Latest / Daniel and Kelly’s Extraordinary Universe / What's happening to the Hyades Cluster?

Transcript

What's happening to the Hyades Cluster? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Kelly, what's your favorite feature in the night sky? Mmmmm?
• 0:13
  Speaker 1: You know I like spotting the Orion constellation. Oh yeah,
• 0:17
  Speaker 1: what makes that one top your list? I like that
• 0:19
  Speaker 1: it's easy to spot. That makes it easier to point
• 0:22
  Speaker 1: it out to my kids. And you know, since it's
• 0:24
  Speaker 1: so easy to find, I'd like to imagine that, like,
• 0:27
  Speaker 1: even as the Earth has changed for thousands of years,
• 0:30
  Speaker 1: other people have been able to find it as well,
• 0:32
  Speaker 1: and that pulls us together. Mmm. And it's nice to
• 0:35
  Speaker 1: think about the sweep of history. But you know that
• 0:38
  Speaker 1: constellations aren't forever, right? Oh? What is that our fault?
• 0:43
  Speaker 1: Did humans manage to ruin the sky and the planet?
• 0:46
  Speaker 1: Nothing to do with us this time? But you know
• 0:48
  Speaker 1: the sky is in motion. A t Rex looking up
• 0:52
  Speaker 1: at this guy probably never saw the Orion constellation. Well,
• 0:56
  Speaker 1: you know what, that's okay, because their little arms would
• 0:59
  Speaker 1: have been too short to point it out to their
• 1:01
  Speaker 1: t rex kids. Anyway, I can't tell what you're pointed to. Mom. Hi,
• 1:21
  Speaker 1: I'm Daniel I'm a particle physicist and a professor at
• 1:24
  Speaker 1: UC Irvine. And I'm Kelly Weener Smith. I'm a parasitologist
• 1:28
  Speaker 1: and an adjunct professor with Rice University, and even though
• 1:31
  Speaker 1: I'm technically also a professor of astronomy, I've never really
• 1:35
  Speaker 1: been that into constellations. And you know what, neither have
• 1:38
  Speaker 1: I Ryan Ryan and the Big Dipper are one of
• 1:42
  Speaker 1: the two that I'm able to name. When I was
• 1:44
  Speaker 1: really young, I like looking up at this guy and
• 1:46
  Speaker 1: seeing the stars, of course, and who can't help but
• 1:49
  Speaker 1: look for patterns. But I remember as a kid discovering
• 1:51
  Speaker 1: that the constellations are sort of artificial. You only see
• 1:55
  Speaker 1: those patterns in the sky because of where the Earth
• 1:57
  Speaker 1: happens to be. Some of those stars are like really
• 2:00
  Speaker 1: close to us, and some of them are really far away.
• 2:02
  Speaker 1: It's not like an inherent part of the sky or
• 2:05
  Speaker 1: the universe. Anybody looking at the sky from another perspective
• 2:08
  Speaker 1: would see something totally different. And I think it wasn't
• 2:10
  Speaker 1: until college that I realized, like, oh, constellations are not
• 2:14
  Speaker 1: like a helpful astronomy thing. They're just a human pattern
• 2:18
  Speaker 1: finding thing. It was kind of weirdly disappointing, I know,
• 2:21
  Speaker 1: and it sort of encourages the false impression that the
• 2:24
  Speaker 1: sky is two dimensional, that you're like looking at a screen.
• 2:28
  Speaker 1: I think it's much more thrilling to look up at
• 2:30
  Speaker 1: the night sky and see it in three D, to
• 2:33
  Speaker 1: imagine that some of these things are much deeper and
• 2:35
  Speaker 1: some are much closer than the others. Instead of looking
• 2:38
  Speaker 1: at an image, it makes you feel like you're looking
• 2:40
  Speaker 1: at a view, like the best view in the cosmos. Yes,
• 2:44
  Speaker 1: I remember. Also when I was in college, I got
• 2:46
  Speaker 1: to look through a giant telescope at sort of part
• 2:49
  Speaker 1: of a constellation, and it kind of blew my mind
• 2:52
  Speaker 1: that in all of the stories that I was able
• 2:54
  Speaker 1: to see, they were like, you know, clusters are swirling
• 2:57
  Speaker 1: things happening in between there, and they were sort of
• 3:00
  Speaker 1: part of the constellation too, and like, ah, it's I
• 3:03
  Speaker 1: don't even know what the point was, but it just
• 3:06
  Speaker 1: sort of the closer you look, the more surprising it is.
• 3:08
  Speaker 1: So even though I was disappointed at first to learn
• 3:10
  Speaker 1: that constellations are sort of a pattern finding thing, the
• 3:14
  Speaker 1: closer you look and the more you learn, the like
• 3:16
  Speaker 1: more exciting it gets, indeed, and so welcome to the podcast.
• 3:20
  Speaker 1: Daniel and Jorge explain the Universe, in which we try
• 3:23
  Speaker 1: to take a closer look as possible into the very
• 3:26
  Speaker 1: nature of this crazy universe. We zoom in on the
• 3:30
  Speaker 1: tiniest details and try to understand how quantum particles really move,
• 3:34
  Speaker 1: what is really going on, and we zoom out to
• 3:36
  Speaker 1: the biggest, deepest, oldest, most dramatic questions of the universe.
• 3:41
  Speaker 1: How old is everything, how does it all work? What's
• 3:43
  Speaker 1: going on up there in the night sky. We take
• 3:46
  Speaker 1: all of that and we try to explain all of
• 3:48
  Speaker 1: it to you. And as you may have, guest Horrie
• 3:50
  Speaker 1: isn't with us today, he's on a brake, and so
• 3:53
  Speaker 1: we're very glad to have with us one of our
• 3:54
  Speaker 1: favorite guest hosts, Kelly. Kelly, thanks for joining us today. Thanks.
• 3:58
  Speaker 1: I love being here. I always love it when Jorge
• 4:00
  Speaker 1: takes a break and I get to geek out with you. Well,
• 4:01
  Speaker 1: today we're gonna be talking about one of the most
• 4:04
  Speaker 1: accessible things in physics and astronomy, a place where a
• 4:07
  Speaker 1: lot of people get attracted to the big questions of
• 4:09
  Speaker 1: the universe, and that's just looking up at the night
• 4:12
  Speaker 1: sky and seeing the stars. I think everybody who has
• 4:15
  Speaker 1: questions about the universe, everybody who wonders what's out there,
• 4:18
  Speaker 1: probably got started by just looking up and seeing those
• 4:21
  Speaker 1: twinkling lights and wondering what it all means and So
• 4:24
  Speaker 1: what part of the night sky are we going to
• 4:26
  Speaker 1: focus on today? Today? I want to talk about the
• 4:28
  Speaker 1: illusion that is the night sky. On one hand, we
• 4:31
  Speaker 1: say that the night sky seems like it's two dimensional,
• 4:34
  Speaker 1: but really it's three D. And it takes this sort
• 4:36
  Speaker 1: of mental exercise to unhook yourself from the illusion that
• 4:40
  Speaker 1: it's a screen and to remember that it's a deep,
• 4:42
  Speaker 1: deep view that you're looking across billions of miles of
• 4:46
  Speaker 1: empty space. But there's another illusion of the night sky,
• 4:49
  Speaker 1: and that's that it seems to be sort of static,
• 4:52
  Speaker 1: that it seems to be fixed. And it's true that
• 4:54
  Speaker 1: a thousand years ago astronomers looked up at the same
• 4:57
  Speaker 1: night sky that we see, and in a thousand year
• 5:00
  Speaker 1: as astronomers will still be looking at basically the same
• 5:03
  Speaker 1: night sky. But that's because the time scales for the
• 5:06
  Speaker 1: nights guy and for the Solar system and for the
• 5:08
  Speaker 1: universe are just much much longer than we tend to
• 5:11
  Speaker 1: think about in human history, and that on those long
• 5:14
  Speaker 1: time scales, the universe is actually quite chaotic. So like
• 5:18
  Speaker 1: a thousand years ago, was it a little bit different?
