Latest / Daniel and Kelly’s Extraordinary Universe / Where are all the medium-sized black holes?

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Where are all the medium-sized black holes? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, how do you like your coffee in my mouth?
0:11
Speaker 1: I guess usually or maybe sometimes in ice cream. I mean, like,
0:15
Speaker 1: do you like to drink the tiny, strong Italian coffees
0:19
Speaker 1: or the big week American style coffees? Hmmm, I guess
0:23
Speaker 1: I like the sort of medium sized coffee, you know,
0:25
Speaker 1: strong enough to be for grown ups, but not like
0:28
Speaker 1: a punge in the face. I see. And does that
0:31
Speaker 1: apply to particles too? Do you prefer tiny particles or
0:35
Speaker 1: massive ones? I don't know. I like them heavy enough
0:37
Speaker 1: to be rare and worthy of winning a Nobel Prize,
0:40
Speaker 1: but light enough that we can discover them at Collider's.
0:44
Speaker 1: And you're so middle of the road. Sometimes the middle
0:47
Speaker 1: of the road is exactly where the mysteries lie. Hi
1:05
Speaker 1: am Jorge, handmade cartoonists and the creator of PhD comics. Hi.
1:08
Speaker 1: I'm Daniel. I'm a particle physicist, and I usually eat
1:12
Speaker 1: a medium size portion of cookies for breakfast, for lunch,
1:17
Speaker 1: or all of the above. Every time you start eating cookies,
1:20
Speaker 1: you can't just have one. You try to avoid having
1:23
Speaker 1: the whole box, so I end up somewhere in the middle,
1:25
Speaker 1: somewhere like half of a box of cookies. Depends are
1:28
Speaker 1: you're doing arithmetic half or geometric half, you know, it
1:32
Speaker 1: depends on the day. Then you can do zenos paradox
1:34
Speaker 1: that can eat half the box, and then you eat
1:36
Speaker 1: the other half, and then the half the remaining half,
1:38
Speaker 1: and pretty you ate everything but a crumb. Yeah, well,
1:41
Speaker 1: that's a great way to avoid eating the whole box, right,
1:44
Speaker 1: Wisdom from the ancient Greeks. It's the Greek diet, it's
1:47
Speaker 1: the new Mediterranean diet. Only eat half of the remaining
1:50
Speaker 1: box of cookies. But welcome to a podcast. Daniel and
1:52
Speaker 1: Jorge Explained the Universe, a production of I Heart Radio,
1:55
Speaker 1: in which we take a bite of the entire box
1:58
Speaker 1: of universe cookies. We chew on the bits to talk
2:01
Speaker 1: about black holes, We think about all the little chocolate
2:03
Speaker 1: chips that are particles. We dig down into the crumbs
2:06
Speaker 1: and try to understand everything that's going out there in space,
2:10
Speaker 1: in the universe, in history, and in the future. We
2:14
Speaker 1: very humbly try to explain the entire universe to you.
2:17
Speaker 1: That's right. There are amazing mysteries all over the universe,
2:20
Speaker 1: and those mysteries range from gigantic size galaxy cluster billions
2:25
Speaker 1: of light years wide mysteries and really really tiny mysteries
2:29
Speaker 1: in the particles and the little quarks and tiny quantum
2:33
Speaker 1: fluctuations that make up who we are. Are you saying
2:35
Speaker 1: I'm just a quantum fluctuation that I could just disappear tomorrow.
2:39
Speaker 1: Well we can all disappear tomorrow, Daniel, depends on what
2:42
Speaker 1: you guys are working on at the large handring collider there. Well,
2:45
Speaker 1: if we make a black hole, will make a little
2:47
Speaker 1: itty bitty when I promise good, I'm glady that's an option.
2:51
Speaker 1: I'm so glad you're not tempted at all to just
2:53
Speaker 1: dial it up. We'll have a knob here in front
2:56
Speaker 1: of me, you know, So tell me what what size
2:58
Speaker 1: black hole should we be making here the late see?
3:00
Speaker 1: How about a zero sized black hole? That's no fun?
3:04
Speaker 1: And how are we going to learn the secrets of
3:06
Speaker 1: the universe? Keep you inside the tiny black holes? I'm
3:09
Speaker 1: okay where they are right now. But black holes are amazing.
3:12
Speaker 1: They are fascinating. They do contain amazing secrets of the
3:16
Speaker 1: universe inside them. But there are also really fascinating questions
3:20
Speaker 1: about how they get made and why they are the
3:22
Speaker 1: size they are or the size they aren't. Yeah, they
3:25
Speaker 1: seem to be everyone's favorite space mystery. Do you think
3:29
Speaker 1: maybe it was all in the name, Like if you
3:30
Speaker 1: had called them, I don't know, vacuum holes or gravity pits,
3:35
Speaker 1: do you think people would still be as interested in
3:37
Speaker 1: the I think they would. I think it's their fundamentally
3:40
Speaker 1: alien nature that makes themselves fascinating. We know they are
3:43
Speaker 1: really deeply, weirdly different from anything we have seen before,
3:48
Speaker 1: and I think that's what sparks our curiosity. You know,
3:50
Speaker 1: we want to go there and see it and explore
3:52
Speaker 1: it because we want to understand what's possible in the universe.
3:55
Speaker 1: As we say often on the podcast, it's the extreme
3:57
Speaker 1: situations that teach us what the rules really are because
4:00
Speaker 1: they show us the limits. Yeah, and as you say that,
4:03
Speaker 1: you can find them in all kinds of sizes out
4:05
Speaker 1: there in space. There are black holes that are humongous
4:08
Speaker 1: and warm the center of galaxies and help keep galaxies
4:11
Speaker 1: kind of together, and you can make them tiny little
4:13
Speaker 1: ones that evaporate right away. Yeah, that's right. There are
4:16
Speaker 1: these funny, two different populations of black holes, the ones
4:19
Speaker 1: that seem to come from the collapse of stars and
4:21
Speaker 1: the huge galaxy gobblers at the center of many galaxies,
4:25
Speaker 1: and the weak thing is that there don't seem to
4:27
Speaker 1: be any in between. Really, there's no like Goldilocks black holes.
4:31
Speaker 1: There's only two options, like VENTI and X are large.
4:35
Speaker 1: That's right. You either don't open the box of cookies
4:38
Speaker 1: or you eat the whole thing. The universe never goes
4:40
Speaker 1: for half a box. Yeah, so there are mostly two
4:43
Speaker 1: sizes of black holes in the universe. One you're saying
4:46
Speaker 1: it are the ones that come from the collapse of stars.
4:48
Speaker 1: Those are I mean, they're pretty big. There's still like
4:50
Speaker 1: the size of you know, many suns. Yes, these are small,
4:54
Speaker 1: only on the sort of like cosmic galactic scale, right,
4:57
Speaker 1: smaller than a whole galaxy. Still a normal is still
5:00
Speaker 1: more massive than our entire solar system. But yeah, tiny
5:04
Speaker 1: compared to other things. And then you have the huge ones,
5:08
Speaker 1: the ones that are how many, like millions of times
5:10
Speaker 1: the mass of the Sun up to millions or even
5:12
Speaker 1: billions of solar masses, so many stars compacted into a
5:17
Speaker 1: tiny little space at the center of some of these
5:19
Speaker 1: galaxies really just mind bogglingly massive and incredibly powerful objects. Yeah,
5:25
Speaker 1: and so black holes can be any size really in between,
5:28
Speaker 1: and you know, from tiny, two huge, But apparently you
5:32
Speaker 1: don't see a lot of ones in the middle out
5:34
Speaker 1: there in the cosmos. Most of the ones that you
5:36
Speaker 1: see out there are either kind of supernova size or
5:39
Speaker 1: gigantic galaxy center size. Yeah, it's even more dramatic than that.
5:43
Speaker 1: We have never seen any in between. There's not an example,
5:47
Speaker 1: a single example of a black hole in between those two.
5:51
Speaker 1: So we don't actually know if it's possible to have
5:53
Speaker 1: an intermediate size black hole. Maybe the laws of physics
5:56
Speaker 1: just don't allow it. So that's the question will be
5:59
Speaker 1: tackling today. So to be on the program, we'll be
6:01
Speaker 1: asking the question where are all the intermediate mass black holes?
