Latest / Daniel and Kelly’s Extraordinary Universe / What happened to M33's black hole?

Transcript

What happened to M33's black hole? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: All right, Hey, Daniel, are you ready to record?
• 0:10
  Speaker 2: Oh wait just a minute, I lost something.
• 0:13
  Speaker 1: Well what are you looking for?
• 0:14
  Speaker 2: Oh, you know, nothing important, just this black hole?
• 0:18
  Speaker 1: A black hole. How can you lose a black hole?
• 0:20
  Speaker 2: I don't know, but it really sucks.
• 0:23
  Speaker 1: Yeah, you have a massive problem there to be. Your
• 0:25
  Speaker 1: parents teach you to always take care of your black holes.
• 0:28
  Speaker 2: I seem to just be accreting problems.
• 0:45
  Speaker 3: Hi.
• 0:45
  Speaker 1: I'm Joorne Mack, cartoonist. I'm the author of Oliver's Great
• 0:48
  Speaker 1: Big Universe.
• 0:49
  Speaker 2: Hi I'm Daniel. I'm a particle physicist and a professor
• 0:52
  Speaker 2: at UC Irvine, and I really do want a personal
• 0:55
  Speaker 2: black hole.
• 0:56
  Speaker 1: Like your own little black hole in your backyard or
• 0:58
  Speaker 1: like in your.
• 0:58
  Speaker 2: Pocket, like in a lab at work, in a basement,
• 1:02
  Speaker 2: behind lots of shielding, et cetera. But yeah, I'd love
• 1:05
  Speaker 2: to have a black hole to study.
• 1:07
  Speaker 1: M wouldn't the shielding fall into the black hole?
• 1:11
  Speaker 2: You know? If you build a small enough black hole,
• 1:14
  Speaker 2: then it would actually be stable.
• 1:16
  Speaker 1: Wouldn't it evaporate eventually? But do you have to keep
• 1:18
  Speaker 1: feeding it?
• 1:19
  Speaker 2: Yeah? Exactly. You could keep feeding it at just the
• 1:21
  Speaker 2: same rate it was evaporating, and you could keep it
• 1:24
  Speaker 2: there safe and sustainable.
• 1:26
  Speaker 1: Hmmm, I wonder how stable that would be. It might
• 1:28
  Speaker 1: turn it to runaway process by accident.
• 1:30
  Speaker 2: Oh yeah, I mean you might accidentally, like consume the
• 1:33
  Speaker 2: whole Earth, et cetera, dot dot dot. But uh huh,
• 1:38
  Speaker 2: you might learn a lot along the way.
• 1:39
  Speaker 1: That would be a problem for the rest of us.
• 1:42
  Speaker 2: You wouldn't worry about it afterwards, I mean, you wouldn't
• 1:44
  Speaker 2: be around.
• 1:45
  Speaker 1: I'm pretty sure we would learn not to give you
• 1:46
  Speaker 1: a black hole.
• 1:48
  Speaker 2: Yeah. Well, it's a one time mistake, that's for sure.
• 1:51
  Speaker 1: But anyways, welcome for a podcast Daniel and Jorge Explain
• 1:54
  Speaker 1: the Universe, a production of iHeartRadio.
• 1:56
  Speaker 2: In which we tap into your desire to understand the
• 1:59
  Speaker 2: whole universe, your absolutely desperate need to know how the
• 2:03
  Speaker 2: universe actually works. What's out there, how does it function,
• 2:07
  Speaker 2: what rules is it following, what are its fundamental basic bits,
• 2:11
  Speaker 2: and what's controlling all of it? Is there reason and
• 2:14
  Speaker 2: in order to the universe or is it all just
• 2:16
  Speaker 2: a big chaotic swirl.
• 2:18
  Speaker 1: That's right. We like to talk about everything that's happening
• 2:20
  Speaker 1: in the universe before you lose your mind or any
• 2:23
  Speaker 1: giant gravitational objects out there in space.
• 2:27
  Speaker 2: I think I'm more likely to lose a black hole
• 2:29
  Speaker 2: than lose my mind.
• 2:30
  Speaker 1: I think if you own a black hole, you might
• 2:32
  Speaker 1: have already lost your mind. Guilty, or maybe the rest
• 2:36
  Speaker 1: of us lost our minds for letting you have a
• 2:38
  Speaker 1: black hole that might destroy the Earth.
• 2:41
  Speaker 2: Sometimes I do think people were crazy to give me
• 2:44
  Speaker 2: this job.
• 2:44
  Speaker 1: But that is an interesting scenario to have, like a
• 2:46
  Speaker 1: personal black hole in a lab to study. But what
• 2:48
  Speaker 1: happens if you have to move labs? How can you
• 2:50
  Speaker 1: move a black hole?
• 2:51
  Speaker 2: A black hole is just a thing, so you can
• 2:53
  Speaker 2: move it the way you move everything else, you know, But.
• 2:56
  Speaker 1: How do you push it? You can't push it, can you?
• 2:58
  Speaker 1: You can't pick it up?
• 3:00
  Speaker 2: I mean, I wouldn't put your hand in it, But
• 3:03
  Speaker 2: it has massed so you could attract it with other gravity.
• 3:06
  Speaker 2: I suppose.
• 3:07
  Speaker 1: I suppose it makes you think about this a little
• 3:11
  Speaker 1: bit more before creating a black hole here on Earth.
• 3:13
  Speaker 2: I mean, if you have the capacity to create a
• 3:15
  Speaker 2: black hole in a lab, then you could just stop
• 3:17
  Speaker 2: feeding it, let it evaporate away, and then create a
• 3:20
  Speaker 2: new one somewhere else.
• 3:21
  Speaker 1: But would it be sort of a potentially unstable or
• 3:24
  Speaker 1: are black holes relatively stable? Like if a p fill
• 3:28
  Speaker 1: in or a speck of dust. Would it be too
• 3:30
  Speaker 1: much and then suddenly we'll grow out of control.
• 3:32
  Speaker 2: They're definitely unstable. So you'd be writing the knife's edge
• 3:35
  Speaker 2: between learning something about the universe and destroying all of humanity.
• 3:39
  Speaker 2: It'd be a very delicate balance, because, as you're saying,
• 3:42
  Speaker 2: it grows too big, then it has more gravity. Then
• 3:44
  Speaker 2: it can grow bigger faster, and then it'll have even
• 3:47
  Speaker 2: more gravity. Dot dot dot, and there's no way to
• 3:49
  Speaker 2: turn it off.
• 3:51
  Speaker 1: Yeaha YadA YadA, we all die horrible dead. I don't
• 3:57
  Speaker 1: like this, physicist, YadA YadA.
• 3:58
  Speaker 2: The problem is that there's no way to shrink a
• 4:00
  Speaker 2: black hole except for letting it evaporate, and that's a
• 4:04
  Speaker 2: very slow process. Especially as the black hole gets bigger,
• 4:07
  Speaker 2: it evaporates less and less, so once it starts to
• 4:11
  Speaker 2: run away, there's like no safety valve. There's no like
• 4:13
  Speaker 2: black hole extinguisher you can spray on it.
• 4:16
  Speaker 1: M I guess you can't shoot it with like antimatter.
• 4:20
  Speaker 1: That wouldn't help, right.
• 4:21
  Speaker 2: Antimatter wouldn't just make it stronger. Nuclear weapons just make
• 4:24
  Speaker 2: it stronger. More black holes just make it stronger. Any
• 4:27
  Speaker 2: kind of energy just makes it stronger.
• 4:29
  Speaker 1: So that's like, it'd be a bad idea to try
• 4:31
  Speaker 1: to create black holes here on Earth, right, Like, who
• 4:34
  Speaker 1: would do that? That's insane?
• 4:38
  Speaker 2: Well, we are literally trying to create black holes at
• 4:40
  Speaker 2: the Large Hadron Collider.
• 4:42
  Speaker 1: I know, That's why I bring it up. But it
• 4:45
  Speaker 1: sounds like a terrible idea.
• 4:47
  Speaker 2: Think of all we could learn, man.
• 4:50
  Speaker 1: Yeah, again, we could learn not to trust physicists too
• 4:53
  Speaker 1: experiment with black holes here on Earth.
• 4:55
  Speaker 2: Maybe, But you know, black holes are such amazing mysteries.
• 4:58
  Speaker 2: We don't know how they form, know what's inside them.
• 5:01
  Speaker 2: We don't know how gravity and relativity come together to
• 5:03
  Speaker 2: make it all make sense, or if it does even
• 5:06
  Speaker 2: make sense, or if behind that veil the universe is
• 5:09
  Speaker 2: like broken and chaotic in some weird way. But the
• 5:12
  Speaker 2: most frustrating thing is that they're all so far away.
• 5:16
  Speaker 2: There are no black holes nearby for us to study.
• 5:18
  Speaker 1: And that's a bad thing.
• 5:20
  Speaker 2: That's a bad thing if you want to learn about that.
• 5:22
  Speaker 1: Yes, I get it, they're very mysterious and interesting. They
• 5:26
  Speaker 1: might potentially unlock the mysteries of the universe. But maybe
• 5:29
  Speaker 1: we should send you there instead of trying to bring
• 5:33
  Speaker 1: them here.