• 5:21
  Speaker 1: And that's how we know it's way different, like a
• 5:24
  Speaker 1: billion or a million years from now, or do we
• 5:25
  Speaker 1: know that some other way exactly? The night sky is
• 5:28
  Speaker 1: changing very slowly, So if you have very precise measurements
• 5:32
  Speaker 1: of where all the stars were, you could see those
• 5:34
  Speaker 1: things in action. But mostly we understand the night sky
• 5:38
  Speaker 1: is dynamic because we understand the processes behind it. We
• 5:41
  Speaker 1: know that these stars are in motion. We see these
• 5:44
  Speaker 1: crazy effects. We see snapshots of all these processes back
• 5:48
  Speaker 1: through time, because the further we can look out into
• 5:51
  Speaker 1: the universe, the further back in time we see. And
• 5:54
  Speaker 1: so we can see things happening to other galaxies and
• 5:57
  Speaker 1: other stars, galaxies, colliding stars swirling around each other, all
• 6:02
  Speaker 1: sorts of crazy stuff is happening out there. It's sort
• 6:04
  Speaker 1: of like we are in the middle of a white
• 6:06
  Speaker 1: water rapids, but we're just looking at things in super
• 6:09
  Speaker 1: slow motion, so it seems like nothing's happening, right, So
• 6:13
  Speaker 1: can we go from like this more sort of abstract,
• 6:16
  Speaker 1: grandiose discussion to like a more concrete example, So, like,
• 6:21
  Speaker 1: what's happening with the Hyades Cluster. That's right, it's been
• 6:24
  Speaker 1: in the news recently. There's a blob of stars out
• 6:27
  Speaker 1: there called the Hyades Cluster, and astronomers have discovered that
• 6:31
  Speaker 1: something quite dramatic is going on to this cluster. So
• 6:34
  Speaker 1: on today's episode, let's talk about what's happening to the
• 6:43
  Speaker 1: Hyades Cluster. And before you get too worried, you know,
• 6:46
  Speaker 1: this is a group of stars out there. They don't
• 6:48
  Speaker 1: have emotions or feelings, so you don't have to worry
• 6:51
  Speaker 1: about them too much. Although I guess if there are
• 6:54
  Speaker 1: aliens out there, you know, living on planets in this cluster,
• 6:57
  Speaker 1: what's happening to the cluster could be disrupting their lives.
• 7:01
  Speaker 1: So now I'm worried. So yeah, actually I changed my mind.
• 7:04
  Speaker 1: You should totally be worried about those aliens. I'm having
• 7:08
  Speaker 1: a bit of an existential crisis now, and so as usual,
• 7:12
  Speaker 1: I went out there into the Internet to ask people
• 7:15
  Speaker 1: if they knew what was happening to the Hyades Cluster,
• 7:17
  Speaker 1: and I should have asked them how they felt about it.
• 7:20
  Speaker 1: But if you are interested in participating for future episodes
• 7:23
  Speaker 1: of the podcast and lending your voice to these questions
• 7:26
  Speaker 1: and hearing your voice on the podcast, please don't be shy.
• 7:30
  Speaker 1: Just right to me two questions, add Daniel and Jorge
• 7:33
  Speaker 1: dot com. So before you listen to these answers, think
• 7:35
  Speaker 1: to yourself, do you know what's going on to the
• 7:38
  Speaker 1: high these cluster. Here's what people had to say. If
• 7:42
  Speaker 1: it's a stock cluster, then it could be spinning itself
• 7:44
  Speaker 1: a pot or flinging stuff out of it. Or if
• 7:48
  Speaker 1: it's a galaxy cluster them maybe it's uh combining galaxies
• 7:52
  Speaker 1: together or just again flinging them out of each flinging
• 7:56
  Speaker 1: them away from each other. I have never heard of
• 7:58
  Speaker 1: the Hyades cluster, and I'm not even sure i'm pronouncing
• 8:01
  Speaker 1: it correctly. The Hayvis cluster, if I remember correctly, is
• 8:05
  Speaker 1: a star cluster quite close to us, or maybe even
• 8:09
  Speaker 1: the closest one. And if I'm correct, it's falling apart
• 8:14
  Speaker 1: or dissipating, or at least it's the stars are not
• 8:18
  Speaker 1: staying together in the cluster as they are, But I'm
• 8:22
  Speaker 1: not sure what the reason for that is anymore. I'm
• 8:24
  Speaker 1: not sure what's happening to it, but I really hope
• 8:27
  Speaker 1: it's okay. I'm again not sure I know that much
• 8:30
  Speaker 1: that this cluster is the closest one to us or
• 8:32
  Speaker 1: to the Sun, but haven't actually heard what's happening to it,
• 8:37
  Speaker 1: so I'm not sure. I assume this has to do
• 8:39
  Speaker 1: with a constellation of stars not in our galaxy to
• 8:44
  Speaker 1: my knowledge, but should be outside of our galaxy, and
• 8:48
  Speaker 1: clearly it is, since you're asking a question, it is
• 8:52
  Speaker 1: clearly an interaction or something that has not been observed
• 8:56
  Speaker 1: by humans before. So breaking the mold pussy? Is it
• 9:02
  Speaker 1: moving towards another cluster creating a giant explosion in space?
• 9:07
  Speaker 1: I think that the Hades clusters all dying out. I
• 9:09
  Speaker 1: think it's a clusters does and to go off of
• 9:14
  Speaker 1: the name Hades, I think they're all going to the underworld.
• 9:17
  Speaker 1: May be confusing the Hyades cluster with another one, but
• 9:21
  Speaker 1: I think that's a youngish cluster where a lot of
• 9:25
  Speaker 1: the dust and such from formation has already been you
• 9:30
  Speaker 1: accumulated or blown off, and now the stars are moving apart.
• 9:35
  Speaker 1: Their answers were a nice mix of, you know, honestly
• 9:38
  Speaker 1: admitting that they don't know what's going on to one
• 9:41
  Speaker 1: person who was maybe having a bit of an existential crisis,
• 9:44
  Speaker 1: really hoping that the Hyades cluster was okay. But since
• 9:48
  Speaker 1: nobody like seemed to have gotten it totally right, can
• 9:51
  Speaker 1: you explain to us what what is it? Right? So,
• 9:54
  Speaker 1: the Hyades cluster is something that astronomers call an open cluster.
• 9:59
  Speaker 1: This is basically a group of stars that formed together.
• 10:03
  Speaker 1: I think this is really interesting because I think it
• 10:05
  Speaker 1: gives you a window and understanding how and when and
• 10:09
  Speaker 1: where stars are formed. People might imagine that the stars
• 10:13
  Speaker 1: just sort of like pop into existence in random places
• 10:16
  Speaker 1: in the universe, but there's really actually a lot more
• 10:18
  Speaker 1: structure and pattern to it than that. And star clusters
• 10:23
  Speaker 1: are these groups of stars that all formed together and
• 10:25
  Speaker 1: give us an opportunity to study exactly how and when
• 10:28
  Speaker 1: stars are formed. And if they're still in the cluster,
• 10:31
  Speaker 1: does that mean it's a younger group of stars. Does
• 10:34
  Speaker 1: the clustering tell you something about age? It does, and
• 10:37
  Speaker 1: it tells you something about mass, So you have to
• 10:39
  Speaker 1: go back to the original blob of stuff that formed
• 10:43
  Speaker 1: this cluster. Remember that most stars are formed from like
• 10:46
  Speaker 1: huge clouds of gas and dust and left over remnants
• 10:50
  Speaker 1: from other stars. You know, we're like fourteen billion years
• 10:54
  Speaker 1: into the history of the universe that have already been
• 10:57
  Speaker 1: generations of stars that burned for millions or billions of
• 11:00
  Speaker 1: years and then exploded and sent their shrapnel, their dust,
• 11:04
  Speaker 1: their compost out into the universe. To see new generations
• 11:08
  Speaker 1: of stars. So you have this sort of like raw
• 11:10
  Speaker 1: material floating out there, but it doesn't always just necessarily
• 11:14
  Speaker 1: like come together into a star. There's nobody out there
• 11:17
  Speaker 1: like scooping up huge blobs of hydrogen to form stars.
• 11:21
  Speaker 1: Something has to happen to make those stars formed, to
• 11:24
  Speaker 1: make this huge cloud of gas and dust actually coalesced
• 11:27
  Speaker 1: into these burning, bright blobs. So what happens. So it's
• 11:31
  Speaker 1: fascinating because two things have to happen. One is the
• 11:34
  Speaker 1: blob has to get cold, like you think of stars
• 11:37
  Speaker 1: is like obviously really really hot. But in order for
• 11:40
  Speaker 1: them to come together, gravity has to pull those things together,
• 11:44
  Speaker 1: and it can't do that if the particles inside it
• 11:47
  Speaker 1: are moving really really fast. So if you have like
• 11:49
  Speaker 1: a cloud of really really hot gas, it's never going
• 11:52
  Speaker 1: to form a star if it can't cool down somehow.
• 11:55
  Speaker 1: Those particles have to slow down because remember that gravity
• 11:59
  Speaker 1: is really weak. It's the weakest force in the universe
• 12:02
  Speaker 1: by huge number. It's much much weaker than magnetism or electricity.