6:10
Speaker 1: You've gotta made it easier for me, Daniel, and just
6:12
Speaker 1: medium mass. Well, that was going to be my next
6:15
Speaker 1: question is what would you have called these things? Because
6:17
Speaker 1: intermediate size black holes or intermediate mass black holes is
6:21
Speaker 1: quite a mouthful. Yeah, I don't know, just go with
6:23
Speaker 1: like the Starbucks rude and call them large black holes,
6:26
Speaker 1: which are really the medium sized black holes. That's true,
6:28
Speaker 1: but everything in the universe is enormous, right, so maybe
6:31
Speaker 1: the Starbucks naming scheme makes sense. Yeah, large, extra large,
6:35
Speaker 1: super large, and galectically large, cosmic large. That's right. It's
6:39
Speaker 1: like ordering fries and McDonald's there are no more small fries,
6:42
Speaker 1: Is that true? I think so. I think you can
6:43
Speaker 1: only order large or extra large. I will admit not
6:46
Speaker 1: having been to McDonald since I worked there when I
6:48
Speaker 1: was six. And yeah, you seem to know a lot
6:50
Speaker 1: about their menu, Danniel. I'm a member of society. I
6:53
Speaker 1: participate in society. I read memes on the internet to
6:56
Speaker 1: educate me about humanity. You turn your your nose up
6:59
Speaker 1: at fast food change, sure, like everyone else in society.
7:03
Speaker 1: But yeah, maybe I would call medium sized black holes.
7:05
Speaker 1: You know that kind of makes sense. Yeah, you know,
7:08
Speaker 1: as a middle child, I'm sort of sensitive to this naming.
7:10
Speaker 1: You know, middle seems to like be defined by the others.
7:13
Speaker 1: There's nothing like unique and identifying about being in the middle.
7:16
Speaker 1: You're like defining yourself by what you're not instead of
7:18
Speaker 1: by what you are. We just opened up a whole
7:21
Speaker 1: black hole of psychological trauma. There issues there and Daniel,
7:25
Speaker 1: your middle children out there. You know you know that well,
7:28
Speaker 1: you have like ninety seven brothers and sisters, right, so
7:30
Speaker 1: you you've got to understand and is this why you
7:32
Speaker 1: started a podcast just to err on your sibling rivalry issues. Yes,
7:37
Speaker 1: it's been a three hundred episode plan to get to
7:40
Speaker 1: this moment exactly. All right, tell me, Daniel, tell me
7:44
Speaker 1: about your childhood. I feel defined by my more massive
7:47
Speaker 1: and less massive brothers. I see now you're making swipes
7:52
Speaker 1: at their body weight there, man, I meant intellectual gravitas,
7:56
Speaker 1: of course, yes, of course, of course, but yeah, I'll
7:59
Speaker 1: rate that. Are talking about black holes, Daniel, and how
8:01
Speaker 1: there aren't any real middle of the ones out there
8:04
Speaker 1: in space. You mostly see big ones or smaller ones
8:07
Speaker 1: the size of a few sons, And so that's the question,
8:09
Speaker 1: where are all the intermediate mass black holes? So it's
8:12
Speaker 1: usually we were wondering how many people out there knew
8:14
Speaker 1: that these black holes are are missing from the universe
8:17
Speaker 1: and where they could be. So thanks to everybody who
8:20
Speaker 1: volunteered to answer my random questions with no preparation or
8:24
Speaker 1: reference materials. If you'd like to participate in future episodes,
8:28
Speaker 1: please write to me two questions at Daniel and Jorge
8:31
Speaker 1: dot com. We love your contributions and I promise you
8:34
Speaker 1: it's fun. So think about it for a second. Where
8:36
Speaker 1: do you think all the medium or intermediate mass black
8:40
Speaker 1: holes in the universe are. Here's what people had to say.
8:44
Speaker 1: That's a good question. I think that there's no proof
8:47
Speaker 1: that they even exist, but that they do. Maybe they
8:50
Speaker 1: are lurking somewhere in the intergalactic space where there's just
8:53
Speaker 1: no stuff for them to eat and growth. They don't
8:56
Speaker 1: don't form those Christian disks, And basically the only way
8:59
Speaker 1: that we can spot a black hole is by looking
9:02
Speaker 1: at the Christian disk and figuring out indirectly that there
9:05
Speaker 1: must be a black hole in the middle of it.
9:07
Speaker 1: But if there is no a Christian disk, that we
9:09
Speaker 1: may have a black hole that is somewhere out there,
9:11
Speaker 1: but we just have no chance of ever spotting it.
9:14
Speaker 1: So I would bet for intergalactic space. I know at
9:18
Speaker 1: the center of a galaxy you get really big black holes.
9:22
Speaker 1: I think they're called supermassive black holes. So they won't
9:25
Speaker 1: be there, but maybe be an intergalactic space. But I'm
9:35
Speaker 1: not sure. All right, not a lot of clarity here
9:38
Speaker 1: from our listeners. I like the idea that maybe they're
9:41
Speaker 1: floating out there in space and we just can't see them.
9:44
Speaker 1: This one president said, made they're lurking in intergalactic space. Yeah,
9:48
Speaker 1: it's a cool idea. If you're a black hole, can
9:50
Speaker 1: you do anything else in space except lurk? Oh? Come on,
9:52
Speaker 1: you could be very dramatic. You could swoop into us
9:54
Speaker 1: always system and gobble it up and destroy everything. Right,
9:57
Speaker 1: that's the opposite of lurking. That's like leaping. Yeah, but
10:01
Speaker 1: then afterwards you go back to lurking. Well, I like
10:03
Speaker 1: this idea because it suggests that you know, there are
10:05
Speaker 1: things out there and intergalactic space that we don't know
10:08
Speaker 1: about that we can't see. That it might surprise us
10:11
Speaker 1: that basically you could hide anything out there as long
10:14
Speaker 1: as it's dark enough. And you know, that's a reasonable point.
10:17
Speaker 1: And I guess the real mysteries that you know there
10:19
Speaker 1: there could be intermediate mass black holes out there, Like,
10:23
Speaker 1: there's nothing that we know about so far that would
10:26
Speaker 1: would prevent them. Theoretically they're possible, but you just don't
10:29
Speaker 1: see them. Yeah. Well, that's the problem with black holes
10:31
Speaker 1: is that you can't see them directly, right because they
10:34
Speaker 1: are black. All you can do is see their effect
10:37
Speaker 1: on stuff behind them or around them. And so if
10:40
Speaker 1: you had a black hole deep in the middle of
10:42
Speaker 1: space with nothing around it, how would you detect it, it
10:45
Speaker 1: it would be undetectable, it would be very effectively lurking.
10:50
Speaker 1: And so this is actually a good point. The question
10:52
Speaker 1: that needs to know how did it get made? How
10:54
Speaker 1: did you form a black hole out there in the
10:55
Speaker 1: middle of space with nothing around you. Usually black holes
10:58
Speaker 1: are made from stuff, and then there's other stuff around
11:01
Speaker 1: that didn't get black holeified, and you can use that
11:03
Speaker 1: to detect it. That's the mystery. And so I guess maybe, Daniel,
11:06
Speaker 1: let's start at the beginning and let's talk about how
11:10
Speaker 1: you would even define an intermediate black hole, like, what
11:12
Speaker 1: is there a technical range of masses that we qualify
11:16
Speaker 1: as intermediate Yeah, there actually is. Unfortunately for the psychology
11:20
Speaker 1: of intermediate mass black holes, they are defined by what
11:23
Speaker 1: they are, not they're defined by their bigger and larger siblings. Right,
11:27
Speaker 1: So it's a black hole that's between a solar mass
11:32
Speaker 1: black hole like one that comes from a collapsed star,
11:35
Speaker 1: and we can talk about it, but there's definitely an
11:36
Speaker 1: upper limit on how big that can be, because there's
11:39
Speaker 1: an upper limit of how big a star can be.
