Latest / Daniel and Kelly’s Extraordinary Universe / What does the center of the galaxy look like?

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What does the center of the galaxy look like? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, or hey, does the town you live in have
• 0:10
  Speaker 1: a real center, like a downtown.
• 0:13
  Speaker 2: It does, Yeah, it has a little kind of town
• 0:15
  Speaker 2: square where everyone hangs out. There's also downtown LA which
• 0:19
  Speaker 2: is about ten minutes away.
• 0:20
  Speaker 1: And does anybody ever go to downtown La? Is it
• 0:22
  Speaker 1: like a destination?
• 0:24
  Speaker 2: Kind of? Sometimes we just went to like a science
• 0:26
  Speaker 2: festival there, but not typically it's pretty rare.
• 0:29
  Speaker 1: I guess it's also like the center of traffic in LA. Yeah.
• 0:34
  Speaker 1: What about Irvine? Irvine has no center. It's just one
• 0:38
  Speaker 1: hundred percent pure sprawl.
• 0:40
  Speaker 2: It's all edges, it's.
• 0:41
  Speaker 1: All parking lots and shopping centers.
• 0:43
  Speaker 2: So if you find yourself in the middle of a
• 0:45
  Speaker 2: parking lot all of a sudden, you might be totally lost.
• 0:48
  Speaker 1: It's actually the law in Irvine that everything is legally
• 0:51
  Speaker 1: required to be exactly identically bland, even the people. We're
• 0:55
  Speaker 1: all beige down here because of the sunshine in.
• 0:57
  Speaker 3: More ways than one.
• 1:13
  Speaker 2: Hi. I'm Poorgammy, cartoonist and the creator of PhD comics. Hi,
• 1:17
  Speaker 2: I'm Daniel.
• 1:17
  Speaker 1: I'm a particle physicist and a professor. You see Irvine,
• 1:21
  Speaker 1: and I've learned to distinguish fifty shades of beige.
• 1:24
  Speaker 2: Sounds like a fan fiction version of fifty Shades of Gray,
• 1:28
  Speaker 2: but less seamy.
• 1:31
  Speaker 1: Totally safe for work. When we moved into our house
• 1:34
  Speaker 1: in Irvine, real story, they gave us a set of
• 1:37
  Speaker 1: options of the colors, and at the topa said color
• 1:39
  Speaker 1: makes a world of difference, and then there were four
• 1:42
  Speaker 1: shades of beige you could choose from.
• 1:44
  Speaker 2: Wow, that's a lot of options of beige. So you
• 1:47
  Speaker 2: can't paint your house green if you wanted to.
• 1:49
  Speaker 1: No, we are restricted from painting our house various colors.
• 1:52
  Speaker 1: We actually once did paint our garage crazy rainbow stripes,
• 1:56
  Speaker 1: and we've got a stern letter M.
• 1:58
  Speaker 2: And what happens if you don't change it.
• 2:00
  Speaker 1: They repaint it for you, and then they send you
• 2:01
  Speaker 1: the bill.
• 2:03
  Speaker 2: The city will send them a painter to your house.
• 2:06
  Speaker 2: Sounds very nineteen eighty fourge.
• 2:08
  Speaker 1: That's why all the exciting stuff that's happening in Irvine
• 2:10
  Speaker 1: is happening inside people's houses.
• 2:12
  Speaker 2: Oh, fifty shades of hidden page. But anyways, Welcome to
• 2:17
  Speaker 2: our podcast Daniel and Jorge Explain the Universe, a production
• 2:20
  Speaker 2: of iHeartRadio.
• 2:21
  Speaker 1: In which we try to illuminate all the amazing shades
• 2:24
  Speaker 1: of meaning and nuance in the universe. We go all
• 2:27
  Speaker 1: the way from black holes to white dwarfs and everything
• 2:31
  Speaker 1: in between. The incredible color and ferocity of the processes
• 2:35
  Speaker 1: in the universe, the intensity in the screaming jets, from
• 2:38
  Speaker 1: the centers of galaxies to the very quiet outer edges
• 2:42
  Speaker 1: of stellar clusters. We talk about all of it. We
• 2:45
  Speaker 1: dig into every little bit of it. We touch on
• 2:47
  Speaker 1: our curiosity to understand the universe around us, and we
• 2:51
  Speaker 1: explain all of it to you.
• 2:52
  Speaker 2: That's right, because it is a pretty colorful universe, and
• 2:55
  Speaker 2: we try to paint the whole rainbow of knowledge that
• 2:58
  Speaker 2: humans have managed to figure out over Leniam about this
• 3:01
  Speaker 2: amazing universe that we live in, which is not all
• 3:05
  Speaker 2: concentrated in one place, but it's also not all evenly
• 3:08
  Speaker 2: distributed across the universe.
• 3:10
  Speaker 1: Yeah, that's right. And we look at the world around
• 3:12
  Speaker 1: us in all sorts of crazy colors, reds and greens
• 3:15
  Speaker 1: and blues.
• 3:16
  Speaker 2: But when we look.
• 3:17
  Speaker 1: Out into the wider universe, we can use other frequencies
• 3:20
  Speaker 1: of light, frequencies that don't even have color, all the
• 3:23
  Speaker 1: way down from the radio waves up to a gamma rays,
• 3:26
  Speaker 1: light that wiggles super duper fast, and light that wiggles
• 3:29
  Speaker 1: much much slower.
• 3:30
  Speaker 2: I just had this interesting conversation recently where I learned
• 3:33
  Speaker 2: that magenta is not really a color. Do you know
• 3:36
  Speaker 2: that it's just a word? What is magenta exactly? Not really? Well,
• 3:40
  Speaker 2: I guess it's not really a frequency of color. It's
• 3:43
  Speaker 2: like a color we see when you combine certain frequencies
• 3:47
  Speaker 2: in your head.
• 3:48
  Speaker 1: Oh, I see, there's no single frequency of light that
• 3:50
  Speaker 1: if you shoot it at an eyeballer person will experience magenta.
• 3:53
  Speaker 2: Yeah. Or I think related is color pink? Like, there's
• 3:56
  Speaker 2: no color pink. Isn't that true? Then for white?
• 3:58
  Speaker 1: Also, you can't have like a white light because white
• 4:00
  Speaker 1: is every frequency together. Mmm.
• 4:03
  Speaker 2: Interesting, Yeah, I guess white. Well, white was never a color.
• 4:06
  Speaker 2: What white is not a color? Wow?
• 4:11
  Speaker 1: This has quickly become a philosophy of color. Podcast Is
• 4:16
  Speaker 1: black not a color either?
• 4:17
  Speaker 2: Right? I don't know. Is it is the lack of
• 4:19
  Speaker 2: light of color? I don't know.
• 4:21
  Speaker 1: I think color is just something you experience in your mind. Anyway,
• 4:24
  Speaker 1: It's not a property of the photons.
• 4:26
  Speaker 2: Right.
• 4:26
  Speaker 1: Infrared photons and gamma ray photons don't have any color,
• 4:29
  Speaker 1: so either do photons that stimulate a green response in
• 4:33
  Speaker 1: your mind? The green is just in your head, man,
• 4:35
  Speaker 1: so is magenta, so is black, So as white. Color
• 4:38
  Speaker 1: is just an experience. So beige is also just in
• 4:41
  Speaker 1: your head. Nothing to complain about.
• 4:44
  Speaker 2: No, now you run the beige within me. Ah, that
• 4:49
  Speaker 2: is my fault. You are beige inside and out, Daniel,
• 4:53
  Speaker 2: Oh my.
• 4:54
  Speaker 1: God, all this time I thought I'd escape the bigeness.
• 4:56
  Speaker 2: But you're right, Irvine has gone into you. It's seeped
• 4:59
  Speaker 2: into your por and you're Europe. I'm beage through and through,
• 5:03
  Speaker 2: that's what you're saying. But anyways, and there are a
• 5:05
  Speaker 2: lot of colors out there in the universe, but it's
• 5:08
  Speaker 2: not all evenly disturbed. Like if you look out into
• 5:10
  Speaker 2: the night sky, you don't see it just all light.
• 5:12
  Speaker 2: There are patches of not light and patches of intense light.
• 5:16
  Speaker 1: Yeah, as we build these technological eyeballs that can see
• 5:19
  Speaker 1: photons of various colors when we look out and use
• 5:21
  Speaker 1: it to build a map of what's out there in
• 5:23
  Speaker 1: the universe. Where are all the other stars in the universe?
• 5:26
  Speaker 1: How do they cluster together? What's going on around the corner?
• 5:30
  Speaker 1: Are we in the boring part of the universe or
• 5:32
  Speaker 1: are we at the hopping city center?
• 5:34
  Speaker 2: Yeah, where are the happening places in the universe. So
• 5:37
  Speaker 2: today on the podcast, we'll be tackling the question what
• 5:44
  Speaker 2: does the center of the galaxy look like? And more important,
• 5:48
  Speaker 2: what does it smell like? And this is the thing
• 5:51
  Speaker 2: that smells in space.
• 5:52
  Speaker 1: There are smells in space, absolutely, because there's lots of
• 5:54
  Speaker 1: fascinating organic molecules out there. Remember that whole episode we
• 5:58
  Speaker 1: did about the smells of space astronauts coming in from
• 6:01
  Speaker 1: spacewalks and reporting that their suits smelled like barbecue.
• 6:05
  Speaker 4: Mm.
• 6:06
  Speaker 2: So you're saying it space malls like death. No, space
• 6:09
  Speaker 2: smells like lunch. Space smells like you're never going to
• 6:13
  Speaker 2: breathe again if you actually smell space.
• 6:16
  Speaker 1: Yeah, that's right. And it's interesting that the galaxy has
• 6:19
  Speaker 1: a center. You know, our solar system has the center,
• 6:21
  Speaker 1: the Earth has a center, the galaxy has a center.