• 12:08
  Speaker 1: So for a star to form, gravity has to be
• 12:10
  Speaker 1: able to gather together those tiny little particles, and that
• 12:14
  Speaker 1: can only happen if the particles are really slow moving.
• 12:17
  Speaker 1: So you have some big cloud of gas and dust,
• 12:19
  Speaker 1: it needs a way to cool down, like radiating off
• 12:22
  Speaker 1: its energy, sending photons out into deep space. That gives
• 12:26
  Speaker 1: you the raw material that gravity can then use to
• 12:29
  Speaker 1: form those stars. But usually these clouds are not just
• 12:32
  Speaker 1: like enough cloud to make one star. There are enough
• 12:34
  Speaker 1: cloud to make hundreds or thousands of stars all at
• 12:37
  Speaker 1: the same time. So I'm having a little trouble wrapping
• 12:40
  Speaker 1: my head around this. So when you say cool down,
• 12:42
  Speaker 1: you mean like cool for a star but still ridiculously hot,
• 12:47
  Speaker 1: or is it like actually cool, no, really cool even
• 12:51
  Speaker 1: for you Like these are freezing, freezing cold clouds of
• 12:55
  Speaker 1: gas and dust. They need to be moving very slowly
• 12:58
  Speaker 1: for gravity to take over. So we say two things
• 13:01
  Speaker 1: have to happen. One is they need to be cooled down,
• 13:04
  Speaker 1: not like thousands of degrees Calvin, but you know, much
• 13:07
  Speaker 1: smaller values, actually cold values. And then you need gravity
• 13:10
  Speaker 1: to be sort of like get a foothold to like
• 13:13
  Speaker 1: make these clouds collapse into a cluster of stars. And
• 13:16
  Speaker 1: for that to happen, either you need like one blob
• 13:19
  Speaker 1: that's extra dense and it starts to gather the other
• 13:22
  Speaker 1: ones because it has stronger gravity. Than anything else around it,
• 13:25
  Speaker 1: or you have some external event, like a supernova nearby
• 13:29
  Speaker 1: sends a shock wave, and that can trigger the collapse
• 13:32
  Speaker 1: because it sort of pushes a bunch of particles into
• 13:34
  Speaker 1: another bunch of particles and then they have more density
• 13:37
  Speaker 1: than everything else around them. So you need like a
• 13:40
  Speaker 1: cold cloud of gas. It's like the raw ingredients, you know,
• 13:43
  Speaker 1: like when you make a recipe and they say, like,
• 13:45
  Speaker 1: you know, use chilled butter or whatever. It's important for
• 13:48
  Speaker 1: the texture of your pie that you start with cold butter. Right,
• 13:52
  Speaker 1: You're not gonna get your lamonation in your flaky crust.
• 13:54
  Speaker 1: In the same way, you need to start with like
• 13:56
  Speaker 1: cold gas for your stars, and then you need to
• 13:59
  Speaker 1: trigger that lapse somehow. So it's this two step process
• 14:02
  Speaker 1: of forming new stars and so the one once you
• 14:04
  Speaker 1: get that you know the right pieces of the recipe
• 14:07
  Speaker 1: so you can make your cosmic pie. What does it
• 14:10
  Speaker 1: end up looking like? Like what kind of stars do
• 14:12
  Speaker 1: you make? And how big is the product? It depends
• 14:15
  Speaker 1: a lot on exactly how much metal there is in
• 14:18
  Speaker 1: this cloud. The universe started out with only hydrogen and
• 14:21
  Speaker 1: helium and very very tiny amounts of everything else, and
• 14:24
  Speaker 1: astronomers called everything above helium a metal, like I know,
• 14:28
  Speaker 1: biologists and chemists had their own definition of metals, but
• 14:31
  Speaker 1: for astronomers, anything above helium they call the metal. And
• 14:34
  Speaker 1: so you know, I don't know what they call heavy
• 14:36
  Speaker 1: metal music, but you know, probably anything with a beat
• 14:38
  Speaker 1: to it. Do astronomers listen to heavy metal? I guess
• 14:41
  Speaker 1: some of them must. Almost everything is heavy metals for astronomers.
• 14:45
  Speaker 1: And if your cloud has more heavy metals in it,
• 14:47
  Speaker 1: heavier elements carbon, oxygen, nitrogen, even iron, then it's easier
• 14:52
  Speaker 1: for it to coalesce, and so you get reasonably sized stars.
• 14:56
  Speaker 1: If you have really really big clouds without any heavy metals,
• 15:00
  Speaker 1: and it's harder for it to sort of cool down
• 15:02
  Speaker 1: and to coalesce, and so you get really big stars.
• 15:05
  Speaker 1: You get these huge clouds, and so we think like
• 15:08
  Speaker 1: the first population of stars ever reformed in the universe
• 15:11
  Speaker 1: were probably like enormous mega stars for that reason, whereas
• 15:16
  Speaker 1: in later clouds of gas and dust that had these
• 15:19
  Speaker 1: like smaller pockets of metals in them, they formed these
• 15:23
  Speaker 1: points for the stars to form, and so you've got
• 15:25
  Speaker 1: a larger number of sort of reasonably sized stars, you know,
• 15:29
  Speaker 1: stars like half to ten times the mass of our sun,
• 15:32
  Speaker 1: and do these stars are these stars that will last
• 15:34
  Speaker 1: for a long time. There's a really close connection. They're
• 15:37
  Speaker 1: actually the bigger the star, the greater the gravitational pressure.
• 15:40
  Speaker 1: Once it does start to burn, the higher the temperature,
• 15:43
  Speaker 1: and the faster it burns through its fuel. That's why
• 15:46
  Speaker 1: that first generation of stars that had almost no metals
• 15:48
  Speaker 1: in them, only lasted a few hundred million years, whereas
• 15:51
  Speaker 1: the second generation of stars, some of those are still
• 15:54
  Speaker 1: around there more than ten billion years old, and the
• 15:56
  Speaker 1: smaller ones might even burn for trillions of years. So
• 16:00
  Speaker 1: the smaller the star at the longer the lifetime. And
• 16:02
  Speaker 1: the thing to realize is that these stars are not
• 16:04
  Speaker 1: just formed one at a time. Right, you have a
• 16:06
  Speaker 1: huge cloud of gas and dust, and so a bunch
• 16:09
  Speaker 1: of stars are formed together. And so earlier you asked
• 16:11
  Speaker 1: me like, well, how long do these clusters last? And
• 16:14
  Speaker 1: so it depends on how many stars you get into
• 16:17
  Speaker 1: that cluster. So if you get like a huge cloud
• 16:20
  Speaker 1: of gas and dust that gives you like thousands and
• 16:22
  Speaker 1: thousands of stars, then those stars which are formed together
• 16:26
  Speaker 1: will hang out together for quite a long time. A
• 16:29
  Speaker 1: smaller cloud which gives you fewer stars like you know,
• 16:31
  Speaker 1: ten or maybe a hundred. They don't have the gravitational
• 16:33
  Speaker 1: strength to resist the rest of the galaxy, and they
• 16:36
  Speaker 1: mostly just end up going their own way. I have
• 16:40
  Speaker 1: been in some social groups like that. So typically these
• 16:44
  Speaker 1: clusters can last, you know, millions or hundreds of millions
• 16:47
  Speaker 1: of years. Scientists are really surprised if they see a
• 16:50
  Speaker 1: cluster that's like a billion years old, because it's hard
• 16:53
  Speaker 1: for these clusters to resist like the tug of the
• 16:55
  Speaker 1: rest of the galaxy, which tends to sort of pull
• 16:57
  Speaker 1: them apart. Do they all stick around for about the
• 17:00
  Speaker 1: same amount of time because they started at the same
• 17:02
  Speaker 1: amount of time, or do some of them disappear at
• 17:04
  Speaker 1: different rates? Well, the stars inside the cluster can be
• 17:07
  Speaker 1: of varying sizes, and so because some of them are bigger,
• 17:11
  Speaker 1: they burn brighter, they burn bluer, they tend to disappear.
