Latest / Daniel and Kelly’s Extraordinary Universe / How important is cosmic dust?

Transcript

How important is cosmic dust? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, you're kind of a neat freak, aren't you.
• 0:11
  Speaker 2: I do like to keep my laptop nicely, well dusted.
• 0:15
  Speaker 1: The weight dust it like you put dust in it,
• 0:17
  Speaker 1: or you take out dust, or you wipe dust out
• 0:20
  Speaker 1: of it.
• 0:20
  Speaker 2: Good question. I mean, I like my cookies well dusted
• 0:23
  Speaker 2: with sugar, but my laptop keyboard well dusted with zero dust.
• 0:28
  Speaker 1: Yeah, household dust is less delicious, and powdered sugar is
• 0:32
  Speaker 1: in regular dust, like fifty percent skin cells.
• 0:34
  Speaker 2: That sounds like a pretty gross thing to put on
• 0:36
  Speaker 2: your cookies. On the other hand, it would be pretty
• 0:38
  Speaker 2: weird if powdered sugar just like accumulated in your.
• 0:41
  Speaker 1: House, it'd be pretty sweet.
• 0:44
  Speaker 2: We might call for some sweeping changes.
• 0:46
  Speaker 1: Uh, I'm glad you got to dust off that old punt.
• 1:05
  Speaker 2: Hi.
• 1:05
  Speaker 1: I'm Poor hammy cartoonas and the author of Oliver's Great
• 1:08
  Speaker 1: Big Universe.
• 1:08
  Speaker 2: Hi. I'm Daniel. I'm a particle physicist and a professor
• 1:11
  Speaker 2: at UC Irvine, and I don't like dust as much
• 1:14
  Speaker 2: as astronomers do.
• 1:15
  Speaker 1: But do you still like it a little bit?
• 1:17
  Speaker 2: I like dust the way I like the sun. It's fascinating,
• 1:19
  Speaker 2: it's interesting, it's useful, It tells us about the cosmos.
• 1:23
  Speaker 2: But I don't really want it on my laptop or
• 1:26
  Speaker 2: on my table.
• 1:27
  Speaker 1: But everywhere else it's okay.
• 1:29
  Speaker 2: Yeah, study it from a distance, you know, the way
• 1:32
  Speaker 2: like I'm fascinated by cheetahs, but I don't really want
• 1:34
  Speaker 2: to have a cheat on my lap.
• 1:37
  Speaker 1: Do you carry a duster with you at all times?
• 1:39
  Speaker 3: Then?
• 1:39
  Speaker 2: I actually do have this very fancy little machine for
• 1:42
  Speaker 2: removing dust from your keyboard.
• 1:44
  Speaker 1: Is it called blowing on it? Or did you Did
• 1:46
  Speaker 1: you actually pay for a machine to do that?
• 1:48
  Speaker 2: I actually have a nice little machine. It's really quite good. Yeah,
• 1:51
  Speaker 2: I should call it mini made.
• 1:52
  Speaker 1: Wait, what is it like a vacuum?
• 1:54
  Speaker 2: No, it's like a little blower, you know. It replaces
• 1:55
  Speaker 2: those disposable cans that I thought were not very environmentally friendly,
• 1:59
  Speaker 2: though I do love them.
• 2:00
  Speaker 3: Mmm.
• 2:01
  Speaker 1: Oh, I see you mean like the dust between the keys,
• 2:04
  Speaker 1: like you want to get rid of it, like in
• 2:06
  Speaker 1: the nooks and crannies.
• 2:07
  Speaker 2: Yeah, exactly. I like a nice clean keyboard.
• 2:10
  Speaker 3: Oh.
• 2:10
  Speaker 1: I thought you meant like on your screen, because I
• 2:12
  Speaker 1: think you can just wipe that off.
• 2:13
  Speaker 2: I think you can. But probably that dust contains all
• 2:16
  Speaker 2: sorts of fascinating stories where each of those bits has
• 2:19
  Speaker 2: been But you.
• 2:20
  Speaker 1: Know, if you just blow the dust, it's just getting
• 2:22
  Speaker 1: in the air and then it's going to come back
• 2:24
  Speaker 1: down on your keyboard.
• 2:25
  Speaker 2: I know it's a cycle. Unless I'm willing to live
• 2:27
  Speaker 2: in a clean room, I can never escape it.
• 2:29
  Speaker 1: So you don't like living in clean rooms.
• 2:31
  Speaker 2: I don't have to wear a hairnet and booties all
• 2:33
  Speaker 2: the time.
• 2:34
  Speaker 1: No, just some of the time. But anyways, welcome for
• 2:39
  Speaker 1: a podcast Daniel and Jorge Explain the Universe, a production
• 2:42
  Speaker 1: of our Heart Radio.
• 2:43
  Speaker 2: In which we dive deep into the cycles of the universe,
• 2:47
  Speaker 2: the ones that produce massive stars and tiny grains of dust.
• 2:51
  Speaker 2: Everything out there in the universe has a history and
• 2:54
  Speaker 2: tells a story, and if we can unpack it, unravel
• 2:57
  Speaker 2: it and study it, you can reveal those stories and
• 2:59
  Speaker 2: the history of our own cosmos. To learn about the
• 3:03
  Speaker 2: formation of the planets and stars and the universe itself,
• 3:07
  Speaker 2: from the biggest clues to the tiniest speck of dust.
• 3:10
  Speaker 1: That's right, we blow the dust off of the universe,
• 3:13
  Speaker 1: trying to uncover what's underneath, What shiny surface or interesting
• 3:16
  Speaker 1: facts are there for us to understand and to learn about.
• 3:19
  Speaker 2: I love in archaeology, how every time they're going to
• 3:21
  Speaker 2: discover something amazing, they always have to blow dust off
• 3:24
  Speaker 2: of it, pull cobwebs off of it. That's like your
• 3:27
  Speaker 2: visual cue that you're about to learn something ancient.
• 3:29
  Speaker 1: Wait, wait, what do you mean?
• 3:30
  Speaker 2: I mean? I just watched a new Indian Jones. I guess.
• 3:33
  Speaker 2: So you know anytime they unde earth something from the
• 3:35
  Speaker 2: olden days, it's always covered in dust.
• 3:37
  Speaker 1: Of course, mm to see they carry a dust with
• 3:40
  Speaker 1: them at all times. Maybe you can buy one of
• 3:42
  Speaker 1: those devices and you didn't have to waste electricity.
• 3:46
  Speaker 2: I'd be that neat freak archaeologist. I don't think i'd
• 3:49
  Speaker 2: get very far in the field.
• 3:50
  Speaker 1: Yeah, it is a dusty universe full of amazing things,
• 3:53
  Speaker 1: where even the dust is interesting. In the universe.
• 3:55
  Speaker 2: Down here on Earth we see dust is sort of
• 3:57
  Speaker 2: a nuisance, something to brush out of our But out
• 4:00
  Speaker 2: in space dust plays a very important role in the
• 4:03
  Speaker 2: formation of stars and planets, and it can reveal that history.
• 4:08
  Speaker 2: Dust is not just a nuisance. It's a fascinating pile
• 4:11
  Speaker 2: of tiny clues.
• 4:12
  Speaker 1: So today end podcast, we'll be asking the question how
• 4:20
  Speaker 1: important is cosmic dust? Now? Hopefully this episode won't be
• 4:24
  Speaker 1: a bust.
• 4:27
  Speaker 2: Should we just be sweeping cosmic dust under the cosmic
• 4:30
  Speaker 2: rug or should we take it seriously and study it
• 4:33
  Speaker 2: in detail.
• 4:34
  Speaker 1: That's a bit of a dusty pun there, you used
• 4:36
  Speaker 1: it already, But yeah, it's an interesting question here cosmic dust.
• 4:40
  Speaker 1: I guess it's different than regular dust.
• 4:42
  Speaker 2: Well, I think there's fewer dead skin cells and leftover
• 4:45
  Speaker 2: bits of insects out there floating between the stars than
• 4:47
  Speaker 2: there is here on Earth. But cosmic dust also falls
• 4:50
  Speaker 2: to Earth.
• 4:51
  Speaker 1: You mean it gets sprinkled from space like powdered sugar.
• 4:54
  Speaker 2: Well, you know that space isn't empty, and there's dust
• 4:56
  Speaker 2: out there between the stars but also between the planets,
• 4:59
  Speaker 2: and as the Earth moves through these cosmic dust clouds,
• 5:02
  Speaker 2: it accumulates some of them. Some tons of dust fall
• 5:05
  Speaker 2: to Earth every year from interplanetary space out there in
• 5:08
  Speaker 2: the Solar System.
• 5:09
  Speaker 1: WHOA is it like dandruff space? Dandruff? Or is that
• 5:12
  Speaker 1: too embarrassing?
• 5:15
  Speaker 2: We had a whole fun episode about where this stuff
• 5:17
  Speaker 2: comes from. It's a bit of a mystery. There's a
• 5:19
  Speaker 2: recent experiment though, that tries to pin the blame on Mars.