• 5:34
  Speaker 2: Maybe I'll send the probe. Haven't that?
• 5:36
  Speaker 1: Oh there you go, all right, we'll compromise. But yeah,
• 5:39
  Speaker 1: black holes are super mysterious and as you said, maybe
• 5:42
  Speaker 1: hold the key to the universe, and sometimes they can
• 5:45
  Speaker 1: get lost.
• 5:45
  Speaker 2: Apparently, maybe some aliens out there are creating black holes
• 5:50
  Speaker 2: and then accidentally losing them.
• 5:52
  Speaker 1: So today on the podcast, we'll be digging the question.
• 6:00
  Speaker 1: So what happened to M thirty three's central black hole?
• 6:04
  Speaker 1: Now there's a lot of numbers here. M thirty three
• 6:06
  Speaker 1: central black hole is that someone's black holes.
• 6:11
  Speaker 2: I don't know who made that black hole or where
• 6:14
  Speaker 2: they put it or why they lost it. But M
• 6:16
  Speaker 2: thirty three is a galaxy fairly nearby one without a
• 6:21
  Speaker 2: black hole seen at its center?
• 6:25
  Speaker 1: Is there evidence that it had a black hole before?
• 6:27
  Speaker 2: There is no evidence that it ever had a black hole,
• 6:30
  Speaker 2: And so that's sort of the question is like, how
• 6:32
  Speaker 2: do you form a galaxy without a black hole? Or
• 6:34
  Speaker 2: did you form it and lose it? How is that
• 6:36
  Speaker 2: even possible? What's going on?
• 6:39
  Speaker 1: So maybe the real question is like, why doesn't M
• 6:42
  Speaker 1: thirty three have a black hole in the middle.
• 6:44
  Speaker 2: Yeah, that's another way to say it.
• 6:46
  Speaker 1: It seems like me it's the more a great way
• 6:48
  Speaker 1: to say it, Like if I never had a million
• 6:50
  Speaker 1: dollars and I went around asking what happened to my
• 6:52
  Speaker 1: million dollars?
• 6:53
  Speaker 2: Might get some weird looks with like everybody in your
• 6:56
  Speaker 2: neighborhood wears pants, and then you walk around without pants,
• 6:59
  Speaker 2: people might say, hey, what happened to his pants? And
• 7:02
  Speaker 2: saying hey, I never wore pants isn't really an explanation,
• 7:06
  Speaker 2: all right, Well.
• 7:07
  Speaker 1: To dig into this interesting mystery, and as usual, Daniel
• 7:10
  Speaker 1: went out there asking people if they knew what happened
• 7:13
  Speaker 1: to M three three's central black hole.
• 7:15
  Speaker 2: I didn't ask anybody if they wear pants, and that's
• 7:18
  Speaker 2: a piece of information they can keep to themselves. And
• 7:20
  Speaker 2: you don't have to wear pants to participate in this
• 7:23
  Speaker 2: part of the podcast. It all happens online via email,
• 7:27
  Speaker 2: So if you would like to give answers to future
• 7:29
  Speaker 2: physics questions, please write to me two questions at Danielandjorge
• 7:33
  Speaker 2: dot com whether or not you have a black hole
• 7:36
  Speaker 2: or pants.
• 7:37
  Speaker 1: So think about it for a second. What do you
• 7:39
  Speaker 1: think happened to M three three's central black hole?
• 7:42
  Speaker 3: Did something happen to M thirty three central black hole?
• 7:46
  Speaker 3: I don't know. I can only assume that it's either
• 7:49
  Speaker 3: dissipated or it's getting bigger. I don't think you know,
• 7:54
  Speaker 3: because over time, don't they give off hawking radiation? Right,
• 7:58
  Speaker 3: so over galactic periods of time then it would disperse.
• 8:05
  Speaker 3: But you make it sound like it's happened more suddenly
• 8:08
  Speaker 3: than that, because I don't think we'd be able to
• 8:10
  Speaker 3: observe that, because you know that's over billions of years.
• 8:12
  Speaker 3: So I can maybe assume that something spectacular has happened.
• 8:18
  Speaker 3: Maybe it's like swallowed something huge and it's it's maybe
• 8:21
  Speaker 3: I don't know, the accretion disk is glowing more than
• 8:23
  Speaker 3: it would normally.
• 8:25
  Speaker 2: I don't know.
• 8:25
  Speaker 1: Did it get absorbed by another black hole and produce
• 8:30
  Speaker 1: gravitational waves? I'm going to guess something epic happened to it.
• 8:34
  Speaker 1: Did it collapse and disappear?
• 8:37
  Speaker 2: All right?
• 8:37
  Speaker 1: Well, now, Daniel, you've made me wonder whether these people
• 8:40
  Speaker 1: that were telling us their answer if they had pants
• 8:42
  Speaker 1: on or not.
• 8:45
  Speaker 2: That's the detail you're wondering, right, you have no idea
• 8:47
  Speaker 2: what they look like where they live, but now you're
• 8:49
  Speaker 2: curious about whether they're wearing pants.
• 8:51
  Speaker 1: Well, I'm wondering if you gave him permission to do
• 8:53
  Speaker 1: it pantless, and whether they followed your instruction.
• 8:57
  Speaker 2: I mean I didn't tell them to take off their pants.
• 9:00
  Speaker 2: That would have been kind of weird.
• 9:03
  Speaker 1: Yeah, what kind of business are you running here? The
• 9:08
  Speaker 1: Pantless Businesses Club?
• 9:11
  Speaker 2: It's pants optional, not pantless. It's very different.
• 9:14
  Speaker 1: Everyone has to wear kilt.
• 9:17
  Speaker 2: Where whatever you're like, we don't care.
• 9:22
  Speaker 1: Wait, are you saying you can be naked? Is this
• 9:25
  Speaker 1: like the clothing optional Physicist Club?
• 9:27
  Speaker 2: Absolutely? Where would ever be like? Wear nothing where? Everything
• 9:31
  Speaker 2: doesn't matter. It's all online doesn't.
• 9:35
  Speaker 1: To get to wear your wear your curiosity.
• 9:36
  Speaker 2: I guess you go wear your curiosity on your sleeve
• 9:40
  Speaker 2: whether or not you can have a sleep.
• 9:42
  Speaker 1: I feel like you have low standards for your online friends, Daniel.
• 9:46
  Speaker 2: I'm just focusing on most important.
• 9:49
  Speaker 1: Like can you tweet? Then you're my friend clothes. I
• 9:52
  Speaker 1: need to know nothing else.
• 9:55
  Speaker 2: What was that about tweeting?
• 9:57
  Speaker 1: You just have to tweet. I don't care about anything else, Bud.
• 9:59
  Speaker 2: You think I'm friends with everybody on.
• 10:01
  Speaker 1: Twitter, Well not everyone on Twitter.
• 10:02
  Speaker 2: I do like interacting with our listeners on Twitter. If
• 10:05
  Speaker 2: you like being on Twitter, come and tweet us a question.
• 10:08
  Speaker 2: We will answer it.
• 10:09
  Speaker 1: Well, nobody seemed to have an idea of what happened
• 10:11
  Speaker 1: to this galaxies central black hole. In fact, people seem
• 10:15
  Speaker 1: to be sort of alarmed by your question. You're like, what,
• 10:17
  Speaker 1: what did something happen.
• 10:20
  Speaker 2: Exactly? And you're the number one suspect. Do you have
• 10:23
  Speaker 2: an alibi for where you were when this.
• 10:26
  Speaker 1: Black hole disappeared? I was out buying pants apparently.
• 10:31
  Speaker 2: Where you were donating all your pants.
• 10:33
  Speaker 1: It sounds like, yes, I was having a grase cell
• 10:36
  Speaker 1: for all my pants. I was helping you look for
• 10:39
  Speaker 1: your black hole. That's what I was doing.
• 10:42
  Speaker 2: Story keeps changing pretty ciss.
• 10:44
  Speaker 1: Well, let's jump right into this, Daniel. So why are
• 10:47
  Speaker 1: we talking about black holes? What are they? And how
• 10:50
  Speaker 1: can we miss them or lose them?
• 10:51
  Speaker 2: So we talk about black holes a lot on the podcast,
• 10:54
  Speaker 2: and people who listen regularly will know that black holes
• 10:57
  Speaker 2: are this theoretical concept of prediction of general relativity that
• 11:01
  Speaker 2: if you have enough mass or just energy in a
• 11:04
  Speaker 2: localized spot, it will bend space so dramatically that no
• 11:08
  Speaker 2: information will be able to leave past an event horizon.
• 11:11
  Speaker 2: We don't actually know what's going on beyond the event horizon,
• 11:14
  Speaker 2: but general relativity predicts that there's a singularity, a dot
• 11:17
  Speaker 2: of infinitely dense matter curving space so intensely that even
• 11:22
  Speaker 2: photons cannot escape. We've seen black holes out there in
• 11:26
  Speaker 2: the wild, or things we identify with black holes. We
• 11:29
  Speaker 2: can't actually verify that they have this event horizon. But
• 11:32
  Speaker 2: there are some very dense, very massive objects that seem
• 11:36
  Speaker 2: to give off no radiation, and black holes are the
• 11:39
  Speaker 2: most popular suspects to explain those weird dense objects. M.