• 17:15
  Speaker 1: So as you're looking in older cluster, you tend to
• 17:18
  Speaker 1: see fewer blue stars in them and more of the
• 17:21
  Speaker 1: red stars and the yellow stars. So an older cluster
• 17:24
  Speaker 1: tends to have like more yellow and red stars. One
• 17:27
  Speaker 1: weird thing is that they have been looking at open
• 17:29
  Speaker 1: clusters and globular clusters, which are similar and even larger,
• 17:33
  Speaker 1: and they see something really weird, which that they see
• 17:35
  Speaker 1: a bunch of bright blue stars even inside these clusters
• 17:39
  Speaker 1: that are supposed to be pretty old, where all the
• 17:42
  Speaker 1: blue stars should have already burned up. WHOA, So why
• 17:44
  Speaker 1: do we think that they're sticking around? Scientists aren't sure,
• 17:47
  Speaker 1: of course, but that's what makes it exciting. They call
• 17:49
  Speaker 1: these things blue stragglers. And one idea, which I think
• 17:52
  Speaker 1: is really fun, is that these blue stragglers might be
• 17:56
  Speaker 1: new combinations of old stars. Like maybe you had a
• 18:00
  Speaker 1: couple of stars that are red or yellow and are
• 18:03
  Speaker 1: burning happily and planning to burn for billions of years,
• 18:06
  Speaker 1: but then they merge. They smashed together, they like gravitationally
• 18:10
  Speaker 1: bound to each other. Maybe they were in a binary
• 18:12
  Speaker 1: system to start with, and they just sort of like
• 18:14
  Speaker 1: fall into each other and become a big hot star. WHOA,
• 18:18
  Speaker 1: So I wonder like the social media and that galaxy,
• 18:21
  Speaker 1: is it like benefer when Ben Affleck and Jennifer what
• 18:25
  Speaker 1: Lopez come together? You know, these stars have names that combine.
• 18:28
  Speaker 1: I don't know, but instellar marriages. There are no divorces,
• 18:31
  Speaker 1: right once you get gravitationally married to each other. I
• 18:33
  Speaker 1: don't know how you can get separated again. You better
• 18:36
  Speaker 1: like each other. So you've mentioned an open cluster, and
• 18:41
  Speaker 1: I think I also heard you say globular cluster? Are
• 18:44
  Speaker 1: there clothes clusters? How many kinds of clusters do we have?
• 18:48
  Speaker 1: You know, if astronomical names made sense, then yes, there
• 18:51
  Speaker 1: would be open clusters and close clusters, globular clusters, and
• 18:54
  Speaker 1: I guess non globular clusters. But no, these things come
• 18:58
  Speaker 1: from history of people noticing, just as you were saying earlier,
• 19:01
  Speaker 1: they would like zoom in on a star and then discover,
• 19:03
  Speaker 1: way a second, that's not a star, that's actually a
• 19:06
  Speaker 1: bunch of stars and a little cluster. That's why it
• 19:08
  Speaker 1: looked a little bit like a hazy blob instead of
• 19:11
  Speaker 1: a bright pinpoint. And as we study these things, we
• 19:14
  Speaker 1: discover that these categories, which is sort of historical based
• 19:16
  Speaker 1: on who found them and what they called them, might
• 19:19
  Speaker 1: actually just sort of sit in a spectrum. That the
• 19:22
  Speaker 1: difference between an open cluster, you know, which tends to
• 19:25
  Speaker 1: have tens of thousands of stars, and a globular cluster
• 19:28
  Speaker 1: that has like a hundred thousand stars might just be
• 19:31
  Speaker 1: the size that there might be like clusters of stars
• 19:33
  Speaker 1: of all sizes, and we just sort of like found
• 19:36
  Speaker 1: a few here and found a few there and gave
• 19:38
  Speaker 1: them different names, when really it's just like a smooth
• 19:40
  Speaker 1: spectrum and there's no like fundamental difference. But that's something
• 19:43
  Speaker 1: astronomers are studying, like the concept of this open cluster
• 19:46
  Speaker 1: and is it different from a globular cluster and how
• 19:49
  Speaker 1: does it all fit together in the sort of history
• 19:51
  Speaker 1: of the galaxy is an exciting area of research right now.
• 19:54
  Speaker 1: It's got to be a tough thing to study, but
• 19:55
  Speaker 1: I found it really fascinating because it gives you like
• 19:57
  Speaker 1: a hint as to what's going on in the Ga galaxy.
• 20:00
  Speaker 1: You know, it's not like we just got these stars
• 20:02
  Speaker 1: and they're gonna be burning. We're making new stars, like
• 20:05
  Speaker 1: right now, like everyday, new stars are being formed. And
• 20:08
  Speaker 1: these clusters are especially fascinating because not only do you
• 20:11
  Speaker 1: have stars in there, but they still have clues in
• 20:14
  Speaker 1: the structure of the cluster about the thing that made them,
• 20:17
  Speaker 1: this huge cloud which formed them. And so I think
• 20:20
  Speaker 1: these clusters are super fascinating because there's sort of like
• 20:23
  Speaker 1: little mini sub galaxies within the galaxy. They give you
• 20:26
  Speaker 1: a clue as like the texture of the galaxy and
• 20:28
  Speaker 1: it's particular history that is so cool. So do we
• 20:31
  Speaker 1: have a sense for like what kind of things you
• 20:33
  Speaker 1: most commonly find at the center of the clusters? How
• 20:35
  Speaker 1: many of these have we've been able to study in detail? Well,
• 20:38
  Speaker 1: you know, these things are not made that often. There's
• 20:40
  Speaker 1: like one of these open clusters we think formed every
• 20:43
  Speaker 1: few thousand years in the Milky Way, so like it's
• 20:46
  Speaker 1: not like they're always popping into the night sky. But
• 20:49
  Speaker 1: because the Milky Way is pretty old, there are a
• 20:52
  Speaker 1: bunch of them. And we've identified more than a thousand
• 20:55
  Speaker 1: open clusters just in our galaxy, but we think there
• 20:58
  Speaker 1: are lots and lots more so we've they're all over
• 21:00
  Speaker 1: the place. A thousand that's a pretty nice data set
• 21:03
  Speaker 1: to work with. Yeah, it's something that you can you
• 21:05
  Speaker 1: really use to study because you're going to see them
• 21:07
  Speaker 1: at all different points in their history. Recently, foreign clusters,
• 21:10
  Speaker 1: clusters that are just falling apart, all sorts of stuff.
• 21:13
  Speaker 1: Of course, the one that astronomers really like to study
• 21:16
  Speaker 1: is the one that's closest to the Earth, and is
• 21:18
  Speaker 1: that the Hyades cluster. That is all right now that
• 21:21
  Speaker 1: everybody's excited to learn about the Hyades Cluster. Let's wait
• 21:25
  Speaker 1: and take a break to hear from our sponsors. All right,
• 21:41
  Speaker 1: the moment you've all been waiting for, we're back. Let's
• 21:44
  Speaker 1: hear about the Hyades Cluster. So you were just telling
• 21:47
  Speaker 1: us that it is the closest of the clusters. So
• 21:49
  Speaker 1: if I look out in the night sky, where should
• 21:52
  Speaker 1: I be looking if I want to be looking in
• 21:53
  Speaker 1: the right direction to find the Hyades cluster. The Hyse
• 21:56
  Speaker 1: Cluster is actually part of a constellation. So if you
• 21:59
  Speaker 1: know that Horace constellation, the Face of the Bull, you know,
• 22:03
  Speaker 1: then there's this part of that constellation that's sort of
• 22:05
  Speaker 1: like a v The High These Cluster is part of that.
• 22:08
  Speaker 1: Another part of that constellation is sort of a famous
• 22:10
  Speaker 1: star called Aldera Bond, which I think is famous maybe
• 22:14
  Speaker 1: just because it sounds like the name of a planet
• 22:15
  Speaker 1: in Star Wars, but it's also one of the brightest
• 22:18
  Speaker 1: stars in the night sky. And so would we be able,
• 22:22
  Speaker 1: like if we were looking at the Tourist constellation, would
• 22:25
  Speaker 1: we see something kind of fuzzy or would it just
• 22:29
  Speaker 1: sort of look like a point. Well, it's about a
• 22:31
  Speaker 1: hundred and fifty three light years away, which means that
• 22:34
  Speaker 1: it's pretty far away, right, it's not that close, and
• 22:37
  Speaker 1: so to the naked eye it just looks like a point.
• 22:40
  Speaker 1: But if you have a strong enough telescope, you can
• 22:42
  Speaker 1: zoom in on it and you can tell that's not
• 22:43
  Speaker 1: just a star, it's actually a cluster of stars. It
• 22:47
  Speaker 1: doesn't take that powerful a telescope. So if you have
• 22:50
  Speaker 1: a pretty good telescope in your backyard, zoom in on
• 22:53
  Speaker 1: the high these cluster and you can see it looks
• 22:55
  Speaker 1: like a bit of a fuzzy blob, and that's how
• 22:57
  Speaker 1: it was discovered to be a cluster. How wide is this?
