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

Episode Date: September 21, 2023

Daniel and Jorge dust off their knowledge of the tiny-but-mighty grains of space dust which help form our world and block our view of the cosmos.See omnystudio.com/listener for privacy information.

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We continue to be moved and inspired. by our guests and their courageously told stories. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hey, Daniel, you're kind of a neat freak, aren't you? I do like to keep my laptop nicely well-dusted. Wait, dusted like you put dust in it, or you take out dust? Or you wipe dust out of it. Good question.

I mean, I like my cookies well dusted with sugar, but my laptop keyboard well dusted with zero dust. Yeah, household dust is less delicious than powdered sugar. Isn't regular dust like 50% skin cells? That sounds like a pretty gross thing to put on your cookies. On the other hand, it would be pretty weird if powdered sugar just like accumulated in your house. It'd be pretty sweet. We might call for some sweeping changes.

Ah, I'm glad you got to dust off that old pun. Hi, I'm Horhamy Cartoonist and the author of Oliver's Great Big Universe. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I don't like dust as much as astronomers do. But do you still like it a little bit? I like dust the way I like the sun. It's fascinating. It's interesting. It's useful.

It tells us about the cosmos. But I don't really want it on my laptop or on my table. But everywhere else, it's okay? Yeah. Study it from a distance, you know, the way like I'm fascinated by cheetahs, but I don't really want to have a cheetah on my lap. Do you carry a duster with you at all times then? I actually do have this very fancy little machine for removing dust from your keyboard.

Is it called blowing on it? Or did you actually pay for a machine to do that? I actually have a nice little machine. It's really quite good, yeah. I should call it mini-made. Wait, what is it? Like a vacuum? No, it's like a little blower.

You know, replaces those disposable cans that I thought were not very environmentally friendly, though I do love them. Oh, I see. You mean like the dust between the keys, like in, you want to get rid of it like in the nooks and crannies. Yeah, exactly. I like a nice clean keyboard. Oh, I thought you meant like on your screen because I think you can just wipe that off. I think you can. but probably that dust contains all sorts of fascinating stories

where each of those bits has been. But you know if you just blow the dust, it's just getting in the air and then it's going to come back down on your keyboard. I know it's a cycle. Unless I'm willing to live in a clean room, I can never escape it. So you don't like living in clean rooms? I don't have to wear a hairnet and booties all the time, no. Just some of the time.

But anyways, welcome to our podcast, Daniel and Jorge, Explain the Universe, a production of Our Heart Radio. In which we dive deep into the cycles of the universe, the ones that produce massive stars and tiny grains of dust. Everything out there in the universe has a history and tells a story. And if we can unpack it, unravel it, and study it, we can reveal those stories and the history of our own cosmos to learn about the formation of planets and stars and the universe itself. From the biggest clues to the tiniest speck of dust. That's right. We blow the dust off of the universe.

trying to uncover what's underneath, what shiny surface or interesting facts are there for us to understand and to learn about. I love in archaeology how every time they're going to discover something amazing, they always have to blow dust off of it, pull cobwebs off of it. That's like your visual cue that you're about to learn something ancient. Wait, wait, what do you mean?

I mean, I just watched a new Indiana Jones, I guess. So, you know, anytime they unearth something from the olden days, it's always covered in dust, of course. To see, they carry a duster with them at all times. Maybe you can buy one of those devices and you didn't have to waste electricity. I'd be that neat freak archaeologist. I don't think I'd get very far in the field. But yeah, it is a dusty universe full of amazing things where even the dust is interesting in the universe.

Down here on Earth, we see dust is sort of a nuisance, something to brush out of our way. But out in space, dust plays a very important role in the formation of stars and planets. And it can reveal that history. Dust is not just a nuisance. It's a fascinating pile of tiny clues. So today on the podcast, we'll be asking the question. How important is cosmic dust? Now, hopefully this episode won't be a bust.

Should we just be sweeping cosmic dust under the cosmic rug? Or should we take it seriously and study it in detail? That's a bit of a dusty pun there. You used it already. But yeah, it's an interesting question here. Cosmic dust, I guess it's different than regular dust. Well, I think there's fewer dead skin cells and leftover bits of insects out there floating between the stars than there is here on Earth, but cosmic dust also falls to Earth. You mean it gets sprinkled from space like powdered sugar?

Well, you know, that space isn't empty and there's dust out there between the stars, but also between the planets. And as the Earth moves through these cosmic dust clouds, it accumulates some of them. Some tons of dust fall to Earth every year from interplanetary space out there in the solar system. Whoa. Is it like dandruff? Space dandruff? Or is that too embarrassing? We had a whole fun episode about where this stuff comes from. It's a bit of a mystery. There's a recent experiment, though, that tries to pin the blame on Mars. It might be that dust storms on Mars are blowing that stuff out into space and the Earth is flying through Mars's dust cloud. So, yeah, I guess it's all Martian dandruff.

