or myrna.
33:14
Speaker 1: We don't know but in a lot of theories there
33:16
Speaker 1: is anti dark matter, and so it could bump into
33:18
Speaker 1: itself and it could annihilate. Right until the idea then
33:22
Speaker 1: is that you have a normal star with like a
33:25
Speaker 1: dark matter turbo. They're generating extra radiation. Yeah, but it's
33:28
Speaker 1: not even a normal star. Is just a cloud of stuff.
33:31
Speaker 1: It's not compact enough to do fusion, and the dark
33:34
Speaker 1: matter is preventing it from collapsing. It's got this like
33:37
Speaker 1: little glow of dark matter radiation that's keeping it from
33:41
Speaker 1: actually getting compact enough to become a real star. These
33:44
Speaker 1: things are huge. They could be like one or two
33:46
Speaker 1: thousand a U in radius, like really really enormous clouds,
33:51
Speaker 1: but not very dense. Right, au is the width of
33:53
Speaker 1: our solar system right A use the distance between the
33:56
Speaker 1: Sun and the Earth. So two thousand a U would
33:59
Speaker 1: be much much bigger than even our solar system. So
34:02
Speaker 1: we're talking about a really huge cloud and it would
34:04
Speaker 1: be gently warmed by this dark matter annihilation, not very
34:08
Speaker 1: very warm, not very hot. In fact, the temperature of
34:11
Speaker 1: this thing would be so low that it would basically
34:13
Speaker 1: be invisible. Right. But then maybe the question is what
34:16
Speaker 1: would the dark matter be doing there? Why would it
34:19
Speaker 1: annihilate there and not elsewhere, or are you saying it's
34:22
Speaker 1: annihilating everywhere. This is assuming that dark matter somehow clumps, right,
34:26
Speaker 1: If it's going to be able to annihilate, that means
34:28
Speaker 1: it has some kind of interaction, which means it's a
34:30
Speaker 1: little bit sticky, and so it could clump. And so
34:34
Speaker 1: dark matter could annihilate anywhere. Anywhere the dark matter bumps
34:37
Speaker 1: into other dark matter, it could annihilate. It would be
34:39
Speaker 1: more likely to happen in places where there is more
34:42
Speaker 1: of it. In fact, we have experiments looking for exactly this.
34:44
Speaker 1: It's called the Firmy Space telescope. It points to the
34:47
Speaker 1: center of the galaxy where we think there's a lot
34:49
Speaker 1: of dark matter, to see if it can see special
34:52
Speaker 1: flashes of light that come from annihilating dark matter. So
34:55
Speaker 1: far nothing, but the idea behind this theory is that
34:58
Speaker 1: maybe that happens, and may You've got clumps of dark
35:01
Speaker 1: matter in the early universe which then annihilate, and if
35:03
Speaker 1: they happen to also be in the center of a
35:05
Speaker 1: big cloud of gas and dust, it gently warms it
35:08
Speaker 1: and you can call that a dark star. So what
35:10
Speaker 1: would do this look like if we look out into
35:11
Speaker 1: the nice guy. You would would look like a cloud
35:14
Speaker 1: of dust that was glowing a little extra more than usual. Yeah,
35:17
Speaker 1: it would look like a big cloud of dust, which
35:19
Speaker 1: would be mostly invisible unless you use the right frequencies
35:22
Speaker 1: to see it. And it would be a little bit warm.
35:25
Speaker 1: So it would be a cloud of gas and dust
35:27
Speaker 1: that would be a little bit warm and would give
35:29
Speaker 1: off some weird radiation. You might be able to see
35:32
Speaker 1: that dark matter radiation, like really high energy photons or
35:35
Speaker 1: a bunch of extra neutrinos from that dark matter annihilation
35:39
Speaker 1: at the heart of this dark star. Wow, And that's
35:41
Speaker 1: the boring possibility here for a dark star. That's like
35:44
Speaker 1: most detailed, worked out possibility. The rest of it is
35:47
Speaker 1: just sort of speculation. You know. If you're going to
35:50
Speaker 1: go that way, then you can say, well, dark matter
35:53
Speaker 1: might be more complicated. Why do we think dark matter
35:56
Speaker 1: is just one kind of particle? Right? Our matter is many,
35:59
Speaker 1: man the kinds of particles. We have different kinds of
36:01
Speaker 1: quirks and leptons that do all sorts of crazy stuff.