11:42
Speaker 1: So it has to be bigger than the black hole
11:44
Speaker 1: that could come from a star, but then smaller than
11:47
Speaker 1: black holes we see the center of galaxies, which is
11:49
Speaker 1: about ten thousand or fifty thousand times the mass of
11:52
Speaker 1: the Sun. So there's a huge range there between a
11:55
Speaker 1: hundred and like ten thousand solar masses. We call the
11:59
Speaker 1: intermedi a mass range for black holes. Oh, I see
12:02
Speaker 1: there's a limit due to the sizes of stars. Exactly
12:05
Speaker 1: what kind of black hole do you imagine when you
12:06
Speaker 1: think about black holes? Probably are the ones that come
12:09
Speaker 1: from when a star collapses, Right, you know that stars
12:12
Speaker 1: are formed from gases that are collected by gravity, and
12:15
Speaker 1: then you get fusion burning, which prevents further collapse. Right,
12:18
Speaker 1: gravity would just go directly to a black hole if
12:21
Speaker 1: the star didn't ignite fusion inside of it, which was
12:23
Speaker 1: pushing out with radiation to prevent the collapse. That happens
12:27
Speaker 1: for you know, several billion years or so until the
12:29
Speaker 1: fuel runs out and turns into heavy ash, which accelerates
12:33
Speaker 1: the gravitational collapse instead of preventing it, and then the
12:36
Speaker 1: whole thing collapses into a black hole. But there's a range.
12:40
Speaker 1: They're like, it can't collapse into a black hole if
12:42
Speaker 1: it doesn't have enough mass. So the lower limit on
12:45
Speaker 1: a black hole that comes from the Sun is like
12:47
Speaker 1: ten solar masses. Smaller than that, and it collapses into
12:51
Speaker 1: like a neutron star or something else because it can
12:53
Speaker 1: still resist the gravitational pressure. But what about larger than that, Like,
12:58
Speaker 1: can bigger star collapse into a bigger black hole? It can,
13:02
Speaker 1: but you can only get up to about eighty or
13:04
Speaker 1: ninety times the mass of the Sun. And the reason
13:07
Speaker 1: is that you can't have a star that's much bigger
13:09
Speaker 1: than about three hundred times the mass of the Sun.
13:12
Speaker 1: You try to make a star bigger than that, Remember
13:15
Speaker 1: we talked about this on an episode about the biggest
13:17
Speaker 1: stars in the universe. Then those stars aren't stable. They
13:19
Speaker 1: blow themselves apart because as the star gets bigger and
13:23
Speaker 1: the inside of it gets higher pressure, and that higher
13:25
Speaker 1: pressure means the fusion burns hotter, and so it produces
13:29
Speaker 1: more radiation. It's very nonlinear, and so a little bit
13:32
Speaker 1: more stuff means a much higher temperature inside, which means
13:36
Speaker 1: radiation blowing out. So then the star literally tears itself apart.
13:39
Speaker 1: So the biggest star you can have is about three
13:42
Speaker 1: hundred times the mass of our Sun, which means that
13:44
Speaker 1: there's a limit on how big a black hole you
13:46
Speaker 1: can get that comes from a star, I see, But
13:49
Speaker 1: the limit is smaller than the biggest star. So the
13:52
Speaker 1: biggest stars can be three hundred times the mass of
13:55
Speaker 1: our sign, but the ones that turn into black holes
13:59
Speaker 1: are only the ones that go up to about eighty
14:01
Speaker 1: times the mass of our Sun. No, no, it's because
14:03
Speaker 1: not all the stuff in the star ends up in
14:06
Speaker 1: the black hole, right it's tearing itself apart, and not
14:09
Speaker 1: all of it collapses in the black hole. You still
14:11
Speaker 1: get a huge amount of stuff outside the black hole
14:13
Speaker 1: that it's blown out. You know. Sometimes you get like
14:15
Speaker 1: a supernova before you get a black hole, and that
14:18
Speaker 1: shoots a huge amount of energy and mass out into
14:21
Speaker 1: the universe. So the process to go from star to
14:23
Speaker 1: black holes not ad efficient, which is why three hundred
14:26
Speaker 1: solar mass stars turned into about eighty or ninety solar
14:29
Speaker 1: mass black holes. You're talking about the kind of the
14:32
Speaker 1: limit of the size of the black hole that can
14:35
Speaker 1: come from a star. But the stars usually started off
14:37
Speaker 1: with three hundred times the mass of the Sun, and
14:39
Speaker 1: then they collapse into eight times the mass of the Sun,
14:42
Speaker 1: and those are very rare. Like stars that massive are
14:45
Speaker 1: very very rare because they're very unstable and short lived.
14:48
Speaker 1: Most stars are much much smaller than that. So most
14:51
Speaker 1: of the stellar black holes you see out there are
14:54
Speaker 1: in the lower end of the ten to eighty range.
14:56
Speaker 1: Eight is like really extreme and crazy and rare. So
14:59
Speaker 1: then that's like one kind of limit, like the biggest
15:01
Speaker 1: stars kind of defines what the biggest black holes that
15:05
Speaker 1: can come from the Sun with their masses exactly nicee.
15:08
Speaker 1: And we see a lot of those out in the space, right. Yeah,
15:11
Speaker 1: those are all over the galaxy. Every time you have
15:13
Speaker 1: a star that's that big, its path will lead it
15:16
Speaker 1: to become a black hole, And so those black holes
15:18
Speaker 1: are appearing all the time. They're not rare, they're not weird,
15:21
Speaker 1: that not unusual, and we see lots of those black
15:23
Speaker 1: holes around the universe. That's the kind of lower range
15:26
Speaker 1: of black holes, and then there's like the upper range
15:29
Speaker 1: of black holes. Yeah, the black holes that we see
15:31
Speaker 1: at the centers of galaxies are like completely different beasts.
15:34
Speaker 1: I mean, they are similar from the general relativity point
15:37
Speaker 1: of view in that they are very compact objects that
15:40
Speaker 1: are very dense that have incredible gravity, but they seem
15:43
Speaker 1: like monsters compared to these stellar black holes because they
15:47
Speaker 1: tend to have masses like a million or a billion
15:50
Speaker 1: times the mass of one son, and so these are
15:54
Speaker 1: just really enormous and they really like drive the gravity
15:57
Speaker 1: of a galaxy. They sit at the center of the
15:59
Speaker 1: galaxy and they are you know, like one one hundreds
16:03
Speaker 1: of the mass of the whole galaxy is in that
16:05
Speaker 1: single black hole and it's pulling on the whole galaxy
16:08
Speaker 1: and it's slurping everything around and it's gobbling stars at
16:11
Speaker 1: the middle. We have one like this at the center
16:13
Speaker 1: of our galaxy. They're pretty common, I guess, Like I
16:16
Speaker 1: think most galaxies have a supermassive black hole at its center.
16:19
Speaker 1: Like when you look out into space and you see,
16:22
Speaker 1: you know, millions and millions of galaxies, most of them
16:24
Speaker 1: have one of these giant black holes in the middle.
16:26
Speaker 1: We don't actually know the fraction of these galaxies that
16:29
Speaker 1: have one, And that's one of these questions, Like we
16:31
Speaker 1: know that black holes in the center of galaxies tend
16:34
Speaker 1: to be proportional to the mass of the galaxy. So
16:37
Speaker 1: bigger galaxy, bigger black hole the center. Smaller galaxy, smaller
16:40
Speaker 1: black hole the center. We don't know if they all
16:43
Speaker 1: have black holes, like we've seen a lot without them.
16:45
Speaker 1: We don't know the fraction of galaxies that have black holes, actually,
16:49
Speaker 1: but it's not rare. I guess that's what I mean.
16:51
Speaker 1: You see them often. Yeah, it's not uncommon. Absolutely, They
16:53
Speaker 1: kind of all over the place, yes, And so what's
16:56
Speaker 1: the range of size as we've seen for those? So
16:59
Speaker 1: up to billion, right, like ten billion solar masses is
17:02
Speaker 1: the biggest black hole we've ever seen. And as far
17:05
Speaker 1: as we can tell, there's no upper limit to how
17:08
Speaker 1: big a black hole can get. Like, you keep feeding
17:10
Speaker 1: that thing, it'll just keep getting bigger. The limit really
17:12
Speaker 1: is just like cann be around enough stuff and have
17:15
Speaker 1: enough time to gobble it. On the lower end of
17:18
Speaker 1: super massive black holes, the smallest one we've seen is
17:21
Speaker 1: about fifty thousand times the mass of the Sun. This
17:25
Speaker 1: is in a little mini galaxy we call these dwarf galaxies,
17:28
Speaker 1: about three hundred forty million light years from here. The
17:31
Speaker 1: galaxy is called r g G one eighteen. And that's
17:34
Speaker 1: the smallest black hole we've ever seen inside a galaxy.