Yeah, Mars needs some head and shoulders. Well, first, they need heads and shoulders. That would be pretty awesome. discovery. Yeah, or maybe just a hat. That might help. But it is an interesting question. How important is cosmic dust, which I guess means, Daniel, that cosmic dust is important. Cosmic dust is more important than you might think. I mean, the word dust makes you think it's insignificant. It's just something to be blown off of something else. Something that gets in your way, something that messes things up, something to be gotten rid of. But dust has clues in it. Just like the dust here on Earth tells you who's been living there and the insects that have been

around. Dust out in space tells you what's been happening in the universe. Because there's There's dust makers and dust consumers, and dust also plays a big role in making stars and planets. Whoa, you just said dust consumers out in space, like aliens who buy dust? That's what it sounds like. Not dust customers, you know. Ways and with just is created and then dust is destroyed. I should say dust destroyers. Oh, there you go.

See, that's a device I would buy, a dust destroyer. Wait until you learn how dust is destroyed. You don't want one of these things. Maybe I do. Let's find out. Well, as usually, we were wondering how many people had thought about the importance of Cosmic does and what role it has in our search for the meaning of the universe and how it all works. Thanks to everybody who pitches in for this segment of the podcast.

I hear from listeners that they really enjoy hearing your voices and your thoughts on the episode topic. If you would like to share your voice and thoughts, please don't be shy. Write to me to questions at Daniel and Jorge.com. So think about it for a second. How important do you think cosmic dust is? Here's what people have to say. Extrapolating from the universe, I would say that 20% is planet stars, black holes, 60% gas, and the rest 20% is dust. I think that this is the one of those questions that, but you think about some things that you usually take for granted.

So I would say that the Milky Way is mostly composed by dust. All right. Interesting answers here. Some people seem to interpret the question as like how significant is cosmic dust. Yeah. Or like how much of the universe is cosmic dust. And they also seem to be taking it as a leading question. Like because I'm asking it, they're figuring probably it's a big component of the universe and playing an important role. I see.

wouldn't be very interesting if the answer was just like not at all or nope nobody cares yeah like how important are daniel's dirty socks yeah not interesting not important move on that wouldn't be a very fun episode yeah let's not talk about your socks because uh i know you don't wear socks so well then it's a philosophy question right can my socks be unimportant if they don't even exist there you go philosophy of footwear somebody out there is doing a whole PhD thesis on that topic On your socks? On socks in general. I mean, I know you're famous now, Daniel, but geez.

No. On socks, why they disappear, where they go, why dryers consume them. See, dryers are sock destroyers. Maybe it turns them into dust. Maybe it transports them to the ozone layer of the atmosphere. So let's dig into this topic. Daniel, what is cosmic dust? Cosmic dust is an important part of the solar system,

though it's not a big fraction of the solar system. The answer from these listeners made me dig into the question. of like actually what is the mass budget of the solar system, how much of it is cosmic dust and how much of it is made of other stuff? So what does it break down? So the Milky Way weighs about one to one and a half trillion times the mass of the sun. That's like our mass unit, a solar mass. And the total Milky Way is about a trillion, trillion and a half solar masses.

Now most of that, like 90% of that is dark matter. We know that the stuff that's visible in the universe, the stuff that glows, and even the stuff that doesn't glow that much, like rocks and dust and asteroids, that's only like 10% of the mass of the Milky Way. Out there in the larger universe, dark matter is a little bit less common than it is here in the Milky Way. The Milky Way has more dark matter than an average galaxy. And I guess how do we know these things? Like, how do we know how much the Milky Way weighs? Do we put it on a scale or something? We can measure the components of the Milky Way independently and then add them up.

The stars and the interstellar medium and the black hole, all that stuff we can measure independently. And then we can measure the total mass by looking at how fast the Milky Way is rotating because stars are like tracers. They move around the Milky Way and their speed is determined by the gravitational traction of everything closer to the center than they are. Things further away from the center on the outer shell don't affect them at all. Things on the inside do. So by reading the speed of these stars, we can tell how much mass they're raised. radius encloses. And so that measures the total mass of the solar system. And that's how we infer dark matter, sort of the left over a bit that we can't account for with stars and planets

and gas and dust. But we can't see all of the Milky Way, right? Like we're in the Milky Way. Can we really see like the full extent of it and have a good guess about its composition? There's a lot of uncertainty, which is why I said one to one and a half trillion solar masses. So that's like an uncertainty of 500 billion solar masses. And yeah, part of that comes from the fact that we can't see the whole Milky Way because we're looking through it. We're inside of it. And the Milky Way has a good amount of dust in it and that dust obscures our view. So there's a whole region of the Milky Way that we can't see very well in many frequencies

of light. And that leads to a lot of this uncertainty. I see. So then how much of our Milky Way is dust? So it's like 90% dark matter. Then it's like 3% stars. It's like 100 to 200 billion stars. And then left over is this stuff called the interstellar medium, which is maybe like half a

percent or 1% of the mass of the Milky Way and 1% of that is dust. The interstellar medium is mostly gas. It's like hydrogen and a little bit of helium. So 1% of the interstellar medium, which is 1% of the galaxy, is dust. So the dust is like 0.01% or maybe half of that. It's a tiny fraction of the mass of the Milky Way. So I guess you don't count that the gas is dust, right? That's right.