• 5:22
  Speaker 2: It might be that dust storms on Mars are blowing
• 5:25
  Speaker 2: that stuff out into space and the Earth is flying
• 5:28
  Speaker 2: through Mars's dust clouds. So yeah, I guess it's all
• 5:31
  Speaker 2: Martian dandruff.
• 5:32
  Speaker 1: Yeah, Mars needs some head and shoulders.
• 5:36
  Speaker 2: Well first they need heads and shoulders. That'd be pretty
• 5:38
  Speaker 2: awesome discovery.
• 5:39
  Speaker 1: Yeah, or maybe just a hat that might help. But
• 5:42
  Speaker 1: it is an interesting question. How important is cosmic dust?
• 5:46
  Speaker 1: Which I guess means Daniel, that cosmic dust is important.
• 5:49
  Speaker 2: Cosmic dust is more important than you might think. I mean,
• 5:51
  Speaker 2: the word dust makes you think it's insignificant. It's just
• 5:54
  Speaker 2: something to be blown off of. Something else. Man, it
• 5:56
  Speaker 2: gets in your way, something, it messes things up, something
• 5:59
  Speaker 2: to be gotten rid of. But dust has clues in it.
• 6:02
  Speaker 2: This is like the dust here on Earth tells you
• 6:03
  Speaker 2: who's been living there and the insects that have been around.
• 6:06
  Speaker 2: Dust out in space tells you what's been happening in
• 6:08
  Speaker 2: the universe, because there's dust makers and dust consumers, and
• 6:11
  Speaker 2: dust also plays a big role in making stars and planets.
• 6:15
  Speaker 1: Well, you just said dust consumers out in space like
• 6:18
  Speaker 1: aliens who buy dust. That's what it sounds like.
• 6:22
  Speaker 2: Not dust customers. You know, ways in which just is
• 6:25
  Speaker 2: created and then dust is destroyed. I should say dust destroyers.
• 6:29
  Speaker 1: Oh there you go. See that's a device. I would
• 6:31
  Speaker 1: buy a dust destroyer.
• 6:33
  Speaker 2: Wait till you learn how dust is destroyed. You don't
• 6:35
  Speaker 2: want one of these things?
• 6:38
  Speaker 1: Maybe I do. Let's find out. Well, as usual, we
• 6:40
  Speaker 1: were wondering how many people had thought about the importance
• 6:43
  Speaker 1: of cosmic does and what role it has in our
• 6:46
  Speaker 1: search for the meaning of the universe and how it
• 6:48
  Speaker 1: all works.
• 6:49
  Speaker 2: Thanks to everybody who pitches in for this segment of
• 6:52
  Speaker 2: the podcast. I hear from listeners that they really enjoy
• 6:55
  Speaker 2: hearing your voices in your thoughts on the episode topic.
• 6:58
  Speaker 2: If you would like to share your voice and thoughts,
• 7:00
  Speaker 2: please don't be shy. Write me to Questions at Daniel
• 7:03
  Speaker 2: Andandjorge dot com.
• 7:05
  Speaker 1: So think about for a second, how important do you
• 7:07
  Speaker 1: think cosmic dust is. Here's what people have to say.
• 7:11
  Speaker 2: Stop waving from the universe. I would say that twenty
• 7:14
  Speaker 2: percent is planet stars, black holes, sixty percent gus, and
• 7:20
  Speaker 2: the rest twenty percent is dust.
• 7:21
  Speaker 3: I think that this is the one of those questions
• 7:24
  Speaker 3: that but you have to think about some things that
• 7:27
  Speaker 3: you usually take for granted. So I would say that
• 7:32
  Speaker 3: the QA is mostly composed by dust.
• 7:36
  Speaker 1: All right, interesting, answers here, some people seem to interpret
• 7:40
  Speaker 1: the questions like how significant is cosmic? Doest?
• 7:45
  Speaker 2: Yeah?
• 7:45
  Speaker 1: Like, or like how much how much of the universe
• 7:48
  Speaker 1: is cosmic? Does?
• 7:49
  Speaker 2: And they also seem to be taking it as a
• 7:50
  Speaker 2: leading question, like because I'm asking it, they're figuring probably
• 7:54
  Speaker 2: it's a big component of the universe and playing an
• 7:57
  Speaker 2: important role.
• 7:58
  Speaker 1: I see, it wouldn't be very interesting just the answer
• 8:00
  Speaker 1: was just like not at all or nope, nobody cares.
• 8:05
  Speaker 2: Yeah, Like how important are Daniel dirty socks?
• 8:08
  Speaker 3: Yeah?
• 8:08
  Speaker 2: Not interesting, not important? Move on, That wouldn't be a
• 8:11
  Speaker 2: very fun episode.
• 8:13
  Speaker 1: Let's not talk about your socks because I know you
• 8:16
  Speaker 1: don't wear socks, so.
• 8:17
  Speaker 2: Well, then it's a philosophy question, right can my socks
• 8:20
  Speaker 2: be unimportant if they don't even exist?
• 8:22
  Speaker 1: There you go, philosophy of footwear.
• 8:25
  Speaker 2: Somebody out there is doing a whole PhD thesis on
• 8:28
  Speaker 2: that topic, probably.
• 8:29
  Speaker 1: On your socks. On socks, and Jackie, I know you're
• 8:31
  Speaker 1: famous now, Daniel, but geez.
• 8:34
  Speaker 2: No on socks? Why they disappear where they go? Why
• 8:37
  Speaker 2: dryers consume them? See dryers are sock destroyers.
• 8:41
  Speaker 1: Nay, it turns them into dust.
• 8:43
  Speaker 2: Maybe it transports them to the hozone layer of the atmosphere.
• 8:45
  Speaker 1: So let's dig into this topic, Daniel, what is cosmic dust?
• 8:50
  Speaker 2: Cosmic dust is an important part of the Solar system,
• 8:53
  Speaker 2: though it's not a big fraction of the Solar system.
• 8:56
  Speaker 2: The answer from these listeners made me dig into the
• 8:58
  Speaker 2: question of like, actually, but is the mass budget of
• 9:02
  Speaker 2: the Solar system? How much of it is cosmic dust
• 9:04
  Speaker 2: and how much of it is made of other stuff?
• 9:08
  Speaker 1: So what's the breakdown?
• 9:09
  Speaker 2: So the Milky Way weighs about one to one and
• 9:12
  Speaker 2: a half trillion times the mass of the Sun. That's
• 9:15
  Speaker 2: like our mass unit a solar mass, and the total
• 9:19
  Speaker 2: Milky Way is about a trillion trillion and a half
• 9:21
  Speaker 2: solar masses. Now, most of that, like ninety percent of
• 9:24
  Speaker 2: that is dark matter. We know that the stuff that's
• 9:27
  Speaker 2: visible in the universe, the stuff that glows, and even
• 9:30
  Speaker 2: the stuff that doesn't glow that much, like rocks and
• 9:32
  Speaker 2: dust and asteroids, that's only like ten percent of the
• 9:36
  Speaker 2: mass of the Milky Way. Out there in the larger universe,
• 9:38
  Speaker 2: dark matter is a little bit less common than it
• 9:40
  Speaker 2: is here in the Milky Way. The Milky Way has
• 9:42
  Speaker 2: more dark matter than an average galaxy.
• 9:44
  Speaker 1: And I guess. How do we know these things? Like
• 9:46
  Speaker 1: how do we know how much the Milky Way weighs?
• 9:48
  Speaker 1: Do we put it on a scale or something.
• 9:50
  Speaker 2: We can measure the component of the Milky Way independently
• 9:53
  Speaker 2: and then add them up. The stars and the interstellar medium,
• 9:56
  Speaker 2: the black hole, all that stuff we can measure independently,
• 10:00
  Speaker 2: and then we can measure the total mass by looking
• 10:02
  Speaker 2: at how fast the Milky Way is rotating. Because stars
• 10:05
  Speaker 2: are like tracers, they move around the Milky Way, and
• 10:08
  Speaker 2: their speed is determined by the gravitational traction of everything
• 10:12
  Speaker 2: closer to the center than they are. Things further away
• 10:15
  Speaker 2: from the center on the outer shell don't affect them
• 10:17
  Speaker 2: at all, things on the inside do. So by reading
• 10:20
  Speaker 2: the speed of these stars, we can tell how much
• 10:23
  Speaker 2: mass they're radius encloses, and so that measures the total
• 10:26
  Speaker 2: mass of the Solar system. And that's how we infer
• 10:29
  Speaker 2: dark matter, sort of the left over bit that we
• 10:31
  Speaker 2: can't account for with stars and planets and gas and dust.
• 10:34
  Speaker 1: But we can't see all of the Milky Way right
• 10:37
  Speaker 1: Like we're in the Milky Way, can we really see
• 10:40
  Speaker 1: the full extent of it and have a good guess
• 10:42
  Speaker 1: about its composition?