• 6:24
  Speaker 1: But then on a broader scale, we don't think the
• 6:26
  Speaker 1: universe has a center. And it's interesting to me as
• 6:30
  Speaker 1: a sort of human reaction. It's the sort of our
• 6:32
  Speaker 1: way of categorizing stuff, So is that we look for
• 6:35
  Speaker 1: the center of things. Lots of listeners write in and
• 6:37
  Speaker 1: ask about where is the center of the universe, Like
• 6:40
  Speaker 1: it's an important thing to understand where the center of
• 6:43
  Speaker 1: something is.
• 6:44
  Speaker 2: Yeah, I guess it's sort of a way to orient
• 6:46
  Speaker 2: yourself and know where you are relative to other things.
• 6:49
  Speaker 2: Like if you know where the center of town is,
• 6:50
  Speaker 2: and you sort of know where you are. But if
• 6:53
  Speaker 2: it was a whole ingenious population of buildings, then it'd
• 6:57
  Speaker 2: be easy to get lost or feel lost at least.
• 7:00
  Speaker 1: Yeah, that's why I still get lost in an her behind.
• 7:02
  Speaker 1: I think because there is no way to orient yourself.
• 7:05
  Speaker 1: But I think also there's a sense of origin, right,
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  Speaker 1: there's the feeling that like the most important things are
• 7:10
  Speaker 1: happening at the center, or the processes that drive the
• 7:13
  Speaker 1: formation of whatever it is you're talking about the Earth
• 7:15
  Speaker 1: or the Solar system or the galaxy are determined by
• 7:19
  Speaker 1: the stuff happening at the center. It's not usually the
• 7:21
  Speaker 1: case that the outer edges are controlling the structure of
• 7:24
  Speaker 1: the interior. Usually it's the opposite.
• 7:26
  Speaker 2: Well, unless you're California, in which case you know, Sacramento
• 7:29
  Speaker 2: is the capital of the state.
• 7:32
  Speaker 1: Oh, maybe it's the political capital, but it's definitely not
• 7:34
  Speaker 1: the center of the action, that's for sure.
• 7:37
  Speaker 2: Yeah, it is interesting everything kind of has a center
• 7:39
  Speaker 2: and I guess it has to do with gravity, right, Like,
• 7:41
  Speaker 2: gravity is basically one of the biggest laws in the universe,
• 7:44
  Speaker 2: and it sort of dictates the structure of everything, right,
• 7:47
  Speaker 2: the structure of Earth. If we didn't have gravity, Earth
• 7:49
  Speaker 2: would just be a cloud of dust. And if it
• 7:51
  Speaker 2: wasn't for gravity, the Solar system would just be a
• 7:53
  Speaker 2: cloud of dust and gas. It's kind of because of gravity.
• 7:56
  Speaker 2: Gravity is very centralizing.
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  Speaker 1: Yeah, and that's one of my favorite weird facts of
• 8:00
  Speaker 1: about the universe that even though gravity is the weakest
• 8:03
  Speaker 1: force out there by like ten to the thirty two,
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  Speaker 1: you know, it's so much weaker than all the other forces,
• 8:09
  Speaker 1: in the end, it wins, right, It's the only force
• 8:12
  Speaker 1: that can't be neutralized. It can't be balanced by opposite charges.
• 8:16
  Speaker 1: There's only positive masses and attractive gravity, at least on
• 8:19
  Speaker 1: small scales, if we're going to ignore dark energy for
• 8:21
  Speaker 1: a while. And so it clusters things together and it
• 8:25
  Speaker 1: wins the race. It's patient, and it takes forever because
• 8:28
  Speaker 1: gravity is so weak, but eventually it dominates the whole
• 8:31
  Speaker 1: structure of the universe. As you say, the reason we
• 8:34
  Speaker 1: have solar systems and galaxies and the whole larger structure
• 8:37
  Speaker 1: of the universe is because of gravity. It's in charge
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  Speaker 1: of organizing the universe.
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  Speaker 2: You think if we didn't have gravity, we would still
• 8:44
  Speaker 2: be around, Like could life of form without gravity?
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  Speaker 1: Life would definitely not have formed without gravity. Without gravity,
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  Speaker 1: we wouldn't have stars.
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  Speaker 3: Right.
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  Speaker 1: Gravity is what pulled together those clouds of gas and
• 8:56
  Speaker 1: dust into dense packets, which started fusion, which made chemical
• 9:00
  Speaker 1: elements that we use for life. And without gravity, the
• 9:03
  Speaker 1: universe would be smoother, right, Those little extra blobs of
• 9:07
  Speaker 1: over density would never have turned into very hot and
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  Speaker 1: dense stars.
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  Speaker 2: Mmm. But could life have formed anyways in some kind
• 9:15
  Speaker 2: of primordial you know, galactic gas.
• 9:18
  Speaker 1: Perhaps so, though it would be very very different from
• 9:21
  Speaker 1: any life. We imagine just after the Big Bang and
• 9:23
  Speaker 1: before stars formed, we had only hydrogen and very very
• 9:27
  Speaker 1: trace amounts of anything else, a little bit of helium
• 9:29
  Speaker 1: and the tiniest bit of heavier stuff. And it'd be
• 9:32
  Speaker 1: pretty hard to form life out of just that kind
• 9:34
  Speaker 1: of simple basic elements. It's so much harder to build
• 9:37
  Speaker 1: complicated structures like the ones that our life is based on.
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  Speaker 1: But it doesn't mean it's impossible. It just means life
• 9:43
  Speaker 1: as we know it is probably impossible.
• 9:45
  Speaker 2: Mmmm, you're saying, without gravity, the universe would be beige exactly.
• 9:50
  Speaker 2: Gravity makes things colorful. But it is an interesting question.
• 9:53
  Speaker 2: What does the center of the galaxy look like? I
• 9:56
  Speaker 2: guess we can see the center of the galaxy from Earth, right,
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  Speaker 2: I mean, we're the galaxy. We should be able to
• 10:01
  Speaker 2: sort of know where the center is.
• 10:03
  Speaker 1: Well, we can look in the direction of the center
• 10:05
  Speaker 1: of the galaxy, but the same way that you can't always,
• 10:08
  Speaker 1: like see downtown from your house in the urbs, there's
• 10:12
  Speaker 1: often stuff in the way. Right, you can't see around
• 10:14
  Speaker 1: the trees and the other buildings. The center of the
• 10:16
  Speaker 1: galaxy is actually kind of obscured by all the gas,
• 10:20
  Speaker 1: the dust, and the crazy stuff that's going on between
• 10:22
  Speaker 1: us and it, so it's not that easy to see.
• 10:25
  Speaker 4: Mm.
• 10:26
  Speaker 2: Well, as usual, we were wondering how many people out
• 10:28
  Speaker 2: there had wondered what the center of the galaxy looks
• 10:31
  Speaker 2: like and thought about what's in there.
• 10:34
  Speaker 1: So thanks very much to everybody who answers these questions
• 10:37
  Speaker 1: for this fun segment of the podcast. If you'd like
• 10:39
  Speaker 1: to hear your voice, please don't be shy. Every week,
• 10:42
  Speaker 1: somebody writes in and says that after two years of listening.
• 10:45
  Speaker 1: They're finally ready to put their hat in the ring.
• 10:48
  Speaker 1: So let that be you and write to me at
• 10:50
  Speaker 1: questions at Danielandjorge dot com.
• 10:52
  Speaker 2: So think about it for a second. What do you
• 10:54
  Speaker 2: think the center of the galaxy looks like? Here's what
• 10:57
  Speaker 2: people have to say.
• 10:58
  Speaker 4: I think if you're to take radio static and change
• 11:02
  Speaker 4: it to visual light, it would look like that.
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  Speaker 2: In terms of radio waves, I think in the middle
• 11:07
  Speaker 2: of the galaxy, I think there would be a lot
• 11:10
  Speaker 2: of radio waves, except if the black hole in the
• 11:12
  Speaker 2: middle absorbs them all. I feel like it be harder
• 11:15
  Speaker 2: to see things. I don't know, maybe the radio waves
• 11:17
  Speaker 2: get blocked by a lot of gas or you know,
• 11:20
  Speaker 2: the space space things.
• 11:23
  Speaker 4: I think the center of the galaxy is in a turmoil,
• 11:26
  Speaker 4: so it's sending out radiation on all wavelengths. So I
• 11:31
  Speaker 4: would guess that if we look at the center of
• 11:34
  Speaker 4: the galaxy in the radio wave spectrum, we should see
• 11:40
  Speaker 4: like a big bright spot.
• 11:42
  Speaker 2: All right. A lot of people seem to be talking
• 11:44
  Speaker 2: about radio, like is there radio in the center of
• 11:47
  Speaker 2: the galaxy.
• 11:50
  Speaker 1: They're tuned in their station to listen to the center
• 11:52
  Speaker 1: of the galaxy.
• 11:53
  Speaker 2: Be cool to be a galactic dj that's like a
• 11:56
  Speaker 2: cool job.
• 11:57
  Speaker 1: Sounds pretty intense. But they're on the right because when
• 12:01
  Speaker 1: we look at the center of the galaxy in the
• 12:02
  Speaker 1: visual light, it's not very easy to see anything, but
• 12:05
  Speaker 1: radio waves from the center of the galaxy can get here,
• 12:09
  Speaker 1: So radio is actually the best way to see the
• 12:11
  Speaker 1: center of the galaxy.
• 12:12
  Speaker 2: Interesting, and what kind of music do they play in
• 12:15
  Speaker 2: the center of the galaxy? Mostly fuzz, golden oldies, page oldies.
• 12:20
  Speaker 2: We're asking the deep questions today. What music does the
• 12:25
  Speaker 2: Milky Way like?
• 12:26
  Speaker 1: Of course, we can't hear the most modern Milky Way music.
• 12:29
  Speaker 1: We hear stuff that was sent to us twenty six
• 12:31
  Speaker 1: thousand years ago, so it's definitely oldies, though I don't
• 12:35
  Speaker 1: even know how gold it is.
• 12:36
  Speaker 2: Well, let's start with the basics, Daniel, take us on
• 12:38
  Speaker 2: a trip. What does it mean for the galaxy to
• 12:40
  Speaker 2: have a center?