And this is another example of humans putting categories on things where really there's a smooth spectrum. If we call it gas, it means it's like a molecule is like H2 floating out there. We call that gas. If it's a larger clump of stuff, a bunch of molecules together, little grains down like 100 nanometers or larger, we call that dust. You get much bigger, we start to call you like a meteor or an asteroid or even a planet. But in the end, there's a whole spectrum all the way down from individual molecules, which we call gas to larger clumps of stuff, which we call dust, all the way up to much bigger objects, stars and planets. I guess at some point you get to like pebbles, right?

And little rocks. Is there such a thing as space sand? Well, you know, this dust is made of carbon and silicates, right? And sand is mostly silicates. So in the end, like a lot of this space dust is kind of like super fine grains of sand. But then I also imagine there is sort of sand size grains out there in space. There are larger pieces for sure. And so this intermediate category we call dust is not a very important.

very big fraction of the mass of the Milky Way. But to compare, it's about the same mass as the central black hole. 0.01% of the Milky Way sounds like a tiny number. It's a tiny percentage of a huge number, right? One and a half trillion solar masses. So it comes out to be about the mass of the central black hole. And so where did all this dust come from? Like are there giant space aliens shedding off their skin? To understand where the dust comes from, we need to dig into a little bit more about like what is this dust and it's made of like a bunch of different stuff some tiny little portion of it this is really fascinating comes from the atmospheres of stars we know that stars their job is to take hydrogen and helium and low and lighter elements

and fuse them into heavier elements all the way up to iron and even heavier in the case of supernova and in the atmospheres of these stars especially when they get really really big and near the end of their life, their atmospheres produce these little grains that coalesce as they cool and the outflow in the atmosphere of these stars. That's sort of like one source of this stuff. But if you look out into the universe and study this stuff, most of it is not these pre-solar grains, these like pristine little blobs made in the atmospheres of stars. Most of it's been like reprocessed like shattered and ground up and reformed into new bits. Interesting. Just from like the churning of space of stuff in space. Just from the churning of space,

it turns out that you can't just hang out as a grain in the middle of space. There are processes happening out there. They're processes that destroy dust and processes that reform it. The dust destroyers that are out there, it sounds like, you know, some big alien ship coming along to clean up the universe. But actually it's shockwaves from supernova. When supernova collapse and then explode, they produce these huge shockwaves, massive amounts of energy, gamma rays, neutrinos, all sorts of stuff. And that comes along and it shatters these grains. destroying the dust and breaking it back down into gas.

Well, you know, they say space is just a big vacuum, so those would just talk about the dust. Anyways, so you were saying that dust is important in the universe. Is it important to the universe or just to our understanding or to our search for answers about the universe? Well, both. Like the history of dust tells us what's happened out there in the universe. You can take each individual solar grain if it survived,

this like interstellar shattering process. and some of them have, and you can trace it back to an individual star. Like, every star has a different mixture of elements and a different mixture of isotopes. So they leave special fingerprints in their solar grains. And so, like, each solar grain can tell you, like, what that star was. It's like a little sample from that star. And some of them are made during supernova and capture elements and isotopes that only exist, we think, in the atmospheres of supernova during those brief moments that are super energetic

and can tell us about the formation of heavy elements and what's going on in supernova. So there are these amazing capsules that tell us about the history of the universe. But I think maybe you don't mean like each individual grain, do you? You maybe need like a population or like a cloud of this dust to sort of know what the star was like. Well, each individual grain tells you something about that star. Not every grain produced by the star is identical, right? And the star has a variety of stuff in it. But each one traces back to an individual star.

Because each grain would be made out of different things. Yeah, each star would make different kinds of grains. There's going to be some overlap. It's not completely unique, right? But each star is made out of different kinds of stuff, different elements, different mixtures. Each star is a slightly different mass and temperature. And so it produces different mixtures of stuff and different isotopes. And so the grains produced by each star are different.

Like an individual grain would have different things in it and different signatures in it? Yeah, exactly. The isotopes found in an individual grain tell you about the same. star that it came from. Interesting. So how is it important to the universe itself? Because it doesn't seem like it weighs a lot in the microwave. So maybe I wonder if it has a big role in, you know, the dynamics of space.

It does play a big role in the dynamics of space, sort of for two reasons. One is that stuff heavier than gas is the reason that we have like planets and stars and stuff like that. Like the Earth is mostly made out of stuff that's not just hydrogen and helium, right? And that's cosmic dust, gather together to form planets. So most of the rocky stuff of the solar system came originally from what we would call cosmic dust, right? Those heavier elements that were created by stars and spewed out into space. And also we think that this cosmic dust plays a role in the formation of solar systems.