17:37
Speaker 1: It's fifty thousand times the mass of the Sun. That's huge.
17:40
Speaker 1: Imagine fifty of our sons, Yeah, and then collapsing into
17:44
Speaker 1: a black hole like the gravity of fifty thousand suns
17:48
Speaker 1: is nothing to be sneezed at, or if you sneezed
17:50
Speaker 1: at it, your sneeze will get sucked up by that
17:52
Speaker 1: black hole right away. This is not we just gets
17:54
Speaker 1: slurped out of your nose. Probably we should call that
17:56
Speaker 1: black hole is in tight Hey, yeah, then will be
17:58
Speaker 1: a green black hole depending on the size of years
18:00
Speaker 1: these we'll see. All right, Well, it seems like there
18:03
Speaker 1: are these huge populations of black holes out there, kind
18:06
Speaker 1: of the the star sized ones and the gassy size ones,
18:10
Speaker 1: but maybe not so many in the middle. So let's
18:13
Speaker 1: get into whether or not they actually exist or whether
18:17
Speaker 1: or not we're just not seeing them. But first let's
18:19
Speaker 1: take a quick break. All right, Daniel, we're talking about
18:34
Speaker 1: intermediate mass black holes. Now. Is that the official names
18:39
Speaker 1: are an acronym for that, That is the official name.
18:42
Speaker 1: You'll see that in the literature if you search for them.
18:44
Speaker 1: And you know, I call them I m b H.
18:47
Speaker 1: But it sort of reminds me of I MDB, so
18:49
Speaker 1: I think maybe we need a better name for them.
18:51
Speaker 1: M I see. Well, they do sort of collect stars
18:54
Speaker 1: in a way, right, I'm sure there are films of
18:56
Speaker 1: gas clouds I'm really stretching in here. Yeah, well, we
18:58
Speaker 1: should go look this up on the Internet movie black
19:01
Speaker 1: Hole Database. I'm sure there is one, isn't There are
19:03
Speaker 1: dots and physicists kind of keep track of everything and
19:06
Speaker 1: polish it online. I don't know, but after this episode,
19:09
Speaker 1: I'm gonna go type in i mbhdb dot com and
19:11
Speaker 1: see if somebody owns that already. Oh man, maybe you
19:15
Speaker 1: should have checked that before sponsoring it on the podcast.
19:19
Speaker 1: Some family with kids are gonna look that up and
19:20
Speaker 1: then they're gonna be like what. Alright, we're talking about
19:23
Speaker 1: whether or not intermediate mass black holes exist because we
19:28
Speaker 1: don't really see them out there in space. We see
19:30
Speaker 1: the kind that are about the size of suns, a
19:34
Speaker 1: few hundred suns that came from suns. And we talked
19:38
Speaker 1: about black holes that are at the center of galaxies,
19:40
Speaker 1: which are huge tens of thousands or maybe millions or
19:43
Speaker 1: billions of times the mass of our sun out there
19:46
Speaker 1: in the middle of galaxies. But you don't see a
19:48
Speaker 1: lot of black holes in between out there. Yeah, there
19:50
Speaker 1: seems to be this weird gap there, and it makes
19:53
Speaker 1: us wonder, like, are there those black holes out there?
19:56
Speaker 1: But we just can't see them yet, or is there
19:58
Speaker 1: some reason why they don't even exist, like they're unstable,
20:02
Speaker 1: or they accelerate really quickly to becoming supermassive, or they
20:05
Speaker 1: fall apart in some way. Like anytime there's a puzzle
20:08
Speaker 1: like that, something we don't understand, where we see something
20:11
Speaker 1: we don't expect, or we don't see something we do expect,
20:14
Speaker 1: that's a clue. That's an opportunity to figure out something.
20:17
Speaker 1: It's a moment where we can learn something about the
20:19
Speaker 1: universe because we're ready to be surprised by the data. Right. Yeah,
20:23
Speaker 1: it would be like, you know, having a population of
20:25
Speaker 1: people and then seeing only two sizes of people, like
20:28
Speaker 1: not seeing you know, sort of a continuum and like
20:31
Speaker 1: a smooth range of sizes of people. Yeah, and it
20:34
Speaker 1: would make you wonder like how did all those tall
20:36
Speaker 1: people get so tall? At some point they must have
20:39
Speaker 1: been medium height, right, so where are all the future
20:42
Speaker 1: tall people? Why are there no medium height people who
20:45
Speaker 1: are growing into those tall people. That's basically the question
20:48
Speaker 1: we're asking about these intermediate mass black holes. I mean,
20:51
Speaker 1: for example, you wonder about these supermassive black holes. How
20:54
Speaker 1: did they get supermassive? They must have started from something.
20:58
Speaker 1: If they started from something very small, then you know,
21:00
Speaker 1: by simple arguments, they must have at some point been
21:04
Speaker 1: in that intermediate range. Right, Well, I guess that's one
21:07
Speaker 1: of the mysteries, right, Like, we don't actually know where
21:09
Speaker 1: these supermassive ones in the center of galaxies came from
21:13
Speaker 1: or how they came to be so large. That's one mystery, right,
21:16
Speaker 1: that's exactly the mystery. Like the argument had just made
21:18
Speaker 1: that supermassive black holes may have started from small things
21:22
Speaker 1: and then grown to supermassive, we don't actually know if
21:25
Speaker 1: that's true, and we see things about supermassive black holes
21:28
Speaker 1: that we can't explain using that idea. For example, we
21:32
Speaker 1: look really far into the edge of the universe to
21:34
Speaker 1: see old old galaxies, to see galaxies when they were
21:38
Speaker 1: very very young, right like just a billion years after
21:41
Speaker 1: the beginning of the universe, there were already galaxies, and
21:44
Speaker 1: in those galaxies we already see super massive black holes,
21:49
Speaker 1: like black holes that have two billion solar masses. So like,
21:53
Speaker 1: only a billion years have passed and already you've made
21:55
Speaker 1: stars and galaxies and supermassive black holes inside them. We
21:59
Speaker 1: don't know how it's possible to go from nothing to
22:02
Speaker 1: supermassive black hole in just a billion years. So it's
22:05
Speaker 1: a mystery. How did those black holes get started. We
22:07
Speaker 1: don't know. I see a billion years from the Big Bang,
22:10
Speaker 1: you're saying, we already had black holes that are billions
22:12
Speaker 1: of times the massive US Sun. Yeah, exactly, And we
22:14
Speaker 1: can see them because those super massive black holes have
22:18
Speaker 1: really big accretion disks around them, like this disc of
22:21
Speaker 1: gas and dust and other stuff that's getting swirled in
22:24
Speaker 1: it gets really hot and it glows. It sends off
22:27
Speaker 1: a huge amount of radiation. Those are called quasars. So
22:30
Speaker 1: we see these quasars in the very very distant universe
22:33
Speaker 1: from the very early universe, and if you model the
22:36
Speaker 1: formation of galaxies, it's really hard to get a black
22:39
Speaker 1: hole that big that fast. We talked about this in
22:42
Speaker 1: our episode about supermassive black holes, so you can dig
22:45
Speaker 1: into that if you want more details. But very briefly,
22:47
Speaker 1: there's sort of like a limit at how fast a
22:49
Speaker 1: black hole can grow. It's called Eddington limit. And as
22:52
Speaker 1: you pump more stuff near a black hole than actually
22:55
Speaker 1: the radiation from the stuff near it pushes stuff away
22:57
Speaker 1: from the black hole. So it's hard to feed a
22:59
Speaker 1: black back hole fast enough to have a grow to
23:02
Speaker 1: be that big that quickly. So it's a mystery. We
23:04
Speaker 1: don't know if these black holes actually started from something
23:07
Speaker 1: small and then passed through this intermediate mass black hole
23:10
Speaker 1: region and then became supermassive black hole, or if they
23:13
Speaker 1: somehow skipped it. Could they have just you know, drunken
23:16
Speaker 1: a lot of strong coffee or Italian style and black espresso,
23:20
Speaker 1: or maybe American style boxes of cookies. You know, there
23:23
Speaker 1: are other ideas to explain the supermassive black holes, like,
23:25
Speaker 1: for example, maybe there were black holes that begin in
23:30
Speaker 1: the very beginning of the universe, before there were even particles,
23:33
Speaker 1: before they were stars, before there was even really matter.