• 12:41
  Speaker 1: So people have been trying to figure this out for
• 12:43
  Speaker 1: several hundred years. People look up at the night sky
• 12:45
  Speaker 1: and see the stars and then wonder, like, where is
• 12:48
  Speaker 1: the sun in our neighborhood. Is it just a bunch
• 12:51
  Speaker 1: of stars sprinkle out through the universe? Is there a
• 12:53
  Speaker 1: collection of stuff? Is there one spot that's more interesting
• 12:56
  Speaker 1: than another. So for the last couple hundred years, people
• 12:59
  Speaker 1: have been building the star maps and trying to gain
• 13:01
  Speaker 1: a sense of where we are. I remember, it was
• 13:04
  Speaker 1: only like one hundred years ago that we realized that
• 13:07
  Speaker 1: we were in a galaxy. That's when Hubble noticed that
• 13:09
  Speaker 1: some of the smudges that are up there in the
• 13:11
  Speaker 1: sky that look just like clouds of gas and dust,
• 13:14
  Speaker 1: are actually super duper far away. They're actually outside of
• 13:18
  Speaker 1: our galaxy. That's when we first realized that we have
• 13:21
  Speaker 1: a galaxy, this blob of stars, and that there are
• 13:23
  Speaker 1: other galaxies out there, so that our galaxy is just
• 13:26
  Speaker 1: one of many. And people have continued making maps of
• 13:29
  Speaker 1: the stars, so trying to get a picture of what
• 13:31
  Speaker 1: our galaxy looks like, which is complicated because of course
• 13:34
  Speaker 1: we're inside the galaxy, so we can't like ever step
• 13:37
  Speaker 1: outside and see what it looks like. We can only
• 13:40
  Speaker 1: map it from the inside, which is a challenge.
• 13:42
  Speaker 2: Yeah, it's interesting to think about what people thought about
• 13:45
  Speaker 2: before we need other galaxies, right, Like, are there scientific
• 13:48
  Speaker 2: papers from that time or people writing about it. Did
• 13:51
  Speaker 2: we think that we were in like a cloud of
• 13:54
  Speaker 2: stars or just an infinite space filled with stars? What
• 13:58
  Speaker 2: was the general thinking about what the rest of the
• 14:02
  Speaker 2: universe looked like before we knew there were other galaxies.
• 14:04
  Speaker 1: Yeah, it's a great question. The first sort of maps
• 14:06
  Speaker 1: were from like the late seventeen hundreds. A guy named
• 14:09
  Speaker 1: Herschel sort of drew all the stars that you could
• 14:11
  Speaker 1: see and mid like the first map of these stars
• 14:14
  Speaker 1: try to orient where the sun was, and we just
• 14:17
  Speaker 1: really couldn't see very far, so we didn't have a
• 14:19
  Speaker 1: sense for what was going on beyond that, and people
• 14:22
  Speaker 1: imagine that all of space was just filled with stars
• 14:25
  Speaker 1: that just sort of like hung out there. But then
• 14:26
  Speaker 1: people noticed this, like, oh, there's this disk in the
• 14:28
  Speaker 1: middle right where the stars get denser. So as our
• 14:31
  Speaker 1: ability to see things got better, we were able to
• 14:34
  Speaker 1: notice more and more that there was a pattern things
• 14:36
  Speaker 1: got denser in one direction, and so like in the
• 14:39
  Speaker 1: early nineteen hundreds, we have more detailed catalogs that show
• 14:42
  Speaker 1: us that the stars are not just sprinkled out through
• 14:44
  Speaker 1: the whole universe, but that there's sort of a flat
• 14:46
  Speaker 1: disc structure.
• 14:47
  Speaker 2: And this all came about because of photography. I think, right,
• 14:50
  Speaker 2: like you just look with your naked eye at the
• 14:52
  Speaker 2: night sky. You see some stars, but it's only when
• 14:54
  Speaker 2: you sort of have a photography setup and you can
• 14:57
  Speaker 2: expose a sheet of paper or photo paper for a
• 15:00
  Speaker 2: long time do you get to sort of see really
• 15:03
  Speaker 2: what's out there. Right.
• 15:04
  Speaker 1: Yeah, the name of the game is capturing more light,
• 15:07
  Speaker 1: and you can do that by longer exposure. And you
• 15:09
  Speaker 1: can also do that by having a larger aperture. So
• 15:12
  Speaker 1: building telescopes with larger light gathering capacities is also key.
• 15:17
  Speaker 1: If you're going to gather light over time, you need
• 15:18
  Speaker 1: to also track the objects. It doesn't make a smear
• 15:21
  Speaker 1: in your photograph, but both of those things are crucial.
• 15:23
  Speaker 1: Gathering light over time and having a larger aperture that
• 15:27
  Speaker 1: lets you see dimmer things which are further away things,
• 15:30
  Speaker 1: which lets you expand the sort of mental map in
• 15:32
  Speaker 1: your mind of where we are, what our cosmic neighborhood is.
• 15:36
  Speaker 2: And I guess before we would look at the Milky Way.
• 15:39
  Speaker 2: Like the Milky Way you can't see with your naked
• 15:40
  Speaker 2: eye on a super clear night, right if you are
• 15:43
  Speaker 2: in the middle of nowhere, you can see sort of
• 15:44
  Speaker 2: a white streak across the sky. Did people think that
• 15:47
  Speaker 2: that was just like some sort of galactic cloud or
• 15:50
  Speaker 2: did they have an intuition like, oh, my goodness, there's
• 15:52
  Speaker 2: tons of stars in that strip.
• 15:54
  Speaker 1: Well, once we identified other galaxies, we could study them,
• 15:57
  Speaker 1: and that gave us a lot of clues about the
• 15:59
  Speaker 1: nature of our galaxy. The same way that like, once
• 16:02
  Speaker 1: you look at other planets, you notice, oh boy, those
• 16:04
  Speaker 1: are around Probably our planet is round two really solidifies
• 16:08
  Speaker 1: the idea that planets are spears, right when you can
• 16:10
  Speaker 1: see other planets being spears. So when we could study,
• 16:13
  Speaker 1: for example, Andromeda, because we had telescopes, we could see, oh, look,
• 16:16
  Speaker 1: that looks like a big flat disc with all these
• 16:19
  Speaker 1: spiral arms. That's a very strong clue that maybe our galaxy.
• 16:22
  Speaker 2: Looks like that also.
• 16:24
  Speaker 1: And then you could look up at the night sky
• 16:25
  Speaker 1: you can see the pattern of stars, so you can
• 16:28
  Speaker 1: fit it into that shape. And in fact, our galaxy
• 16:30
  Speaker 1: looks a lot like Andromeda. I mean, it's smaller, but
• 16:33
  Speaker 1: it has roughly the same shape. It's a big elliptical
• 16:36
  Speaker 1: swirl with a central blob and a few arms that
• 16:39
  Speaker 1: spiral out.
• 16:41
  Speaker 2: So those two things sort of came about at the
• 16:42
  Speaker 2: same time, like we noticed that in this direction there's
• 16:45
  Speaker 2: a whole bunch more stars, and also, hey, we're a galaxy.
• 16:48
  Speaker 2: So maybe this direction is where the center of the
• 16:50
  Speaker 2: galaxy is.
• 16:51
  Speaker 1: Yeah, that kind of understanding really crystallized in the early
• 16:53
  Speaker 1: nineteen hundreds, and now we have a pretty good map
• 16:56
  Speaker 1: of the galaxy. Very recently, there's a spacecraft called Gaya
• 17:00
  Speaker 1: which is doing a super precise map of billions of
• 17:03
  Speaker 1: stars to give us a very accurate picture of our
• 17:05
  Speaker 1: galactic neighborhood. Un let's ask all sorts of really fun
• 17:08
  Speaker 1: interesting questions. But we now know that we live like
• 17:11
  Speaker 1: sort of halfway out from the center of the galaxy
• 17:14
  Speaker 1: along one of these spiral arms.
• 17:17
  Speaker 2: Yeah, break down what we know about the Milky Way.
• 17:20
  Speaker 2: So it's like a cluster of stars, but it's sort
• 17:24
  Speaker 2: of flat shape, right, It sort of looks like a disc,
• 17:27
  Speaker 2: but it's not a perfect disc because it's sort of
• 17:29
  Speaker 2: organized in terms of streaks or swirls.
• 17:32
  Speaker 1: Right, Yeah, it's not even a perfectly flat disc. Remember
• 17:34
  Speaker 1: we did an episode about how the Milky Way itself
• 17:37
  Speaker 1: is a little bit twisted. It's sort of like a
• 17:39
  Speaker 1: hat where it's like tilted up on one side and
• 17:41
  Speaker 1: tilted down on the other side. Maybe because of recent
• 17:44
  Speaker 1: mergers or gravitational interactions with other galaxies.
• 17:47
  Speaker 2: Wait, like a horse saddle kind of.
• 17:48
  Speaker 1: Yeah, sort of, it's like tilted up on one side
• 17:50
  Speaker 1: and tilts it down on the other side.
• 17:52
  Speaker 2: Whoa, we have like a cowboy milky way.
• 17:55
  Speaker 1: Yeah, exactly. It's got a little flare to it. So
• 17:57
  Speaker 1: that's the disc. It's mostly a disc, but this little
• 18:00
  Speaker 1: bit of a tweak to it. But then, as you say,
• 18:02
  Speaker 1: the disc itself is not perfectly smooth. We have these arms.
• 18:06
  Speaker 1: So there's like a central bulge, a big blob in
• 18:08
  Speaker 1: the center of stars, and then that's surrounded by a
• 18:11
  Speaker 1: central bar. It's like long bar of stars, which is
• 18:15
  Speaker 1: itself embedded in the nuclear bulge, which is like circular
• 18:20
  Speaker 1: blob at the very center of the galaxy.
• 18:21
  Speaker 2: Wait, what do you mean like a bar like two
• 18:23
  Speaker 2: arms that shoot straight out from the center.
• 18:25
  Speaker 1: Yeah, they're not really called arms. They're sort of short
• 18:28
  Speaker 1: compared to what we call the galactic arms themselves. But yeah,
• 18:30
  Speaker 1: it's two lines that shoot out from the center, and
• 18:33
  Speaker 1: it's embedded inside this larger nuclear bulge. So we have
• 18:37
  Speaker 1: this central bar and a nuclear.