You have a huge gas cloud that eventually collapses into a bunch of stars. Why does it collapse? It collapses because it's a little spot here that's denser, that's heavier. That's cosmic dust. Man, those are like the iron grains and the little bits of heavy elements. bits of heavy elements floating around that seed that gravitational collapse. Wait, are you saying the Bible was right? We all come from dust, from dust to dust.

And even ashes, right? Star ashes. Cool. And so then how does it help us study the universe? Or how does it not help us study the universe? Yeah, it both hurts our ability to study the universe and helps us. Like, it prevents us from seeing things in the universe because it absorbs light and it blocks our view.

The center of the Milky Way, which is choked with dust, is famously called. called by astronomers the zone of avoidance because they have to look away from that region. You can't see through the center of the Milky Way in optical light. So you can't see what's on the other side of the galaxy very easily. So it's sort of a pain for astronomers, but it also captures this history, right? And in order to understand the cycles of star formation in the universe, we do have to understand the cosmic dust. Because the cosmic dust plays a role in the formation of those stars and is also then destroyed by the supernovas and then reforms. It's all part of the cycle of the Milky Way.

You might imagine the Milky Way is just like a bunch of stars floating in space basically doing nothing, but it's churning and burning, this stuff going on, just sort of a much longer time scales than we're used to thinking about. Interesting. All right, well, let's get into how we know where the dust in the universe is and the very important question, where does it all come from? Who's making this mess in the universe?

So let's dig into that, but first, let's take a quick break. Hey, sis, what if I could promise you you never had to listen to a condescending finance bro? Tell you how to manage your money again. Welcome to Brown Ambition. This is the hard part when you pay down those credit cards. If you haven't gotten to the bottom of why you were racking up credit or turning to credit cards, you may just recreate the same problem a year from now. When you do feel like you are bleeding from these high interest rates,

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which is not a drug, I imagine. It sort of sounds like in my piece. something you'd sell on the streets. I don't know. If you walk down the street in Berkeley and you ask people for cosmic dust, I'm pretty sure they'll sell you something. They'll sell you something.

But we're talking about the dust that's out there in space between the stars and it's important because we're all made out of dust. Stars and planets, they're all essentially made come from dust that gravity pulls together.

And so it's important for that reason, but it also sort of helps us understand the origins of stars in the universe, right? Even though it's tiny, it's a little bitty part of the mass budget of the solar system, it tells us about how things work

and it plays a role in getting those things started. But I imagine maybe at some point in the universe's history, it was all dust, basically, right? That's where all those stars came from. No, I guess you went from gas to stars and then those made dust. Exactly. We think that the universe began dustless, right?

So it's actually an interesting open question in astronomy right now. It's like, when was the first dust made? People really want to understand the process by which dust is created and destroyed and helps form new stars. And there's a lot of open questions out there. We don't really fully understand the process of it. But we're pretty sure that the universe began with just hydrogen and helium

and the tiny trace elements of things heavier. And no larger molecules, of course. And it's only when stars began to burn that dust was created. But I wonder if in the big band, you know, things were so intense, there was so much pressure, there was so much violent processes going on. So many of those that I wonder if some hydrogen started emerging together and make dust without any stars. Is that possible? Well, the earliest dust we've seen is like several hundred million years after the Big Bang.

It's possible that hydrogen formed and crystallized somehow earlier on. I don't think we would call that cosmic dust though. If it's just pure hydrogen, probably just call that hydrogen crystals. I think to be called dust probably needs to have some like carbon and some silicon and some heavier elements in it. But I mean, could a little bit of carbon and silicon have, formed during the Big Bang? Big Bang nucleosynthesis is a pretty precise science, and it tells us based on the temperature and like the quark density, exactly how much of what was made.

And we think that it's almost overwhelmingly hydrogen with just tiny trace elements of helium. And then the little tiny, any bitty bits of heavier stuff, carbon probably not, because carbon requires the merging of three helium simultaneously because lithium is so unstable. So very unlikely that any carbon was formed. But you can't say no. It's possible there were tiny, tiny grains of carbon form during the Big Bang. So there could be primordial dust out there, like OG dust. That's right.

The most ancient dust is possible. Though the oldest dust we've ever seen is a few hundred million years after the Big Bang. All right. Well, that brings us to our next question, which is how do we know where the dust in the universe is? It doesn't glow in space, right? It actually kind of does glow in space. Not the way that stars do, right? Stars create their own light through fusion.

They light up the whole universe. But everything out there has a temperature and everything that has a temperature glows. Even the Earth glows, right? It gives off infrared radiation. And so dust glows in the very, very infrared because dust is pretty cold. So you can see the dust if you use telescopes

that can see infrared light. And so like the Spitzer Space Telescope and the James Webb Space Telescope, these things out there can see dust in our galaxy and in other galaxies by its thermal emissions. Like I guess you could, tell where there was a lot of dust and where there isn't a lot of dust.