• 23:00
  Speaker 1: So the thing is about sixty light years across, right,
• 23:03
  Speaker 1: and so it's a hundred fifty three light years away
• 23:05
  Speaker 1: and sixty light years across. So that gives you a
• 23:07
  Speaker 1: sense for like how broad this thing is relative to
• 23:11
  Speaker 1: its distance, And that means that it's large enough and
• 23:14
  Speaker 1: close enough that we can actually measure its distance directly
• 23:17
  Speaker 1: using parallax. Remember that the distance two stars can be
• 23:21
  Speaker 1: hard to estimate because you can't necessarily tell the difference
• 23:24
  Speaker 1: between a star that's really bright and far away or
• 23:28
  Speaker 1: a star that's not so bright and closer up. They
• 23:31
  Speaker 1: look the same in the night sky, but we have
• 23:33
  Speaker 1: all these cool techniques for measuring how far away a
• 23:36
  Speaker 1: star is from, like looking at type one a supernova
• 23:38
  Speaker 1: for stars and other galaxies, just seeing if they're near
• 23:41
  Speaker 1: one of these variable stars, these sephids, or if they're
• 23:44
  Speaker 1: close enough, we can see how the star moves in
• 23:47
  Speaker 1: the night sky as the Earth goes around the Sun,
• 23:51
  Speaker 1: because as the Earth goes around the Sun, you get
• 23:52
  Speaker 1: a slightly different view of the night sky. And for
• 23:56
  Speaker 1: stars that are close enough, it's sort of like opening
• 23:58
  Speaker 1: and closing one eye and looking at your finger. You've
• 24:01
  Speaker 1: got a different view of that finger, and your brain
• 24:04
  Speaker 1: actually automatically uses that binocular information to give you a
• 24:07
  Speaker 1: sense for how far away something is. So Hyades is
• 24:10
  Speaker 1: close enough that we can do that. We can use
• 24:12
  Speaker 1: parallax to measure how far away it is. Interesting, and
• 24:15
  Speaker 1: of course you know now that you've mentioned that I
• 24:16
  Speaker 1: have to be blinking and looking at my finger in
• 24:18
  Speaker 1: this room by myself. So we talked a little bit
• 24:21
  Speaker 1: ago about how you need something in the center to
• 24:24
  Speaker 1: pull the cloud together. Do we know what is pulling
• 24:28
  Speaker 1: things together in the Hyades cluster? So probably all of
• 24:31
  Speaker 1: those gravitational centers then became stars, right, So you have
• 24:35
  Speaker 1: this like big cloud of gas and dust that forms it,
• 24:38
  Speaker 1: and then you need these seeds, these gravitational seeds to
• 24:41
  Speaker 1: pull stuff together. Each of those are the progenitors of
• 24:44
  Speaker 1: a star, and so what you end up with instead
• 24:46
  Speaker 1: of a big cloud of gas and dust, is then
• 24:48
  Speaker 1: just a bunch of stars. And interestingly, all the gas
• 24:51
  Speaker 1: and dust that didn't get gathered into a star gets
• 24:55
  Speaker 1: blown out of the cluster because of the radiation from
• 24:58
  Speaker 1: those stars. So sort of like musical chairs, like you
• 25:01
  Speaker 1: gotta find a star to join, and if you don't,
• 25:03
  Speaker 1: then the radiation just like blows you away and you're
• 25:06
  Speaker 1: alone forever. You're just floating out there destined to be
• 25:11
  Speaker 1: you know, in some next generation of stars, maybe the
• 25:14
  Speaker 1: fourth or the fifth time around, you'll win the game
• 25:16
  Speaker 1: of musical stars and you'll get to burn brightly in
• 25:19
  Speaker 1: the universe. I don't know though, if gas really wants
• 25:21
  Speaker 1: to be part of a star and get fused into
• 25:23
  Speaker 1: something heavy, or if it's happy just the way it is. Well,
• 25:26
  Speaker 1: some of us are loaners, and so you know, I'm
• 25:28
  Speaker 1: glad there's lots of options out there for the dust particles,
• 25:30
  Speaker 1: and I hope they'll get what they want. I like
• 25:32
  Speaker 1: the introvert extrovert theory of gas. That's nice. Well, I
• 25:37
  Speaker 1: study animal behavior. So, so about how many stars are
• 25:41
  Speaker 1: in this particular cluster. So the high these clusters sort
• 25:44
  Speaker 1: of like a big spherical blob, and right now it
• 25:46
  Speaker 1: has hundreds of stars in it. And as we said earlier,
• 25:49
  Speaker 1: probably all these stars around the similar age, and they
• 25:52
  Speaker 1: come from the same cloud and so that the same
• 25:54
  Speaker 1: sort of chemical makeup. And interestingly, we think, based on
• 25:59
  Speaker 1: the light that comes from these stars, that there's more
• 26:02
  Speaker 1: metals in those stars than there is in sort of
• 26:05
  Speaker 1: our stellar neighborhood. So you told us that astronomers think
• 26:08
  Speaker 1: anything more than helium is a metal, right, So that
• 26:12
  Speaker 1: might not mean what I think it means. Does that
• 26:15
  Speaker 1: just mean it has less helium and hydrogen? Yeah, when
• 26:18
  Speaker 1: a star is formed, it's usually it is mostly hydrogen
• 26:21
  Speaker 1: and helium, and that's really what the star starts to burn,
• 26:24
  Speaker 1: because stars are factories for turning helium and hydrogen into
• 26:28
  Speaker 1: heavier elements. But of course they often come with some
• 26:32
  Speaker 1: left over remnants of previous stars, and at the beginning
• 26:35
  Speaker 1: of a star's lifetime, those heavy elements just sort of
• 26:37
  Speaker 1: hang out and get hot. If the star burns long
• 26:40
  Speaker 1: enough so that they can fuse those heavier elements. Then
• 26:43
  Speaker 1: eventually they can participate in the star itself. One thing
• 26:46
  Speaker 1: we can do is we can measure the emissions from
• 26:49
  Speaker 1: those elements. We can look at a star, we can
• 26:51
  Speaker 1: see in what frequencies it's sending us light, and that
• 26:55
  Speaker 1: those frequencies tell us what the star is made out of,
• 26:58
  Speaker 1: because different elements glow with different colors. Like if you
• 27:01
  Speaker 1: remember middle school chemistry, you probably got to put like
• 27:04
  Speaker 1: weird chemicals and a bunsen burner and see the flame
• 27:07
  Speaker 1: turn green or blue or whatever. Chemistry. That's part of chemistry,
• 27:11
  Speaker 1: you know, the whiz bang factor. And so we can
• 27:13
  Speaker 1: do the same thing with stars. You say, oh, this
• 27:15
  Speaker 1: one is burning green, that has more copper in it. Whatever.
• 27:18
  Speaker 1: And so this tells you, like the particular context of
• 27:21
  Speaker 1: the neighborhood wherever the high these cluster was when it
• 27:23
  Speaker 1: was born, happen to have more medals in it because
• 27:27
  Speaker 1: it just happened to have like more compost from other
• 27:30
  Speaker 1: stars that had blown up and spread those medals into
• 27:33
  Speaker 1: the universe. Interesting, I'm trying to figure out a hippie
• 27:37
  Speaker 1: joke or something about composting, but it's just not it's
• 27:40
  Speaker 1: not coming together. It's a cycle of life or something,
• 27:43
  Speaker 1: or the cycle of star life. Yes, the cycle of
• 27:46
  Speaker 1: star life. And as you look at these clusters, you
• 27:48
  Speaker 1: can also compare them to the other clusters nearby, and
• 27:51
  Speaker 1: I can tell you more of like the story of
• 27:53
  Speaker 1: what happened. I feel like this is sort of like
• 27:55
  Speaker 1: space archaeology, you know, wondering like how did this form
• 27:59
  Speaker 1: and what was going on here? While the high these
• 28:01
  Speaker 1: cluster is near another cluster where there similarly difficult to
• 28:05
  Speaker 1: pronounce a name. It might be Presepi, but it has
• 28:08
  Speaker 1: similar metallicity and it's sort of moving in the same direction.
• 28:12
  Speaker 1: So they might have been formed together like one big
• 28:14
  Speaker 1: mega cluster and then gotten split up by title forces,
• 28:18
  Speaker 1: by the gravitational forces of the Milky Way, into two
• 28:21
  Speaker 1: separate clusters. Or they could have just come from the
• 28:23
  Speaker 1: same neighborhood which had like the same sort of leftover
• 28:26
  Speaker 1: bits of stars. But all these things are remnants, you know,
• 28:30
  Speaker 1: sort of like when you see a church and it's
• 28:32
  Speaker 1: built on top of the foundations of something else, which
• 28:35
  Speaker 1: is built on top of the foundations of something else.