• 18:39
  Speaker 2: Bulge sort of like if you took a pen and
• 18:41
  Speaker 2: stabbed it through an orange. That's kind of what it looks, I.
• 18:45
  Speaker 1: Guess so I think of it more like a half
• 18:47
  Speaker 1: closed eye, you know, has like a slit through it.
• 18:50
  Speaker 2: All right. So then so we're about halfway out from
• 18:53
  Speaker 2: the center to the edge.
• 18:54
  Speaker 1: Yeah, this central blob sort of looks like an eye
• 18:56
  Speaker 1: winking at you, and then you have these arms that
• 18:58
  Speaker 1: shoot out from it. The Milky Way has four of
• 19:01
  Speaker 1: these arms. They start at this nuclear bulge, either the
• 19:05
  Speaker 1: orange or the eyeball, whgever you prefer, and then they
• 19:08
  Speaker 1: streak out, they swirl around the center. And so there's
• 19:11
  Speaker 1: four of these arms. And we actually live on a
• 19:14
  Speaker 1: spur that comes off of one of those arms. We
• 19:16
  Speaker 1: don't even live on one of those arms.
• 19:19
  Speaker 2: Whoa, we're like in the suburb of the suburb exactly.
• 19:22
  Speaker 1: It's called the Orion spur. So when you're camping and
• 19:25
  Speaker 1: it's very dark and you look up at the night
• 19:27
  Speaker 1: sky and you see this white streak that we call
• 19:30
  Speaker 1: the milky Way, which you're looking at is the next
• 19:33
  Speaker 1: arm over you're looking towards the center of the galaxy
• 19:36
  Speaker 1: and you're looking at the next arm.
• 19:39
  Speaker 2: Well, you're sort of looking at all of it, aren't you, Like,
• 19:41
  Speaker 2: isn't some of that also the center of the galaxy
• 19:43
  Speaker 2: coming through and hitting your eyeballs.
• 19:45
  Speaker 1: Well, you're looking through everything, of course, and so you're
• 19:47
  Speaker 1: seeing nearby stars that are in our arm. Those are
• 19:50
  Speaker 1: the stars you see. And then you also see sort
• 19:53
  Speaker 1: of the outer edge of the next arm. But these
• 19:55
  Speaker 1: arms have gas and dust in them, and so it's
• 19:58
  Speaker 1: hard to see all the way through them. Some of
• 20:00
  Speaker 1: the light from the center also does make it through,
• 20:03
  Speaker 1: but this gas and dust is really good at obscuring
• 20:06
  Speaker 1: the light behind it, so it's very difficult to see
• 20:09
  Speaker 1: all the way through it. So none of the light
• 20:10
  Speaker 1: that hits your eyeball really is coming from the center
• 20:13
  Speaker 1: of the galaxy. It's in the direction of the center
• 20:15
  Speaker 1: of the galaxy. But you're seeing the stuff that's between
• 20:18
  Speaker 1: us and the center mostly, right. I mean, there might
• 20:21
  Speaker 1: be some light that's coming through, Yes, there might be some,
• 20:25
  Speaker 1: but visible light is really really quenched by the galactic dust.
• 20:29
  Speaker 2: All right, Well, I guess that begs the question what
• 20:31
  Speaker 2: is going on there in the center of the galaxy?
• 20:33
  Speaker 2: What can we see? And most important, at least for me,
• 20:36
  Speaker 2: is how do we know this If we're in the
• 20:38
  Speaker 2: Milky Way galaxy? How do we know what the Milky
• 20:41
  Speaker 2: Way galaxy looks like? So let's get into that, but
• 20:44
  Speaker 2: first let's take a quick break. All right, we're talking
• 20:59
  Speaker 2: about the center of the galaxy and how it's a
• 21:02
  Speaker 2: lot more exciting there. Are you suffering from some sort
• 21:04
  Speaker 2: of galactic fomo fear of missing out?
• 21:10
  Speaker 1: No, I'm pretty happy here on Earth. The galactic center
• 21:13
  Speaker 1: is kind of a crazy place, lots of pulsing, lots
• 21:16
  Speaker 1: of radiation. Not a place that I would survive very long.
• 21:19
  Speaker 2: But if you're in Irvine, that means you're in sort
• 21:20
  Speaker 2: of like the suburb of the suburb of the suburb
• 21:23
  Speaker 2: of the suburb of the galaxy.
• 21:25
  Speaker 1: Yeah, it turns out it's a pretty nice place to
• 21:26
  Speaker 1: raise kids, So I'm not too.
• 21:27
  Speaker 2: Really happy it's a super suburb. Yeah.
• 21:31
  Speaker 1: So we turn out to be about twenty six thousand
• 21:33
  Speaker 1: light years away from the center of the galaxy. The
• 21:37
  Speaker 1: whole galaxy is like one hundred thousand light years across,
• 21:40
  Speaker 1: so we're like halfway between the center and like sort
• 21:43
  Speaker 1: of the outskirts, the last visible stars.
• 21:46
  Speaker 2: And so how do you define what the center of
• 21:49
  Speaker 2: the galaxy is?
• 21:50
  Speaker 3: Like?
• 21:50
  Speaker 2: Is there a limit? Does it get super dense all
• 21:53
  Speaker 2: of a sudden as you go towards the center? Is
• 21:55
  Speaker 2: there like a ball in the middle of stars or
• 21:57
  Speaker 2: is it pretty fuzzy.
• 21:58
  Speaker 1: So there's a few ways to define it. One way
• 22:01
  Speaker 1: is the geometrical center, to say, like, here's the whole
• 22:04
  Speaker 1: Milky Way, what's literally at the center. And that's like
• 22:07
  Speaker 1: taking the United States and saying, okay, Kansas is the
• 22:10
  Speaker 1: center of the United States.
• 22:11
  Speaker 2: It's literally in the middle.
• 22:12
  Speaker 1: A more sensible way to define it is the gravitational center.
• 22:16
  Speaker 1: To add up all the stuff in the Milky Way
• 22:19
  Speaker 1: and wait its location by its gravity, and find like
• 22:22
  Speaker 1: the center of mass of the Milky Way, like the
• 22:24
  Speaker 1: point around which everything is spinning.
• 22:27
  Speaker 2: Which might be different than the geographical location.
• 22:31
  Speaker 1: In principle, it could be different. If the Milky Way
• 22:32
  Speaker 1: was asymmetric somehow, then it could be different. We think
• 22:36
  Speaker 1: in our case that those two things mostly line up
• 22:39
  Speaker 1: because the density profile of the Milky Way is that
• 22:42
  Speaker 1: it's densest at the center and mostly symmetric as it
• 22:45
  Speaker 1: goes out. Then there's the definition of the center of
• 22:48
  Speaker 1: the galaxy. And astronomers have just like picked a spot
• 22:51
  Speaker 1: it's called Sagittarius A and it's a radio emitter, and
• 22:54
  Speaker 1: said we define this to be the center of the galaxy.
• 22:57
  Speaker 1: It's like the coordinate system. That's a little arbitrary. You
• 23:00
  Speaker 1: could put it anywhere, but everybody has to agree on
• 23:03
  Speaker 1: an exact location, and so that's where they put it.
• 23:05
  Speaker 2: Wait, there's a star in the middle of the galaxy
• 23:07
  Speaker 2: that we can make out and see. Well, there's a
• 23:11
  Speaker 2: radio source, right.
• 23:12
  Speaker 1: And when people started to look up at the night
• 23:14
  Speaker 1: sky and realize that we could look at the night
• 23:16
  Speaker 1: sky in other wavelengths than just visible light, they started
• 23:20
  Speaker 1: to build radio telescopes to listen to radio waves from space.
• 23:25
  Speaker 1: They noticed a very bright source of radio waves coming
• 23:28
  Speaker 1: from the direction of the center of the galaxy. So
• 23:31
  Speaker 1: that's what we call Sagittarius A. It's a bright radio
• 23:34
  Speaker 1: source and that's where we put the center of the galaxy.
• 23:37
  Speaker 1: So it's not a star, it's a radio source.
• 23:41
  Speaker 2: I guess we'll dig into what it actually is, maybe
• 23:44
  Speaker 2: step us through what is at the center? Then? Is
• 23:46
  Speaker 2: it like a cluster stars? There's a big black hole
• 23:48
  Speaker 2: there too.
• 23:48
  Speaker 1: Right, So there is a big black hole and that's
• 23:50
  Speaker 1: what's generating all those radio emissions. Sagittarius A star is
• 23:55
  Speaker 1: the black hole at Sagittarius A, which is the radio emitter.
• 23:59
  Speaker 2: And so there's a huge black hole.
• 24:00
  Speaker 1: There are almost five million solar masses. That's the densest
• 24:04
  Speaker 1: part of the galaxy. But the whole blob near the
• 24:07
  Speaker 1: center is very, very dense with stars. There's like ten
• 24:10
  Speaker 1: million stars in the sort of central cubic parsec and
• 24:14
  Speaker 1: parsek is around three light years.
• 24:17
  Speaker 2: Wait, there's ten million stars per cubic parsk near the center.
• 24:23
  Speaker 1: Yeah, exactly, so that's about a million stars per cubic
• 24:26
  Speaker 1: light year.
• 24:27
  Speaker 2: How dense is that? Like, if we were there, would
• 24:29
  Speaker 2: we just be toast? Would it be super bright? Could
• 24:32
  Speaker 2: you survive? Could there be like an Earth there? Or
• 24:35
  Speaker 2: would it just be too intense?
• 24:37
  Speaker 1: It would be really intense. The density around here is
• 24:40
  Speaker 1: much much lower. It's like three or four light years
• 24:42
  Speaker 1: to the nearest star, so the density around here is
• 24:45
  Speaker 1: like less than one star per cubic parsec. There, it's
• 24:48
  Speaker 1: ten million stars per cubic parsec, so it's much more intense.