Yeah, exactly. You can't see an individual grain, but you can see like huge clouds of dust here and there. You can see it glowing in the very far infrared. You can also see dust by how it blocks light. Like we think we understand how stars glow and the light that they give off. And dust blocks that light. You know, it absorbs some frequencies of it. It reflects other frequencies of it. And so by looking at what astronomers call the extinction curve, like where's light being blocked, they can measure how much dust there is between us and something. So we measure it by how much it blocks light, not how much it reflects light? We measure it by how much it blocks light and also it emits a little bit of light in the

infrared. So it depends a lot on the frequency. It will reflect blue light mostly. Infrared light can mostly pass through dust, shorter frequencies where the light has like roughly the wavelength of the dust that will get reflected or absorbed. So when light passes through a dust cloud, it basically gets reddened because the blue light gets reflected and the red light makes it through. It's a little bit of the opposite of what happens here during a sunset. No, it's the same. It's the same.

The light gets reddened, right? The atmosphere tends to reflect blue light. So the sky looks blue because indirect sunlight gets scattered down to your eye. Then at sunset, the light is coming straight at you and the blue light is being reflected away and you're seeing the red light. It filters, like it filters out blue light. Mm-hmm. Exactly.

It filters out blue light. And so when astronomers look out into the sky, they can see that some stars appear to be dimmed and they appear to be dimmed differently across the spectrum, right? It's not just like the whole star is dimmer, which might mean it just further away, but it's dimmed more in the red than in the blue. So these extinction curves are really important for astronomers to study because every time they're looking at something in the universe, they want to know like, how much dust are we looking through? How much is dust distorting what we're seeing? So technically does that mean that dust is space dust is blue? Like if you were, when you said to look at it, it's blue-ish. I guess it reflects blue light.

It glows in the far infrared, but it reflects blue light. So I guess that would make it kind of blue, yeah. And have we ever, like, got in a sample of dust? Like, have we ever gone out there and grab the, you know, vacuumed up some dust to study it? We do actually have samples of space dust. It's super fascinating. All the dust that we have sampled is only stuff in our solar system. So we've never sampled stuff outside of our solar system.

The furthest probes we've ever sent have like just barely left the solar system. But there's plenty of space dust here in our solar system and many, many satellites that we send have little dust collectors. It's kind of a challenge because these satellites are moving in very high speeds relative to the dust. So it can be tricky to like caps the dust. But there are some missions like the Star Dust mission specifically to capture dust and bring it back.

But then lots of other satellites have like a little space dust collector on it. We talked once about the Juno mission that went to Jupiter in 2011. had sort of an accidental star dust collector on it. The dust was slamming into the back of the solar panels on the satellite and then spolating off little bits, which got picked up by a camera, and it turned out to be like a huge, effective dust collector. And this is how we learned that Mars is giving off all of this dust,

which is probably responsible for causing the zodiacal light. We have also captured some dust and brought it down to Earth and studied it under a microscope. And seen, like, some fraction of this stuff really are pre-solar grains. bits of dust that are older than our solar system. Whoa, super old dust. Super old dust. Our solar system is like four and a half billion years old.

But of course, stars have been around for much longer than that. And some of them died and created these grains, which amazingly survived out there in space and then formed into asteroids or formed as part of the Earth or still just floating out there. It's incredible that some of these little grains have lasted so long. And we also know how much dust is out there because it's polarized, right? It's got some sort of electrical chargedness to it. Yeah, the dust grains are not spherical, right? They have little shapes.

They're irregular, which means that they tend to be longer in one direction than another. And because they're made of electromagnetic stuff, sometimes they have an overall charge. You know, the dust like bumps against itself. It gets like static electricity, essentially. And then interstellar space, it will align with magnetic fields. You know, the Earth has a magnetic field. The sun has a magnetic field. The whole galaxy has magnetic fields.

We think there might even be magnetic fields out there in between super clusters. We talked once about primordial magnetic fields. Anyway, the dust grains are a great way to measure those magnetic fields because they align with the magnetic fields. And then when light passes through them, it tends to polarize the light because the dust itself is pointing in a specific direction. So light passing through this region can tell you about the dust and about the magnetic fields in that region.

It's sort of an amazing way to like learn about these huge regions of space. which otherwise look empty. Whoa, it's like having special glasses to see the universe. Yeah, exactly. So we have lots of ways to study cosmic dust and to look at the spectrum. And looking at the spectrum also tells you what's in there. Because if it has like a certain crystal,

then that crystal has rotational and vibrational frequencies and they will absorb those frequencies or emitted those frequencies. And so they can tell what's in cosmic dust, even if we can't sample it. Like cosmic dust that's far, far away in the Milky Way, they can tell what it's made out of. based on how it glows and how it absorbs light.

Because that can change, I guess, right? Depending on what was happening there that made the dust. Exactly, because cosmic dust is not static, right? One of the big mysteries is like, where is all this cosmic dust come from? And, you know, we think that a lot of it is made in stars. It's made in supernova. It's made in these stars called asymptotic giant branch stars. It's made in super red giant stars.