• 28:36
  Speaker 1: It's like ten layers deep of human history. There that's
• 28:40
  Speaker 1: sort of what we're looking at when we're looking at
• 28:41
  Speaker 1: the stars. There's so many generations of cosmic dramatic history,
• 28:46
  Speaker 1: and yet you have to try to disentangle it from
• 28:49
  Speaker 1: light years away. It remains amazing to me that we
• 28:51
  Speaker 1: know anything at all about the night sky. And you
• 28:53
  Speaker 1: asked a really interesting question earlier about how we can
• 28:56
  Speaker 1: know that these things are happening because we're seeing them
• 28:58
  Speaker 1: in slow motion. I think that's a really important question,
• 29:01
  Speaker 1: because you're right. We can't like look at one star
• 29:04
  Speaker 1: and see its whole life cycle and say, Okay, we
• 29:06
  Speaker 1: saw it get born, and we saw burn, and we
• 29:08
  Speaker 1: saw it die. All we can do is look at
• 29:10
  Speaker 1: lots of different examples. It's sort of like if you
• 29:12
  Speaker 1: look at a town and you see there are kids,
• 29:15
  Speaker 1: and there are teenagers, and there are grown ups, and
• 29:17
  Speaker 1: there are people who are old and dying, and then
• 29:19
  Speaker 1: you can sort of put together the lifespan of a human,
• 29:22
  Speaker 1: even though you don't ever get to see a human
• 29:24
  Speaker 1: go through the whole cycle just from one snapshot. That's
• 29:27
  Speaker 1: sort of what we're doing in the night sky. We
• 29:29
  Speaker 1: don't get to see a star's entire life cycle, and
• 29:32
  Speaker 1: we definitely don't get to see an open clusters entire cycle.
• 29:35
  Speaker 1: But we can sort of put the story together by
• 29:37
  Speaker 1: looking at lots of them. And as you said earlier,
• 29:39
  Speaker 1: there's like more than a thousand of them, So that
• 29:41
  Speaker 1: gives us a pretty good picture what's going on in
• 29:44
  Speaker 1: terms of the dynamics. And so when these clusters go away,
• 29:48
  Speaker 1: do they go away because the stars die, or do
• 29:51
  Speaker 1: they go get pulled aparts and sort of spread out
• 29:53
  Speaker 1: in the night sky? What what happens to these clusters
• 29:56
  Speaker 1: as time goes on. It depends a little on the age.
• 29:59
  Speaker 1: Sometimes of the cluster lasts a long time. Then the
• 30:01
  Speaker 1: stars can live their whole life in the cluster and
• 30:04
  Speaker 1: never have to leave. But the rest of the Milky
• 30:06
  Speaker 1: Way is tugging on these things. Remember that there's rarely
• 30:09
  Speaker 1: strong gravitational forces from the center of the Milky Way.
• 30:12
  Speaker 1: All of these stars, they're not just hanging out in space.
• 30:15
  Speaker 1: They're zooming through space because they're whirling around the galaxy,
• 30:19
  Speaker 1: which is spinning. That means that there's a very strong
• 30:21
  Speaker 1: gravitational force towards the center of the galaxy, but their
• 30:25
  Speaker 1: velocity keeps them from falling into it, sort of like
• 30:27
  Speaker 1: the way the Earth doesn't fall into the Sun because
• 30:30
  Speaker 1: it's moving so fast, and so these stars are getting
• 30:33
  Speaker 1: pulled on by the gravity of the Milky Way, but
• 30:35
  Speaker 1: doesn't pull on all of them equally. Some of them
• 30:38
  Speaker 1: are closer to the center and some of them are
• 30:39
  Speaker 1: further from the center, so they're effectively getting pulled apart,
• 30:43
  Speaker 1: and we call it tidal forces. Anytime gravity is pulling
• 30:46
  Speaker 1: on one part of something with a different force than
• 30:49
  Speaker 1: it pulls on the other part of it, effectively it's
• 30:51
  Speaker 1: pulling it apart. So we call those tidal forces. And
• 30:55
  Speaker 1: the Milky Way is doing that to the open cluster,
• 30:57
  Speaker 1: just like us doing it to everything else. Is trying
• 30:59
  Speaker 1: to basically pull it apart. So if you we're living
• 31:03
  Speaker 1: on a habitable planet and it could be anywhere in
• 31:06
  Speaker 1: the Solar System, would you not want your habitable planet
• 31:09
  Speaker 1: to be in a cluster because it's getting pulled on
• 31:12
  Speaker 1: a lot, and you'd be more likely to, I don't know,
• 31:15
  Speaker 1: get thrown out of whack. Or is it not more
• 31:17
  Speaker 1: chaotic there than other places? These things are denser than
• 31:20
  Speaker 1: other places, So the rest of the Milky Way sort
• 31:22
  Speaker 1: of less dense in terms of stars, like in our
• 31:25
  Speaker 1: neighborhood of the Milky Way, it's like one star every
• 31:27
  Speaker 1: three or four cubic light years, so not very dense,
• 31:31
  Speaker 1: whereas in the center of a globular cluster, for example,
• 31:34
  Speaker 1: there's like one star every cubic light year, so they're
• 31:36
  Speaker 1: much closer to each other. Normally, that doesn't really affect
• 31:40
  Speaker 1: you because like that's still really far away, like a
• 31:42
  Speaker 1: light year is a big distance. However, it really can
• 31:45
  Speaker 1: affect you because if stars are near each other, they
• 31:48
  Speaker 1: can perturb each other's Solar system. So, for example, if
• 31:52
  Speaker 1: another star came close to our Sun, it might knock
• 31:55
  Speaker 1: some things in the or cloud out. This this huge
• 31:59
  Speaker 1: cloud of lillions of icy objects orbiting really far from
• 32:02
  Speaker 1: the Sun. If one of them gets knocked out of orbit,
• 32:05
  Speaker 1: you can fall into the Solar system and become a comet.
• 32:08
  Speaker 1: And sometimes those things smack into planets, causing catastrophes. Yeah,
• 32:14
  Speaker 1: so it's not great actually to have neighbors. You want
• 32:17
  Speaker 1: to live out in the middle of nowhere, and this
• 32:19
  Speaker 1: neighbors maybe getting a little bit too close. We should
• 32:22
  Speaker 1: see if they're following all the h O rules exactly.
• 32:26
  Speaker 1: Probably they're coming up and they're saying, hey, you'r or
• 32:28
  Speaker 1: cloud is out of whack, and you're like, hey, that's
• 32:30
  Speaker 1: because you came too close. Get out of here. It's
• 32:32
  Speaker 1: your phone. You're gonna have to pay for the property
• 32:36
  Speaker 1: damage if a comet gets too close, exactly. And so
• 32:39
  Speaker 1: living in the center of a stellar cluster and open
• 32:41
  Speaker 1: cluster or a globular cluster probably not great for life
• 32:45
  Speaker 1: because you could probably get more common bombardments. Got it.
• 32:48
  Speaker 1: It's a dangerous place out there on long time scales.
• 32:51
  Speaker 1: So what is Hyades is history? How old is it
• 32:54
  Speaker 1: and is it breaking up a lot right now or
• 32:56
  Speaker 1: is it still pretty well held together so high these
• 32:59
  Speaker 1: we think is around six hundred million years old, which
• 33:02
  Speaker 1: is pretty old for one of these clusters. We think
• 33:05
  Speaker 1: that usually these clusters only last for like fifty to
• 33:08
  Speaker 1: a hundred million years before basically they get pulled apart
• 33:11
  Speaker 1: and they just become dissolved into the background structure of
• 33:14
  Speaker 1: the Milky Way. So this one is pretty old, which
• 33:16
  Speaker 1: means probably it started out really big and really massive,
• 33:20
  Speaker 1: and while we're looking at is sort of like the
• 33:22
  Speaker 1: leftover bits. What's been able to resist those tidal forces
• 33:26
  Speaker 1: for six hundred million years. That's incredible because that's not
• 33:30
  Speaker 1: just a little bit longer than usual. That's longer than usual.