23:37
Speaker 1: Maybe there were these primordial black holes right because the
23:40
Speaker 1: Big Band was pretty crazy, I imagine, or at least
23:43
Speaker 1: how the universe was before the Big Bang, and you know,
23:46
Speaker 1: things were pretty chaotic and crazy, and so maybe why not,
23:50
Speaker 1: why couldn't you just have black holes form and that
23:52
Speaker 1: kind of primordial high energy soup. Yeah, you could have.
23:56
Speaker 1: And if you did that, then you could have gotten
23:58
Speaker 1: a bunch of really tiny black holes and intermediate mass
24:01
Speaker 1: black holes and maybe even supermassive black holes, or big
24:04
Speaker 1: enough at least to become a seed which later turned
24:07
Speaker 1: into these early supermassive black holes. And so it might
24:11
Speaker 1: be possible that the supermassive black holes were seeing were
24:14
Speaker 1: never intermediate mass, that they formed like suddenly during the
24:17
Speaker 1: Big Bang, already fifty thousand solar masses and then just
24:21
Speaker 1: grew to a billion masses. So the point there is
24:24
Speaker 1: just because you have really big black holes doesn't mean
24:27
Speaker 1: they were once medium sized. Right. It's it's kind of
24:30
Speaker 1: like having a birthmark, like a mall you're born with,
24:34
Speaker 1: not a mall of that shows up later. Yeah, and
24:37
Speaker 1: there's a lot of really fun stuff. We have a
24:38
Speaker 1: whole episode about primordial black holes, which is a really
24:41
Speaker 1: fascinating topic because they might actually be real and out there,
24:44
Speaker 1: and some people still think they might account for the
24:46
Speaker 1: dark matter. So it's a really fun topic. The problem
24:49
Speaker 1: with primordial black holes is that if you make them,
24:51
Speaker 1: you expect to make them out all sizes, like really
24:53
Speaker 1: big ones and then also really little ones and the
24:56
Speaker 1: smaller ones. We should see those, and we should see
24:58
Speaker 1: them evaporating, because from small black holes evaporate and they
25:02
Speaker 1: give off radiation and as they give off radiation, they
25:05
Speaker 1: get smaller, and as they get smaller, they give off
25:07
Speaker 1: more radiation, so they would evaporate very brightly and we
25:10
Speaker 1: should see that, and we haven't. So there's some skepticism
25:13
Speaker 1: about whether primordial black holes are a thing. You're saying, like,
25:16
Speaker 1: at the beating of the universe, we don't see evidence
25:19
Speaker 1: for those little tiny black holes for me. Yeah, we
25:21
Speaker 1: don't see evans for it. It doesn't mean that they
25:22
Speaker 1: didn't happen, but we don't see evidence for it. So
25:25
Speaker 1: if primordial black holes are the explanation for super massive
25:29
Speaker 1: black holes, you need some reason why they basically only
25:32
Speaker 1: got made on the larger size and they didn't make
25:34
Speaker 1: littler ones that we would also be seen. But that's
25:36
Speaker 1: not the only problem with that theory, right that Also
25:39
Speaker 1: the theory is that even if you had started with
25:41
Speaker 1: tiny black holes from the Big Bang, there's no way
25:44
Speaker 1: they could have grown that big to what we see today. Yeah, well,
25:47
Speaker 1: you need to make primordial black holes to be pretty big,
25:50
Speaker 1: so you need to start from pretty large primordial black
25:53
Speaker 1: holes so that they could be big enough to seed
25:56
Speaker 1: the supermassive black holes we see today. You'd make them
25:59
Speaker 1: at all ales in the Big Bang from tiny to
26:01
Speaker 1: really massive. And I see. And the problem is that
26:03
Speaker 1: we don't see evidence for those large seeds or what well,
26:06
Speaker 1: that would explain the supermassive black holes. But we would
26:09
Speaker 1: also expect to see the little ones, and we don't
26:11
Speaker 1: see the little ones anywhere. Like the little ones. We
26:13
Speaker 1: should see those evaporating all over the galaxy like they
26:16
Speaker 1: should last, you know, a few billion years, and they
26:18
Speaker 1: should be evaporating in these bright flashes of light as
26:21
Speaker 1: they disappear. But we don't see that. So that means
26:24
Speaker 1: that there aren't little primordial black holes. Doesn't mean there
26:27
Speaker 1: weren't really big primordial black holes, but it means there
26:29
Speaker 1: weren't really little primorial black holes. And that means that
26:32
Speaker 1: it's a little bit more complicated to explain. Oh, I
26:35
Speaker 1: see right, because we can see back in time. Right
26:37
Speaker 1: when we look at into space, we can sort of
26:39
Speaker 1: see back in time towards what was there close to
26:42
Speaker 1: the Big Bang. Exactly, we do literally see back in
26:45
Speaker 1: time because light takes time to get here from Earth.
26:47
Speaker 1: We're seeing now what happened a million or a billion,
26:51
Speaker 1: or five or ten billion years ago. As we look
26:53
Speaker 1: deeper into the universe. It's really pretty awesome that we
26:55
Speaker 1: can look backwards in time. But there are also other
26:58
Speaker 1: ways that you could form these sue for massive black
27:00
Speaker 1: holes without going through the intermediate mass black hole route right.
27:05
Speaker 1: You could, for example, even without forming them in the
27:07
Speaker 1: Big Bang, you could have this scenario where super massive
27:10
Speaker 1: black holes formed directly from clouds of gas and dust.
27:14
Speaker 1: It's called direct collapse. They never stopped and become a
27:16
Speaker 1: star and burn for billions of years. First they just
27:19
Speaker 1: go straight to black hole. Really, you can do that.
27:21
Speaker 1: You can just form a black hole without igniting and
27:25
Speaker 1: with fusion and everything. It's a theory. We've never proven
27:27
Speaker 1: it and we've never seen one, but it's a theory
27:29
Speaker 1: that people can't rule out. If you have enough stuff,
27:32
Speaker 1: like a really big blob of stuff, then it collapses
27:36
Speaker 1: fast enough the fusion doesn't have a chance to slow
27:39
Speaker 1: it down and repel it, and it just goes straight
27:41
Speaker 1: to black hole. And you can sort of simulate it,
27:44
Speaker 1: and that can actually happen, like if you like the
27:46
Speaker 1: clouds somehow takes up enough speed compressing that it starts
27:50
Speaker 1: to night in the middle, but it's too late. There's
27:52
Speaker 1: more stuff falling in and then poof, it becomes a
27:55
Speaker 1: black hole. Yeah, grand gravity wins. And again it's still
27:57
Speaker 1: just a theory, but the calculations check out out. We've
28:00
Speaker 1: never seen when we don't have direct evidence for it.
28:02
Speaker 1: But it's a way to potentially explain how these supermassive
28:05
Speaker 1: black holes got started and then had a chance to grow.
28:09
Speaker 1: And it would be another way to have really big
28:11
Speaker 1: black holes without ever going through this middle phase, this
28:14
Speaker 1: awkward teenage years of the black hole, when you head
28:17
Speaker 1: between a hundred and ten thousand solar masses. They could
28:21
Speaker 1: have directly collapsed to something really really big fifty tho
28:24
Speaker 1: solar masses and then just kept growing from there. Isn't
28:26
Speaker 1: there another theory that these supermassive black holes come from
28:30
Speaker 1: smaller black holes colliding and merging into bigger and bigger ones.