• 24:53
  Speaker 1: The light and the other forms of radiation are crazy
• 24:57
  Speaker 1: in the center of the galaxy. It's hard to imagine
• 24:59
  Speaker 1: lifelike ours thriving or surviving even in the middle of
• 25:03
  Speaker 1: the galaxy.
• 25:04
  Speaker 2: Well, it'd be super bright, but I wonder, are there
• 25:07
  Speaker 2: still I mean there are still stars there, so there
• 25:09
  Speaker 2: must be solar systems, right, and planets there just be
• 25:13
  Speaker 2: super bright everywhere you look.
• 25:14
  Speaker 1: There are definitely stars there, and we can see some
• 25:16
  Speaker 1: of them, like there's this star S two that we
• 25:19
  Speaker 1: see orbiting the central black hole, and by watching it
• 25:22
  Speaker 1: move we can tell how massive that black hole is.
• 25:25
  Speaker 1: Are there solar systems there? Is harder to answer because
• 25:28
  Speaker 1: the crazy intense environment is not very conducive to stable orbits. Remember,
• 25:32
  Speaker 1: if another star comes near our solar system, it could
• 25:35
  Speaker 1: disrupt Earth's orbit or Jupiter's orbit and we could lose
• 25:38
  Speaker 1: a planet. So in an environment where there are so
• 25:40
  Speaker 1: many stars jostling around each other, it's probably a lot
• 25:43
  Speaker 1: harder to hold onto planets.
• 25:45
  Speaker 2: So maybe can you paint as a picture like how
• 25:47
  Speaker 2: close are these solar systems together? Like if you were
• 25:50
  Speaker 2: in a solar system like ours, how close would the
• 25:52
  Speaker 2: next solar system be, like several solar systems away or
• 25:56
  Speaker 2: right next door? Or are they all sort of bunched
• 25:57
  Speaker 2: together or what's going on?
• 25:59
  Speaker 1: Yeah, the density of stars is literally ten million times
• 26:02
  Speaker 1: as dense as it is here. Ten million times denser
• 26:05
  Speaker 1: means stars are on average two hundred times closer together,
• 26:10
  Speaker 1: So instead of having a few light years between stars,
• 26:13
  Speaker 1: the average distance between stars is like two percent of
• 26:16
  Speaker 1: a light year, which is like twenty five times the
• 26:20
  Speaker 1: radius of Pluto's orbit. So other stars are not like
• 26:23
  Speaker 1: literally next door, but they're much closer than around here,
• 26:27
  Speaker 1: where the next star over is like five thousand Pluto orbits.
• 26:30
  Speaker 1: So there'd be a lot more stars a lot brighter,
• 26:32
  Speaker 1: Like there would be no darkness on a planet orbiting
• 26:35
  Speaker 1: one of those stars because the night sky would be
• 26:37
  Speaker 1: so bright with stars that would be so close. Remember,
• 26:40
  Speaker 1: when stars get closer, they get brighter fast because the
• 26:44
  Speaker 1: brightness goes as the distance squared, So if a star
• 26:47
  Speaker 1: gets ten times closer, it's one hundred times brighter.
• 26:50
  Speaker 2: Well, I guess it's all relative, right, Like if you
• 26:51
  Speaker 2: were sunglasses, Yeah, it might look just like it here.
• 26:57
  Speaker 1: Yeah, But the stars there are also different from the
• 26:59
  Speaker 1: stars here because it's not a very good place to
• 27:02
  Speaker 1: make stars because it's so crazy and there's so much radiation.
• 27:05
  Speaker 1: And remember that to make stars you need like cold
• 27:08
  Speaker 1: gas that can very gradually get pulled together by gravity.
• 27:11
  Speaker 1: So most of the stars in the center of the
• 27:13
  Speaker 1: galaxy are old stars because it's not a star forming region.
• 27:17
  Speaker 1: So you have these really old, small red stars, so
• 27:21
  Speaker 1: they're dimmer and they're redder, but there's a lot of them.
• 27:24
  Speaker 2: You mean, like they were formed outside of the center
• 27:27
  Speaker 2: and then they all congregated in the middle because of gravity.
• 27:30
  Speaker 1: Yeah, or they were formed when the center wasn't as
• 27:33
  Speaker 1: crazy during early days of the Milky Way. Remember the
• 27:36
  Speaker 1: Milky Way is almost as old as the universe. It's
• 27:39
  Speaker 1: like thirteen billion years old, and some of the stars
• 27:42
  Speaker 1: in the center might be about as old as the
• 27:45
  Speaker 1: Milky Way itself. Stars that are small can burn for
• 27:48
  Speaker 1: billions and billions of years. We think our star is
• 27:50
  Speaker 1: going to burn for about ten billion, but our star
• 27:53
  Speaker 1: is a little bit heavier than the typical star. Most stars,
• 27:56
  Speaker 1: like red dwarfs could burn for much longer and may
• 27:59
  Speaker 1: have been around at the very formation of the galaxy.
• 28:02
  Speaker 1: So those stars could predate the galaxy having like an
• 28:05
  Speaker 1: active center, you know, just the way you could have
• 28:07
  Speaker 1: like an old building in the center of downtown with
• 28:09
  Speaker 1: all these skyscrapers built around it.
• 28:11
  Speaker 2: But of course here in La all the stars live
• 28:13
  Speaker 2: in Beverly Hills and up in the Hollywood Hills, and
• 28:19
  Speaker 2: some in Pasadena. Know the big podcast stars all live
• 28:22
  Speaker 2: in South Pasadena. All right, So that's the center of
• 28:25
  Speaker 2: the galaxy. There's a big black hole there, and it's
• 28:28
  Speaker 2: chalk full of stars. I guess my biggest question is,
• 28:30
  Speaker 2: like how do we know all of these things? Like
• 28:33
  Speaker 2: how can you tell what's there or what the structure
• 28:36
  Speaker 2: the whole galaxy looks like if we're in the middle
• 28:39
  Speaker 2: of it, you know, like you can't take a selfie.
• 28:41
  Speaker 2: We haven't taken a selfie. How do we know about
• 28:43
  Speaker 2: all these structures like the arms and the orion spur, Like,
• 28:46
  Speaker 2: how do we know all of this, you know, sort
• 28:48
  Speaker 2: of detailed structure if we're in the middle of it.
• 28:50
  Speaker 1: Yeah, great question. For most of the stuff that's not
• 28:53
  Speaker 1: at the center of the galaxy, we still can see it.
• 28:56
  Speaker 1: We can see through our spur to other spurs. We
• 28:59
  Speaker 1: can figure out where those stars are. But a lot
• 29:01
  Speaker 1: of it is obscured by the gas and the dust,
• 29:04
  Speaker 1: especially in the direction of the center of the Milky Way,
• 29:07
  Speaker 1: and so visible light just doesn't work. Like I get
• 29:09
  Speaker 1: a sense for how little we can see the center
• 29:12
  Speaker 1: of the galaxy. If you sent a trillion photons to
• 29:16
  Speaker 1: us from the center of the galaxy, one of them
• 29:19
  Speaker 1: would survive. So it's like a dipping by a factor
• 29:21
  Speaker 1: of a trillion from all of this gas and dust
• 29:25
  Speaker 1: in the visible spectrum. But there are other frequencies of
• 29:28
  Speaker 1: light that are better at getting through that gas and
• 29:31
  Speaker 1: dust that we can use to see what's going on
• 29:33
  Speaker 1: in the rest of the galaxy.
• 29:34
  Speaker 2: M Like, certain light waves don't get stopped by gas
• 29:38
  Speaker 2: and dust. Those atoms out there floating just ignore the light.
• 29:41
  Speaker 1: Right exactly. We just did an episode on transparency. We
• 29:44
  Speaker 1: talked all about how different frequencies of light interact with
• 29:47
  Speaker 1: matter differently. So visible light goes through our atmosphere, which
• 29:51
  Speaker 1: is why we can see stuff, but UV light is
• 29:54
  Speaker 1: often blocked by the stuff in our atmosphere, so the
• 29:57
  Speaker 1: atmosphere is partially opaque to UV light. Different frequencies of
• 30:00
  Speaker 1: light interact with objects differently. Some things are transparent in
• 30:04
  Speaker 1: some frequencies and opaque in other frequencies. And so cosmic dust,
• 30:08
  Speaker 1: which is basically just like little tiny rocks, tiny little
• 30:12
  Speaker 1: bits of old planets and the hearts of stars that
• 30:15
  Speaker 1: blew up and got spread out. Those things are good
• 30:18
  Speaker 1: at interacting with high frequency light because they're so small,
• 30:22
  Speaker 1: but low frequency light, radio waves and infrared, it's big
• 30:26
  Speaker 1: enough that it basically doesn't see them, just passes right
• 30:29
  Speaker 1: through them.
• 30:30
  Speaker 2: Big enough in the sense that like the atoms that
• 30:32
  Speaker 2: are floating out there can't do anything with that light, right.
• 30:34
  Speaker 1: Yeah, the general rule of thumb is if you're seeing
• 30:37
  Speaker 1: something in light, you can't really see stuff that's smaller
• 30:39
  Speaker 1: than the wavelength of light that you are using. And
• 30:42
  Speaker 1: so if you use very long wavelength light, it basically
• 30:46
  Speaker 1: ignores everything that's smaller than its wavelength. So long wavelength
• 30:50
  Speaker 1: light is really good at getting through clouds of tiny
• 30:53
  Speaker 1: little particles. So that's why radio waves and infrared can
• 30:57
  Speaker 1: get through this stuff, whereas UV light and visit a
• 31:00
  Speaker 1: light which has shorter wavelengths, can't really get through this dust.
• 31:04
  Speaker 2: It's literally like having X ray vision of the galaxy.
• 31:07
  Speaker 2: Like if you could see in the X ray yet
• 31:08
  Speaker 2: X ray glasses, you could see the center of the
• 31:10
  Speaker 2: galaxy more clearly.