36:04
Speaker 1: Why would we imagine that dark matter would just be
36:06
Speaker 1: one particle. That's boring, and the universe seems to be complex.
36:10
Speaker 1: So let's imagine like a whole different spectrum of dark
36:13
Speaker 1: matter with lots of different kinds of dark particles and
36:15
Speaker 1: maybe even new dark forces that they can use to
36:17
Speaker 1: interact with each other. M I see. The idea is
36:20
Speaker 1: that maybe dark matter is not this like homogeneous cloud
36:23
Speaker 1: of one stuff, but rather it's like complex like we are,
36:26
Speaker 1: like like our matter, Like there's maybe different kinds of it,
36:29
Speaker 1: and they're all interacting with new, different kinds of forces.
36:33
Speaker 1: Although they're all invisible to us, they have like a
36:35
Speaker 1: rich life in their little clouds of dark matter. Yeah, exactly,
36:38
Speaker 1: because there's two separate ideas. There can dark matter interact
36:41
Speaker 1: with us, and that might be only through gravity, But
36:45
Speaker 1: even if it can only interact with us through gravity,
36:47
Speaker 1: it might have really complex self interactions and might be
36:50
Speaker 1: able to do all sorts of crazy things to itself
36:53
Speaker 1: with itself that we can't see and we can't do.
36:56
Speaker 1: And so then maybe you could use some of these
36:59
Speaker 1: interesting forces, dark forces and different kinds of dark particles
37:03
Speaker 1: to make a dark matter sun. Exactly now, to be
37:06
Speaker 1: consistent with what we see in the universe that mostly
37:08
Speaker 1: dark matter is cold and slow and fluffy, you can't
37:11
Speaker 1: have all the dark matter doing this crazy stuff. But
37:14
Speaker 1: you know, we can't probe all of the dark matter,
37:16
Speaker 1: even if like only of the dark matter is this cold, slow,
37:20
Speaker 1: fluffy gas of particles. That still leaves you with ten
37:22
Speaker 1: percent of the dark matter to do crazy interesting stuff with,
37:26
Speaker 1: and we wouldn't notice. It wouldn't change the distribution of
37:29
Speaker 1: dark matter that we look at. And ten percent of
37:30
Speaker 1: the dark matter is about the same mass as all
37:33
Speaker 1: the normal matter in the universe. And so if you'd
37:35
Speaker 1: like allocate ten percent of the dark matter to have
37:37
Speaker 1: complicated interactions and do complicated things, then it might form
37:41
Speaker 1: really weird interesting emergent phenomena like we're talking about before.
37:45
Speaker 1: It would be really hard to predict what quirks and
37:48
Speaker 1: leptons look like when you get ten to the forty
37:51
Speaker 1: of them into a star. Right, what happens in the
37:54
Speaker 1: universe when you get these things together and wait a
37:55
Speaker 1: billion years, and now you have new kinds of particles
37:58
Speaker 1: with new kinds of interactions that might form dark stars,
38:01
Speaker 1: but they might also form something else totally crazy we
38:04
Speaker 1: never even imagined because we've never seen that kind of
38:07
Speaker 1: matter before. Right, it would have his own interactions, and
38:10
Speaker 1: then what would this dark star emit would it emit
38:14
Speaker 1: like a different kind of light, like, can we call
38:16
Speaker 1: it dark light? Yeah, dark photons exactly. There could be
38:19
Speaker 1: a copy of electromagnetism, which only works on dark particles,
38:24
Speaker 1: particles with a dark charge, and they could emit a
38:27
Speaker 1: special photon called a dark photon, and it could be
38:30
Speaker 1: very very similar to the kinds of things we see
38:32
Speaker 1: over here. It could be like a copy. You know,
38:34
Speaker 1: we see that a lot also in particle physics, that
38:36
Speaker 1: structures we see in one place are replicated elsewhere because
38:39
Speaker 1: they refer to deeper patterns in the universe we haven't
38:42
Speaker 1: understood yet. So it could be that all the forces
38:44
Speaker 1: we see over here in normal matter are copied over
38:47
Speaker 1: in dark matter. There's just a special dark version of them,
38:50
Speaker 1: in which case you could very well get dark stars
38:52
Speaker 1: having dark fusion with a dark strong force and emitting
38:55
Speaker 1: dark photons and dark neutrinos, and to have dark planets
38:58
Speaker 1: around them. Yeah, and that the whole universe of light
39:02
Speaker 1: and matter would be existing right on top of us
39:05
Speaker 1: right basically and just be kind of invisible to us,
39:07
Speaker 1: intangible to us, intangible and invisible. Yeah, it can be
39:11
Speaker 1: literally here with us and we wouldn't even know it existed.