28:34
Speaker 1: For sure, But that takes a long time, right. If
28:37
Speaker 1: you think that these big black holes came from really
28:40
Speaker 1: tiny black holes, then they spend a long time in
28:43
Speaker 1: the tiny stage, right because the gravity is proportional to
28:47
Speaker 1: the size of it. And so if you start from
28:49
Speaker 1: just like one stellar black hole and then at another
28:52
Speaker 1: and at another, there's not enough time in the universe
28:54
Speaker 1: to get up to billions of solar masses. That's the problem, right,
28:58
Speaker 1: because I guess you know it thinks in space on
29:01
Speaker 1: just like collapse head on. Right, they have to circle
29:03
Speaker 1: each other for a while, you have to date, you know,
29:06
Speaker 1: you have to go grab some coffee, eat some cookies,
29:09
Speaker 1: and then eventually they collapse into each other. Right, that's
29:11
Speaker 1: kind of the idea, Like things just don't running to
29:13
Speaker 1: each other out there in space. Yeah, it's not like
29:15
Speaker 1: some huge cosmic kid out there is trying to build,
29:17
Speaker 1: you know, a supermassive black hole by sticking the black
29:20
Speaker 1: hole legos together. It's got to happen. And for that
29:22
Speaker 1: to happen, the things have to be in the right
29:24
Speaker 1: arrangement and they have to collapse into each other. And
29:26
Speaker 1: it gets easier as your black hole gets bitter because
29:29
Speaker 1: it's more powerful and it can gobble stuff, so like
29:31
Speaker 1: the sphere of its influence grows and where it can
29:34
Speaker 1: eat from grows, so then it grows more quickly. But
29:37
Speaker 1: that's why a black hole that starts from a really
29:39
Speaker 1: small object spends most of its time small before it
29:42
Speaker 1: accelerates its growth near the later phase. So we would
29:46
Speaker 1: see those and they would take too long to get
29:48
Speaker 1: to the supermassive black hole stage, so they can't explain
29:51
Speaker 1: all the really old, huge black holes that we see, right,
29:55
Speaker 1: and so that's the big mysteries that we know where
29:58
Speaker 1: the smaller size black holes come from. They come from stars,
30:01
Speaker 1: and then we see a bunch of the huge black
30:05
Speaker 1: holes in the center of galaxies, but we don't see
30:08
Speaker 1: the ones in between, and we don't know how the
30:10
Speaker 1: big ones got as big as they did, Yeah, exactly.
30:12
Speaker 1: We don't know those big ones were once intermediate size,
30:15
Speaker 1: and we can't see any examples of the intermediate sized ones,
30:18
Speaker 1: which seems like a head scratcher, right. Yeah, it's kind
30:21
Speaker 1: of like a double mystery, like we don't know how
30:22
Speaker 1: they got so big, and also we don't see any
30:25
Speaker 1: of the middle ones. Yeah, and we'd love to unravel
30:28
Speaker 1: that mystery. We'd love to understand how these supermassive black
30:30
Speaker 1: holes form. And so finding one like when it was
30:33
Speaker 1: a child might really give us a clue to how
30:36
Speaker 1: they formed, or if we could prove that they never
30:38
Speaker 1: were children, they were like fully born as supermassive black holes,
30:42
Speaker 1: then one fell swoop that would also be fascinating. That
30:45
Speaker 1: is a possibility, is that maybe they were made super
30:47
Speaker 1: big in the big bank as primordial black holes or
30:50
Speaker 1: through direct collapse. There are some mechanisms to make these
30:54
Speaker 1: things and skip that intermediate phase. Right, That would make sense, right,
30:57
Speaker 1: you know, to have their own proper origin story that
31:01
Speaker 1: doesn't involve growing. Yeah, it does make sense. But you know,
31:04
Speaker 1: galaxies come in all sizes. There are really big galaxies
31:08
Speaker 1: and there are smaller galaxies, and it goes down to
31:11
Speaker 1: pretty small like galaxies can be down to just a
31:14
Speaker 1: few thousand stars. And so if black holes inside galaxies
31:19
Speaker 1: are proportional to the mass of the black hole, and
31:21
Speaker 1: again we don't know that, we've just seen that relationship
31:23
Speaker 1: for larger galaxies, then it stands to reason that these
31:26
Speaker 1: smaller galaxies should have smaller black holes inside them. Well
31:30
Speaker 1: that's the mystery, and so let's talk about now how
31:33
Speaker 1: we could find them or are people looking for these
31:36
Speaker 1: medium sized black holes and is it theoretically possible to
31:39
Speaker 1: see them or that they can exist. So let's get
31:42
Speaker 1: into that, but first let's take another quick break. Alright,
31:57
Speaker 1: we're talking about the ignored middle child, i'll black holes
32:01
Speaker 1: of the universe, And I know this is a personal
32:04
Speaker 1: topic for you. Daniel I'm sticking up for these black holes.
32:07
Speaker 1: You're just trying to make them the cool ones. I think, Yeah,
32:10
Speaker 1: we're like, who cares about? The little ones are the
32:12
Speaker 1: big ones, They get all the attention. The cool ones
32:15
Speaker 1: are the ones that you know, sit in the back
32:17
Speaker 1: and plot their revenge with a podcast years later, decades,
32:21
Speaker 1: decades into making This is My Revenge. No, set the
32:28
Speaker 1: record straight. I love my brothers. They're wonderful and they're supportive,
32:31
Speaker 1: and we're all very good friends. Right, Yes, did that
32:35
Speaker 1: not sound sincere I meant it to. That sounded a
32:39
Speaker 1: little tacked on at the end, But hey, you know,
32:42
Speaker 1: I know how it goes your lawyer or a therapist.
32:46
Speaker 1: Is there supposed to be a difference? Really? All right, well,
32:50
Speaker 1: let's get into this mystery of the medium sized black holes.
32:53
Speaker 1: We can't see them anywhere, now, Daniel. Do you think
32:55
Speaker 1: we don't see them because we can't see them or
32:57
Speaker 1: because they don't exist? That's the question. We don't know
33:00
Speaker 1: the answer too, because frustratingly, smaller black holes are harder
33:04
Speaker 1: to see. Like, one thing we're pretty good at is
33:07
Speaker 1: figuring out what we're good at, and we're good at
33:10
Speaker 1: seeing really big black holes because we can see them
33:12
Speaker 1: affect how stars move in the center of galaxies, or
33:15
Speaker 1: sometimes they have like huge quasars. We also know that
33:19
Speaker 1: we're not very good at seeing smaller black holes, and
33:22
Speaker 1: so we haven't seen any. But we also know that
33:25
Speaker 1: we're not great at spotting them, so that leaves the
33:27
Speaker 1: questions sort of up in the air. Right. Yeah, even
33:29
Speaker 1: the ones that come from giants sons, they're kind of
33:31
Speaker 1: hard to spot in space, right, It's not like they glow,
33:35
Speaker 1: they're transparent invisible, and space is pretty dark, and maybe
33:39
Speaker 1: they're not heavy enough to kind of like have a
33:41
Speaker 1: big impact in the stars around them. Yeah, you have
33:43
Speaker 1: to infer them. You have to be lucky. So you
33:45
Speaker 1: have to see for example, gravitational lensing where the light
33:49
Speaker 1: that passes near them gets bent as if there was
33:51
Speaker 1: a huge invisible mass of stuff there, and you know,
33:54
Speaker 1: you have to know that it's really compact and dense,
33:56
Speaker 1: so it's not just like some big diffuse cloud or
33:58
Speaker 1: dark matter, or you have to see their impact on
34:01
Speaker 1: other nearby stars with nothing else to explain it. So
34:04
Speaker 1: it's usually just like a process of elimination. We see
34:07
Speaker 1: something happening in space and we can't explain it in
34:09
Speaker 1: any other way other than a black hole. It's pretty rare.
34:12
Speaker 1: You get very direct evidence of a black hole though sometimes,
34:15
Speaker 1: and that's usually in the center of a galaxy, when
34:17
Speaker 1: they're really big and there's like quasar emissions and other
34:21
Speaker 1: stars moving very close to them. Have we seen the
34:23
Speaker 1: smaller black holes, like, is there a catalog of them
34:26
Speaker 1: or are they still kind of theoretical that they exist? Now,
34:29
Speaker 1: we have definitely observed stellar mass black holes. Absolutely, we've
34:32
Speaker 1: seen their gravitational lensing, we have seen their effect on
34:35
Speaker 1: other bodies. In fact, we did a whole fun podcast
34:37
Speaker 1: episode about the history of how people became convinced that
34:40
Speaker 1: was not just a mathematical concept, but they were real
34:43
Speaker 1: and they were out there, and the first one was
34:45
Speaker 1: at the center of our galaxy is supermassive black hole.