• 11:44
  Speaker 1: Yeah, we've talked about this a little bit before that.
• 11:46
  Speaker 1: You know, there are pictures online of what physicists think
• 11:48
  Speaker 1: might be black holes, and they look like black holes, right, Like,
• 11:51
  Speaker 1: if you look at these images, they're just black circles.
• 11:54
  Speaker 1: But as you said, maybe these could not be black holes.
• 11:57
  Speaker 2: Yeah, they actually kind of look like Krispy Kreme donuts
• 12:00
  Speaker 2: because what you're looking at in the image is this halo,
• 12:02
  Speaker 2: this accretion disk, this blob of gas swirling around the
• 12:07
  Speaker 2: black hole at the center of it. You're right, there's
• 12:09
  Speaker 2: this black circle, and they say, oh, that's the black hole,
• 12:11
  Speaker 2: but it's more like an absence of information that tells
• 12:14
  Speaker 2: you something we don't actually know what is there. It
• 12:17
  Speaker 2: could be a black hole, it could be a dark star,
• 12:19
  Speaker 2: it could be a fuzzball. It could be lots of
• 12:22
  Speaker 2: other things that don't emit light and are super duper dense.
• 12:26
  Speaker 1: Now, how do you get a black hole or how
• 12:28
  Speaker 1: would you get a black hole if they existed?
• 12:30
  Speaker 2: Black Holes out in the universe come in two different varieties,
• 12:34
  Speaker 2: which is kind of weird. There's like the smaller black hole,
• 12:37
  Speaker 2: which forms when a star finishes its life. A star,
• 12:41
  Speaker 2: when it's burning, the fusion the radiation puffs it out
• 12:44
  Speaker 2: and keeps it from collapsing gravitationally into a black hole.
• 12:48
  Speaker 2: But when it's done burning, when it's no longer producing
• 12:51
  Speaker 2: that radiation, gravity eventually wins, and if the star had
• 12:55
  Speaker 2: enough stuff to begin with, it collapses into a black hole.
• 12:59
  Speaker 2: These are typical like ten times up to thirty, forty
• 13:02
  Speaker 2: fifty eighty times the mass of our sun, So we
• 13:05
  Speaker 2: call those stellar black holes, and those sound pretty big,
• 13:08
  Speaker 2: like eighty times the mass of our Sun is a
• 13:11
  Speaker 2: lot of stuff, but that's actually small compared to the
• 13:14
  Speaker 2: other category of black holes we see out there in
• 13:16
  Speaker 2: the universe.
• 13:17
  Speaker 1: Right. These are called super massive black holes.
• 13:20
  Speaker 2: Exactly, and these are only found at the hearts of galaxies,
• 13:24
  Speaker 2: a place where there's a lot of matter already very
• 13:26
  Speaker 2: very dense. These super massive black holes can be tens
• 13:31
  Speaker 2: of thousands of solar masses up to billions of solar masses,
• 13:35
  Speaker 2: really just incredible concentrations of matter in the universe.
• 13:40
  Speaker 1: So you have these two kinds of black holes, and
• 13:42
  Speaker 1: is there like small ones kind of and super duper
• 13:45
  Speaker 1: big ones. Is there nothing in between them?
• 13:47
  Speaker 2: In between? There's this category called intermediate mass black holes,
• 13:51
  Speaker 2: and it's a category with a name, but we don't
• 13:54
  Speaker 2: have any observations there. It's kind of a mystery. We
• 13:57
  Speaker 2: did a podcast a couple years ago about where are
• 14:00
  Speaker 2: all the intermediate mass black holes? Part of the mystery
• 14:03
  Speaker 2: of super massive black holes. We don't know how they formed,
• 14:06
  Speaker 2: how they got so big. It'd be interesting to see
• 14:08
  Speaker 2: intermediate mass black holes because they might just be like
• 14:12
  Speaker 2: baby versions of super massive black holes. So it's part
• 14:16
  Speaker 2: of the mystery of how these really really big ones formed,
• 14:18
  Speaker 2: why we don't see them forming, why we don't see
• 14:21
  Speaker 2: intermediate mass ones instead of a whole spectrum. We have
• 14:24
  Speaker 2: these two populations.
• 14:26
  Speaker 1: Now, the ones we've actually sort of seen are the
• 14:28
  Speaker 1: super massive black hole kind, right, and the pictures they
• 14:32
  Speaker 1: found a couple of years ago that they took were
• 14:35
  Speaker 1: of super massive black holes, because we don't have pictures
• 14:37
  Speaker 1: of the smaller black holes, do we.
• 14:39
  Speaker 2: We don't the images that we're talking about. We only
• 14:42
  Speaker 2: have images of the Milky Way and this messy eighty
• 14:44
  Speaker 2: seven galaxy. Those are the two black holes that we
• 14:48
  Speaker 2: have these images of where you can go online and
• 14:50
  Speaker 2: see a picture of the accretion disk, etc. Those are
• 14:53
  Speaker 2: very very difficult to take. Those pictures requires a lot
• 14:56
  Speaker 2: of observation from many different telescopes, all coordinated, sort of
• 15:00
  Speaker 2: piece that together over several years, and also requires that
• 15:03
  Speaker 2: the galaxy be like close enough that we can see it,
• 15:06
  Speaker 2: but tilted in just the right way so that we
• 15:08
  Speaker 2: can look at the black hole, et cetera. So we've
• 15:11
  Speaker 2: only done that for a couple but we have identified
• 15:14
  Speaker 2: super massive black holes in a couple hundred other galaxies,
• 15:18
  Speaker 2: not directly with images, but with other techniques.
• 15:21
  Speaker 1: Right, that's what I mean. Like the ones that you
• 15:23
  Speaker 1: see in the pictures that are online, those are super
• 15:26
  Speaker 1: massive black holes, right, the two that you mentioned, And
• 15:29
  Speaker 1: we don't actually have pictures of even the small ones.
• 15:31
  Speaker 1: We just know they're out there from their gravity.
• 15:34
  Speaker 2: That's right. We see them out there because of their gravity.
• 15:36
  Speaker 2: For example, You'll see a star and you'll see it
• 15:38
  Speaker 2: orbiting something invisible, and you can calculate with the mass
• 15:42
  Speaker 2: of that thing is. You can see how close that
• 15:44
  Speaker 2: star gets to it, and that tells you how big
• 15:46
  Speaker 2: it can't be, like that's a limit on the size
• 15:49
  Speaker 2: of the thing. That's how black holes were first discovered,
• 15:52
  Speaker 2: is that we saw these things orbiting what looked like nothing,
• 15:55
  Speaker 2: and then we could deduce the mass of the object
• 15:57
  Speaker 2: and get an idea of the size of it, and
• 15:59
  Speaker 2: from that to douce the existence of the black hole.
• 16:02
  Speaker 2: That's the kind of indirect evidence we have for stellar
• 16:05
  Speaker 2: mass black holes. And we can do the same kind
• 16:07
  Speaker 2: of thing to try to look for super massive black
• 16:10
  Speaker 2: holes and the hearts of galaxies.
• 16:11
  Speaker 1: Right Like, if you see some stars swirling around but
• 16:14
  Speaker 1: you don't see anything bright in the middle, then you
• 16:16
  Speaker 1: sort of assumed that there is a super massive black
• 16:19
  Speaker 1: hole there.
• 16:20
  Speaker 2: Yeah, exactly. And in the case of our own Milky Way,
• 16:23
  Speaker 2: we've pointed telescopes at the heart of the galaxy and
• 16:27
  Speaker 2: gotten a lot of details. We followed individual stars as
• 16:30
  Speaker 2: they come very close to Sagittarius, a star the black
• 16:33
  Speaker 2: hole at the center of our galaxy, and we can
• 16:36
  Speaker 2: measure its mass as those stars swing around, because we
• 16:39
  Speaker 2: understand the gravitational effect, and when a cloud of dust
• 16:43
  Speaker 2: passes nearby, and we can see how big is this thing?
• 16:46
  Speaker 2: How close can you get to it without falling in?
• 16:49
  Speaker 2: There was actually Nobel Prize given in the last few
• 16:51
  Speaker 2: years for these detailed studies of the super massive black
• 16:54
  Speaker 2: hole the heart of our galaxy. So even before we
• 16:57
  Speaker 2: had that image, we had a pretty good idea for
• 16:59
  Speaker 2: the mass and the radius of this thing, just by
• 17:02
  Speaker 2: studying the stellar dynamics the stars whizzing around it, from
• 17:05
  Speaker 2: which we're inferring the gravitational effect of that black hole.
• 17:09
  Speaker 1: Right, And you can sort of infer or deduce that
• 17:11
  Speaker 1: it's something super compact and dense, right, Like, that's a
• 17:15
  Speaker 1: really strong gravitational effect around the stars that are swirling
• 17:19
  Speaker 1: around it. But when you look there, you not only
• 17:22
  Speaker 1: not see anything bright, but you also just see kind
• 17:24
  Speaker 1: of the space, the space behind there, right, So whatever's
• 17:27
  Speaker 1: there is super massive and it doesn't take up a
• 17:30
  Speaker 1: lot of room.