39:14
Speaker 1: The only way we could communicate with it would be
39:16
Speaker 1: through gravity. Like imagined that on top of us is
39:19
Speaker 1: another solar system with a dark star at its center
39:22
Speaker 1: and dark planets in orbit, and we don't know about it.
39:24
Speaker 1: The only way they could, for example, here about it
39:26
Speaker 1: is if you, like, we create a black hole the
39:28
Speaker 1: Large Hadron collider. They would notice that. Yeah, I think
39:31
Speaker 1: everyone would notice that. Unfortunately, we would have noticed that
39:36
Speaker 1: we're very long. Yeah, and there could even be like
39:39
Speaker 1: you know, dark podcasts host talking in a dark podcast
39:43
Speaker 1: episode about what we're made out of? Right, Yeah, because
39:47
Speaker 1: to them we are dark. Right if we can't see them,
39:50
Speaker 1: if they are intangible to us, then the reverse is
39:52
Speaker 1: also true. Right. We call ourselves normal matter, but they
39:56
Speaker 1: might be calling us dark matter because they can't see us,
39:59
Speaker 1: or touch us, or interact with us. I mean, they
40:01
Speaker 1: would call us light matter. Maybe that would be cool, maybe, yeah,
40:05
Speaker 1: I suppose, But they wouldn't even know what's going on
40:07
Speaker 1: with us. They wouldn't understand how we interact because they
40:10
Speaker 1: wouldn't be able to probe us other than through gravity.
40:13
Speaker 1: So in this picture where dark matter only interacts with
40:16
Speaker 1: normal matter through gravity, which is the only thing we've
40:18
Speaker 1: ever seen but has really complex, rich self interactions, which
40:22
Speaker 1: is possible as long as it's not all of the
40:24
Speaker 1: dark matter. We could have it be fairly simple copy
40:27
Speaker 1: of our matter and our particles and our interactions. But
40:29
Speaker 1: it could also be something totally wacky and different. And
40:32
Speaker 1: that's the scenario that I'm hoping for, you know, something
40:34
Speaker 1: totally weird and new, because then it would form weird
40:36
Speaker 1: structures that we wouldn't even have names for. You could
40:39
Speaker 1: come up with the names for them when we discover them.
40:41
Speaker 1: Do you have that sign above your door, like hoping
40:43
Speaker 1: for wackiness, looking for waking. I'm rooting for the bonkersness
40:47
Speaker 1: in the universe for sure. And then also these dark stars,
40:50
Speaker 1: could they form dark matter galaxies and more absolutely, you know,
40:54
Speaker 1: we don't know what kind of structures they form. We
40:56
Speaker 1: know that our galaxy started with dark matter. The reason
41:00
Speaker 1: that we have a galaxy today is because there was
41:03
Speaker 1: a big blob of dark matter around that pulled together
41:06
Speaker 1: the normal matter and let it form these stars and
41:08
Speaker 1: form these galaxies. Right, so you could imagine also just
41:12
Speaker 1: a pure dark matter blob, Like what if you had
41:15
Speaker 1: a huge blob of dark matter out there in space
41:17
Speaker 1: with no normal matter in it. So the dark matter
41:20
Speaker 1: is not just there to help the normal matter turn
41:22
Speaker 1: into a galaxy. It's just going to turn into its
41:24
Speaker 1: own galaxy, and it makes its own dark matter stars
41:27
Speaker 1: that certainly could be out there, all right, Yeah, well
41:29
Speaker 1: then I guess maybe to answer the question of the episode,
41:32
Speaker 1: can you make a star out of dark matter? It
41:35
Speaker 1: sounds like the answer is maybe, but not likely. Maybe,
41:40
Speaker 1: but we're totally clueless on the critical question of whether
41:44
Speaker 1: dark matter can interact with itself. If dark matter has
41:47
Speaker 1: no self interactions, then to be pretty tough to see
41:49
Speaker 1: it making a star. If some subset of dark matter
41:52
Speaker 1: has really complicated self interactions, then yeah, absolutely you can
41:55
Speaker 1: make stars and all sorts of other crazy stuff. Right,
41:58
Speaker 1: But from what we know of dark matter, you know,
42:00
Speaker 1: it seems like what we know of it is that
42:01
Speaker 1: it's kind of diffused and blobby and cloudy out there.