• 33:33
  Speaker 1: So we've got a thousand data points. Is six hundred
• 33:36
  Speaker 1: million years old and extreme value? Are we lucky to
• 33:39
  Speaker 1: live next to this extreme open cluster? Or is there
• 33:42
  Speaker 1: a lot of variability around that fifty to one hundred
• 33:44
  Speaker 1: million years? There is a lot of variability, though they
• 33:47
  Speaker 1: tend to peek at much smaller values, so six hundred
• 33:50
  Speaker 1: is pretty rare that we have seen some up to
• 33:52
  Speaker 1: like maybe a billion if they're really really massive. But
• 33:55
  Speaker 1: this suggests the high these is definitely on the more
• 33:58
  Speaker 1: massive end of clusters. All right, Well, so we opened
• 34:02
  Speaker 1: by saying what's happening to Hyades? Which suggests that something
• 34:05
  Speaker 1: interesting is happening to Hyades. So let's make everybody wait
• 34:08
  Speaker 1: when we take a break before we get back to
• 34:11
  Speaker 1: the big question. And we're back. So, now that we've
• 34:26
  Speaker 1: all learned about Hyades background, we all, you know, are
• 34:30
  Speaker 1: sort of emotionally attached to it. But you told us
• 34:32
  Speaker 1: that something is happening to it, which we all hope
• 34:34
  Speaker 1: is nothing bad. What is happening to Hyades? So what
• 34:38
  Speaker 1: you usually happens to these clusters is that they get
• 34:40
  Speaker 1: pulled apart by the galaxy, right and usually tidal forces
• 34:43
  Speaker 1: have a very distinctive effect on something. They tend to
• 34:46
  Speaker 1: pull it apart into long strands, and so you get
• 34:49
  Speaker 1: like a forward tail and a trailing tail instead of
• 34:52
  Speaker 1: just being a blob that like pulls the closer bits
• 34:55
  Speaker 1: harder and doesn't pull on the back bits as hard.
• 34:58
  Speaker 1: So it gets sort of like stretched out. You get
• 35:00
  Speaker 1: these really long tails, and so that's what typically happens
• 35:03
  Speaker 1: to these clusters. They get stretched out and eventually dispersed.
• 35:06
  Speaker 1: And so people have been studying the high these cluster
• 35:10
  Speaker 1: and they see these tails, but one of these tails
• 35:13
  Speaker 1: is missing. The trailing tails seems to sort of have
• 35:16
  Speaker 1: been like chopped off. WHOA where did it go. It's
• 35:19
  Speaker 1: like finding a lizard in nature and be like, oh,
• 35:22
  Speaker 1: somebody took a bite out of this one, right right,
• 35:24
  Speaker 1: the predator got him. Yeah. And so what that means
• 35:27
  Speaker 1: is that there's something big out there that's disrupting this thing.
• 35:30
  Speaker 1: It's not just the normal process of the galaxy tearing
• 35:34
  Speaker 1: this thing apart gently. Something sort of more brutal is happening.
• 35:37
  Speaker 1: And I say more brutal as a direct quotation from
• 35:40
  Speaker 1: one of these astronomy papers I read. And when astronomers say,
• 35:43
  Speaker 1: you know who are used to like stars burning and
• 35:46
  Speaker 1: exploding and supernovas. When they say something's brutal, you know,
• 35:49
  Speaker 1: it's pretty severe. I'm scared. What is the brutal thing
• 35:52
  Speaker 1: that's happening? Do they know? We don't know exactly because
• 35:55
  Speaker 1: all we can do is measure the gravity, right. What
• 35:57
  Speaker 1: we know is that these things are disrupted by grab,
• 36:00
  Speaker 1: of course, the gravity of the galactic center. But here
• 36:02
  Speaker 1: there's some new source of gravity. Something else is tugging
• 36:06
  Speaker 1: on this thing, and it's like slurred up the tail
• 36:09
  Speaker 1: of this cluster, it's like gobbled it up. And so
• 36:11
  Speaker 1: there's some massive invisible structure out there that's tearing the
• 36:16
  Speaker 1: high these cluster apart. So why don't the clumps get
• 36:19
  Speaker 1: like pulled away and then form something bigger? Where where
• 36:22
  Speaker 1: are they going? Yeah, that's a great question. It depends
• 36:25
  Speaker 1: on the sort of the shape of this new thing
• 36:27
  Speaker 1: that's pulling on them. It's possible that it's just sort
• 36:29
  Speaker 1: of like yanks them out, and they get tossed out
• 36:32
  Speaker 1: because of their high velocity, into some new direction and
• 36:35
  Speaker 1: they can't necessarily like coalesce around this new heavy, invisible object.
• 36:39
  Speaker 1: But in order to tear this thing apart. It needs
• 36:42
  Speaker 1: to be some object that has like ten million times
• 36:45
  Speaker 1: the mass of the Sun, so it's much more massive
• 36:48
  Speaker 1: than the entire cluster, and we can't see it, and
• 36:51
  Speaker 1: we can't see it directly. When we look, we don't
• 36:53
  Speaker 1: see anything there, and that of course suggests that it
• 36:56
  Speaker 1: might be something really fascinating, like you know, a supermassive
• 37:01
  Speaker 1: black hole that somehow escaped its galaxy and it isn't
• 37:04
  Speaker 1: surrounded by you know, glowing accretion disks and other stars.
• 37:08
  Speaker 1: Or it could be like a huge blob of dark matter.
• 37:11
  Speaker 1: WHOA which one do we think it is? Are those
• 37:14
  Speaker 1: equally plausible? I think it's more likely to be dark matter,
• 37:17
  Speaker 1: although you know, it's a bit of a catch all.
• 37:20
  Speaker 1: Like every time we say, oh, there's gravity, and we
• 37:23
  Speaker 1: can see the gravitational effects because we see it tugging
• 37:26
  Speaker 1: on the stars, we don't see anything there. Then we say, okay,
• 37:29
  Speaker 1: there's some invisible matter, and it's easy to say, well,
• 37:32
  Speaker 1: that must be dark matter, sort of like the go
• 37:34
  Speaker 1: to explanation for a black hole to be like ejected
• 37:38
  Speaker 1: from its galaxy or to lose all of its stars.
• 37:41
  Speaker 1: That could happen. Also, if you get two galaxies that
• 37:43
  Speaker 1: merge and then one of them gobbles all these stars
• 37:46
  Speaker 1: and the other ones sort of orbit each other for
• 37:48
  Speaker 1: a while, but then one of them gets ejected. But
• 37:50
  Speaker 1: it's much less likely to happen. So I think dark
• 37:53
  Speaker 1: matter is the sort of current best explanation that we
• 37:56
  Speaker 1: don't have any direct evidence that it is dark matter. Okay,
• 37:59
  Speaker 1: how do we know any of this? Yeah, we can
• 38:01
  Speaker 1: only see this stuff because of the gravitational effects, right,
• 38:04
  Speaker 1: So what we do is we look at the path
• 38:06
  Speaker 1: of all of these stars really, really carefully and really
• 38:09
  Speaker 1: accurately in order to try to understand these dynamics. And
• 38:12
  Speaker 1: we're actually entering a really exciting era in astronomy where
• 38:16
  Speaker 1: we're getting much more precise pictures of what's going on
• 38:19
  Speaker 1: in the Milky Way. We talked earlier about how we
• 38:22
  Speaker 1: look at the stars is sort of like a two
• 38:23
  Speaker 1: D screen in the sky. It takes it sort of
• 38:25
  Speaker 1: like mental gymnastics to remember that it's three dimensions. Well,
• 38:29
  Speaker 1: recently we've launched some telescopes that really help us build
• 38:32
  Speaker 1: that three D map of the Milky Way. This is
• 38:34
  Speaker 1: this thing called the Gaia satellite, whose entire job is
• 38:37
  Speaker 1: essentially just to map the Milky Way really really precisely.
• 38:41
  Speaker 1: Is that a NASA project or did somebody else launch it?
• 38:44
  Speaker 1: That's from the European Space Agency, so thanks to our
• 38:47
  Speaker 1: European colleagues, and they launched it in two thousand thirteen.
• 38:50
  Speaker 1: Has two really powerful telescopes on it, and so what
• 38:53
  Speaker 1: it does is it focuses on a star and it
• 38:55
  Speaker 1: can measure the brightness of the star. But because has
• 38:57
  Speaker 1: two telescopes, it can also do parallax. It sort of
• 39:00
  Speaker 1: sort of like looking at the sky with binoculars. So
• 39:02
  Speaker 1: it measures the angular precision, the distance, and the brightness
• 39:06
  Speaker 1: really really accurately. And it also measures the velocity of
• 39:10
  Speaker 1: those stars. Because we can look at the spectrum of
• 39:12
  Speaker 1: the light that comes from the stars, we can say
• 39:15
  Speaker 1: what frequency are the photons that come from those stars,
• 39:19
  Speaker 1: and based on this frequency, we can measure the speed
• 39:21
  Speaker 1: of the stars from the Doppler shift on those photons.