They have, like, just the right conditions in their atmosphere to coalesce this stuff, like outflowing and cooling gases will create these grains and shoot them out into the universe. And that's cool, but it can't explain all the dust that we see out there. There's like not enough stars and not enough formation of this dust to explain all the dust that's out there in the universe. Because as we said earlier, the dust doesn't survive forever, right? The dust is like shattered by supernova. So we have like stars pumping dust out in the universe. Supernova is shattering it back in the gas. And that leaves sort of a mystery because there's not. enough being made by the stars to explain all the stuff that we see out there, all the dust in the

Milky Way. I see. So like dust is sort of like they're bigger molecules basically, right? They're like little tiny pebbles. And inside of the stars, they just burn up, I guess, right? Because it's so hot and under so much pressure. Yeah, that's why they're made like in the outer atmosphere, the outflowing cooling gases coalesce into these grains. If that ever happened inside the star, they would just burn up as fuel, yeah. Like the carbon and all the silicon, it's sort of gassy, it with in the sun, but once it gets out of the sun, it tends to form into molecules and maybe little clumps. But then you're saying, like, once it's out there in space, then if there's a supernova, the supernova breaks it up back into carbon and silicon. Exactly. So like the typical

lifetime for a grain of dust, it's like 100 million years. It can float out there. And then on average, it's going to get shattered after about 100 million years, some longer, some shorter, but on average, 100 million years. There are that many supernovas happening to shatter dust. so frequently? There are not that many supernovas, but they're frequent enough and powerful enough to shatter this cosmic dust. So like on average for any point in space, you experience a shattering supernova every 100 million years? Yeah, the supernova are more common than every 100 million years. There's a supernova in our galaxy roughly every 50 years. So in 100 million years, you're going to get 2 million supernova across the galaxy. And they're very, very powerful. So the

modeling at least tells astronomers that these things should be shattered on average within 100 million years. But the Earth has been around longer than that, and have we experienced such a shattering supernova? The Earth has been around much longer than that, but it would take a very close-by supernova to shatter the Earth. These grains are more delicate than the Earth, which has been, like, compressed, right? So, like, if there's a bit of dust circling the Earth, it would get shattered by the

supernova, but not our atmosphere or us. Yeah, dust is more fragile. You know, it's floating out there in space. It's very low pressure. These things are sort of fragile compared to, like, a rock. on Earth. All right. So then the mystery you're saying is like how it's made then.

Yeah, the mystery is like, why is there still so much of it? There's a lot more cosmic dust out there than can be explained by this combination of stars producing it and then supernova is destroying it. There's a lot more cosmic dust that can be explained by just that process. Maybe the universe just hasn't bought that neat device you have to get rid of dust. Well, one theory about what's going on is that cosmic dust itself can reform out there between the stars. So you take these little pebbles, these little grains, you send them out there. They get shattered back into gas, but there's like a tiny little seed left. You know, a few

molecules still cleaning together. And then those can accrete because they're flowing through these molecular clouds, which are super duper cold. And basically because you have a few tiny little grains left, they can like pick up more. Like ice can form on these things. And you get these layers that surround the original tiny core that rebuilds this. thing back up into what you would call dust. I see. Yeah, it just reforms because and also because of gravity, I imagine, right? Like even if you split a little grain of dust out there, eventually gravity is going to put it back together, isn't it?

Yeah, exactly. And that's the process that eventually forms stars and planets, right? These little gravitational seeds gather together over very long periods. But it begins with gathering a little bits of ice here and there and reforming. And so some of the cosmic dust that's out there are like OG grains that came from their stars and haven't been shattered. But most of it probably comes from this process where they have been shattered and then they coalesce collecting ice and reforming into grains. All right. Well, you mentioned that there are some things called dust destroyers out there in space

and also mysterious ways that dust is made. And so let's dig deeper into those things. But first, let's take a quick break. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime.

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Hola, it's Honey German, and my podcast, Grasasas Come Again, is back. This season, we're going even deeper into the world of music and entertainment with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't auditioned in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah.

We've got some of the biggest actors, musicians, content creators, and culture shifters sharing their real stories of failure and success. You were destined to be a start. We talk all about what's viral and trending with a little bit of chisement, a lot of laughs, and those amazing vivras you've come to expect. And of course, we'll explore deeper topics dealing with identity, struggles, and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the,

code switching? I won't say white watch because at the end of the day, you know, I'm me. Yeah. But the whole pretending and cold, you know, it takes a toll on you. Listen to the new season of Grasas Come Again

as part of my Cultura podcast network on the IHartRadio app, Apple Podcast, or wherever you get your podcast. I had this, like, overwhelming sensation that I had to call it right then. And I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation,

and I just wanted to call on and let her know. There's a lot of people battling some of the very, you're saying things you're battling and there is help out there. The Good Stuff podcast Season 2 takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran and he actually took his own life to suicide.