• 10:43
  Speaker 2: There's a lot of uncertainty, which is why I said
• 10:45
  Speaker 2: one to one and a half trillion solar masses. So
• 10:48
  Speaker 2: that's like an uncertainty of five hundred billion solar masses.
• 10:52
  Speaker 2: And yeah, part of that comes from the fact that
• 10:53
  Speaker 2: we can't see the whole Milky Way because we're looking
• 10:55
  Speaker 2: through it, we're inside of it, and the Milky Way
• 10:58
  Speaker 2: has a good amount of dust in it, and that
• 11:00
  Speaker 2: dust obscures our view. So there's a whole region of
• 11:03
  Speaker 2: the Milky Way that we can't see very well in
• 11:05
  Speaker 2: many frequencies of light, and that leads to a lot
• 11:08
  Speaker 2: of this uncertainty. I see.
• 11:09
  Speaker 1: So then how much of our Milky Way is dust?
• 11:12
  Speaker 2: So it's like ninety percent dark matter, Then it's like
• 11:14
  Speaker 2: three percent stars, it's like one hundred to two hundred
• 11:17
  Speaker 2: billion stars. And then leftover is this stuff called the
• 11:20
  Speaker 2: interstellar medium, which is maybe like half a percent or
• 11:24
  Speaker 2: one percent of the mass of the Milky Way, and
• 11:26
  Speaker 2: one percent of that is dust. The interstellar medium is
• 11:30
  Speaker 2: mostly gas, it's like hydrogen and a little bit of helium.
• 11:33
  Speaker 2: So one percent of the interstellar medium, which is one
• 11:35
  Speaker 2: percent of the galaxy, is dust. So the dust is
• 11:38
  Speaker 2: like point zho one percent or maybe half of that.
• 11:41
  Speaker 2: It's a tiny fraction of the mass of the Milky Way.
• 11:44
  Speaker 1: So I guess you don't count that gas is dust, right.
• 11:47
  Speaker 2: That's right. And this is another example of humans putting
• 11:50
  Speaker 2: categories on things where really there's a smooth spectrum. If
• 11:54
  Speaker 2: we call it gas, it means it's like a molecule,
• 11:56
  Speaker 2: there's like h two floating out there, we call that gas.
• 11:59
  Speaker 2: If it's a larger clump of stuff, a bunch of
• 12:02
  Speaker 2: molecules together, little grains down like one hundred nanometers or larger,
• 12:06
  Speaker 2: we call that dust. Get much bigger, we start to
• 12:09
  Speaker 2: call you like a meteor or an asteroid or even
• 12:12
  Speaker 2: a planet. But in the end, there's a whole spectrum
• 12:14
  Speaker 2: all the way down from individual molecules which we call gas,
• 12:18
  Speaker 2: to larger clumps of stuff which we call dust, all
• 12:21
  Speaker 2: the way up to much bigger objects stars and planets.
• 12:24
  Speaker 1: I guess at some point you get to like pebbles, right,
• 12:27
  Speaker 1: and little rocks. Is there such a thing as space sand?
• 12:32
  Speaker 2: Well, you know this dust is made of carbon and silicates, right,
• 12:35
  Speaker 2: and sand is mostly silicates. So in the end, like
• 12:38
  Speaker 2: a lot of this space dust is kind of like
• 12:41
  Speaker 2: super fine grains of sand.
• 12:43
  Speaker 1: But then I also imagine there is sort of sand
• 12:45
  Speaker 1: sized grains out there in space.
• 12:47
  Speaker 2: There are larger pieces for sure, And so this intermedia
• 12:50
  Speaker 2: category we call dust is not a very big fraction
• 12:53
  Speaker 2: of the mass of the Milky Way. But to compare,
• 12:55
  Speaker 2: it's about the same mass as the central black Hole.
• 12:58
  Speaker 2: Point oh one percent of the Milky Way sounds like
• 13:01
  Speaker 2: a tiny number. It's a tiny percentage of a huge number, right,
• 13:04
  Speaker 2: one and a half trillion solar masses. So it comes
• 13:07
  Speaker 2: out to be about the mass of the central black Hole.
• 13:11
  Speaker 1: And so where did all this dust come from? Like
• 13:13
  Speaker 1: are there giant space aliens shedding of their skin?
• 13:16
  Speaker 2: To understand where the dust comes from, we need to
• 13:18
  Speaker 2: dig into a little bit more about like what is
• 13:20
  Speaker 2: this dust? And it's made of like a bunch of
• 13:23
  Speaker 2: different stuff, some tiny little portion of it, this is
• 13:26
  Speaker 2: really fascinating, comes from the atmospheres of stars. We know
• 13:30
  Speaker 2: that stars their job is to take hydrogen and helium
• 13:34
  Speaker 2: and lighter elements and fuse them into heavier elements, although
• 13:38
  Speaker 2: I have to iron and even heavier in the case
• 13:39
  Speaker 2: of supernova and in the atmospheres of these stars, especially
• 13:42
  Speaker 2: when they get really really big and near the end
• 13:45
  Speaker 2: of their life. Their atmospheres produce these little grains. They're
• 13:48
  Speaker 2: like coalesce as they cool, and the outflow in the
• 13:51
  Speaker 2: atmosphere of these stars. That's sort of like one source
• 13:54
  Speaker 2: of this stuff. But if you look out into the
• 13:57
  Speaker 2: universe and study this stuff, most of it is not
• 14:00
  Speaker 2: these presolar grains, these like pristine little blobs made in
• 14:03
  Speaker 2: the atmospheres of stars. Most of it's been like reprocessed,
• 14:06
  Speaker 2: like shattered and ground up and reformed into new bits.
• 14:10
  Speaker 1: Interesting just from like the churning of space, of stuff
• 14:13
  Speaker 1: in space.
• 14:13
  Speaker 2: Just from the churning of space. It turns out that
• 14:15
  Speaker 2: you can't just hang out as a grain in the
• 14:18
  Speaker 2: middle of space. There are processes happening out there. There
• 14:20
  Speaker 2: are processes that destroy dust and processes that reform it.
• 14:24
  Speaker 2: The dust destroyers that are out there. It sounds like,
• 14:26
  Speaker 2: you know, some big alien ship coming along to clean
• 14:29
  Speaker 2: up the universe, but actually it's shock waves from supernova.
• 14:33
  Speaker 2: When supernova collapse and then explode, they produce these huge
• 14:37
  Speaker 2: shock waves, massive amounts of energy, gamma, rays, neutrinos, all
• 14:41
  Speaker 2: sorts of stuff, and that comes along and it shatters
• 14:44
  Speaker 2: these grains, destroying the dust and breaking it like back
• 14:47
  Speaker 2: down into gas.
• 14:48
  Speaker 1: Well you know they say space is just a big vacuum,
• 14:50
  Speaker 1: so those are just suckle. Anyways, So you were saying
• 14:56
  Speaker 1: that dust is important in the universe. Is it important
• 14:59
  Speaker 1: to the universe or just to our understanding or to
• 15:02
  Speaker 1: our search for answers about the universe?
• 15:04
  Speaker 2: Well both, Like the history of dust tells us what's
• 15:06
  Speaker 2: happened out there in the universe. You can take each
• 15:09
  Speaker 2: individual solar grain if it survived this like interstellar shattering process,
• 15:14
  Speaker 2: and some of them have, and you can trace it
• 15:16
  Speaker 2: back to an individual star. Like every star has a
• 15:19
  Speaker 2: different mixture of elements and a different mixture of isotopes,
• 15:22
  Speaker 2: so they leave special fingerprints in their solar grains, and
• 15:26
  Speaker 2: so like ular grain can tell you, like what that
• 15:29
  Speaker 2: star was. It's like a little sample from that star.
• 15:32
  Speaker 2: And some of them are made during supernova and capture
• 15:35
  Speaker 2: elements and isotopes that only exist, we think, in the
• 15:39
  Speaker 2: atmospheres of supernova during those brief moments that are super
• 15:42
  Speaker 2: energetic and can tell us about the formation of heavy
• 15:45
  Speaker 2: elements and what's going on in supernova. So there are
• 15:48
  Speaker 2: these amazing capsules that tell us about the history of
• 15:51
  Speaker 2: the universe.
• 15:51
  Speaker 1: But I think maybe you don't mean like each individual grain,
• 15:54
  Speaker 1: do you look? You maybe need like a population or
• 15:57
  Speaker 1: like a cloud of this dust to sort of know
• 15:59
  Speaker 1: what the star was like.
• 16:01
  Speaker 2: Well, each individual grain tells you something about that star.
• 16:04
  Speaker 2: Not every grain produced by the star is identical, right,
• 16:07
  Speaker 2: and the star has a variety of stuff in it,
• 16:10
  Speaker 2: but each one traces back to an individual star.
• 16:12
  Speaker 1: Just each grain would be made out of different things.