• 31:11
  Speaker 1: And in general, that's why it's so powerful to have
• 31:14
  Speaker 1: telescopes that can see in different frequencies, because some parts
• 31:18
  Speaker 1: of the galaxy are like really bright in X rays
• 31:20
  Speaker 1: and dim in the visible, so you need X ray
• 31:22
  Speaker 1: telescopes to see them. Other parts of the galaxy you
• 31:24
  Speaker 1: can only see in radio and infrared because of this
• 31:27
  Speaker 1: reddening from the cosmic dust. So you got to have
• 31:30
  Speaker 1: those infrared telescopes. James Web for example, is an infrared telescope.
• 31:34
  Speaker 1: It's really good at looking at the center of the
• 31:36
  Speaker 1: galaxy and this kind of stuff.
• 31:38
  Speaker 2: All Right, I guess I see how you can see
• 31:40
  Speaker 2: the center of the galaxy using X ray vision. But
• 31:43
  Speaker 2: I guess my question is, like, how do you know
• 31:45
  Speaker 2: the structure of the Milky Way from the point of
• 31:47
  Speaker 2: view where we are now? Like, how do you not
• 31:49
  Speaker 2: has these arms? Can you actually see those arms from
• 31:52
  Speaker 2: this point of view? But then it all looks sort
• 31:53
  Speaker 2: of like a fuzzy streak, Like if you look at
• 31:57
  Speaker 2: a frisbee from the side, you can't tell what it
• 31:59
  Speaker 2: looks like from the side. Yeah.
• 32:01
  Speaker 1: A crucial thing are distance measurements. So you need to
• 32:04
  Speaker 1: know how far away things are. You look at an
• 32:06
  Speaker 1: individual star out in space, you want to know how
• 32:08
  Speaker 1: far away it is. That lets you build a three
• 32:11
  Speaker 1: D map of the galaxy. So rather than just having
• 32:13
  Speaker 1: everything like pasted on a celestial sphere and not knowing
• 32:17
  Speaker 1: where things actually are, if you can say this star
• 32:20
  Speaker 1: is really far away, this one is really close. It
• 32:22
  Speaker 1: lets you build a three D map of everything and
• 32:24
  Speaker 1: from that you can build up the structure. And so
• 32:27
  Speaker 1: to know the distance of these stars, we need things
• 32:29
  Speaker 1: like cephids and parallax and all sorts of other tricks
• 32:32
  Speaker 1: that we've talked about before to figure out how far
• 32:34
  Speaker 1: away each star is. And that's one of the things
• 32:37
  Speaker 1: this Guya satellite is really good at. It does parallax
• 32:40
  Speaker 1: on all these stars and understands their location and also
• 32:43
  Speaker 1: their velocity, which is super cool. So we built up
• 32:46
  Speaker 1: sort of a three D map of the galaxy, and
• 32:48
  Speaker 1: of course we have better information about the side of
• 32:51
  Speaker 1: the galaxy that we're in and the spur that we
• 32:54
  Speaker 1: are in, so it gets fuzzier as you get to
• 32:56
  Speaker 1: the other side of the galaxy. And just as an example,
• 32:58
  Speaker 1: almost all of the X planets that we discovered are
• 33:01
  Speaker 1: in a little spot on our side.
• 33:03
  Speaker 2: Of the galaxy.
• 33:04
  Speaker 1: We can't like do exoplanet research on the other side
• 33:06
  Speaker 1: of the galaxy because we can't like see through the
• 33:09
  Speaker 1: center of the galaxy to that other side as well.
• 33:11
  Speaker 2: So we know a.
• 33:12
  Speaker 1: Lot more about our neighborhood on our side of the
• 33:14
  Speaker 1: galaxy than the rest of it.
• 33:16
  Speaker 2: I see you sort of use stereovision to try to
• 33:18
  Speaker 2: get a three D view from our point of view.
• 33:20
  Speaker 2: But this three D idea, the parallax only works for
• 33:24
  Speaker 2: close by things, right, does it actually work to see
• 33:27
  Speaker 2: how far something is on the other side of the galaxy.
• 33:29
  Speaker 1: Parallax is most powerful for close by things, but we
• 33:32
  Speaker 1: have this distance ladders. We have parallax for close by stuff,
• 33:36
  Speaker 1: and then we have cephids the variable stars for more
• 33:38
  Speaker 1: distant things on the other side of the galaxy. These
• 33:41
  Speaker 1: are stars where their period of variability when they get
• 33:44
  Speaker 1: bright and dim and brightened dim is connected to their
• 33:47
  Speaker 1: true brightness. And so by noticing how they get bright
• 33:49
  Speaker 1: and dim and the period of that, we can figure
• 33:52
  Speaker 1: out how right they actually are, and therefore we can
• 33:54
  Speaker 1: tell how far away they are. So you can use
• 33:57
  Speaker 1: sephids to understand how far away things are in the
• 33:59
  Speaker 1: other side side of the galaxy.
• 34:01
  Speaker 2: Aren't those pretty rare? Though?
• 34:02
  Speaker 1: Those are pretty rare, But the galaxy is huge, so
• 34:05
  Speaker 1: we have found several thousand sephids I think more than
• 34:08
  Speaker 1: thirty three hundred last time I checked, But we still
• 34:11
  Speaker 1: have some of those, so we can use those together
• 34:14
  Speaker 1: with parallax to get a kind of a picture, but
• 34:16
  Speaker 1: it's not perfect, and it's especially bad in the direction
• 34:18
  Speaker 1: of the center of the galaxy because the center tends
• 34:21
  Speaker 1: to redden things because of the dust. Dust only lets
• 34:24
  Speaker 1: redder light through, lower frequency light through, and so we
• 34:27
  Speaker 1: don't always know, like always that actually a dimmer star
• 34:30
  Speaker 1: or is it just reddened by all the dust. So,
• 34:33
  Speaker 1: like one thing people argue about it is like how
• 34:35
  Speaker 1: far away is the center of the galaxy exactly? And
• 34:37
  Speaker 1: there's all these measurements, some of which disagree with each
• 34:40
  Speaker 1: other about exactly how far away it is. It's really
• 34:42
  Speaker 1: a challenge to measure the distance to the center of
• 34:45
  Speaker 1: the galaxy.
• 34:46
  Speaker 2: Right. That's kind of what I'm trying to get at,
• 34:47
  Speaker 2: which is that, you know, we see all these illustrations
• 34:50
  Speaker 2: of what the Milky Way looks like online and in books, like, hey,
• 34:54
  Speaker 2: this is what the milk Away looks like, but we
• 34:55
  Speaker 2: really don't know what the Milky Way looks like. And
• 34:58
  Speaker 2: I'm just kind of wondering, like, what does the picture
• 35:01
  Speaker 2: of what we actually know look like. Maybe we have
• 35:03
  Speaker 2: some sense of structure around us, but then for the
• 35:07
  Speaker 2: rest of the galaxy, like the other arms on the
• 35:09
  Speaker 2: other side, how many sephids, do we actually know are there?
• 35:13
  Speaker 2: And what is that the map of the data actually
• 35:15
  Speaker 2: looks like.
• 35:16
  Speaker 1: I think we do know roughly the shape of the
• 35:18
  Speaker 1: Milky Way. I mean, we know those other spurs and
• 35:20
  Speaker 1: the guy A satellite and the sephids do paint that
• 35:23
  Speaker 1: picture for us. It's definitely fuzzier on the other side
• 35:26
  Speaker 1: of the galaxy than it is here, and we don't
• 35:28
  Speaker 1: have like the crystal picture we'd love to have if
• 35:31
  Speaker 1: you were like out on top of the galaxy and
• 35:33
  Speaker 1: just took a picture from it. So it definitely limited
• 35:35
  Speaker 1: as we go to the other side of the galaxy.
• 35:37
  Speaker 1: But these illustrations you see about the shape of the galaxy,
• 35:40
  Speaker 1: those are pretty right on. I mean, we don't have
• 35:42
  Speaker 1: every single star in those arms on the other side
• 35:45
  Speaker 1: the way we do on our spur or even in
• 35:47
  Speaker 1: the neighboring spur, but we're pretty sure about the shape
• 35:50
  Speaker 1: of the Milky Way.
• 35:52
  Speaker 2: All right, let's get back to the center of the galaxy.
• 35:54
  Speaker 1: But first let's take a quick break. We're back and
• 36:09
  Speaker 1: we're thinking about how to actually see the center of
• 36:12
  Speaker 1: the galaxy. So there was recently a really cool image
• 36:16
  Speaker 1: of the center of the galaxy taken by a radio telescope.
• 36:19
  Speaker 1: This is an array of telescopes in South Africa. It's
• 36:22
  Speaker 1: called Meerkat, and radio is still the best way to
• 36:25
  Speaker 1: see the center of the galaxy because of course it's
• 36:27
  Speaker 1: the longest wave length, and so it gets through the
• 36:30
  Speaker 1: gas and the dust and it gives us this awesome
• 36:32
  Speaker 1: picture of what's going on. This like morphology, shows us
• 36:35
  Speaker 1: the shapes of stuff in the center of the galaxy,
• 36:38
  Speaker 1: as if we could like X ray through all that
• 36:40
  Speaker 1: gas and dust. So the Meerkat radio telescope is basically
• 36:44
  Speaker 1: an array eight by eight of these sixty four antennas
• 36:47
  Speaker 1: spread across five miles of desert in South Africa, and
• 36:51
  Speaker 1: they put out of paper recently with this incredible picture
• 36:54
  Speaker 1: of the center of the galaxy.
• 36:56
  Speaker 2: Now, now these are not telescopes like maybe we think
• 36:59
  Speaker 2: of when we see are the word toscode. They don't
• 37:01
  Speaker 2: have lenses that they don't look like it too. They
• 37:03
  Speaker 2: look more like giant dishes, right, like the kind you
• 37:06
  Speaker 2: see in the movie Contact. Yeah, that's right.
• 37:09
  Speaker 1: It's an array of dishes, and so each one looks
• 37:12
  Speaker 1: like a satellite dish. You might be using it to
• 37:14
  Speaker 1: broughout your favorite sports team on but you have an
• 37:17
  Speaker 1: array of them spread across the desert. What you'd love,
• 37:19
  Speaker 1: of course, is just to have like a five mile
• 37:22
  Speaker 1: wide dish to gather all of that information. You can't
• 37:25
  Speaker 1: afford to build that. But it's better to have sixty
• 37:28
  Speaker 1: four separate dishes that have greater distance between them than
• 37:31
  Speaker 1: to have one big dish that's.