One Tribe saved my life twice. There's a lot of love that flows through this place and it's sincere. Now it's a personal mission. I don't have to go to any more funerals, you know. I got blown up on a React mission. I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff.

Listen to the Good Stuff podcast on the Iheart Radio app, Apple Podcasts, or wherever you get your podcasts. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness, the way it has echoed and reverberated throughout your life. life, impacting your very legacy. Hi, I'm Danny Shapiro, and these are just a few of the profound and powerful stories

I'll be mining on our 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me

and my extraordinary guests for this new season of family secrets. Listen to Family Secrets Season 12 on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Okay, we're talking about dust, and Daniel, you're saying the big question is where does it come from? Because most of the dust, if you just put dust out there

in space, within 100 million years, some distant supernova's shockwave is going to shatter that back into its constituent atoms, like carbon and silicon. It doesn't seem that fragile here on earth, right? Like if I blow on dust, it doesn't break up into carbon gas. I mean, you're pretty tough dude, but are you saying that your breath is as powerful as a supernova? Well, some mornings, yeah. But I mean, like, it's weird to think that. it's so powerful because here on Earth we don't feel these supernovas. But you're saying it's trying enough to like split apart molecules

in space. The dust is more fragile than the Earth is. Yeah. And it hasn't been a supernova in our Milky Way in quite a few hundred years. So it's not like we're feeling these things every 10 years or so. Even these supernovas are not that common. But yeah, the lifetime of dust is shorter than

the lifetime of the Earth. So the Earth and planets and stars definitely survive these supernova shock waves in ways that the stellar dust doesn't. So then the mystery is like if it is being destroyed out there in space, why is there still dust? Why isn't it all just gas and individual atoms? Exactly. And it's important that the dust is there because the dust sees planetary formation and star formation.

You know, in ways that we didn't always understand. Like back in the 70s before we really understood cosmic dust at all, people thought that our solar system started just from gas, that you could start from just like a blob of hydrogen and helium and form all of this stuff. which doesn't really make sense to me because I'm like, where are you getting all the iron and all the stuff to make planets? But now it's very well understood that most of the iron and most of the heavy metals are bound up in these cosmic dust grains and you need them to form solar systems with interesting bits on them like rocks and people. So then are you saying that like just gravity, you know, pulling all of this stuff out there floating in space into dust is not enough to account for the dust we're seeing? Why not?

So just stellar production of dust isn't enough to account for the dust that we're seeing. You need some way to reform dust in the interstellar medium. Otherwise, as you say, it would be just gas. But we think that these little grains probably do gather back together from gravity and from just accretion of ice crystals as you pass through a molecular cloud. There's going to be chemical bonds that form because these things are a little sticky, right? And so that is a process that they think might explain where the gas comes from. I talked to one scientist at the University of Waseda in Japan, who's super interested in cosmic dust.

And she said that this is like the leading theory for how cosmic dust is being regenerated. But nobody's like demonstrated this in the lab. They haven't done tests where they take like a little grain and pass it through a dust cloud and see this stuff reform. It's also like theoretical chemistry at this point. Well, you need to replicate zero gravity, wouldn't you? Yeah, exactly. It's the kind of experiment you'd want to do out in space or out on the ISS or something. So then that's the best answer to this mystery.

That's the best answer to this mystery. So it sounds like you're saying like there's a giant vacuum in space. He's gathering all this dust. Well, you know, again, it's the supernovae, right? Those are the dust destroyers, shattering it back into gas. And then they think that it's probably reforming. But another really fascinating way that they're trying to understand this process is by trying to answer a related question,

which is like, how early did dust form in the universe? So now that we have like a super powerful infrared telescope, We can look deeper into the history of the universe and look for evidence of dust very, very early on. Like, what is the oldest dust that we can see in the universe? And they'll give us a sense for these processes. Because remember, like, stars didn't turn on for a few hundred million years. So the origin of the dust can really tell us about, like, who is making this dust. Right.

I think you mean, like, if you look out into deep space with your telescopes, you're looking back in time. So, like, the light you're getting from those deep places in the universe is, really old light which might be old dust exactly and we think that most of the dust out there in the universe right now is probably produced by these super red giant stars and this asymptotic giant branch stars these special stars are super big and have just the right conditions for this like outflowing gas to cool and form these little blobs which then flow down into space but the james web space telescope recently saw direct evidence for really really old grains of stars like several hundred million years or up to a billion years after the Big Bang too long ago for these

stars like we don't think that there were these super red giant stars early on in the universe so probably the first dust made in the universe were made by supernova from the first generation of stars whoa wait so how do we know we're looking at dust that old because we're looking at images of galaxies that are super duper far away and so you can look at a galaxy you can understand from its redshift how fast it's moving away from us and therefore how far away it is and therefore the age of the thing we're looking at. Isn't most of that light coming from the stars in the galaxy? Yeah, most of that light does come from the stars, but we're looking at an infrared telescope and stars are much quieter in the infrared. So we're seeing information from the dust also.