• 16:15
  Speaker 2: Yeah, each star would make different kinds of grains. There's
• 16:17
  Speaker 2: going to be some overlap. It's not completely unique, right,
• 16:20
  Speaker 2: But each star is made out of different kinds of stuff,
• 16:23
  Speaker 2: different elements, different mixtures. Each star is a slightly different
• 16:26
  Speaker 2: mass and temperature and so produces different mixtures of stuff
• 16:29
  Speaker 2: and different isotopes, and so the grains produced by each
• 16:32
  Speaker 2: star are different.
• 16:33
  Speaker 1: Like an individual grain would have different things in it
• 16:36
  Speaker 1: and different signatures in it.
• 16:38
  Speaker 2: Yeah, exactly. The isotopes found in an individual grain tell
• 16:42
  Speaker 2: you about the star that it came from.
• 16:43
  Speaker 1: Mmmm. Interesting, So how is it important to the universe itself?
• 16:47
  Speaker 1: Because it doesn't seem like it weighs a lot in
• 16:49
  Speaker 1: the Milca way, So maybe I wonder if it has
• 16:51
  Speaker 1: a big role in you know, the dynamics of space.
• 16:54
  Speaker 2: It does play a big role in the dynamics of
• 16:55
  Speaker 2: space sort of for two reasons. One is that stuff
• 16:59
  Speaker 2: heavier than gas is the reason that we have like
• 17:02
  Speaker 2: planets and stars and stuff like that. Like the Earth
• 17:05
  Speaker 2: is mostly made out of stuff that's not just hydrogen
• 17:08
  Speaker 2: and helium, right, and that's cosmic dust gathered together to
• 17:11
  Speaker 2: form planets. So most of the rocky stuff of the
• 17:15
  Speaker 2: Solar system came originally from what we would call cosmic dust, right,
• 17:19
  Speaker 2: those heavier elements that are created by stars and spewed
• 17:23
  Speaker 2: out into space. And also we think that this cosmic
• 17:26
  Speaker 2: dust plays a role in the formation of solar systems.
• 17:28
  Speaker 2: You have a huge gas cloud that eventually collapses into
• 17:31
  Speaker 2: a bunch of stars. Why does it collapse. It collapses
• 17:34
  Speaker 2: because it's a little spot here that's denser, that's heavier,
• 17:37
  Speaker 2: that's cosmic dust. Man, Those are like the iron grains
• 17:41
  Speaker 2: and the little bits of heavy elements floating around that
• 17:44
  Speaker 2: seed that gravitational collapse.
• 17:46
  Speaker 1: Wait, are you saying the Bible was right? We all
• 17:48
  Speaker 1: come from dust, from dust to dust.
• 17:50
  Speaker 2: And even ashes, right, star ashes.
• 17:53
  Speaker 1: Cool And so then how does it help us study
• 17:55
  Speaker 1: the universe or how does it not help us study
• 17:58
  Speaker 1: the universe.
• 17:58
  Speaker 2: Yeah, it both hurts our ability to study the universe
• 18:01
  Speaker 2: and helps us. Like it prevents us from seeing things
• 18:04
  Speaker 2: in the universe because it absorbs light and it blocks
• 18:07
  Speaker 2: our view. The center of the Milky Way, which is
• 18:09
  Speaker 2: choked with dust, is famously called by astronomers the zone
• 18:13
  Speaker 2: of avoidance because they have to look away from that region.
• 18:16
  Speaker 2: You can't see through the center of the Milky Way
• 18:18
  Speaker 2: in optical lights, so you can't see what's on the
• 18:21
  Speaker 2: other side of the galaxy very easily. So it's sort
• 18:23
  Speaker 2: of a pain for astronomers, but it also captures this
• 18:26
  Speaker 2: history right, And in order to understand the cycles of
• 18:29
  Speaker 2: star formation in the universe, we do have to understand
• 18:32
  Speaker 2: the cosmic dust because the cosmic dust plays a role
• 18:35
  Speaker 2: in the formation of those stars and is also then
• 18:37
  Speaker 2: destroyed by the supernovas and then reforms. It's all part
• 18:40
  Speaker 2: of the cycle of the Milky Way. You might imagine
• 18:42
  Speaker 2: the Milky Way is just like a bunch of stars
• 18:44
  Speaker 2: floating in space basically doing nothing, but it's churning and burning.
• 18:48
  Speaker 2: This stuff going on just sort of much longer time
• 18:51
  Speaker 2: scales than we're used to thinking about.
• 18:53
  Speaker 1: Hmm. Interesting all right, Well, let's get into how we
• 18:56
  Speaker 1: know where the dust in the universe is and the
• 18:59
  Speaker 1: very important question where does it all come from? Who's
• 19:02
  Speaker 1: making this mess in the universe. So let's dig into that,
• 19:05
  Speaker 1: But first let's take a quick break. All right, we're
• 19:20
  Speaker 1: talking about cosmic dust, which is not a drug, I imagine,
• 19:25
  Speaker 1: so it sounds like it might be something you'd sell
• 19:28
  Speaker 1: on the streets.
• 19:28
  Speaker 2: I don't know. If you walk down the street in
• 19:30
  Speaker 2: Berkeley and you ask people for cosmic dust, I'm pretty
• 19:32
  Speaker 2: sure they'll sell you something.
• 19:33
  Speaker 1: They'll sell you something. But we're talking about the dust's
• 19:37
  Speaker 1: out there in space between the stars, and it's important
• 19:41
  Speaker 1: because we're all made out of dust. Stars and planets,
• 19:44
  Speaker 1: they're all essentially come from dust that gravity pulls together,
• 19:48
  Speaker 1: and so it's important for that reason. But it also
• 19:50
  Speaker 1: sort of helps us understand the origins of stars in
• 19:53
  Speaker 1: the universe.
• 19:54
  Speaker 2: Right, even though it's tiny, it's a little bitty part
• 19:57
  Speaker 2: of the mass budget of the Solar system. It tells
• 20:00
  Speaker 2: about how things work and it plays a role in
• 20:02
  Speaker 2: getting those things started.
• 20:03
  Speaker 1: But I imagine maybe at some point in the universe's
• 20:05
  Speaker 1: history dust it was all dust, basically, right, That's where
• 20:09
  Speaker 1: all those stars came from No, I guess you went
• 20:11
  Speaker 1: from gas to stars and then those made dust exactly.
• 20:15
  Speaker 2: We think that the universe began and dust lists right.
• 20:18
  Speaker 2: So it's actually an interesting open question in astronomy right now.
• 20:21
  Speaker 2: It is like when was the first dust made? People
• 20:25
  Speaker 2: really want to understand the process by which dust is
• 20:27
  Speaker 2: created and destroyed and helps form new stars, and there's
• 20:32
  Speaker 2: a lot of open questions out there. We don't really
• 20:34
  Speaker 2: fully understand the process of it. But we're pretty sure
• 20:37
  Speaker 2: that the universe began with just hydrogen and helium and
• 20:40
  Speaker 2: the tiny trace elements of things heavier and no larger
• 20:44
  Speaker 2: molecules of course, and it's only when stars began to
• 20:47
  Speaker 2: burn that dust was created.
• 20:49
  Speaker 1: But I wonder if in the Big Band, you know,
• 20:51
  Speaker 1: things were so intense, there was so much pressure, there
• 20:54
  Speaker 1: was so much violent processes going on, so many of
• 20:57
  Speaker 1: those that I wonder if some hydrogens aret it e
• 21:00
  Speaker 1: merging together and make dust without any stars? Is that possible?
• 21:04
  Speaker 2: With the earliest dust we've seen is like several hundred
• 21:06
  Speaker 2: million years after the Big Bang, and it's possible that
• 21:09
  Speaker 2: hydrogen formed and crystallized somehow earlier on. I don't think
• 21:13
  Speaker 2: we would call that cosmic dust. Though if it's just
• 21:15
  Speaker 2: pure hydrogen, probably you just call that hydrogen crystals. I
• 21:18
  Speaker 2: think to be called dust probably needs to have some
• 21:21
  Speaker 2: like carbon and some silicon and some heavier elements in it.
• 21:23
  Speaker 1: But I mean, could a little bit of a carbon
• 21:25
  Speaker 1: and silicon have formed in the big during the Big Bang?
• 21:28
  Speaker 2: Big Bang nuclear synthesis is a pretty precise science, and
• 21:32
  Speaker 2: it tells us, based on the temperature and like the
• 21:34
  Speaker 2: cork density, exactly how much of what was made. And
• 21:38
  Speaker 2: we think that it's almost overwhelmingly hydrogen, with just tiny
• 21:41
  Speaker 2: trace elements of helium and then little tiny, anty bitty
• 21:44
  Speaker 2: bits of heavier stuff carbon. Probably not because carbon requires
• 21:49
  Speaker 2: the merging of three helium simultaneously. Because lithium is so unstable,
• 21:53
  Speaker 2: so very unlikely that any carbon was formed, but you
• 21:56
  Speaker 2: can't say no, it's possible there were tiny, tiny grains
• 21:59
  Speaker 2: of carbon form during the Big Bang.
• 22:01
  Speaker 1: So there could be primordial dust out there, like og dust.