• 17:30
  Speaker 2: Yeah, exactly. And then you look at your menu of like, well,
• 17:33
  Speaker 2: what out in nature can do that? What can be
• 17:36
  Speaker 2: so massive and so small and the only sort of
• 17:39
  Speaker 2: widely accepted thing is a black hole. There are other
• 17:42
  Speaker 2: speculative ideas for what might be able to do that
• 17:45
  Speaker 2: we talked about on the podcast other times, dark stars
• 17:48
  Speaker 2: and fuzzballs that could potentially also do that, And there
• 17:50
  Speaker 2: are various theories of quantum gravity to predict things. But
• 17:54
  Speaker 2: the black holes these days like the vanilla explanation for
• 17:57
  Speaker 2: what could be doing it.
• 17:58
  Speaker 1: You mean the chocolate explanation, the.
• 18:00
  Speaker 2: Dark chocolate explanation exactly.
• 18:03
  Speaker 1: But I guess what makes it a better theory than
• 18:05
  Speaker 1: some of these other ideas that you talked about, like
• 18:07
  Speaker 1: why is this one preferred? Why is this one vanilla?
• 18:09
  Speaker 2: It's vanilla because it doesn't require any new physics. You
• 18:12
  Speaker 2: don't have to add to our theories of physics to
• 18:15
  Speaker 2: explain it. You just have to rely on good old
• 18:17
  Speaker 2: general relativity, which predicts these black holes and very accurately
• 18:21
  Speaker 2: describes their radiation and everything we see from the outside.
• 18:25
  Speaker 2: So from the outside, general relativity works perfectly to describe
• 18:28
  Speaker 2: these objects. It's just when you're wondering about, like what's
• 18:30
  Speaker 2: inside of it, that you might need some new physics theories,
• 18:34
  Speaker 2: some quantum gravity to explain the combination of very intense
• 18:37
  Speaker 2: gravity and very very small objects to account for the
• 18:40
  Speaker 2: quantum nature that we know has to play a role
• 18:43
  Speaker 2: inside these black holes.
• 18:46
  Speaker 1: Now, that's how we can see the one here in
• 18:48
  Speaker 1: the Milky Way galaxy, the black hole center of our galaxy.
• 18:51
  Speaker 1: But in other galaxies, I mean, they're so far away
• 18:53
  Speaker 1: you can't really see individual stars swirling around, right.
• 18:57
  Speaker 2: That's right. You can't track individual stars in other galaxies.
• 19:00
  Speaker 2: We don't have telescopes that can do that. But you
• 19:03
  Speaker 2: can build up an idea of the stellar dynamics the
• 19:06
  Speaker 2: velocities for nearby galaxies by looking at the general brightness
• 19:10
  Speaker 2: near the center of the galaxy. We can get a
• 19:13
  Speaker 2: sense for the velocity of those stars by looking at
• 19:15
  Speaker 2: their spectra, like how is the light from those stars
• 19:18
  Speaker 2: red shifted? And piecing it together with a whole lot
• 19:21
  Speaker 2: of computing power, we can get a model for what
• 19:23
  Speaker 2: is the velocity of the stars near the center of
• 19:26
  Speaker 2: the galaxy, and from that we can deduce how massive
• 19:30
  Speaker 2: a black hole has to be there to explain the
• 19:33
  Speaker 2: stellar velocities we see.
• 19:35
  Speaker 1: Oh interesting, It's like if there are a bunch of
• 19:38
  Speaker 1: stars swirling at the center of a faraway galaxy. You
• 19:41
  Speaker 1: can't see them individual stars, but you can sort of
• 19:43
  Speaker 1: get a far away view of the churn that's happening
• 19:46
  Speaker 1: there in that galaxy. Right, Like, if there's a lot
• 19:49
  Speaker 1: of stars moving really fast, then their light is going
• 19:52
  Speaker 1: to be red shifted as the stars move away from you,
• 19:55
  Speaker 1: and blue shit as the stars move towards you. And
• 19:59
  Speaker 1: so the more red blue light that you see coming
• 20:01
  Speaker 1: from the center with the galaxy means there's a lot
• 20:02
  Speaker 1: of movement going on.
• 20:03
  Speaker 2: There, exactly. We can tell the difference between a galaxy
• 20:07
  Speaker 2: that has a really fast churn with massive stars and
• 20:10
  Speaker 2: a galaxy it's more like a lazy river, you know,
• 20:12
  Speaker 2: where things are just like bobbing along slowly and sedately.
• 20:15
  Speaker 1: So you see a galaxy where the center is moving
• 20:17
  Speaker 1: a lot, there's a lot of turn in there, but
• 20:19
  Speaker 1: the center's not super bright, then there must be something
• 20:22
  Speaker 1: really compact, something really dark in there that is probably
• 20:26
  Speaker 1: a super massive black hole exactly.
• 20:27
  Speaker 2: And it's very similar to how we infer the existence
• 20:30
  Speaker 2: of dark matter. You know, this is an indirect measurement
• 20:33
  Speaker 2: of mass. You say, well, these things are moving, and
• 20:36
  Speaker 2: therefore there has to be gravity to hold them in place.
• 20:39
  Speaker 2: Why they're not being flung out of the galaxy. The
• 20:41
  Speaker 2: answer is there's some gravity there that's holding it in place,
• 20:45
  Speaker 2: and that gravity should be explained by mass, So we
• 20:47
  Speaker 2: can measure how much mass is needed to explain these
• 20:51
  Speaker 2: stellar motions. This is how dark matter was discovered. We
• 20:55
  Speaker 2: noticed that you couldn't add enough mass throughout the whole
• 20:57
  Speaker 2: galaxy to explain the motion of the stars. And here
• 21:00
  Speaker 2: we're pinpointing the very very center of the galaxy.
• 21:04
  Speaker 1: Yeah, and so it teams that most galaxies have a
• 21:07
  Speaker 1: super massive black hole in the middle, but not all
• 21:09
  Speaker 1: of them. Some of them seem to be missing they're
• 21:12
  Speaker 1: black holes. So let's dig into this mystery for the
• 21:15
  Speaker 1: galaxy M thirty three. But first let's take a quick break.
• 21:31
  Speaker 1: All right, we're trying to find Daniel's missing black hole. Now, Daniel,
• 21:35
  Speaker 1: can a black hole technically be missing? Like, isn't a
• 21:38
  Speaker 1: hole the missing of something?
• 21:42
  Speaker 2: There's a chunk of space missing. Every black hole is
• 21:45
  Speaker 2: a missing piece of space, I suppose.
• 21:48
  Speaker 1: Well, it's like a hole in your backyard. A hole
• 21:51
  Speaker 1: is the absence of some dirt. So really, how can
• 21:53
  Speaker 1: you be missing the absence of some dirt?
• 21:57
  Speaker 2: Yeah, it's tempting to think of a black hole as
• 21:59
  Speaker 2: a whole, as like a missing piece of the universe,
• 22:02
  Speaker 2: and in some sense they are. There's an event horizon there.
• 22:05
  Speaker 2: Whatever is behind it is not really part of our
• 22:07
  Speaker 2: universe because it can't interact with us. On the other hand,
• 22:11
  Speaker 2: it is part of our space because it's bending our space,
• 22:14
  Speaker 2: it's causing distortions, it generates gravitational waves, it changes the
• 22:18
  Speaker 2: trajectories of things that are outside of it. So it's
• 22:21
  Speaker 2: definitely a thing, right, it has an influence on our universe.
• 22:25
  Speaker 1: I see, it's not a chunk of space that's missing.
• 22:28
  Speaker 1: It's more of a whole, as in like a place
• 22:31
  Speaker 1: where things can fall into and never come out. Yeah,
• 22:33
  Speaker 1: but at the center of it, or in general, it
• 22:35
  Speaker 1: has mass and a position and it can move around.
• 22:39
  Speaker 1: It's a thing.
• 22:40
  Speaker 2: Yeah, it's a thing. It's something, and they're very powerful,
• 22:43
  Speaker 2: these black holes at the hearts of galaxies. It's hard
• 22:46
  Speaker 2: to really wrap your mind around how massive these things are.
• 22:50
  Speaker 2: Billions of stars all compressed down into tiny areas, and
• 22:55
  Speaker 2: it makes you wonder, like what's going on at the
• 22:57
  Speaker 2: particle level and what it would be like to be there.
• 23:00
  Speaker 1: Yeah, it must be pretty intense to be a near
• 23:02
  Speaker 1: a black hole. But as we're talking about, like how
• 23:05
  Speaker 1: we see them, and so sometimes you can see them
• 23:07
  Speaker 1: from their gravitational effect. But sometimes there are black holes
• 23:10
  Speaker 1: that kind of glow, right.
• 23:11
  Speaker 2: Yeah, some black holes that we call quasars, are actually
• 23:14
  Speaker 2: very very bright. If they have a strong magnetic field
• 23:17
  Speaker 2: and they're feeding a lot, like a lot of matter
• 23:20
  Speaker 2: is falling into them. Sometimes not all of that matter
• 23:22
  Speaker 2: actually ends up in the black hole. The magnetic field
• 23:26
  Speaker 2: can tend to spiral them around and then shut them
• 23:29
  Speaker 2: up and down towards the north and south magnetic poles,
• 23:32
  Speaker 2: sort of like the inverse of the Aurora borealis. There's
• 23:36
  Speaker 2: a bunch of particles coming from space and then spiraling
• 23:39
  Speaker 2: around magnetic fields to the north pole before falling into
• 23:42
  Speaker 2: the planet. These guys spiral along the magnetic field but
• 23:45
  Speaker 2: then get shunted up in these very powerful beams north
• 23:49
  Speaker 2: and south. And so a black hole the center of
• 23:52
  Speaker 2: a galaxy can create these incredibly bright particle jets, which
• 23:56
  Speaker 2: you can see from across the galaxy.