Oh, I see. Like we see the galaxy with a regular light and then we switch the filter over to infrared and then you're basically getting the light from the dust. Exactly. And specifically what they're seeing here is extinction, right? They're seeing an absorption feature at a very specific wavelength, 2175 angstroms, that they think is like a dust wavelength, that that's what dust absorbs. So they see like a dip in the light in this galaxy at just the right wavelength that tells them that there's dust in this very, very old galaxy. Oh, because I guess the size of your thing affects what kind of light you're absorbing, right? Because you kind of have to be at about the same size as a wavelength to absorb it.

Exactly. Earlier, we were talking about how dust absorbs at various frequencies. In general, the picture is that it interacts more with blue light. It reflects that blue light. And it doesn't interact as much with redder light because, as you say, it's too

small. Like, the wavelength of light is bigger than these dust grains. So it doesn't interact with them. But also these things contain specific chemicals and sometimes little crystals and those have features that absorb at certain wavelengths, like little oscillations and vibrational energy

levels of these little crystals inside these dust grains will absorb at specific wavelengths that are known to be dust wavelengths. So they saw this in this signature from the James Webb Space telescope from the super duper ancient galaxy, a galaxy too old to hold any of these red giant stars or ASB stars. So they think probably this is ancient dust maybe from the first round of generation of dust in the universe, probably from supernova. Like the first supernova is right? Because that's that's when the heavier elements are made and it's fascinating because supernova make this stuff and then also destroy it so they kind of like clean up after themselves right wait how can it make them and destroy them at the same time these dust grains are made by supernovas who's sort of in the last

dying minutes of a star's life where you know these shockwaves create really intense environments and specific isotopes and then the outflow and the cooling makes these grains but then shock waves from supernovas also destroy dust right supernova are the dust destroyers of the universe so they both created and they also are responsible for destroying it. Which do they do first? Do they first clean up and then put a bunch of dust there? Or do they put a bunch of dust and then immediately destroyed? Can't be the latter, can it?

Because then we wouldn't have any dust. It must be that the shockware from the supernova travels out faster than dust grains, which means that first they're cleaning up and then they're making a mess. So I guess you're right. Actually, it's in the wrong order where they're destroying the dust grains from other supernovas and to make space for their own. So they're not cleaning up after themselves. they're just cleaning it so that they can make a miss.

Yeah, they're sort of like scrubbing the graffiti off the wall and then writing their own name on it. Yeah, that's all right. I take it back. I take it back everything positive I said about supernovas. Well, they're the reason we hear, so I'm glad they haven't wiped us off, I guess. And we're glad that they made us. All right, well, what does it all mean about our understanding of the history of the universe?

It means that all these processes, the ones that form stars, that lead to supernovas, that lead to dust creation and dust destruction. It's all part of this huge cosmic dance. You know, we tend to think of the Milky Way as like, done. We've made all these stars. They're just sort of like hanging out and burning now. But it's a process, you know, and everything is connected. There's like dust flowing and swirling.

These things are being created. They're being destroyed. They're being reformed. A whole thing is a big frothing, active, lively mess of processes, all of which are important to creating the universe as we know it. Yeah. And it sounds kind of precarious, right? Like basically we need a supernova to make all this dust

and we need the dust to basically clump together into planets and stars quickly before the next supernova tries to wipe the board clean. Right? Like if another supernova had gone off near us or not even near us but around us before the sun, you know, got put together and the earth got put together, we might not be here.

Is that true? It definitely would have affected things. But it's not something we understand very well. well and supernovas contribute in lots of different ways like first of all they destroy these grains but then later on a supernova shockwave can actually precipitate the gravitational collapse of surviving grains into a new star so supernova shockwaves play lots of different complex roles and to say like that we even understand this story would be to overstate it for sure there's a lot of parts of this that we still don't understand but we do know is that it's complicated and everything is connected

Sounds like our knowledge of it is a little dusty. There's definitely a lot of ancient wisdom out there we haven't yet collected and we can look forward to blowing the dust off of all of these secrets. But not too hard because then you might destroy the dust, right? Only if you have supernova morning breath. All right. I guess the next time you look at into the night sky, know that you're looking at a bunch of dust as well,

not just the beautiful twinkling stars. These tiny but mighty grains play an important role in the formation of the solar system in helping us understand what's out there and also in blocking our view of part of the glorious cosmos. You hope you enjoyed that? Thanks for joining us. See you next time.

Hey, it's Jorge from the podcast and I'm super excited to announce that my new book, Oliver's Great Big Universe, is available to order now. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio,

visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. I'm Dr. Joy Hardin-Bradford, host of the Therapy for Black Girls podcast. I know how overwhelming it can feel if flying makes you anxious. In session 418 of the Therapy for Black Girls podcast, Dr. Angela Neal-Barnett and I discuss flight anxiety.

What is not a norm is to allow it to prevent you from doing the things that you want to do, the things that you were meant to do. Listen to Therapy for Black Girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Do we really need another podcast

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