• 37:33
  Speaker 2: In the end smaller.
• 37:35
  Speaker 1: You in effect have a larger aperture.
• 37:37
  Speaker 2: Sort of like having tapas for dinner instead of it
• 37:41
  Speaker 2: big dish.
• 37:42
  Speaker 1: That's right, And you can get more information by having
• 37:45
  Speaker 1: these dishes like further apart.
• 37:46
  Speaker 2: Like a sampler plate of appetize.
• 37:49
  Speaker 1: As the information washes across your array, you can tell
• 37:53
  Speaker 1: which direction it came from. You can do interferometry to
• 37:55
  Speaker 1: get all sorts of useful information. So it's almost as
• 37:58
  Speaker 1: good as having a single telescope that's like actually five
• 38:03
  Speaker 1: miles wide, so it doesn't look like a traditional telescope.
• 38:06
  Speaker 1: There's nobody like peering through a lens and seeing the
• 38:08
  Speaker 1: center of the galaxy. They get this data, which again
• 38:11
  Speaker 1: is not even visible light, it's radio waves, and they
• 38:14
  Speaker 1: process it and they convert it into something that you
• 38:17
  Speaker 1: can see with your eyes. And so there's this wavelength
• 38:20
  Speaker 1: shifting right, you would never see this image yourself. It
• 38:23
  Speaker 1: comes in light that your eyeballs can't see. But we
• 38:25
  Speaker 1: do all this computing. We crunch the numbers and we
• 38:28
  Speaker 1: figure out where are the bright sources of radio. So
• 38:31
  Speaker 1: if you google this image from meercap, what you're looking
• 38:34
  Speaker 1: at is where there are intense radio sources and where
• 38:37
  Speaker 1: there's less intense radio.
• 38:39
  Speaker 2: Sources, and it's sort of focused to the center of
• 38:41
  Speaker 2: the galaxy. That's kind of the idea, right, That's why
• 38:43
  Speaker 2: you having so far apart is that you can sort
• 38:45
  Speaker 2: of triangulate and be confident that what you're seeing is
• 38:49
  Speaker 2: coming from the center and it's not just some artifact
• 38:51
  Speaker 2: that's in between.
• 38:52
  Speaker 1: And you can see at the very heart of this
• 38:54
  Speaker 1: image is Sagittarius astar. We know this is a really
• 38:57
  Speaker 1: big black hole there, and we know it generates a
• 38:59
  Speaker 1: lot of radio waves from the gas that's swirling around it,
• 39:03
  Speaker 1: and it's the brightest thing in radio. So it's at
• 39:05
  Speaker 1: the very center. It's very small, it's very bright. So
• 39:08
  Speaker 1: that's super cool because it shows you, like, wow, the
• 39:10
  Speaker 1: center of the galaxy really does have this very intense core,
• 39:14
  Speaker 1: and then spread around it is the beginning of the
• 39:16
  Speaker 1: galactic disc.
• 39:18
  Speaker 2: No, the black hole is sucking stuff in, but the
• 39:20
  Speaker 2: stuff that's falling into it, that's the stuff that's really bright.
• 39:23
  Speaker 2: That's right.
• 39:23
  Speaker 1: We don't see anything from the black hole itself. Right,
• 39:26
  Speaker 1: the black hole is the black hole. We're not seeing
• 39:28
  Speaker 1: hawking radiation or anything. Black hole we think is totally black.
• 39:31
  Speaker 1: But the stuff that's swirling around it and falling in
• 39:34
  Speaker 1: that is accelerating and giving off radiation. We can only
• 39:37
  Speaker 1: see it in the radio because everything else is blocked.
• 39:40
  Speaker 2: Cool. So we have this picture from the center of
• 39:41
  Speaker 2: the galaxy. You can look it up. It's called meer
• 39:44
  Speaker 2: Cat And what do we learn from it?
• 39:45
  Speaker 1: So the black hole is no surprise, but there's a
• 39:48
  Speaker 1: bunch of other cool features. You can see these blobs
• 39:50
  Speaker 1: from the beginning of the galactic disc, and it's sort
• 39:53
  Speaker 1: of cool that it's tilted. They've plotted in these celestial coordinates,
• 39:57
  Speaker 1: which is declination versus right ascension, which is just sort
• 40:00
  Speaker 1: of like a grid around the Earth that uses the
• 40:02
  Speaker 1: north and the South poles, and so it's tilted pretty
• 40:05
  Speaker 1: hard in those angles, and it shows you, like the
• 40:07
  Speaker 1: angle of the Earth relative to the angle of the
• 40:10
  Speaker 1: disk of the galaxy. Right, the north pole of the
• 40:12
  Speaker 1: Earth is not aligned with the north pole of the galaxy,
• 40:15
  Speaker 1: like the equator is not aligned with the galactic disk.
• 40:18
  Speaker 1: It's actually quite tilted. So that's sort of cool. It
• 40:20
  Speaker 1: orients you, right, It shows you that, like, whoa, we're
• 40:23
  Speaker 1: kind of leaning.
• 40:23
  Speaker 2: Over, we're leaning into the galaxy. But I guess there
• 40:27
  Speaker 2: is there any reason to expect that they would be
• 40:29
  Speaker 2: aligned or it's is it kind of random?
• 40:31
  Speaker 1: It's kind of random. I mean, the Earth is kind
• 40:34
  Speaker 1: of aligned with the spin of the Sun and the
• 40:36
  Speaker 1: disk of the Solar system, though of course there's a
• 40:38
  Speaker 1: tilt there. But the spin of our Sun is not
• 40:42
  Speaker 1: necessarily aligned with the spin of the galaxy, right, because
• 40:46
  Speaker 1: all the stars basically have random directions. It just comes
• 40:48
  Speaker 1: from the spin of the blob of gas and dust
• 40:51
  Speaker 1: that formed our Solar system. But it just helps orient
• 40:54
  Speaker 1: you and show you that, like, our north pole is
• 40:56
  Speaker 1: not like the galactic north pole.
• 40:58
  Speaker 2: M Our north pole is not the Sun's north pole
• 41:02
  Speaker 2: you were saying. It just kind of gives us a
• 41:04
  Speaker 2: sense of which where we're actually going.
• 41:06
  Speaker 1: Yeah, And even though it makes no sense, it gives
• 41:08
  Speaker 1: me a little bit of vertigo because I feel like
• 41:11
  Speaker 1: I'm standing here on the Earth and I'm like, whoa,
• 41:13
  Speaker 1: I'm leaning over, and everybody in the center of the
• 41:15
  Speaker 1: galaxy looking at us is like, whoa, those guys are
• 41:17
  Speaker 1: leaning over. And I mean it makes no sense obviously,
• 41:20
  Speaker 1: but it sort of gives me this sense of vertigo.
• 41:22
  Speaker 2: Yeah. I mean, everyone knows South Pasadena is the true
• 41:24
  Speaker 2: north pole of the galaxy, and so I feel it
• 41:27
  Speaker 2: just fine.
• 41:28
  Speaker 1: Right, yeah, well that's the north pole of the podcast
• 41:29
  Speaker 1: universe also. But you also see these other really cool features.
• 41:33
  Speaker 1: Some of my favorite features are super nova remnants, So
• 41:37
  Speaker 1: a bunch of stars that used to be near the
• 41:39
  Speaker 1: center of the galaxy and then blew up. You can
• 41:41
  Speaker 1: see their clouds. You can see these like puffs from
• 41:44
  Speaker 1: the super nova that are left over from these stars
• 41:47
  Speaker 1: having exploded.
• 41:48
  Speaker 2: Where did those come from?
• 41:49
  Speaker 1: Those just came from stars that lived and burned and
• 41:52
  Speaker 1: then died. And then the other really fascinating thing are
• 41:55
  Speaker 1: these filaments above and below the disk of the galaxy.
• 41:59
  Speaker 1: Are these shooting lines sort of like the galaxy has
• 42:02
  Speaker 1: these hairs or something, and they stretch for like hundreds
• 42:06
  Speaker 1: of light years.
• 42:07
  Speaker 2: You mean, like sort of like geysers or just as
• 42:09
  Speaker 2: structures of stars.
• 42:11
  Speaker 1: Well, we don't really understand what they are exactly. But
• 42:13
  Speaker 1: they don't just shoot up and down from the black hole.
• 42:15
  Speaker 1: They're shooting like up and down from the whole disc.
• 42:18
  Speaker 1: So in this picture you could see like dozens of
• 42:21
  Speaker 1: these things. There are these streaks up and down above
• 42:23
  Speaker 1: and below the disc, these huge filaments, And we've known
• 42:27
  Speaker 1: about these for a few decades that we've only ever
• 42:29
  Speaker 1: seen a few of them. People think that they're like
• 42:32
  Speaker 1: maybe these weird magnetized tubes of gas that funnel high
• 42:37
  Speaker 1: energy particles and then those particles are emitting in the
• 42:40
  Speaker 1: radio because they're getting accelerated by the magnetic field. But
• 42:43
  Speaker 1: nobody has any theory for like why these things exist.
• 42:46
  Speaker 1: When we found them a few decades ago, it was
• 42:48
  Speaker 1: a pretty big surprise to see these like hairs sticking
• 42:51
  Speaker 1: up and down from the top and bottom of the galaxy.
• 42:54
  Speaker 2: M just sort of like tornadoes. Kind of sounds like, yeah.
• 42:58
  Speaker 1: Exactly, they're like magnetic parts article tornadoes. And so there's
• 43:01
  Speaker 1: some clue there about like the turbulence at the center
• 43:04
  Speaker 1: of the galaxy. Maybe the stars are interacting somehow with
• 43:07
  Speaker 1: their magnetic fields and the larger galactic magnetic field. We
• 43:11
  Speaker 1: don't really know. But one thing that's really cool about
• 43:13
  Speaker 1: this picture is that it's the first time we have
• 43:15
  Speaker 1: like enough of these things to start to do like statistics,
• 43:18
  Speaker 1: to say like how often are they here or are
• 43:20
  Speaker 1: they connected to stars or whatever. So it's the first
• 43:23
  Speaker 1: picture that really gives us enough detail to start to
• 43:26
  Speaker 1: understand the crazy dynamics at the heart of the galaxy.