• 23:59
  Speaker 1: They're super bright, right, They're sort of brighter than the
• 24:01
  Speaker 1: whole galaxy if it happens to point in your direction exactly.
• 24:04
  Speaker 2: They're incredibly bright, so bright that for a long time
• 24:07
  Speaker 2: people didn't even really believe they could be galaxies because
• 24:11
  Speaker 2: they were visibly very bright, and we knew they were
• 24:14
  Speaker 2: very very far away, which means that like at their source,
• 24:17
  Speaker 2: they were mind bogglingly bright. When people first wrote down
• 24:19
  Speaker 2: the numbers and were like, what, this doesn't make sense.
• 24:22
  Speaker 2: How could anything be that bright? It would take an
• 24:24
  Speaker 2: incredible amount of power to accelerate those particles and then
• 24:27
  Speaker 2: shunt them up north and south, and in the end
• 24:30
  Speaker 2: of black hole is the only thing we know that
• 24:32
  Speaker 2: can explain that that has that kind of power.
• 24:35
  Speaker 1: But you can only see them if they're kind of
• 24:36
  Speaker 1: pointing directly at you, right. It's sort of like a
• 24:39
  Speaker 1: flashlight far away flashlight has pointing at you. Otherwise you're
• 24:42
  Speaker 1: probably not going to see it in the middle of
• 24:43
  Speaker 1: the night.
• 24:44
  Speaker 2: Yeah, exactly. They need to be pointed at you, and
• 24:47
  Speaker 2: they need to be beaming. Not every super massive black
• 24:49
  Speaker 2: hole out there is a quasar. Quasars are just the
• 24:52
  Speaker 2: ones that happened to be feeding right now and be
• 24:55
  Speaker 2: very hot emitting all these X rays.
• 24:58
  Speaker 1: What's the percentage of super massive black hole does it
• 25:00
  Speaker 1: have quasars?
• 25:01
  Speaker 2: Quasars turned out to be quite rare. It's a smaller
• 25:03
  Speaker 2: percentage of galaxies, But we don't understand exactly why there's
• 25:07
  Speaker 2: a quasar sometimes and why there isn't, So it's not
• 25:10
  Speaker 2: something we've measured very very well. We haven't seen that
• 25:12
  Speaker 2: many quasars, so we don't have a great handle on
• 25:15
  Speaker 2: the fraction of galaxies that are quasars. What we do
• 25:18
  Speaker 2: know is that quasars were much more common earlier in
• 25:21
  Speaker 2: the universe. Like the quasar epic of the universe seems
• 25:24
  Speaker 2: to be kind of over. It seems to have peaked
• 25:27
  Speaker 2: like ten billion years ago.
• 25:28
  Speaker 1: Wait, what quasar's peak and what happens to them?
• 25:32
  Speaker 2: Quasar's peak? And then they fade? You know, they're not
• 25:35
  Speaker 2: always blasting this incredible bright light out into the universe.
• 25:38
  Speaker 1: Like they're run out of stuff or what like.
• 25:40
  Speaker 2: They just stop being quasars. You know, there's still super
• 25:42
  Speaker 2: massive black holes, but if they're not feeding as actively,
• 25:46
  Speaker 2: then they're not necessarily generating these big beams. The feeding
• 25:49
  Speaker 2: of a black hole is not so simple. As it
• 25:51
  Speaker 2: gets more powerful, the stuff around it gets hot and
• 25:54
  Speaker 2: creates radiation, which pushes away it's fuel, and so there's
• 25:57
  Speaker 2: this Eddington limit to how fast a black hole can grow.
• 26:00
  Speaker 2: If it grows too quickly, it can end up starving itself.
• 26:03
  Speaker 2: So there's a lot of complicated dynamics for how black
• 26:06
  Speaker 2: holes grow.
• 26:07
  Speaker 1: But what it means starving itself, Well, if.
• 26:08
  Speaker 2: You emit a lot of radiation, you can blow away
• 26:10
  Speaker 2: the gas that was sort of like on deck to
• 26:13
  Speaker 2: fall in.
• 26:13
  Speaker 1: So you can be a quasar that quits and you
• 26:16
  Speaker 1: end up being quiet.
• 26:17
  Speaker 2: Yeah, quixotically, yeah, exactly, And it could be that like
• 26:21
  Speaker 2: in billion years ago in the universe, there was just
• 26:23
  Speaker 2: more fuel available for these black holes to gobble, and
• 26:27
  Speaker 2: they ate all the easy fuel, and we're no longer
• 26:29
  Speaker 2: making quaisars. Like the younger galaxies one the more nearby
• 26:32
  Speaker 2: galaxies we don't see quasars, and those we mostly see
• 26:35
  Speaker 2: them in the ancient galaxies about ten billion years ago.
• 26:39
  Speaker 1: Now, does our milk away have a quasar in the
• 26:41
  Speaker 1: middle or is it just the regular super massive black hole.
• 26:44
  Speaker 2: Our galaxy does not have a quasar in the middle,
• 26:47
  Speaker 2: and it's got a black hole, but it's not like
• 26:49
  Speaker 2: that impressed of a black hole. There are other galaxies
• 26:51
  Speaker 2: with bigger black holes.
• 26:53
  Speaker 1: Well, as you mentioned, a lot of galaxies have super
• 26:55
  Speaker 1: massive black holes in the middle, but not all of them.
• 26:57
  Speaker 2: Right, almost every single big galaxy we've seen has a
• 27:02
  Speaker 2: super massive black hole in it. It's like when you're
• 27:04
  Speaker 2: walking around town, you're pretty sure you're going to see
• 27:06
  Speaker 2: everybody wearing pants or shorts or a skirt or something.
• 27:09
  Speaker 2: It's pretty rare to see somebody pantsless out in public.
• 27:13
  Speaker 2: In the same way, when we look at galaxies, like
• 27:15
  Speaker 2: we almost always find a super massive black hole at
• 27:18
  Speaker 2: their heart.
• 27:19
  Speaker 1: Mmm, what's the general percentage?
• 27:21
  Speaker 2: I guess, Well, we've only looked at like a couple
• 27:23
  Speaker 2: of hundred. This is not easy to do. You need
• 27:26
  Speaker 2: to have enough resolving power to see the stellar motion
• 27:29
  Speaker 2: and figure that all out. We can't do that for
• 27:31
  Speaker 2: very very far away galaxies. But of the couple hundred
• 27:35
  Speaker 2: that we've looked at, every single one has a super
• 27:37
  Speaker 2: massive black hole at its heart, except one that we
• 27:40
  Speaker 2: think was ejected in a very recent collision of two galaxies.
• 27:44
  Speaker 2: And then M thirty three, which doesn't have a central
• 27:46
  Speaker 2: black hole.
• 27:48
  Speaker 1: Well, we'll get to M three three a little bit later.
• 27:50
  Speaker 1: But I think, as you were saying, and as I
• 27:52
  Speaker 1: think we've talked about it before, it's kind of a
• 27:54
  Speaker 1: big mystery about why so many galaxies have super massive
• 27:58
  Speaker 1: black holes, Like where do they come from.
• 28:00
  Speaker 2: Exactly, and the heart of the mystery is how they
• 28:02
  Speaker 2: get so massive. It makes sense for there to be
• 28:04
  Speaker 2: a black hole at the center of the galaxy. Stuff
• 28:07
  Speaker 2: falls in, it gets more massive. Eventually you get a
• 28:09
  Speaker 2: black hole that seems obvious, but we don't understand how
• 28:13
  Speaker 2: they get so big. We can build models of galaxy formation.
• 28:17
  Speaker 2: You start with very early massive stars. Some of those collapse,
• 28:21
  Speaker 2: those remnants fall in together and form a dense core
• 28:24
  Speaker 2: at the heart of the galaxy, merging into the seeds
• 28:27
  Speaker 2: of black holes, which then slurp on more and more stuff.
• 28:30
  Speaker 2: But if you do those calculations, you run simulations, you
• 28:34
  Speaker 2: don't get super massive black holes, especially as early as
• 28:37
  Speaker 2: we see them in the universe. When we look back
• 28:40
  Speaker 2: in time and stuff really really far away, we see
• 28:43
  Speaker 2: super massive black holes with a massive a billion stars
• 28:46
  Speaker 2: in galaxies that form just a billion years after the
• 28:49
  Speaker 2: Big Bang. In our calculations, there just isn't enough time
• 28:53
  Speaker 2: for that to happen.
• 28:54
  Speaker 1: So then, what are some hypotheses about how these super
• 28:58
  Speaker 1: massive black holes form?
• 29:00
  Speaker 2: There are some crazy ideas, like one idea is that
• 29:02
  Speaker 2: maybe there are primordial black holes that you don't need
• 29:06
  Speaker 2: black holes to form from dead stars which then fall together.