• 22:05
  Speaker 2: That's right, The most ancient dust is possible, though the
• 22:09
  Speaker 2: oldest dust we've ever seen is a few hundred million
• 22:11
  Speaker 2: years after the Big Bang.
• 22:13
  Speaker 1: All right, Well, that brings us to our next question,
• 22:15
  Speaker 1: which is, how do we know where the dust in
• 22:17
  Speaker 1: the universe is. It doesn't glow in space, right, It.
• 22:19
  Speaker 2: Actually kind of does glow in space, not the way
• 22:21
  Speaker 2: that stars do. Right. Stars create their own light through fusion.
• 22:24
  Speaker 2: They light up the whole universe. But everything out there
• 22:27
  Speaker 2: has a temperature, and everything that has a temperature glows.
• 22:30
  Speaker 2: Even the Earth glows. Right. It gives off infrared radiation,
• 22:34
  Speaker 2: and so dust glows in the very very infrared because
• 22:37
  Speaker 2: dust is pretty cold. So you can see the dust
• 22:40
  Speaker 2: if you use telescopes that can see infrared light and
• 22:43
  Speaker 2: so like the Spitzer Space Telescope and a James Web
• 22:46
  Speaker 2: Space telescope. These things out there can see dust in
• 22:49
  Speaker 2: our galaxy and in other galaxies by its thermal emissions.
• 22:54
  Speaker 1: Like I guess you could tell where there was a
• 22:55
  Speaker 1: lot of dust and where there isn't a lot of dust.
• 22:57
  Speaker 2: Yeah, exactly. You can't see an individual grain. You can
• 23:00
  Speaker 2: see like huge clouds of dust here and there. You
• 23:04
  Speaker 2: can see it glowing in the very far infrared. You
• 23:06
  Speaker 2: can also see dust by how it blocks light. Like
• 23:09
  Speaker 2: we think we understand how stars glow and the light
• 23:11
  Speaker 2: that they give off, and dust blocks that light. You know,
• 23:14
  Speaker 2: it absorbs some frequencies of it, it reflects other frequencies of it,
• 23:18
  Speaker 2: and so by looking at what astronomers call the extinction curve,
• 23:21
  Speaker 2: like where's light being blocked, they can measure how much
• 23:24
  Speaker 2: dust there is between us and something.
• 23:27
  Speaker 1: So we measure it by how it much it blocks light,
• 23:30
  Speaker 1: not how much it reflects light.
• 23:31
  Speaker 2: We measure it by how much it blocks light and
• 23:33
  Speaker 2: also emits a little bit of light in the infrared,
• 23:36
  Speaker 2: so it depends a lot on the frequency it will reflect.
• 23:39
  Speaker 2: Blue light mostly infrared light can mostly pass through dust
• 23:43
  Speaker 2: shorter frequencies where the light has like roughly the wavelength
• 23:45
  Speaker 2: of the dust that will get reflected or absorbed. So
• 23:49
  Speaker 2: when light passes through a dust cloud, it basically gets
• 23:51
  Speaker 2: reddened because the blue light gets reflected and the red
• 23:55
  Speaker 2: light makes it through.
• 23:57
  Speaker 1: It's a little bit of the opposite of what happens
• 23:58
  Speaker 1: here during the sunset. No, it's the same.
• 24:00
  Speaker 2: It's the same. The light gets reddened, right, the atmosphere
• 24:03
  Speaker 2: tends to reflect blue light, so the sky looks blue
• 24:06
  Speaker 2: because in direct sunlight it's scattered down to your eye.
• 24:09
  Speaker 2: That at sunset, the light is coming straight at you
• 24:11
  Speaker 2: and the blue light is being reflected away and you're
• 24:13
  Speaker 2: seeing the red light. Mm.
• 24:15
  Speaker 1: It filters like it filters out blue light.
• 24:17
  Speaker 2: M hmm, exactly, it filters out blue light. And so
• 24:20
  Speaker 2: when astronomers look out into the sky, they can see
• 24:23
  Speaker 2: that some stars appear to be dimmed, and they appear
• 24:25
  Speaker 2: to be dimmed differently across the spectrum. Right, It's not
• 24:28
  Speaker 2: just like the whole star is dimmer, which might mean
• 24:31
  Speaker 2: it just further away, but it's dimmed more in the
• 24:33
  Speaker 2: red than in the blue. So these extinction curves are
• 24:36
  Speaker 2: really important for astronomers to study because every time they're
• 24:39
  Speaker 2: looking at something in the universe, they want to know,
• 24:40
  Speaker 2: like how much dust are we looking through? How much
• 24:43
  Speaker 2: is dust distorting what we're seeing?
• 24:46
  Speaker 1: So technically, does that mean that dust, this space dust
• 24:49
  Speaker 1: is blue like if you were well, when you sort
• 24:52
  Speaker 1: of look at it, it's blueish.
• 24:53
  Speaker 2: I guess it reflects blue light. It glows in the
• 24:56
  Speaker 2: far infrared, but it reflects blue light, so I guess
• 24:59
  Speaker 2: that would make it kind blue.
• 25:00
  Speaker 1: Yeah, And have we ever like got in a sample
• 25:03
  Speaker 1: of dust, Like, have we ever gone out there and
• 25:05
  Speaker 1: grabbed a you know, vacuum up some dust to study it?
• 25:09
  Speaker 2: We do actually have samples of space dust. It's super fascinating.
• 25:12
  Speaker 2: All the dust that we have sampled is only stuff
• 25:14
  Speaker 2: in our solar system, so we've never sampled stuff outside
• 25:18
  Speaker 2: of our solar system. The furthest probes we ever sent
• 25:21
  Speaker 2: have like just barely left the Solar system. But there's
• 25:23
  Speaker 2: plenty of space dust here in our solar system, and
• 25:26
  Speaker 2: many many satellites that we send have little dust collectors.
• 25:30
  Speaker 2: It's kind of a challenge because these satellites are moving
• 25:32
  Speaker 2: in very high speeds relative to the dust, so it
• 25:34
  Speaker 2: can be trickyed like catch the dust. But there are
• 25:37
  Speaker 2: some missions like the Star Dust Mission, specifically to capture
• 25:40
  Speaker 2: dust and bring it back, But then lots of other
• 25:42
  Speaker 2: satellites have like a little space dust collector on it.
• 25:45
  Speaker 2: We talked once about the JUNO mission that went to
• 25:47
  Speaker 2: Jupiter in twenty eleven had sort of an accidental star
• 25:51
  Speaker 2: dust collector on it. The dust was slamming into the
• 25:53
  Speaker 2: back of the solar panels on the satellite and then
• 25:56
  Speaker 2: spilating off little bits which you got picked up by
• 25:59
  Speaker 2: a camera, and it turned out to be like a
• 26:01
  Speaker 2: huge effective dust collector, and this is how we learned
• 26:04
  Speaker 2: that Mars is giving off all of this dust, which
• 26:08
  Speaker 2: is probably responsible for causing the zodiacal light. We have
• 26:11
  Speaker 2: also captured some dust and broad down to Earth and
• 26:13
  Speaker 2: studied it under a microscope and seeing like some fractions
• 26:16
  Speaker 2: of this stuff really are presolar grains, bits of dust
• 26:20
  Speaker 2: that are older than our solar system. Oh, super old dust,
• 26:24
  Speaker 2: super old dust. Our solar system is like four and
• 26:26
  Speaker 2: a half billion years old. But of course stars have
• 26:29
  Speaker 2: been around for much longer than that, and some of
• 26:31
  Speaker 2: them died and created these grains, which amazingly survived out
• 26:35
  Speaker 2: there in space and then formed into asteroids or formed
• 26:38
  Speaker 2: as part of the Earth, or still just floating out there.
• 26:41
  Speaker 2: It's incredible that some of these little grains have lasted
• 26:44
  Speaker 2: so long.
• 26:45
  Speaker 1: And we also know how much dust is out there
• 26:47
  Speaker 1: because it's polarized, right, It's got some sort of electrical charge,
• 26:51
  Speaker 1: noess to it.
• 26:52
  Speaker 2: Yeah, the dust grains are not spherical, right, They have
• 26:54
  Speaker 2: little shapes. They're irregular, which means that they tend to
• 26:57
  Speaker 2: be longer in one direction than another. And because they're
• 27:01
  Speaker 2: made of electromagnetic stuff, sometimes they have an overall charge.
• 27:04
  Speaker 2: You know. The dust like bumps against itself, it gets
• 27:07
  Speaker 2: like static electricity essentially, and then interstellar space it will
• 27:10
  Speaker 2: align with magnetic fields, you know, the Earth has a
• 27:13
  Speaker 2: magnetic field, the Sun has a magnetic field, the whole
• 27:15
  Speaker 2: galaxy has magnetic fields. We think there might even be
• 27:18
  Speaker 2: magnetic fields out there in between superclusters. We talked once
• 27:22
  Speaker 2: about primordial magnetic fields. Anyway, the dust grains are a
• 27:25
  Speaker 2: great way to measure those magnetic fields because they align
• 27:29
  Speaker 2: with the magnetic fields, and then when light passes through them,
• 27:32
  Speaker 2: it tends to polarize the light because the dust itself
• 27:35
  Speaker 2: is pointing in a specific direction. So light passing through
• 27:38
  Speaker 2: this region can tell you about the dust and about
• 27:41
  Speaker 2: the magnetic fields in that region. It's sort of an amazing
• 27:44
  Speaker 2: way to like learn about these huge regions of space
• 27:46
  Speaker 2: which otherwise look empty.