• 43:30
  Speaker 2: M And I guess that's important because you know, understanding
• 43:34
  Speaker 2: what's happening in the center of the galaxy tells us
• 43:36
  Speaker 2: a bit about how galaxies form right and where they're
• 43:39
  Speaker 2: going exactly.
• 43:40
  Speaker 1: And we also know that the galaxy center is very
• 43:43
  Speaker 1: different from the rest of the galaxy. Like we can
• 43:45
  Speaker 1: think about star formation out here in the suburbs and
• 43:48
  Speaker 1: understand it, but star formation in the center of the
• 43:50
  Speaker 1: galaxy is very, very different because the conditions are different.
• 43:54
  Speaker 1: And anytime you have different conditions, you have an opportunity
• 43:57
  Speaker 1: to learn something new because maybe your theory for star
• 44:00
  Speaker 1: formation works, but maybe it doesn't right and maybe there's
• 44:03
  Speaker 1: something else happening. For example, they recently discovered a blob
• 44:07
  Speaker 1: of like one hundred very new stars very close to
• 44:10
  Speaker 1: the center of the galaxy. And again we don't think
• 44:13
  Speaker 1: that the center of the galaxy is a good place
• 44:15
  Speaker 1: to form stars because of all the crazy intense radiation,
• 44:19
  Speaker 1: the heats up the gas, and yet they found this
• 44:22
  Speaker 1: blob of like one hundred very massive, very short lived stars.
• 44:26
  Speaker 1: They don't understand how those formed. Something else is going
• 44:28
  Speaker 1: on that we don't understand. People think maybe there are
• 44:32
  Speaker 1: like these clusters of metals that pull gas together, but
• 44:35
  Speaker 1: nobody can understand why these stars exist. They call it
• 44:38
  Speaker 1: the paradox of youth.
• 44:40
  Speaker 2: And how do we see these stars? Do they emit
• 44:42
  Speaker 2: a lot of radio ways too.
• 44:43
  Speaker 1: Stars actually don't emit in the radio, so we can't
• 44:45
  Speaker 1: see them that way. But stars do emit in the infrared,
• 44:49
  Speaker 1: and so infrared telescopes can see into the center of
• 44:52
  Speaker 1: the galaxy, things like James Web. That's how, for example,
• 44:54
  Speaker 1: we can follow these stars that orbit very close to
• 44:57
  Speaker 1: the black hole. We can't see their visible light, it's
• 44:59
  Speaker 1: blocked by all that, but we can see them in
• 45:01
  Speaker 1: the infrared.
• 45:02
  Speaker 2: So mean, it's just sort of like a pocket of
• 45:04
  Speaker 2: inactivity that maybe that you have in these stars.
• 45:08
  Speaker 1: It could be, but there's a lot of stuff to
• 45:10
  Speaker 1: learn about what's going on in the center of the galaxy.
• 45:12
  Speaker 1: We'd also really like to understand the center of the
• 45:14
  Speaker 1: galaxy because it's where most of the dark matter is.
• 45:17
  Speaker 1: Dark matter is actually most of the mass of the galaxy.
• 45:19
  Speaker 1: Eighty or ninety percent of masses of galaxies are in
• 45:23
  Speaker 1: dark matter, and a lot of that is clustered towards
• 45:26
  Speaker 1: the center. So people who want to understand, like what
• 45:29
  Speaker 1: is the dark matter have all pointed their telescopes towards
• 45:32
  Speaker 1: the center of the galaxy to see if they can
• 45:34
  Speaker 1: observe dark matter doing something weird, like smashing into itself
• 45:38
  Speaker 1: and giving off flashes of light that we might be
• 45:41
  Speaker 1: able to detect.
• 45:42
  Speaker 2: We don't know what it is what dark matter is,
• 45:44
  Speaker 2: but we know there's a higher density of it in
• 45:46
  Speaker 2: the center of the galaxy. Even though we can't actually see.
• 45:49
  Speaker 1: It exactly, we know there's more of it in the
• 45:51
  Speaker 1: center of the galaxy. Just by I understanding the velocity
• 45:54
  Speaker 1: of stars how they swirl around in the galaxy, it
• 45:56
  Speaker 1: gives us like a mass profile. It tells us where
• 45:58
  Speaker 1: the mass in the galaxy is is. Because it's showing
• 46:01
  Speaker 1: us where the gravity is. We could figure that out
• 46:03
  Speaker 1: by how fast stars are rotating a different radii, and
• 46:06
  Speaker 1: so we know there's a lot of dark matter in
• 46:08
  Speaker 1: the center of the galaxy, so people have pointed special
• 46:10
  Speaker 1: telescopes at the center of the galaxy to try to
• 46:12
  Speaker 1: pick up signatures from that dark matter. And about five
• 46:16
  Speaker 1: years ago, actually people saw these weird bumps, these very
• 46:19
  Speaker 1: high energy gamma rays coming from the center of the
• 46:22
  Speaker 1: galaxy that had to be super bright to get through
• 46:25
  Speaker 1: all the gas and dust, but still they were making
• 46:27
  Speaker 1: it to Earth and people were wondering, like, is this
• 46:29
  Speaker 1: a sign of dark matter or is there something else
• 46:32
  Speaker 1: going on at the center of the galaxy. It's hard
• 46:34
  Speaker 1: to know if it's dark matter if you're not sure
• 46:36
  Speaker 1: what else could be emitting radiation to the center of
• 46:39
  Speaker 1: the galaxy. So basically understanding what's at the center of
• 46:42
  Speaker 1: the galaxy gives us an opportunity to learn a lot
• 46:45
  Speaker 1: more different kinds of physics, to do all sorts of
• 46:47
  Speaker 1: tests to look for dark matter, to understand star formation.
• 46:50
  Speaker 1: It's just like a really cool laboratory because the conditions
• 46:53
  Speaker 1: are so weird and different and intense.
• 46:55
  Speaker 2: And I guess it's the closest galactic center to us, right,
• 46:58
  Speaker 2: I mean, we can see other galaxies, but maybe we
• 47:00
  Speaker 2: can't see it as much detail as we can the
• 47:03
  Speaker 2: center of our galaxy.
• 47:04
  Speaker 1: Yeah, it's both good and bad. It's very close, as
• 47:07
  Speaker 1: you say, so we can trace out stellar motion near
• 47:10
  Speaker 1: the black hole, but also it's obscured by gas and dust.
• 47:14
  Speaker 1: So in some ways we can see the centers of
• 47:15
  Speaker 1: other galaxies more clearly, even though they're further away, because
• 47:19
  Speaker 1: we don't have to look through their galactic disk. So
• 47:23
  Speaker 1: it's both studying our galactic center and other galaxies. Galactic
• 47:26
  Speaker 1: centers can teach us different kind of things.
• 47:28
  Speaker 2: All right, Well, then, I guess maybe to summarize, what
• 47:30
  Speaker 2: are some of the big questions we have about the
• 47:32
  Speaker 2: center of the galaxy.
• 47:33
  Speaker 1: So we don't understand a lot about the center of
• 47:35
  Speaker 1: the galaxy, like what is in there? Are there a
• 47:37
  Speaker 1: bunch of pulsars giving us weird blips and bleachs that
• 47:40
  Speaker 1: might be dark matter? We don't understand, like why is
• 47:43
  Speaker 1: there a bar in the center of the galaxy. Why
• 47:45
  Speaker 1: isn't it just like a blob with arms. Some galaxies
• 47:48
  Speaker 1: have bars, other galaxies don't have bars. We don't really
• 47:51
  Speaker 1: understand like how that forms. We don't know if stars
• 47:55
  Speaker 1: are still being made in the center of the galaxy,
• 47:57
  Speaker 1: And that's something We really like to understand how star
• 48:00
  Speaker 1: formation happens, why it stops. We don't understand these filaments,
• 48:03
  Speaker 1: these weird magnetic particle tornadoes, what they mean, what they
• 48:07
  Speaker 1: tell us about the magnetic fields of the stars, If
• 48:10
  Speaker 1: there are super novas down there that are driving it.
• 48:12
  Speaker 1: It's basically a big cloud of mystery.
• 48:14
  Speaker 2: Yeah, and you forgot the biggest question of them all.
• 48:16
  Speaker 2: Is the center of the galaxy bait? Or is it
• 48:20
  Speaker 2: kind of a spicy green?
• 48:21
  Speaker 1: How late do the dance club stay open in the
• 48:23
  Speaker 1: center of the galaxy?
• 48:24
  Speaker 2: Yeah? How big are the parking lots that you can
• 48:26
  Speaker 2: get lost in down there? Are there good food trucks
• 48:30
  Speaker 2: at two am? All right? Well, the next time you
• 48:32
  Speaker 2: look up at the night sky, think about where you
• 48:34
  Speaker 2: are in the galaxy and which way is it tilted?
• 48:37
  Speaker 2: And where are all the exciting things happening in the
• 48:39
  Speaker 2: milky Way? Is it near you? Or is it all
• 48:42
  Speaker 2: happening downtown?
• 48:43
  Speaker 1: And when you think about the broader context, try not
• 48:45
  Speaker 1: to fall over from vertigo when you realize that we're
• 48:48
  Speaker 1: tilted relative to the Sun. Who's tilted relatives to the galaxy?
• 48:51
  Speaker 1: Who's just one of billions of galaxies floating out in space.
• 48:55
  Speaker 2: He'pe you enjoyed that. Thanks for joining us, see you
• 48:59
  Speaker 2: next time.
• 49:07
  Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
• 49:10
  Speaker 1: the Universe is a production of iHeartRadio. For more podcasts
• 49:14
  Speaker 1: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever
• 49:18
  Speaker 1: you listen to your favorite shows.