34:48
Speaker 1: But then later we observed a few candidates whereas a
34:51
Speaker 1: stellar mass black hole m I see. And so we
34:54
Speaker 1: see those, and we sort of see them in our
34:55
Speaker 1: neighborhood kind of in our galaxy at least, but we
34:58
Speaker 1: don't see the ones that are bigger, which you would
35:00
Speaker 1: think we'd see, right because they are more massive and
35:03
Speaker 1: so they would have more more of an impact on
35:06
Speaker 1: the motion of stars around them, but we don't see them.
35:09
Speaker 1: We see them if they're big enough, right, A million
35:11
Speaker 1: mass black hole has a big impact on what's going
35:14
Speaker 1: on in the center of galaxy. And so we can
35:16
Speaker 1: look at those galaxies and we can study the motion
35:19
Speaker 1: of stars in their center, and we can infer the
35:21
Speaker 1: presence of a black hole, just like we do for
35:23
Speaker 1: our galaxy. The problem is that smaller galaxies have fewer
35:27
Speaker 1: stars and smaller black holes. So if you're looking at
35:30
Speaker 1: a smaller galaxy like a dwarf galaxy, and you're trying
35:32
Speaker 1: to understand does the motion of the stars tell me
35:35
Speaker 1: there's some invisible sorts of gravity there? Then these are
35:38
Speaker 1: small galaxies. It's sort of hard to just like get
35:40
Speaker 1: the angular resolution you need to tell the motion of
35:44
Speaker 1: the stars in these far away small galaxies. Oh, I see.
35:48
Speaker 1: So you're saying that maybe they are there in smaller galaxies,
35:51
Speaker 1: but we just can't tell. We know that we can't
35:53
Speaker 1: see them. We know that if they were there, we
35:55
Speaker 1: could not see them today. We just do not have
35:58
Speaker 1: the resolution in current tell lescopes to see these stars
36:02
Speaker 1: moving well enough to answer the question is there an
36:05
Speaker 1: intermediate mass black hole there, Like, we just don't have
36:08
Speaker 1: the eyeballs that we need. So they could be out there,
36:10
Speaker 1: then it could be out there. We know that we
36:12
Speaker 1: couldn't see them if they were there, so they could
36:14
Speaker 1: be out there. And we have big plans like the
36:16
Speaker 1: thirty meter telescope or the extremely large telescope. These are
36:20
Speaker 1: things that are being built now and will come online
36:22
Speaker 1: in tennish years. These will have much better resolution. They'll
36:25
Speaker 1: be able to like get crisper pictures of these small
36:28
Speaker 1: galaxies that are far away, to get a sense for
36:31
Speaker 1: the motion of the stars near their center and tell
36:34
Speaker 1: us if there's an intermediate black hole there or not.
36:37
Speaker 1: We just can't see them today, and we haven't been
36:39
Speaker 1: able to see them, right, Like, we know that they've
36:42
Speaker 1: been kind of hiding from us if they exist, which
36:45
Speaker 1: we don't know if they exist. Yeah, we know they've
36:47
Speaker 1: been hiding from us. But that's just one technique to
36:49
Speaker 1: see intermediate mass black holes, right is to look for
36:52
Speaker 1: the motion of the stars near their center. There are
36:55
Speaker 1: other techniques that people have been trying as well. What
36:57
Speaker 1: are those techniques? Well, another one is not to look
37:00
Speaker 1: at galaxies at all, but to look for other kinds
37:03
Speaker 1: of things. Is this stuff out there in the universe
37:05
Speaker 1: called globular clusters. We had a whole fun podcast EFFS
37:08
Speaker 1: just about what are globular clusters and how much fun
37:11
Speaker 1: it is to say that word. But these are weird
37:14
Speaker 1: spherical collections of stars, and because they're much smaller than galaxies,
37:18
Speaker 1: people think they might have intermediate mass black holes in them.
37:22
Speaker 1: The upside is that they're much closer than other galaxies.
37:24
Speaker 1: They tend to be like orbiting our galaxy. Like we
37:27
Speaker 1: have several globular clusters orbiting our galaxy, so they're nearby,
37:31
Speaker 1: so we can like take pretty good pictures and see
37:34
Speaker 1: the motions of the stars inside them and get a
37:36
Speaker 1: sense for whether or not there's an intermediate mass black
37:39
Speaker 1: hole inside. Oh, I see these clusters. They're busier basically, right,
37:43
Speaker 1: They have more stuff to them, more stars, and so
37:45
Speaker 1: you would be able to maybe see the effects of
37:47
Speaker 1: a medium black hole in them. Yeah, and they're much
37:50
Speaker 1: closer than these other dwarf galaxies which tend to be
37:53
Speaker 1: pretty distant, and so we would have a shot. The
37:55
Speaker 1: problem is that these globular clusters aren't as tightly packed
37:58
Speaker 1: sometimes as a dwarf galaxy, and so the speeds of
38:01
Speaker 1: the stars are slower, so it's hard to tell if
38:04
Speaker 1: there's an intermediate mass black hole. There are not. You
38:06
Speaker 1: need to take pictures over like decades to see the
38:09
Speaker 1: motions of those stars and infer it. And there's a
38:11
Speaker 1: few globular clusters out there where people think maybe there's
38:14
Speaker 1: a black hole there based on the measurements of velocities
38:17
Speaker 1: of the stars, but none of them really hold a
38:19
Speaker 1: to scrutiny. Like somebody announces, wow, look we found an
38:22
Speaker 1: intermediate mass black hole, and then another group looks at
38:25
Speaker 1: the same measurements and they say, no, we can explain
38:27
Speaker 1: this without a black hole, So it doesn't really hold up.
38:29
Speaker 1: You see, it's tricky. It's tricky because you have to
38:32
Speaker 1: kind of like see the footprint of the black hole,
38:35
Speaker 1: and it's not easy to do. And another technique is
38:38
Speaker 1: to look not for the motion of stars, but for
38:41
Speaker 1: the radiation from the accretion disc Right, we know that
38:44
Speaker 1: black holes are not on their own, and especially the
38:46
Speaker 1: massive ones in the centers of galaxies are surrounded by
38:49
Speaker 1: gas and dust that's emitting a lot of radiation, so
38:52
Speaker 1: these are called quasars. And we think that intermediate mass
38:55
Speaker 1: black holes should also have intermediate mass accretion disks and
38:59
Speaker 1: be intermediate as quasars, So we're looking for these as well.
39:02
Speaker 1: Really we've only seen like supermassive quasars or stellar size quasars. Yes,
39:08
Speaker 1: we've only seen supermassive quasars. Stellar mass black holes don't
39:12
Speaker 1: tend to have quasars because they don't have the mass
39:14
Speaker 1: to get their creation disk like up to that energy,
39:17
Speaker 1: so they tend to only be from the centers of galaxies.