• 27:48
  Speaker 1: Well, it's like having special glasses to see the universe.
• 27:51
  Speaker 2: Yeah, exactly. So we have lots of ways to study
• 27:54
  Speaker 2: cosmic dust and to look at the spectrum. And you know,
• 27:56
  Speaker 2: looking at the spectrum also tells you what's in there,
• 27:59
  Speaker 2: because if it has like a certain crystal, then that
• 28:01
  Speaker 2: crystal has rotational and vibrational frequencies and they will absorb
• 28:05
  Speaker 2: with those frequencies or emitted those frequencies, and so they
• 28:08
  Speaker 2: can tell what's in cosmic dust. Even if we can't
• 28:11
  Speaker 2: sample it, like cosmic dust is far far away in
• 28:14
  Speaker 2: the milky Way. They can tell what it's made out
• 28:16
  Speaker 2: of based on how it glows and how it absorbs light.
• 28:19
  Speaker 1: Hmmm, because that can change, I guess, depending on what
• 28:23
  Speaker 1: was happening there that made the dust exactly.
• 28:26
  Speaker 2: Because cosmic dust is not static, right. One of the
• 28:29
  Speaker 2: big mysteries is like where's all this cosmic dust come from?
• 28:32
  Speaker 2: And you know, we think that a lot of it
• 28:34
  Speaker 2: is made in stars. It's made in supernova, It's made
• 28:37
  Speaker 2: in these stars called asymptotic giant branch stars. It's made
• 28:41
  Speaker 2: in super red giant stars to have like just the
• 28:44
  Speaker 2: right conditions in their atmosphere to coalesce this stuff, like
• 28:48
  Speaker 2: outflowing and cooling gases will create these grains and shoot
• 28:51
  Speaker 2: them out into the universe. And that's cool, but it
• 28:54
  Speaker 2: can't explain all the dust that we see out there.
• 28:57
  Speaker 2: There's like not enough stars and not enough for of
• 29:00
  Speaker 2: this dust to explain all the dust that's out there
• 29:03
  Speaker 2: in the universe. Because, as we said earlier, the dust
• 29:05
  Speaker 2: doesn't survive forever. Right. The dust is like shattered by supernova.
• 29:09
  Speaker 2: So we have like stars pumping dust out in the
• 29:11
  Speaker 2: universe supernova shattering it back in the gas, and that
• 29:14
  Speaker 2: leaves sort of a mystery because there's not enough being
• 29:16
  Speaker 2: made by the stars to explain all the stuff that
• 29:19
  Speaker 2: we see out there, all the dust in the Milky
• 29:20
  Speaker 2: Way I see.
• 29:21
  Speaker 1: So like dust is sort of like they're bigger molecules basically, right,
• 29:25
  Speaker 1: they're like little tiny pebbles, and inside of the stars
• 29:28
  Speaker 1: they just burn up I guess, right, because it's so
• 29:31
  Speaker 1: hot and under so much pressure.
• 29:33
  Speaker 2: Yeah, that's why they're made. Like in the outer atmosphere,
• 29:35
  Speaker 2: the outflowing and cooling gases coalesced into these grains. If
• 29:39
  Speaker 2: that ever happened inside the star, that would just burn
• 29:41
  Speaker 2: up as fuel.
• 29:42
  Speaker 1: Yeah, like the carbon and all the silicon. It's sort
• 29:44
  Speaker 1: of gassy within the sun, but once it gets out
• 29:47
  Speaker 1: of the Sun, it tends to form into molecules and
• 29:50
  Speaker 1: maybe little clumps mm hmm. But then you're saying like,
• 29:53
  Speaker 1: once it's out there in space, then if there's a supernova,
• 29:55
  Speaker 1: the supernova breaks it up back into carbon and silicon exactly.
• 29:59
  Speaker 2: So like the typical lifetime for a grain of dust,
• 30:02
  Speaker 2: it's like one hundred million years. It can float out there,
• 30:05
  Speaker 2: and then on average it's going to get shattered after
• 30:07
  Speaker 2: about one hundred million years, some longer, some shorter, but
• 30:10
  Speaker 2: on average one hundred million years.
• 30:12
  Speaker 1: There are that many supernovas happening that to shatter does
• 30:16
  Speaker 1: so frequently.
• 30:16
  Speaker 2: There are not that many supernovas, but they're frequent enough
• 30:19
  Speaker 2: and powerful enough to shatter this cosmic dust.
• 30:22
  Speaker 1: So like on average, for any point in space, you
• 30:25
  Speaker 1: experience this shattering supernova every hundred million years.
• 30:28
  Speaker 2: Yeah, the supernova are more common than every hundred million years.
• 30:31
  Speaker 2: There's a supernova in our galaxy roughly every fifty years,
• 30:35
  Speaker 2: so in one hundred million years, you're going to get
• 30:38
  Speaker 2: two million supernova across the galaxy and they're very very powerful.
• 30:42
  Speaker 2: So the modeling at least tells astronomers that these things
• 30:45
  Speaker 2: should be shattered on average within one hundred million years.
• 30:48
  Speaker 1: But the Earth has been around longer than that, and
• 30:50
  Speaker 1: have we experienced such as shattering supernova.
• 30:53
  Speaker 2: The Earth has been around much longer than that, but
• 30:55
  Speaker 2: it would take a very close by supernova to shatter
• 30:57
  Speaker 2: the Earth. These grains are more delicate than Earth, which
• 31:00
  Speaker 2: has been like compressed right.
• 31:02
  Speaker 1: M So like if there's a bit of dust circling
• 31:05
  Speaker 1: the Earth, it would get shattered by the supernova, but
• 31:07
  Speaker 1: not our atmosphere or US.
• 31:09
  Speaker 2: Yeah, dust is more fragile. You know, it's floating out
• 31:11
  Speaker 2: there into space. It's very low pressure. These things are
• 31:14
  Speaker 2: sort of fragile compared to like a rock on Earth.
• 31:16
  Speaker 1: All right, So then the mystery you're saying is like
• 31:19
  Speaker 1: how it's made?
• 31:20
  Speaker 2: Then, Yeah, the mystery is like why is there still
• 31:22
  Speaker 2: so much of it? There's a lot more cosmic dust
• 31:24
  Speaker 2: out there than can be explained by this combination of
• 31:27
  Speaker 2: stars producing it and then supernova's destroying it. There's a
• 31:30
  Speaker 2: lot more cosmic dust that can be explained by just
• 31:33
  Speaker 2: that process.
• 31:34
  Speaker 1: Maybe the unergy just hasn't bought that neat device you
• 31:36
  Speaker 1: have to get rid of dust.
• 31:40
  Speaker 2: Well, one theory about what's going on is that cosmic
• 31:43
  Speaker 2: dust itself can reform out there between the stars. So
• 31:47
  Speaker 2: you take these little pebbles, these little grains, you send
• 31:50
  Speaker 2: them out there. They get shattered back into gas, but
• 31:53
  Speaker 2: there's like a tiny little seed left, you know, a
• 31:55
  Speaker 2: few molecules still cleaning together, and then those can accrete
• 31:59
  Speaker 2: because they're flowing through these molecular clouds which are super
• 32:02
  Speaker 2: duper cold, and basically because you have a few tiny,
• 32:06
  Speaker 2: little grains left, they can like pick up more like
• 32:08
  Speaker 2: ice can form on these things, and you get these
• 32:11
  Speaker 2: layers that surround the original tiny core that rebuilds this
• 32:15
  Speaker 2: thing back up into what you would call dust.
• 32:18
  Speaker 1: I see. Yeah, just reforms because and also because of gravity.
• 32:21
  Speaker 1: I imagine, right, like even if you split a little
• 32:24
  Speaker 1: grain of dust out there, eventually, gravity is going to
• 32:27
  Speaker 1: put it back together, isn't it.
• 32:28
  Speaker 2: Yeah, exactly? And you know that's the process that eventually
• 32:31
  Speaker 2: forms stars and planets, right, These little gravitational seeds gathered
• 32:36
  Speaker 2: together over very long periods, but it begins with gathering
• 32:40
  Speaker 2: little bits of ice here and there and reforming. And
• 32:43
  Speaker 2: so some of the cognic dust that's out there are
• 32:46
  Speaker 2: like og grains that came from their stars and haven't
• 32:49
  Speaker 2: been shattered, but most of it probably comes from this
• 32:52
  Speaker 2: process where they have been shattered and then they coalesce,
• 32:55
  Speaker 2: collecting ice and reforming into grains.