42:04
Speaker 1: Could it be that there are stars out there, we
42:07
Speaker 1: just see them as the aggregate of them, you know
42:09
Speaker 1: what I mean? Like, maybe the universe is full of
42:11
Speaker 1: dark matter stars, but we don't see them as pinpoints.
42:13
Speaker 1: We just see like a fuzzy version of them. Yeah,
42:15
Speaker 1: that's really the cool idea. It's possible, but that would
42:18
Speaker 1: also change the whole dynamics of how they interact with
42:20
Speaker 1: themselves and the overall speed of them. So I think
42:23
Speaker 1: it would give us sort of a different distribution of stuff.
42:26
Speaker 1: So we can tell a little bit about how slow
42:28
Speaker 1: moving and how diffuse the dark matter is just by
42:31
Speaker 1: like the overall distribution, like the velocity and where it is.
42:35
Speaker 1: So it's much more likely that it's big fluffy clouds
42:38
Speaker 1: than that it's a smaller number of stars these pin pricks. Oh,
42:41
Speaker 1: I see you're saying that maybe dark matters can't exist,
42:44
Speaker 1: but maybe they're rare. They would be rare if they
42:46
Speaker 1: could exist. Yeah, if they do exist, then there would
42:49
Speaker 1: be just a portion of the dark matter, not all
42:51
Speaker 1: of it. But there's plenty of dark matter out there,
42:53
Speaker 1: So if you want to slice off a ten percent
42:55
Speaker 1: of it to make dark matter stars, that would be
42:57
Speaker 1: totally acceptable. Or if you want to make a Marvel
42:59
Speaker 1: superhero called dark Star. It's too late that one already exists,
43:05
Speaker 1: but you can option it for your media. Yeah, I'm
43:07
Speaker 1: sure Marvel was eager to sell out their IP and
43:10
Speaker 1: you know, we have looked out there in the universe,
43:11
Speaker 1: and we have seen some really weird galaxies, like some
43:14
Speaker 1: galaxies have extra dark matter. We found one that has
43:18
Speaker 1: a hundred times more dark matter than our galaxy. So
43:21
Speaker 1: there could certainly blobs of stuff out there that are
43:24
Speaker 1: pure dark matter and we just haven't seen them. Right, Yeah,
43:28
Speaker 1: it just has an enormous amount of icing on that cupcake.
43:30
Speaker 1: That's like my kind of bakery exactly, all right, Well,
43:34
Speaker 1: as usual, the answer is stay tuned. As scientists learn
43:37
Speaker 1: more about dark matter and what it can and cannot
43:40
Speaker 1: do to itself and how sticky it is, we'll know
43:42
Speaker 1: whether or not these stars can exist and how often
43:46
Speaker 1: you find them in the universe, if you can find it.
43:48
Speaker 1: And what we do know is that we are still
43:50
Speaker 1: at the very beginning of understanding even what the universe
43:53
Speaker 1: is made out of, and so we haven't even really
43:56
Speaker 1: begun to think about what that stuff can do. Can
44:00
Speaker 1: stars and camels and all sorts of crazy stuff or
44:02
Speaker 1: something else completely bonkers that nobody has even thought of.
44:06
Speaker 1: All right, Daniel, I think I'll give you a star
44:08
Speaker 1: for the podcast episode, but maybe a dark star so
44:10
Speaker 1: you can't see it or touch it or feel it,
44:12
Speaker 1: but it's there. Trust me. You's gotta you know, close
44:15
Speaker 1: your eyes and feel it's pool well, it's intangible and invisible,
44:19
Speaker 1: and yet it means so much to me. All Right,
44:21
Speaker 1: thanks for joining us, See you next time. Thanks for listening,
44:31
Speaker 1: and remember that Daniel and Jorge explained. The Universe is
44:34
Speaker 1: a production of I Heart Radio. For more podcast from
44:38
Speaker 1: my heart Radio, visit the I heart Radio app, Apple Podcasts,
44:41
Speaker 1: or wherever you listen to your favorite shows. Ye