• 29:10
  Speaker 2: But that during the Big Bang when matter was made,
• 29:13
  Speaker 2: also some black holes were made. Black holes not made
• 29:16
  Speaker 2: of protons and electrons and other kinds of matter. The
• 29:20
  Speaker 2: black holes that were made sort of before matter was matter.
• 29:23
  Speaker 1: What are they made out of?
• 29:24
  Speaker 2: They're made out of the pure energy in those quantum fields.
• 29:27
  Speaker 2: We think of protons and electrons, these particles as being
• 29:30
  Speaker 2: the basic building block of matter, But that's only true
• 29:32
  Speaker 2: when the universe is sort of cold and old. When
• 29:35
  Speaker 2: the universe is sort of younger and denser and hotter,
• 29:39
  Speaker 2: there's so much energy in these quantum fields it doesn't
• 29:41
  Speaker 2: really make sense to point at one little isolated blob
• 29:44
  Speaker 2: of that energy and call it a particle. It's so energetic,
• 29:48
  Speaker 2: it's all just sloshing around. And in that period there's
• 29:51
  Speaker 2: definitely enough energy to make black holes. What you need
• 29:54
  Speaker 2: is energy density, And so there are some theories that
• 29:57
  Speaker 2: in the very early universe, before things cool down enough
• 30:00
  Speaker 2: so you could talk about individual particles, some of that
• 30:03
  Speaker 2: energy was converted into primordial black holes, and if so,
• 30:07
  Speaker 2: they could be around to see the formation of these
• 30:10
  Speaker 2: super massive black holes.
• 30:12
  Speaker 1: Mmmm. Yeah, I definitely had more energy when I was
• 30:15
  Speaker 1: younger and hotter. Now I'm cold and old. So then
• 30:21
  Speaker 1: what's the scenario? Like you had these primorial black holes
• 30:23
  Speaker 1: very early in the universe, and then those just grew
• 30:27
  Speaker 1: a stuff fell into them.
• 30:28
  Speaker 2: Yeah, exactly. If you already had a black hole, it
• 30:31
  Speaker 2: could see the formation of a galaxy, and then you
• 30:34
  Speaker 2: wouldn't have to start from just the stars in that
• 30:36
  Speaker 2: galaxy to make your black hole. You're already starting from
• 30:39
  Speaker 2: half a billion solar masses or something, and then there
• 30:42
  Speaker 2: is time to make a billion, two billion, five billion
• 30:45
  Speaker 2: super massive black holes to the hearts of these galaxies
• 30:48
  Speaker 2: and like supercharges.
• 30:49
  Speaker 1: M I see. The mystery is not like how did
• 30:53
  Speaker 1: they get so big? It's more like how did they
• 30:55
  Speaker 1: get so big so fast?
• 30:57
  Speaker 2: Yeah? Exactly when they were so young?
• 30:58
  Speaker 1: Like there's enough stuff in each gall see to make
• 31:00
  Speaker 1: a super massive black hole given the times the univer
• 31:02
  Speaker 1: has been around, you can't figure out how they actually
• 31:05
  Speaker 1: got that big exactly.
• 31:06
  Speaker 2: Like if you see a seventeen year old with bulging muscles,
• 31:09
  Speaker 2: you're like, Okay, it must have worked out. If you
• 31:11
  Speaker 2: see like a seven month old with bulging muscles, You're like,
• 31:14
  Speaker 2: something is wrong here, what's going on?
• 31:17
  Speaker 1: Yeah? Does sound like a very wrong.
• 31:20
  Speaker 2: Picture pants or not. You don't want to see like
• 31:22
  Speaker 2: massive biceps on a seven month old.
• 31:24
  Speaker 1: All right, So that's one crazy idea. There's other crazy
• 31:28
  Speaker 1: ideas that maybe involve dark.
• 31:29
  Speaker 2: Matter, right, yeah, exactly. We know that dark matter plays
• 31:31
  Speaker 2: a big role in the formation of galaxies. So some
• 31:34
  Speaker 2: people wonder if you can make black holes out of
• 31:37
  Speaker 2: that dark matter. Because remember, dark matter is like eighty
• 31:40
  Speaker 2: percent of the matter in the universe. So if you
• 31:43
  Speaker 2: want to make stuff that's massive, like, you know, go
• 31:45
  Speaker 2: for your number one ingredient. The idea is that maybe
• 31:48
  Speaker 2: this dark matter can collapse into a black hole, again,
• 31:52
  Speaker 2: seeding the formation of these super massive black holes so
• 31:55
  Speaker 2: you don't just have to start from stars.
• 31:57
  Speaker 1: Does that mean that most black holes out there, or
• 32:00
  Speaker 1: most super massive black holes are made out of maybe
• 32:03
  Speaker 1: eighty percent dark matter.
• 32:04
  Speaker 2: It's a really good question and we don't know the answer.
• 32:07
  Speaker 2: We think that dark matter is less likely to collapse
• 32:10
  Speaker 2: into black holes than normal matter because it isn't sticky.
• 32:13
  Speaker 2: It's hard for it to lose its original rotational speed.
• 32:17
  Speaker 2: That's why the dark matter in galaxies tends to be
• 32:20
  Speaker 2: a bigger, puffier halo. You know, all the matter in
• 32:23
  Speaker 2: the galaxy used to be big and puffy and slowly rotating,
• 32:26
  Speaker 2: but then it gradually collapses into smaller, denser objects because
• 32:30
  Speaker 2: it bumps into itself or there's friction, and it slows
• 32:33
  Speaker 2: itself down and falls in towards the center. But dark
• 32:36
  Speaker 2: matter can't do that because it doesn't have those kind
• 32:39
  Speaker 2: of sticky interactions. It can't form big blobs, it can't
• 32:42
  Speaker 2: rub against itself, can't slow down, so it keeps swirling
• 32:46
  Speaker 2: in these big fluffy clouds.
• 32:47
  Speaker 1: Me mean like dark matter is even invisible to itself.
• 32:51
  Speaker 2: Yeah, it's not just invisible, it's intangible. It passes through itself,
• 32:55
  Speaker 2: we think. And so there must be some dark matter
• 32:58
  Speaker 2: in black holes, especially the ones at the center of galaxies,
• 33:01
  Speaker 2: because it's inevitable some dark matter particle will hit a
• 33:04
  Speaker 2: black hole event horizon. But we think that most of
• 33:06
  Speaker 2: the dark matter in the galaxy avoids falling into the
• 33:09
  Speaker 2: central black hole for that reason. But this theory suggests
• 33:12
  Speaker 2: that somehow some of it might have formed an over
• 33:15
  Speaker 2: density the heart of the galaxy and collapsed anyway.
• 33:18
  Speaker 1: To become a dark matter black hole.
• 33:20
  Speaker 2: To become a dark matter black hole, which then seeds
• 33:22
  Speaker 2: a super massive black hole.
• 33:24
  Speaker 1: All right, So most galaxies that we see around us
• 33:27
  Speaker 1: have a super massive black hole. How strong is that correlation?
• 33:31
  Speaker 2: So every single one except for those two exceptions, does
• 33:33
  Speaker 2: have a super massive black hole, And there's also an
• 33:36
  Speaker 2: interesting connection between the mass of that black hole and
• 33:39
  Speaker 2: what's going on in the rest of the galaxy. The
• 33:42
  Speaker 2: galaxy is this big flat disk usually and then this
• 33:45
  Speaker 2: the black hole of the center, but also this is bulge.
• 33:48
  Speaker 2: It's like blob of stars and gas and dust at
• 33:51
  Speaker 2: the center of the galaxy.
• 33:53
  Speaker 1: Sort of like the egg yulgan of fried Ek.
• 33:55
  Speaker 2: Yeah, exactly. And there tends to be a correlation between
• 33:58
  Speaker 2: the mass of the black hole and the mass of
• 34:00
  Speaker 2: that bulge like bigger bulge, bigger black hole, smaller bulge,
• 34:04
  Speaker 2: smaller black hole. And that feels like an important clue
• 34:07
  Speaker 2: because it tells us there's some connection, some correlation between
• 34:11
  Speaker 2: this really tiny but massive speck of the center of
• 34:14
  Speaker 2: the galaxy and what's going on in the rest of
• 34:17
  Speaker 2: the galaxy.
• 34:18
  Speaker 1: Meaning like if there's just a whole bunch more stuff there,
• 34:20
  Speaker 1: then maybe it's more likely that there is a black
• 34:23
  Speaker 1: hole at the center.
• 34:24
  Speaker 2: Yes, somehow there must be a process that affects both
• 34:26
  Speaker 2: of them. Either they're interacting in some way, or they're
• 34:29
  Speaker 2: both formed by the same process. The bulge in the
• 34:32
  Speaker 2: black hole definitely seem to be connected. It's not random.
• 34:35
  Speaker 2: It's not like you get huge bulges in tiny black holes,
• 34:37
  Speaker 2: or huge black holes and tiny bulges. So the bulge
• 34:40
  Speaker 2: is giving us some clue about the formation of the
• 34:42
  Speaker 2: black hole, because the process that made the black hole
• 34:45
  Speaker 2: has to also be involved somehow in the process of
• 34:48
  Speaker 2: making the bulge.