• 32:58
  Speaker 1: All right, Well, you mentioned that there are some things
• 33:00
  Speaker 1: called dust destroyers out there in space and also mysterious
• 33:04
  Speaker 1: ways that dust is made, and so let's dig deeper
• 33:07
  Speaker 1: into those things. But first let's take a quick break. Okay,
• 33:23
  Speaker 1: we're talking about dust and Daniels you're saying, the big
• 33:26
  Speaker 1: question is where does it come from? Because most of
• 33:28
  Speaker 1: the dust. If you just put dust out there in space,
• 33:30
  Speaker 1: within one hundred million years, some distant supernova's shockwave is
• 33:35
  Speaker 1: gonna shatter that back into its constituent atoms like carbon
• 33:39
  Speaker 1: and slogan. It doesn't seem that fragile here on Earth, right,
• 33:42
  Speaker 1: Like if I blow on dust, it doesn't break up
• 33:44
  Speaker 1: into carbon gas.
• 33:46
  Speaker 2: I mean, you're pretty tough, dude, But are you saying
• 33:47
  Speaker 2: that your breath is as powerful as a supernova?
• 33:50
  Speaker 1: Well, some mornings, yeah, But I mean, like it's weird
• 33:55
  Speaker 1: to think that it's so powerful because here on Earth
• 33:57
  Speaker 1: we don't feel these supernovas. But you're saying it's drying
• 34:00
  Speaker 1: enough to like split apart molecules in space.
• 34:02
  Speaker 2: The dust is more fragile than the Earth is. Yeah,
• 34:05
  Speaker 2: and it hasn't been a supernova in our Milky Way
• 34:08
  Speaker 2: in quite a few hundred years, so it's not like
• 34:10
  Speaker 2: we're feeling these things every ten years or so. Even
• 34:12
  Speaker 2: these supernovas are not that common. But yeah, the lifetime
• 34:15
  Speaker 2: of dust is shorter than the lifetime of the Earth.
• 34:19
  Speaker 2: So the Earth and planets and stars definitely survived these
• 34:21
  Speaker 2: super nova shock waves in ways that the stellar dust doesn't.
• 34:25
  Speaker 1: So then the mystery is, like, if it is being
• 34:27
  Speaker 1: destroyed out there in space, why is there still dust?
• 34:30
  Speaker 1: Why is in and auges gas and individual atoms exactly?
• 34:35
  Speaker 2: And it's important that the dust is there because the
• 34:37
  Speaker 2: dust seeds planetary formation and star formation, you know, in
• 34:41
  Speaker 2: ways that we didn't always understand. Like back in the seventies,
• 34:44
  Speaker 2: before we really understood cosmic dust at all, people thought
• 34:47
  Speaker 2: that our solar system started just from gas, that you
• 34:51
  Speaker 2: could start from just like a blob of hydrogen and
• 34:53
  Speaker 2: helium and form all of this stuff, which doesn't really
• 34:56
  Speaker 2: make sense to me because then like where you're getting
• 34:58
  Speaker 2: all the iron and all this stuff to make planets.
• 35:00
  Speaker 2: But now it's very well understood that most of the
• 35:03
  Speaker 2: iron and most of the heavy metals are bound up
• 35:05
  Speaker 2: in these cosmic dust grains and you need them to
• 35:08
  Speaker 2: form solar systems with interesting bits on them like rocks
• 35:12
  Speaker 2: and people.
• 35:14
  Speaker 1: So then are you saying that like just gravity, you know,
• 35:17
  Speaker 1: pulling all of this stuff out there floating in space
• 35:19
  Speaker 1: into dust is not enough to account for the dust
• 35:21
  Speaker 1: we're seeing, Well, why not?
• 35:23
  Speaker 2: So just stellar production of dust isn't enough to account
• 35:26
  Speaker 2: for the dust that we're seeing. You need some way
• 35:28
  Speaker 2: to reform dust in the interstellar medium, otherwise, as you say,
• 35:32
  Speaker 2: it would be just gas. But we think that these
• 35:34
  Speaker 2: little grains probably do gather back together from gravity and
• 35:37
  Speaker 2: from deecretion of ice crystals. As you pass through a
• 35:40
  Speaker 2: molecular cloud, there's going to be chemical bonds that form
• 35:43
  Speaker 2: because these things are a little sticky, right, And so
• 35:46
  Speaker 2: that is a process that they think might explain where
• 35:49
  Speaker 2: the gas comes from. I talked to one scientist at
• 35:52
  Speaker 2: the University of Wasita in Japan who's super interested in
• 35:55
  Speaker 2: cosmic dust, and she said that this is like the
• 35:58
  Speaker 2: leading theory for how cosmic dust is being regenerated. But
• 36:02
  Speaker 2: nobody's like demonstrated this in the lab. They haven't done
• 36:05
  Speaker 2: tests where they take like a little grain and pass
• 36:07
  Speaker 2: it through a dust cloud and see this stuff reform.
• 36:10
  Speaker 2: It's alsort of like theoretical chemistry at this point.
• 36:13
  Speaker 1: Well, you need to replicate zero gravity, wouldn't you.
• 36:16
  Speaker 2: Yeah, exactly. It's the kind of experiment you'd want to
• 36:18
  Speaker 2: do out in space or on the iss or something.
• 36:20
  Speaker 1: So then that's the best answer to this mystery.
• 36:23
  Speaker 2: That's the best answer to this mystery.
• 36:24
  Speaker 1: So it sounds like you're saying, like there's a giant
• 36:26
  Speaker 1: vacuum in space just gathering all this stuff dust.
• 36:31
  Speaker 2: Well, you know again it's the supernova, right, Those are
• 36:33
  Speaker 2: the dust stories shattering it back into gas, and then
• 36:36
  Speaker 2: they think that it's probably reforming. But another really fascinating
• 36:39
  Speaker 2: way that they're trying to understand this process is by
• 36:41
  Speaker 2: trying to answer a related question, which is like how
• 36:44
  Speaker 2: early did dust form in the universe. So now that
• 36:47
  Speaker 2: we have like a super powerful infrared telescope, we can
• 36:51
  Speaker 2: look deeper into the history of the universe and look
• 36:54
  Speaker 2: for evidence of dust very very early on, like what
• 36:57
  Speaker 2: is the oldest dust that we can see in the universe,
• 37:00
  Speaker 2: and they'll give us a sense for these processes because remember,
• 37:03
  Speaker 2: like stars didn't turn on for a few hundred million years,
• 37:06
  Speaker 2: so the origin of the dust can really tell us
• 37:08
  Speaker 2: about like who is making this dust?
• 37:10
  Speaker 1: Right I think I mean, like if you look out
• 37:12
  Speaker 1: into deep space with your telescopes, you're looking back in time,
• 37:16
  Speaker 1: so like the light you're getting from those deep places
• 37:19
  Speaker 1: in the universe is really old light, which might be
• 37:22
  Speaker 1: old dust exactly.
• 37:24
  Speaker 2: And we think that most of the dust out there
• 37:26
  Speaker 2: in the universe right now is probably produced by these
• 37:28
  Speaker 2: super red giant stars and this asymptotic giant branch stars.
• 37:32
  Speaker 2: These special stars are super big and have just the
• 37:34
  Speaker 2: right conditions for this, like outflowing gas to cool and
• 37:38
  Speaker 2: form these little blobs which then flow down into space.
• 37:40
  Speaker 2: But the James Web Space Telescope recently saw direct evidence
• 37:44
  Speaker 2: for really really old grains of stars, like several hundred
• 37:48
  Speaker 2: million years or up to a billion years after the
• 37:51
  Speaker 2: Big Bang, too long ago for these stars, Like, we
• 37:54
  Speaker 2: don't think that there were these super red giant stars
• 37:57
  Speaker 2: early on in the universe. So probably the first dust
• 38:01
  Speaker 2: made in the universe were made by supernova from the
• 38:04
  Speaker 2: first generation of stars.
• 38:06
  Speaker 1: WHOA wait, so how do we know we're looking at
• 38:10
  Speaker 1: dust that old.
• 38:11
  Speaker 2: Because we're looking at images of galaxies that are super
• 38:13
  Speaker 2: duper far away. And so you can look at a
• 38:16
  Speaker 2: galaxy and you can understand from its red shift how
• 38:18
  Speaker 2: fast it's moving away from us, and therefore how far
• 38:21
  Speaker 2: away it is, and therefore the age of the thing
• 38:23
  Speaker 2: we're looking at.
• 38:24
  Speaker 1: Isn't most of that light coming from the stars in
• 38:26
  Speaker 1: the galaxy.
• 38:27
  Speaker 2: Yeah, most of that light does come from the stars,
• 38:29
  Speaker 2: But we're looking at an infrared telescope, and stars are
• 38:32
  Speaker 2: much quieter in the infrared, so we're seeing information from
• 38:35
  Speaker 2: the dust also.