• 39:25
  Speaker 1: Stars that are moving away from us really really fast
• 39:27
  Speaker 1: tend to be more red shifted. Stars that are moving
• 39:30
  Speaker 1: towards us get blue shifted. So as a result, we
• 39:33
  Speaker 1: can build this incredible map of the Milky Way with
• 39:36
  Speaker 1: really high precision. So having two telescopes helps us do
• 39:39
  Speaker 1: all of that. Are these two telescopes like Hubble sized
• 39:43
  Speaker 1: or much smaller. They're not nearly Hubble sized. Remember, anything
• 39:46
  Speaker 1: that we launched in the space is sort of limited
• 39:48
  Speaker 1: because you can only fit an object of a certain
• 39:50
  Speaker 1: size into our rocket. Unfortunately, so neither of them are
• 39:53
  Speaker 1: Hubble class telescopes. But together they can really make this
• 39:57
  Speaker 1: very accurate map of the universe. And it's not just
• 40:00
  Speaker 1: a three D map. It's sort of like a four
• 40:02
  Speaker 1: D map because not only do you know where all
• 40:05
  Speaker 1: the stars are now, but you can tell where they
• 40:08
  Speaker 1: are going. Right, You can tell their velocity, which tells
• 40:11
  Speaker 1: you something about their direction. And that's really exciting because
• 40:14
  Speaker 1: it gives you this picture of the Milky Way as
• 40:17
  Speaker 1: that dynamic entity. Right. It's like looking at all the
• 40:19
  Speaker 1: water droplets in that white water river and knowing which
• 40:22
  Speaker 1: direction they're going, and also gives you a sense for
• 40:25
  Speaker 1: like the snapshot that we have of this crazy chaotic
• 40:28
  Speaker 1: galaxy that's swirling around us. That is incredible. And so
• 40:32
  Speaker 1: it's been out there for less than a decade, but like,
• 40:35
  Speaker 1: you know, eight years or something, how many stars has
• 40:38
  Speaker 1: it mapped so far? It has a map of a
• 40:41
  Speaker 1: billion stars. It's incredible, and it's you know, it's really
• 40:45
  Speaker 1: a new era of astronomy. And every time I talk
• 40:48
  Speaker 1: to astronomers about what they're doing, they're always talking about
• 40:51
  Speaker 1: this data set. You know, they can use this to
• 40:53
  Speaker 1: measure things they could never measure before, to observe effects
• 40:56
  Speaker 1: that they could never study before. You know, I know
• 40:58
  Speaker 1: people here you see Irvine that are studying like how
• 41:00
  Speaker 1: often do we get asteroids impacting on the Earth and
• 41:04
  Speaker 1: can we tell if that's because other stars come nearby?
• 41:07
  Speaker 1: And they can use this guy a data set to
• 41:09
  Speaker 1: like look at the history of stars. So this one's
• 41:12
  Speaker 1: going in that direction. It must have come by our
• 41:14
  Speaker 1: solar system a few million years ago. It's kind of
• 41:16
  Speaker 1: really interesting studies. And so it's it's like we've been
• 41:19
  Speaker 1: looking at a flat screen and now we're getting like
• 41:22
  Speaker 1: the four D picture of the galaxy. We've got our
• 41:24
  Speaker 1: three D goggles and we're ready. And so it sounds
• 41:27
  Speaker 1: like these data are just available to anyone and will
• 41:30
  Speaker 1: be available a thousand years later when people want some
• 41:33
  Speaker 1: like background data to work with. Yeah, because it's the
• 41:36
  Speaker 1: s A, it means that it's available so and we
• 41:38
  Speaker 1: can go and download the data and analyze it. And
• 41:40
  Speaker 1: get in your computer a four D picture of the galaxy.
• 41:43
  Speaker 1: And that's how we're making these really interesting discoveries, like
• 41:46
  Speaker 1: looking at the high these cluster and be like, oh,
• 41:49
  Speaker 1: something is chomping on this tail. Is that something where
• 41:52
  Speaker 1: like if you knew where to look in the night sky,
• 41:54
  Speaker 1: you could pull up the e s A data and
• 41:56
  Speaker 1: you could see a tail sort of disappearing. That's exactly
• 41:59
  Speaker 1: what happened. And then so these astronomers that made this discovery,
• 42:02
  Speaker 1: that's just what they did. They looked at the guide
• 42:04
  Speaker 1: data for the Hyades cluster and they tried to find
• 42:06
  Speaker 1: these tails, and they noticed that this backwards tail was missing.
• 42:10
  Speaker 1: And there's no like really big cloud of gas or
• 42:12
  Speaker 1: other star cluster nearby that could provide this dramatic gravity.
• 42:17
  Speaker 1: And so it's cool because you can think about these
• 42:19
  Speaker 1: stars is sort of like tracers. You know, there's a
• 42:22
  Speaker 1: lot more going on in the galaxy than just the
• 42:25
  Speaker 1: things we can see, but the stars are affected by
• 42:27
  Speaker 1: those because of the gravity of the rest of the galaxy.
• 42:30
  Speaker 1: So you can think of the stars is like giving
• 42:32
  Speaker 1: us a sense for the currents of mass that are
• 42:35
  Speaker 1: flowing through the galaxy and anytime they're moving in a
• 42:38
  Speaker 1: way that we don't understand that tells you there's something there.
• 42:41
  Speaker 1: So is this like I guess my question was more like,
• 42:43
  Speaker 1: is this like Google Maps where I can just sort
• 42:45
  Speaker 1: of like plup my little guy down wherever I want
• 42:48
  Speaker 1: in space? Or is it? Is it more of like
• 42:51
  Speaker 1: an Excel sheet with zeros and ones and you need
• 42:53
  Speaker 1: to know what you're looking for to see that there's
• 42:55
  Speaker 1: a tail there. Yeah, it's more like an Excel sheet.
• 42:57
  Speaker 1: You have to be a little bit familiar with data
• 43:00
  Speaker 1: ealysis techniques to get a handle on it. I don't
• 43:02
  Speaker 1: think they have yet like a Google galaxy, but that
• 43:05
  Speaker 1: would be pretty awesome. You can zoom through the galaxy
• 43:07
  Speaker 1: and look at all the stars. Yeah, that would be great,
• 43:10
  Speaker 1: and then we can see, you know, what aliens are
• 43:11
  Speaker 1: watering their law on today. That sounds great, but whatever
• 43:15
  Speaker 1: is happening to these stars is pretty dramatic. And you know,
• 43:17
  Speaker 1: if these stars are getting yanked out of this cluster,
• 43:20
  Speaker 1: it's a pretty serious force. And so the dynamics of
• 43:22
  Speaker 1: what's happening there could be very dramatic. For those solar systems.
• 43:26
  Speaker 1: They could get like briefly very close to each other
• 43:28
  Speaker 1: and both like induce lots of common rains on the
• 43:31
  Speaker 1: inner planets in their solar systems, or even lose some
• 43:34
  Speaker 1: of their planets if they get close enough each other
• 43:36
  Speaker 1: to like steal planets from each other. So next time
• 43:39
  Speaker 1: you're looking up at the night sky, remember that you're
• 43:41
  Speaker 1: not looking at a flat screen. You're looking at a
• 43:44
  Speaker 1: four dimensional view, a huge three D starscape that's evolving
• 43:49
  Speaker 1: in time, that's crashing and smashing and flowing and doing
• 43:53
  Speaker 1: all sorts of crazy things. And now we have a
• 43:55
  Speaker 1: pretty good picture for what's out there and where it's going.
• 43:59
  Speaker 1: Kid one is going to have a long lesson the
• 44:00
  Speaker 1: next time we look at the Ryan, just be glad
• 44:03
  Speaker 1: your arms are long enough to point it out. I
• 44:09
  Speaker 1: am all right. Thanks for joining us, everybody, and thank
• 44:11
  Speaker 1: you Kelly for guest hosting today. Thanks for a fun afternoon.
• 44:14
  Speaker 1: Have a good one, Daniel, alright, tune in next time.
• 44:17
  Speaker 1: Thanks everybody, thanks for listening, and remember that Daniel and
• 44:27
  Speaker 1: Jorge Explain the Universe is a production of I Heart Radio.
• 44:31
  Speaker 1: For more podcast for my Heart Radio, visit the I
• 44:34
  Speaker 1: Heart Radio app, Apple Podcasts, or wherever you listen to
• 44:38
  Speaker 1: your favorite shows.