• 34:50
  Speaker 1: Now, how important is a super massive black hole to
• 34:53
  Speaker 1: the structure of that galaxy? Like if our galaxy suddenly
• 34:57
  Speaker 1: somebody plucked the super massive black hole in the middle
• 34:59
  Speaker 1: of our galaxy, where a galaxy look different or spiral
• 35:03
  Speaker 1: out of control or dissipate, or would it pretty much
• 35:05
  Speaker 1: be the same?
• 35:06
  Speaker 2: It would pretty much be the same. I mean, you
• 35:08
  Speaker 2: would disturb the orbits of stars in the very very center.
• 35:11
  Speaker 2: But even though super massive black holes sound awesome, their
• 35:15
  Speaker 2: mass is really tiny relative to the whole galaxy, much
• 35:18
  Speaker 2: much less than one percent, less than a tenth of
• 35:21
  Speaker 2: a one percent in many cases, and so it's really
• 35:23
  Speaker 2: an irrelevant part of the whole mass budget of the galaxy,
• 35:27
  Speaker 2: which is in the end what controls the dynamics and
• 35:30
  Speaker 2: the structure of the galaxy.
• 35:32
  Speaker 1: Like to have an impressent named super massive black holes.
• 35:34
  Speaker 1: But they really don't ender at the center of the galaxy.
• 35:37
  Speaker 1: But that's maybe just incidental. It's not like you need
• 35:40
  Speaker 1: a super massive black holes to have a galaxy.
• 35:42
  Speaker 2: Yeah, that's right, you don't. But it does seem like
• 35:44
  Speaker 2: they're connected to the center of the galaxy the rest
• 35:47
  Speaker 2: of it, you know, the ball just some process there
• 35:49
  Speaker 2: that either is connecting them. It's like a feedback mechanism,
• 35:52
  Speaker 2: so as one grows, the other one grows or against
• 35:55
  Speaker 2: some process that leads to both of them. So they
• 35:58
  Speaker 2: do seem to be connected to this to the galaxy.
• 36:00
  Speaker 2: But yeah, you could delete one or yet it out
• 36:02
  Speaker 2: into space without destroying the galaxy. The galaxy would spin on.
• 36:07
  Speaker 1: It's not like an essential ingredient in the formation of
• 36:11
  Speaker 1: a galaxy, No, not at all, but it does seem
• 36:13
  Speaker 1: to be maybe not necessary, but it does seem to
• 36:16
  Speaker 1: always be there because of most galaxies that we see Nero,
• 36:18
  Speaker 1: as you're saying, have a super massive black hole.
• 36:21
  Speaker 2: Yeah, so it seems like an important part of understanding
• 36:24
  Speaker 2: galaxy formation because they seem to almost always be created
• 36:28
  Speaker 2: and to be connected to the rest of the galaxy,
• 36:30
  Speaker 2: and they also might have clues about the expansion of
• 36:33
  Speaker 2: the universe. Remember, like a year ago, there was this
• 36:35
  Speaker 2: paper noticing a correlation between the masses of some of
• 36:39
  Speaker 2: these galaxies and the expansion of the universe, the theory
• 36:43
  Speaker 2: that these super massive black holes might actually be like
• 36:45
  Speaker 2: bubbles of dark energy, that they could be the things
• 36:49
  Speaker 2: expanding the universe and accelerating that expansion.
• 36:52
  Speaker 1: WHOA, all right, Well, as you said, there are two
• 36:55
  Speaker 1: galaxies that we know about that don't have super massive
• 36:59
  Speaker 1: black holes them, and so let's dig into why that is.
• 37:02
  Speaker 1: What happened to them? Did someone stealen did a physicist
• 37:05
  Speaker 1: lose them? So let's dig into that. But first let's
• 37:08
  Speaker 1: take another quick break. All right, we're asking the question
• 37:22
  Speaker 1: what happened to M thirty three's central black hole? And
• 37:26
  Speaker 1: this is a question because most galaxies seem to have
• 37:30
  Speaker 1: a super massive black hole in them, but not all
• 37:32
  Speaker 1: of them. So, Daniel, what happened to their pants?
• 37:36
  Speaker 2: Well, I think every galaxy except for the triangular galaxy
• 37:39
  Speaker 2: M thirty three, really can be connected to a super
• 37:42
  Speaker 2: massive black hole. Like almost all of them. There's a
• 37:45
  Speaker 2: super massive black hole and it's still in the center,
• 37:48
  Speaker 2: a tiny fraction of them no longer have a super
• 37:51
  Speaker 2: massive black hole. But in those situations you can usually
• 37:54
  Speaker 2: identify what happened. You can see the super massive black
• 37:57
  Speaker 2: hole having been tossed out into space in some crazy
• 38:00
  Speaker 2: three body interaction or a super massive black holes like
• 38:04
  Speaker 2: being kicked away from the center of the galaxy. So
• 38:06
  Speaker 2: it's still in the galaxy, but no longer at the core.
• 38:10
  Speaker 2: Except for M thirty three. M thirty three appears to
• 38:13
  Speaker 2: have no super massive black hole currently, and there's no
• 38:16
  Speaker 2: super massive black hole that you can associate with it
• 38:19
  Speaker 2: at all.
• 38:19
  Speaker 1: So it's just the galaxy out there. And so what
• 38:21
  Speaker 1: happens when you try to look in the middle, you
• 38:23
  Speaker 1: don't see any kind of like super quick turning in
• 38:26
  Speaker 1: the middle. Is that how you can tell that it
• 38:28
  Speaker 1: doesn't have a black hole in the middle?
• 38:30
  Speaker 2: Exactly? It's a lazy river. So this is a galaxy
• 38:33
  Speaker 2: that's two point seven light years away. It's in the
• 38:36
  Speaker 2: constellation Triangulum, so it's sometimes called M thirty three, sometimes
• 38:40
  Speaker 2: called the Triangulum galaxy, and it's a big galaxy. Like
• 38:44
  Speaker 2: in our local group, which is the cluster of galaxies
• 38:46
  Speaker 2: that we live in, there's Andromeda the biggest king galaxy.
• 38:50
  Speaker 2: There's the Milky Way, and then there's M thirty three,
• 38:53
  Speaker 2: so it's the third biggest galaxy sort of in the neighborhood.
• 38:56
  Speaker 2: It's got like sixty billion solar masses total.
• 39:00
  Speaker 1: Meaning it has sixty billion stars in them.
• 39:03
  Speaker 2: No, that's just a unit of mass. That's how you
• 39:05
  Speaker 2: measure the mass of something. It's like if somebody says
• 39:08
  Speaker 2: you're four stone, that does mean you're literally made of
• 39:10
  Speaker 2: four stones. Right. In this case, the galaxy is mostly
• 39:14
  Speaker 2: dark matter, So it definitely doesn't have sixty billion stars.
• 39:17
  Speaker 2: It's got a tiny fraction of that. It's mostly dark matter,
• 39:20
  Speaker 2: but it has enough stars that you can follow their
• 39:23
  Speaker 2: path at the core, you can measure the velocity and
• 39:25
  Speaker 2: from that you can infer the mass of any black
• 39:28
  Speaker 2: hole that could be at their center.
• 39:30
  Speaker 1: So this is kind of a small galaxy, right, because
• 39:32
  Speaker 1: our galaxy has a one hundred billion stars.
• 39:35
  Speaker 2: Yes, this is a smaller galaxy than the Milky Way,
• 39:37
  Speaker 2: but it's big compared to the neighborhood. I mean, our
• 39:40
  Speaker 2: galaxy is one of the bigger ones in the neighborhoods
• 39:42
  Speaker 2: is Andromeda, and then Milky Way. We're number two. So
• 39:45
  Speaker 2: this is number three.
• 39:46
  Speaker 1: And so you're saying, when we look in the middle,
• 39:48
  Speaker 1: we don't see a black hole at the center.
• 39:50
  Speaker 2: That's right. As you look at the stars, their orbits
• 39:52
  Speaker 2: don't get much faster as you get closer. If there's
• 39:55
  Speaker 2: a really big, super massive black hole there, then its
• 39:58
  Speaker 2: gravity is very powerful and for us start to stay
• 40:00
  Speaker 2: in orbit very close, it has to be going super
• 40:03
  Speaker 2: dup or fast. If there's no central black hole there,
• 40:06
  Speaker 2: then things can just be sort of like put putting
• 40:08
  Speaker 2: along near the center without being disturbed. It can survive
• 40:11
  Speaker 2: with slow velocities.
• 40:13
  Speaker 1: But I guess if this galaxy is that much smaller
• 40:15
  Speaker 1: than ours, could it be that it has a black
• 40:17
  Speaker 1: hole in the middle. It's just not at the super
• 40:19
  Speaker 1: massive level yet.
• 40:20
  Speaker 2: It could be that there is a black hole there.
• 40:23
  Speaker 2: But they can infer the maximum size a black hole
• 40:26
  Speaker 2: could be to be consistent with the motion of these stars,
• 40:30
  Speaker 2: and it would be a thousand times smaller than the
• 40:32
  Speaker 2: black hole you would expect for a galaxy this size.