• 38:36
  Speaker 1: Oh, I see, like we see the galaxy with a
• 38:38
  Speaker 1: regular light and then we switch the filter over to infrared,
• 38:42
  Speaker 1: and then you're basically getting the light from the dust.
• 38:45
  Speaker 2: Exactly, and specifically, what they're seeing here is extinction, right.
• 38:48
  Speaker 2: They're seeing an absorption feature at a very specific wavelength
• 38:52
  Speaker 2: twenty one seventy five inkstrums that they think is like
• 38:55
  Speaker 2: a dust wavelength, that that's what dust absorbs. So they
• 38:58
  Speaker 2: see like a dip in the light in this galaxy
• 39:00
  Speaker 2: at just the right wavelength that tells them that there
• 39:03
  Speaker 2: is dust in this very very old galaxy.
• 39:06
  Speaker 1: Oh, because I guess the size of your thing affects
• 39:11
  Speaker 1: what kind of light you're absorbing, right, because you kind
• 39:13
  Speaker 1: of have to be at about the same size as
• 39:15
  Speaker 1: the wavelength to absorb it exactly.
• 39:17
  Speaker 2: Earlier we were talking about how dust absorbs as various frequencies.
• 39:21
  Speaker 2: In general, the picture is that it interacts more with
• 39:23
  Speaker 2: blue light. It reflects that blue light, and it doesn't
• 39:25
  Speaker 2: interact as much with redor light because, as you say,
• 39:28
  Speaker 2: it's too small, like the wavelength of light is bigger
• 39:31
  Speaker 2: than these dust grains so it doesn't interact with them.
• 39:35
  Speaker 2: But also these things contain specific chemicals and sometimes little crystals,
• 39:39
  Speaker 2: and those have features that absorb at certain wavelengths, like
• 39:42
  Speaker 2: little oscillations and vibrational energy levels of these little crystals
• 39:46
  Speaker 2: inside these dust grains will absorb at specific wavelengths that
• 39:50
  Speaker 2: are known to be dust wavelengths. So they saw this
• 39:53
  Speaker 2: in this signature from the James Web Space telescope from
• 39:56
  Speaker 2: the duper Ancient galaxy, a galaxy too old to whole
• 40:00
  Speaker 2: any of these red giant stars or ASB stars. So
• 40:03
  Speaker 2: they think probably this is ancient dust, maybe from the
• 40:07
  Speaker 2: first round of generation of dust in the universe, probably
• 40:11
  Speaker 2: from supernova.
• 40:12
  Speaker 1: Like the first supernova's right, because that's that's when the
• 40:15
  Speaker 1: heavier elements are made.
• 40:16
  Speaker 2: And it's fascinating because supernova make this stuff and then
• 40:19
  Speaker 2: also destroy it, so they kind of like clean up
• 40:22
  Speaker 2: after themselves.
• 40:23
  Speaker 1: Right, Wait, how can it make them and destroy them
• 40:25
  Speaker 1: at the same time.
• 40:25
  Speaker 2: These dust grains are made by supernovas sort of in
• 40:27
  Speaker 2: the last dying minutes of a star's life, where you know,
• 40:30
  Speaker 2: these shockwaves create really intense environments and specific isotopes, and
• 40:34
  Speaker 2: then the outflow and the cooling makes these grains, but
• 40:36
  Speaker 2: then shockwaves from supernova's also destroy dust. Right, supernova are
• 40:40
  Speaker 2: the dust destroyers of the universe, So they both create
• 40:44
  Speaker 2: it and they also are responsible for destroying it.
• 40:46
  Speaker 1: Which do they do first? Do they first clean up
• 40:48
  Speaker 1: and then put a bunch of dust there or do
• 40:50
  Speaker 1: they put a bunch of dust and then immediately destroy it.
• 40:52
  Speaker 1: Can't be the latter, can it, because then we wouldn't
• 40:54
  Speaker 1: have any dust.
• 40:55
  Speaker 2: It must be that the shockwave from the supernova travels
• 40:57
  Speaker 2: out faster than dust grains, which means the first they're
• 41:00
  Speaker 2: cleaning up and then they're making a mess. So I
• 41:02
  Speaker 2: guess you're right. Actually it's in the wrong order. Or
• 41:04
  Speaker 2: they're destroying the dust grains from other supernovas and to
• 41:08
  Speaker 2: make space for their own.
• 41:10
  Speaker 1: So they're not cleaning up after themselves. They're just cleaning
• 41:14
  Speaker 1: it so that they can make a mess.
• 41:15
  Speaker 2: Yeah, they're sort of like scrubbing the graffiti off the
• 41:18
  Speaker 2: wall and then writing their own name on it.
• 41:20
  Speaker 1: Yeah.
• 41:23
  Speaker 2: I take it back. I take back everything positive I
• 41:25
  Speaker 2: said about supernovas well.
• 41:26
  Speaker 1: They're the reason we're here, so glad they haven't wiped
• 41:30
  Speaker 1: us off. I guess I'm we're glad that they made us.
• 41:34
  Speaker 1: All right, Well, what does it all mean about our
• 41:37
  Speaker 1: understanding of the history of the universe.
• 41:39
  Speaker 2: It means that all these processes, the ones that form stars,
• 41:42
  Speaker 2: that lead to supernovas, that lead to dust creation and
• 41:44
  Speaker 2: dust destruction, it's all part of this huge cosmic dance.
• 41:49
  Speaker 2: You know. We tend to think of the Milky Way
• 41:50
  Speaker 2: as like done, We've made all these stars. They're just
• 41:53
  Speaker 2: sort of like hanging out and burning now. But it's
• 41:56
  Speaker 2: a process, you know, and everything is connected as like
• 41:58
  Speaker 2: dust flowing and swirling. These things are being created, they're
• 42:01
  Speaker 2: being destroyed, they're being reformed. The whole thing is a big, frothing, active,
• 42:06
  Speaker 2: lively mess of processes, all of which are important to
• 42:09
  Speaker 2: creating the universe as we know it.
• 42:10
  Speaker 1: Yeah, and it sounds kind of precarious, right, Like basically,
• 42:13
  Speaker 1: we need a supernova to make all this dust, and
• 42:16
  Speaker 1: we need the dust to basically clump together into planets
• 42:19
  Speaker 1: and stars quickly before the next supernova tries to wipe
• 42:23
  Speaker 1: the board clean. Right, Like if another supernova had gone
• 42:27
  Speaker 1: off near us, or not even neros, but around us,
• 42:31
  Speaker 1: before the Sun, you know, got put together and the
• 42:35
  Speaker 1: Earth got put together, we might not be here. Is
• 42:37
  Speaker 1: that true?
• 42:37
  Speaker 2: It definitely would have affected things, but it's not something
• 42:40
  Speaker 2: we understand very well. And supernova's contribute in lots of
• 42:42
  Speaker 2: different ways. Like first of all, they destroy these grains,
• 42:46
  Speaker 2: but then later on a supernova shockwave can actually precipitate
• 42:49
  Speaker 2: the gravitational collapse of surviving grains into a new star.
• 42:54
  Speaker 2: So supernova shockwaves play lots of different complex roles. And
• 42:58
  Speaker 2: to say like that we even understand this story would
• 43:00
  Speaker 2: be to overstate it. For sure, there's a lot of
• 43:02
  Speaker 2: parts of this that we still don't understand. What we
• 43:05
  Speaker 2: do know is that it's complicated and everything is connected.
• 43:08
  Speaker 1: Sounds like our knowledge of it is a little dusty.
• 43:12
  Speaker 2: There's definitely a lot of ancient wisdom out there we
• 43:14
  Speaker 2: haven't yet collected, and we can look forward to blowing
• 43:16
  Speaker 2: the dust off of all of these.
• 43:18
  Speaker 1: Secrets, but not too hard, because then you might destroy
• 43:20
  Speaker 1: the dust.
• 43:21
  Speaker 2: Right, only if you have supernova morning breath.
• 43:24
  Speaker 1: All right, I guess the next time you look at
• 43:26
  Speaker 1: into the nice guy, I know that you're looking at
• 43:28
  Speaker 1: a bunch of dust as well, not just the beautiful
• 43:30
  Speaker 1: twinkling stars.
• 43:31
  Speaker 2: These tiny but mighty grains play an important role in
• 43:35
  Speaker 2: the formation of the Solar system, in helping us understand
• 43:38
  Speaker 2: what's out there, and also in blocking our view of
• 43:41
  Speaker 2: part of the glorious cosmos.
• 43:43
  Speaker 1: Hope you enjoyed that. Thanks for joining us. See you
• 43:45
  Speaker 1: next time. Hey, it's hoar Hey from the podcast, and
• 43:48
  Speaker 1: I'm super excited to announce that my new book, Oliver's
• 43:52
  Speaker 1: Great Big Universe, is available to order now.
• 44:02
  Speaker 2: Thanks for listening, and remember that Daniel and Jorge Explain
• 44:05
  Speaker 2: the Universe is a production of iHeartRadio. For more podcasts
• 44:09
  Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever
• 44:14
  Speaker 2: you listen to your favorite shows.