39:20
Speaker 1: And the problem here is that we're looking for like
39:23
Speaker 1: really old galaxies before they got really really big, so
39:26
Speaker 1: like intermediate size galaxies, and these tend to be pretty
39:29
Speaker 1: far away. And if you're looking for the black hole,
39:33
Speaker 1: because it's a quasar, it tends to like drown out
39:35
Speaker 1: the rest of the galaxy, so you can't like really
39:37
Speaker 1: see what's going on in the galaxy. So we have
39:40
Speaker 1: these quasars we've identified as maybe candidates for intermediate mass
39:43
Speaker 1: black holes, but they're so far away we can't like
39:45
Speaker 1: see the stars and really identify whether there's a black
39:48
Speaker 1: hole there. Oh, I see, because there could just be
39:50
Speaker 1: like a bunch of stars, yeah, clustered together. So but
39:53
Speaker 1: that's one thing people are doing. But I think the
39:55
Speaker 1: most exciting is this brand new way we have looking
39:59
Speaker 1: at the universe first seeing things that's not based on
40:01
Speaker 1: light but based on gravitational waves, right, like the ripples
40:05
Speaker 1: and off space. Yes, out there in the universe, the
40:08
Speaker 1: ripples in space itself, because when anything accelerates in the universe,
40:12
Speaker 1: it creates a change in the gravitational field, and that
40:16
Speaker 1: change ripples through space. And if the thing is really
40:19
Speaker 1: really big, really really massive, and moving really really fast,
40:22
Speaker 1: then you can actually measure these gravitational waves billions and
40:26
Speaker 1: billions of light years away, and we have and the
40:29
Speaker 1: things that have generated the gravitational waves that we've been
40:32
Speaker 1: able to see here on Earth in observatories like Lego
40:35
Speaker 1: are the mergers. For example, of two black holes falling
40:38
Speaker 1: into each other, they accelerate around each other in this
40:41
Speaker 1: crazy death spiral, emitting a huge amount of energy as
40:44
Speaker 1: gravitational waves, and that we can use to figure out
40:48
Speaker 1: how massive were the two black holes that fell in
40:50
Speaker 1: and how massive is the resulting black hole, right because
40:53
Speaker 1: you're seeing like the actual ripples and gravity from these
40:56
Speaker 1: black holes, So just the ripple itself kind of tell
41:00
Speaker 1: how big the things are that are crashing into each
41:02
Speaker 1: other it's a very very detailed fingerprint because the ripples
41:05
Speaker 1: tell you how fast things were going, and from that
41:07
Speaker 1: you can back out things like how massive they must
41:09
Speaker 1: have been, how strong was the gravity, and so yeah,
41:12
Speaker 1: you can figure out how massive the individual black holes
41:15
Speaker 1: were before they collapsed, and the mass of the final
41:17
Speaker 1: black hole, which is not just the two black holes
41:19
Speaker 1: added together. Some of the energy from the original two
41:22
Speaker 1: black holes get lost in gravitational radiation, these gravitational waves,
41:26
Speaker 1: and so the idea is that you know, we can
41:28
Speaker 1: listen to when these black holes crashing into each other,
41:32
Speaker 1: and so you're saying, like, maybe one day we'll see
41:34
Speaker 1: or hear are the tag two intermediate black holes crashing
41:38
Speaker 1: into each other, and then we'll be able to say, hey,
41:40
Speaker 1: there's an intermediate one. Yes, absolutely, that's a possibility, because
41:44
Speaker 1: we can use this as a way to weigh black
41:46
Speaker 1: holes and we cannot otherwise directly see right, because remember,
41:49
Speaker 1: gravitational waves can pass through anything. No amount of gas
41:52
Speaker 1: or dust or radiation or whatever can stop them. So
41:55
Speaker 1: it's just another very powerful orthogonal way of looking at
41:58
Speaker 1: the universe, so we can get glimpses. Also, there's another
42:01
Speaker 1: angle there, which is maybe we can see two really
42:04
Speaker 1: really big stellar mass black holes merge. Like what happens
42:08
Speaker 1: when an eighties solar mass black hole and a seventies
42:11
Speaker 1: solar mass black hole get together, Well, they must form
42:15
Speaker 1: a black hole that's heavier, right, that maybe even over
42:18
Speaker 1: that threshold into the intermediate mass range. Here, it's an
42:21
Speaker 1: X rated event there that Yeah, and this has actually happened.
42:28
Speaker 1: And in two thousand nineteen they did see a merger
42:31
Speaker 1: that resulted in a black hole that weighed a hundred
42:34
Speaker 1: and forty two solar masses. And so this is really cool.
42:37
Speaker 1: You can look this up on Lego. They call this
42:39
Speaker 1: the black hole graveyard, and they showed like the masses
42:42
Speaker 1: of the black holes that formed the new black holes.
42:44
Speaker 1: And so we're now seeing more and more of these things,
42:46
Speaker 1: and they're sort of pushing up that limit. Like it's
42:48
Speaker 1: true that you can't make a black hole from a
42:50
Speaker 1: single star that's bigger than eighty but as you said earlier,
42:54
Speaker 1: as you start to combine these, they can creep up
42:56
Speaker 1: a little bit and get over that hundred stellar mass threshold. Right,
42:59
Speaker 1: And we've seen this, right, you're saying, you can go
43:01
Speaker 1: online and look at the data of a hundred and
43:03
Speaker 1: forty two solar mass black hole basically being born. Yes,
43:08
Speaker 1: you can see it. It happened billions of years ago,
43:10
Speaker 1: but just recently seeing the evidence here on Earth, so
43:12
Speaker 1: that's exciting. It sort of cracks that number. It doesn't
43:15
Speaker 1: really answer the mystery, right because it doesn't explain why
43:17
Speaker 1: we don't see them. At A thousand and five thousand
43:19
Speaker 1: and ten thousand, it's like just over the threshold of
43:23
Speaker 1: what you might consider intermediate mass black hole. But we're
43:26
Speaker 1: planning to build future crazy gravitational observatories that might be
43:32
Speaker 1: able to see even bigger ones from further away. I
43:34
Speaker 1: don't know if you've heard about the Lisa experiment. No,
43:37
Speaker 1: what is it. The Lisa experiment is a version of Ligo.
43:40
Speaker 1: This experiment we have mirrors dangling underground in Louisiana and
43:44
Speaker 1: in Washington and in Italy to observe the ripples of space.
43:47
Speaker 1: This is a version of it, but using three satellites
43:50
Speaker 1: in space placed like really really far apart, but precisely
43:54
Speaker 1: aligned relative to each other. Wow, that's pretty cool in space.
43:58
Speaker 1: In space, I know, it's names bonkers, right that you
44:01
Speaker 1: could have like two satellites and have them maintain an
44:04
Speaker 1: exact distance relative to each other. It's going to be
44:07
Speaker 1: very complicated and very expensive. But if they build it
44:11
Speaker 1: this facility, Lisa will be very powerful at seeing gravitational
44:15
Speaker 1: waves and you could detect them from intermediate mass black
44:18
Speaker 1: hole murders Lisa in space. It sounds like a song.
44:23
Speaker 1: He ripped that off from the Beatles, Lisa and the
44:25
Speaker 1: Sky black Holes. All right, Well, I think you convince me, Daniel.
44:29
Speaker 1: I think the middle children are pretty cool or they
44:32
Speaker 1: don't exist one of the two. Sometimes I feel that way.
44:35
Speaker 1: They're definitely lurking, They're big. Middle children are big lurkers.
44:39
Speaker 1: For sure. We are psychological lurkers. Yes, So it's a
44:41
Speaker 1: really fun question like why don't we see these things?
44:44
Speaker 1: How did the supermassive black holes get so big without
44:47
Speaker 1: going through this stage? Or maybe we don't see them
44:49
Speaker 1: just because we don't have the telescopes yet, And in
44:51
Speaker 1: twenty or thirty years we'll see a bunch of them
44:53
Speaker 1: and they'll answer a lot of our questions about how
44:55
Speaker 1: black holes get made because they are, I guess, in general,
44:58
Speaker 1: just a cool family. You know, the youngest siblings and
45:01
Speaker 1: the oldest siblings. They're all pretty cool in their own
45:03
Speaker 1: way and pretty impactful in the universe. Right, everybody contribute
45:07
Speaker 1: to the family. We love every part of it. All right,
45:09
Speaker 1: I guess we'll leave that question dankling. What happened to
45:12
Speaker 1: the intermediate black holes? Nobody knows. It's a black hole
45:16
Speaker 1: in itself of information, but we'll figure it out. Stay
45:18
Speaker 1: tuned for more updates from science. You might have to
45:21
Speaker 1: wait another three episodes until Daniel figures it out his therapist,
45:26
Speaker 1: but we'll get there, okay, all right. We hope you
45:29
Speaker 1: enjoyed that. Thanks for joining us, See you next time.
45:39
Speaker 1: Thanks for listening, and remember that Daniel and Jorge explained.
45:42
Speaker 1: The Universe is a production of I Heart Radio. For
45:45
Speaker 1: more podcast from my Heart Radio, visit the i heart
45:48
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45:52
Speaker 1: favorite shows.