• 40:35
  Speaker 2: So either there's no black hole there, or there's a
• 40:38
  Speaker 2: much smaller black hole than we expect to see for
• 40:41
  Speaker 2: a galaxy this size. If this one has a black hole,
• 40:45
  Speaker 2: then it has to be smaller than like fifteen hundred
• 40:48
  Speaker 2: solar masses. That's tiny. That's almost down to the stellar
• 40:52
  Speaker 2: mass black hole level. It's actually right in the intermediate
• 40:55
  Speaker 2: mass black hole region, which is quite interesting.
• 40:58
  Speaker 1: And so is there anything peculiar about the galaxies? Are
• 41:01
  Speaker 1: there any other clues about it that might tell you
• 41:03
  Speaker 1: why it doesn't have a black hole?
• 41:05
  Speaker 2: One other clue is that it doesn't really have a bulge.
• 41:08
  Speaker 2: We were talking earlier about how most galaxies that have
• 41:11
  Speaker 2: really big massive black holes also have really big bulges. Well,
• 41:15
  Speaker 2: this one's got no black hole or maybe a tiny one,
• 41:18
  Speaker 2: and almost no bulge. So it really suggests that black
• 41:22
  Speaker 2: holes are closely associated with the bulge. Whatever makes the
• 41:25
  Speaker 2: disc is not connected to the black hole, but whatever
• 41:28
  Speaker 2: is making the bulge is deeply connected to the formation
• 41:31
  Speaker 2: of that super massive black hole. So it feels like
• 41:34
  Speaker 2: a clue.
• 41:35
  Speaker 1: Maybe this galaxy just works out a lot. You know,
• 41:37
  Speaker 1: it doesn't have a bulge.
• 41:39
  Speaker 2: Wouldn't that give it a bulge bulging muscles?
• 41:42
  Speaker 1: Well, it depends on your workout, I guess true. Like
• 41:45
  Speaker 1: if you just run a lot, you just a slim and.
• 41:48
  Speaker 2: Trim This is a spelt galaxy.
• 41:51
  Speaker 1: You're saying Yeah, there you go like a runnery galaxy. Yeah,
• 41:54
  Speaker 1: are there other galaxies that we've seen out there that
• 41:56
  Speaker 1: are this size don't have a bulge? But do you
• 42:00
  Speaker 1: have a black hole? Or is there a relationship between
• 42:03
  Speaker 1: bulges and black holes?
• 42:04
  Speaker 2: This is close relationship between bulges and black holes. Other
• 42:07
  Speaker 2: galaxies roughly the size have bulges and have black holes.
• 42:12
  Speaker 2: This is the only one we've seen without a black
• 42:14
  Speaker 2: hole and also without a significant bulge.
• 42:16
  Speaker 1: Is it the only one we've seen without a bulge? Yeah, Like,
• 42:19
  Speaker 1: out of the Brazilian galaxies out there, we've only seen
• 42:22
  Speaker 1: one without a bulge.
• 42:23
  Speaker 2: We see smaller ones with smaller bulges and smaller black holes,
• 42:26
  Speaker 2: but this is the edge of the spectrum. This is
• 42:28
  Speaker 2: the tiniest bulge and tiniest black hole.
• 42:31
  Speaker 1: Oh interesting, So it's truly unique in the entire universe,
• 42:35
  Speaker 1: or we just haven't seen enough galaxies.
• 42:37
  Speaker 2: We've definitely not seen enough galaxies. We've looked at thousands
• 42:40
  Speaker 2: of galaxies and measured the massive black holes of hundreds
• 42:43
  Speaker 2: of them. So this is early days, you know. This
• 42:46
  Speaker 2: is the kind of science where you're discovering individual ones
• 42:49
  Speaker 2: and wondering if they're typical or weird. You know. It's
• 42:52
  Speaker 2: like when we were first discovering exoplanets and we didn't know,
• 42:55
  Speaker 2: is every planet out there hot Jupiter? Oh, it turns
• 42:57
  Speaker 2: out that's just the first ones we see, because that's
• 42:59
  Speaker 2: what we're good at. And so we haven't seen a
• 43:02
  Speaker 2: whole lot of examples of super massive black holes because
• 43:04
  Speaker 2: it's tricky, right, you have to measure the velocities of
• 43:07
  Speaker 2: stars near the centers of other galaxies. In order to
• 43:10
  Speaker 2: do this kind of measurement, it's hard, so we don't
• 43:13
  Speaker 2: have a lot of data, so there's always going to
• 43:15
  Speaker 2: be an outlier when you have a small sample.
• 43:17
  Speaker 1: We've seen like maybe billions of galaxies out there. Are
• 43:20
  Speaker 1: you saying we've only studied a few hundred of them.
• 43:22
  Speaker 2: We've seen zillions and zillions of galaxies. You're right, and
• 43:24
  Speaker 2: James Webb's excellent and the Hubble Deep Field shows us
• 43:27
  Speaker 2: lots and lots of galaxies, But in terms of measuring
• 43:30
  Speaker 2: the super massive black hole, most of those we can't.
• 43:33
  Speaker 2: The only way they do it is for them to
• 43:34
  Speaker 2: be close enough for us to be able to measure
• 43:36
  Speaker 2: the stellar velocities near the heart of the galaxy, or
• 43:41
  Speaker 2: to see the quasar from a really, really old galaxy
• 43:44
  Speaker 2: and that adds up to a few hundred mmm.
• 43:47
  Speaker 1: So then that's the kind of central mystery of today,
• 43:50
  Speaker 1: which is that you have this galaxy. I'm thirty three
• 43:52
  Speaker 1: triangulum and it looks like it's a small galaxy, but
• 43:55
  Speaker 1: it's a pretty regular galaxy and it doesn't have a
• 43:57
  Speaker 1: super massive black hole in it. Yeah, exactly we have
• 44:00
  Speaker 1: is that it doesn't have a bulge.
• 44:01
  Speaker 2: Exactly, and so it's like never worn pants, you know,
• 44:05
  Speaker 2: it's like happy in its pants. Free existence. Doesn't seem
• 44:08
  Speaker 2: like it had a super massive black hole and lost it,
• 44:11
  Speaker 2: because then it would have a bulge with no black hole.
• 44:14
  Speaker 2: And we don't understand how these things form at all,
• 44:16
  Speaker 2: and so there's this interesting clue, but the connection with
• 44:18
  Speaker 2: the bulge and not with the rest of the disk.
• 44:21
  Speaker 2: So as we see more and more of these things,
• 44:23
  Speaker 2: we hope to learn more about how galaxies form and
• 44:25
  Speaker 2: how super massive black holes form. But these exceptions, these outliers,
• 44:29
  Speaker 2: are really important clues because they tell us what rules
• 44:32
  Speaker 2: can be broken, right.
• 44:33
  Speaker 1: It sort of tells you like what's necessary and what isn't,
• 44:36
  Speaker 1: Like you can't have a galaxy without a bulky.
• 44:39
  Speaker 2: You can have a galaxy without a bulge and without
• 44:41
  Speaker 2: a black hole at its heart, you still get a
• 44:43
  Speaker 2: very nice galaxy.
• 44:44
  Speaker 1: And you can get a galaxy without pants, and it
• 44:47
  Speaker 1: seems perfectly happy.
• 44:48
  Speaker 2: I don't recommend doing that, but yeah, it does seem possible.
• 44:52
  Speaker 1: Dan, What happened to your pants right now?
• 44:55
  Speaker 2: No comment?
• 44:56
  Speaker 1: Exactly, it's a mystery.
• 44:58
  Speaker 2: I lost them in the black hole.
• 45:00
  Speaker 1: I went to your black hole that you lost, and
• 45:02
  Speaker 1: so that's why you're looking for your black hole because
• 45:04
  Speaker 1: it it's running away with your pants.
• 45:05
  Speaker 2: But without pants on, it can't go outside and look
• 45:07
  Speaker 2: for it. So now I'm stuck.
• 45:08
  Speaker 1: Oh man, you're gonna have to ask your friends on
• 45:10
  Speaker 1: Twitter to look for your pants and your black hole.
• 45:14
  Speaker 2: Go fund me for new pants for Daniel. There you go.
• 45:17
  Speaker 1: That's what the Internet wasn't there for pants free Fridays?
• 45:22
  Speaker 1: All right? Well, another interesting example of how there is
• 45:25
  Speaker 1: still so much mystery in the universe. Even I feel
• 45:28
  Speaker 1: like this is a mystery wrapped inside of a mystery,
• 45:30
  Speaker 1: because black holes are a mystery. But this is about
• 45:32
  Speaker 1: the missing black hole, so it's like the mystery or
• 45:35
  Speaker 1: the missing mystery?
• 45:36
  Speaker 2: Yeah, exactly where did the mystery go? All right?
• 45:39
  Speaker 1: Well, we hope you enjoyed that. Thanks for joining us,
• 45:43
  Speaker 1: See you next time.
• 45:48
  Speaker 2: For more science and curiosity, come find us on social media,
• 45:52
  Speaker 2: where we answer questions and post videos. We're on Twitter, Discord, Instant,
• 45:56
  Speaker 2: and now TikTok. Thanks for listening and remember that Daniel
• 46:00
  Speaker 2: and Jorge Explain the Universe is a production of iHeartRadio.
• 46:04
  Speaker 2: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,
• 46:09
  Speaker 2: or wherever you listen to your favorite shows.