Daniel and Kelly’s Extraordinary Universe - How metallic is the Sun?

Episode Date: April 11, 2024

Daniel and Jorge explore the enduring mystery of how much heavy metal sits in our Sun.See omnystudio.com/listener for privacy information.

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Hey, Jorge, how's your dad band going? Pretty good. Yeah, we're getting better. It's a lot of fun. Didn't you guys have some clever name? Sort of clever. We call ourselves the Grateful Dads. And is that the kind of music you play, psychedelic 60s rock, or are you more like alternative

or metal? We play a little bit of everything, you know, 80s music, 90s rock, some Marvin Gay, some Pink Floyd, a little bit of reggaeton. All right, so then the physicist in me wants to know, how metal are you guys? I would say we're less than Iron Maiden, maybe, more than the Doobie Brothers. That sounds like it leaves a lot of uncertainty. That's for sure. But we always try to rock it.

Hi, I'm Jorge Ami Kartunis 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 like music with all different kinds of metal. You mean like the instruments or like the genre? The genre, you know, a little heavy metal, a little light metal. Is light metal even a thing? I think some of these heavy metal groups have saw songs.

Does that still count as metal? I'm not even going to weigh in on that. Yeah, we don't want to anger those metal people. They're pretty intense. But anyways, welcome to our podcast, Daniel and Jorge, explain the universe, a production of IHeartRadio. In which we attempt to understand everything in the universe, from the tiny quantum particles to the amazing, shiny metals that make up our universe. We want to know how everything in the universe functions.

We want to know what its smallest bits are and how they come together to explain everything in our amazing, crazy, delicious, and bonkers universe. That's right, because the universe is made out of all kinds of things. And in this podcast, we'd like to explore all of it and to figure out what it's all made out of how it's all put together and what makes things the way they are. How you can go from quantum particles to dad bands in Pasadena or marching bands in New Mexico, the only kind of band I've ever been in. And did you play metal or did you play a metal instrument? Not even. I played the totally unhearable instrument, the clarinet.

Oh. You could only hear the clarinet in the marching band if you're literally in the middle of the clarinet section. Otherwise, it's just trumpets. But the clarinet is made out of metal, isn't it? Or is that one of the woodwinds? It's a woodwind, though there are metal bits, of course. to operate the holes. And what kind of music did you guys play?

Oh, you know, we played marching band versions of all your greatest hits. Including metal songs? Including metal songs, absolutely. There's a marching band version of every song you love and we ruin it. Well, maybe you should start a band with physicists. What would we call it? I don't know. What would you call it?

Maybe some Higgs boson reference. We make everything heavy. How about you two have mass? That's pretty good. or how about the clash of particles all right now I just need some musical talent and I'm all set how about the dovy boson brothers

all right I think we're good on band names but yeah it is interesting to think about all the things that the stuff in the universe is made out of right it is really interesting it's fascinating to understand how all that stuff got made and how it comes together to make our universe because even the tiniest little bits of metal here and there are required, absolutely essential for the universe to operate the way that it does. Yeah, because the universe, I guess, is made out of all kinds of things. Gases, solids,

liquids, metals, non-metals, acids, bases. There's all kinds of ways that you can categorize the stuff that stuff is made out of, right? Yeah, absolutely. And though it's all made out of the same fundamental bits, you take quarks and you mix them together to make protons and neutrons, you add electrons. Those few little ingredients can make all kinds of things out there in the universe. with all kinds of different behaviors. Some of them conduct electricity, some of them don't, some of them are strong, some of them are brittle, some of them are soft, some of them interact and some of them don't.

It's incredible the variety of stuff you can make with just a few basic bits. Some of the stuff is soft rock, some of it is classical physics, and some of it is heavy metals, literally. With the same instruments, you can make any kind of music. And with the same kinds of particles, you can make everything that you see out there in the universe, all the different kinds of stuff out there.

And sometimes it's kind of surprising all the different kinds of things that we're made out of, right? Like we're not just made out of carbon and the basic building blocks, but there's a bunch of weird things that it turns out are sort of essential to our living, right?

Our bodies need copper. Yeah, and oxygen, for example, and all sorts of bits to take advantage of the clever tricks of chemistry. To communicate information along our nerves to capture oxygen in our red blood cells. You need all sorts of elements. And so it's wonderful that these things exist out there in the universe, that they've been somehow manufactured through physics in order to shape our existence.

Now, some of us have more or less metal inside of us, right? I mean, I grew up in the 80s, and so my teeth are full of metals. All kinds of metals in there. Absolutely. You got some of us probably played with mercury as a kid, and so we have more or less mercury in us. Yeah. Did you play with mercury? I played with mercury all the time.

which probably maybe explains a lot. That's why you're in a heavy metal band now, yeah. Yeah, that's why I'm so mercurious. But yeah, it kind of makes you wonder what else the stuff out there in the universe is made out of? You know, even our planet, I'm sure, is mostly iron and rocks and silica. But the stuff out there in space, what is that made out of? Yeah, most of the stuff in the solar system is not us or even the Earth. An overwhelming fraction of the solar system is basically just,

just the sun. And of course, the sun is crucial to life on earth and the operation of the solar system. So it's in our interest to understand like, hey, what's in the sun? Because that affects how long it's going to last and how it behaves. And so today on the podcast, we'll be tackling the question. How much metal is in the sun? Not how much metal is the sun. How metal is the sun?

If it had a dad band, what would it play? Well, it would probably play a lot of songs about the sun. You know, here comes the sun. You are my sunshine. Its opening has to be. Here comes the sun, absolutely. That's its walk-on music for sure. That's their theme music.

Who would the sun be in a band with? Jupiter, I guess. Or other suns. It might outshine Jupiter, yeah. Yeah, or maybe it's a solo act. Can you be a solo metal act? Probably you'd have to be because nobody wants to be in the sun's shadow.

I think if you're next to the sun, you're definitely not in the shadow. I know. I love how that joke makes no sense. I was trying to save it there, but, you know, I'm fighting the loss of physics here, Daniel. No, I was going for maximum nonsense. Right, right. It was on purpose. It was very metal of you.

If you had shouted it out, it would be even more metal. This is a really fascinating topic to me because I love mysteries. in our own neighborhood. You know, we wonder about what's going on at the edge of the universe or the beginning of time, but gosh darn it, we haven't even figured out

what our own solar system is made out of. We live in it, but we don't know kind of what's in it. What's it all made out of? But it's kind of an interesting question because you're particular asking how much metal is in the sun, not like what is the sun made out of?

Because I guess most of the sun is just one thing, right? Yeah, the sun is mostly hydrogen and a little bit of helium. And what you call the rest is kind up for debate. I cringe to inform you that it depends on your definition of metal. Because in astronomy, metal is anything but hydrogen or helium. Right. I was going to mention that. Like, what exactly do you mean by metal? Because a metal means different things to different people,

right? Yeah, exactly. I feel like to us or to the everyday person, a metal is something that's shiny and hard and conducts electricity. Now, is that wrong? No, it's totally reasonable to think metals are things that are metallic that have those properties, right? And that's how chemists, for example, use the word metal. But astronomers think about things differently. Wait, wait. So is there an official definition of metal by chemists that's different than the definition of metals by physicists?

Well, by astronomers in particular, because condensed matter physicists would agree with the chemists because they're sort of almost on the chemistry side of physics. But astronomers, wow, that's their own community. And, you know, they got their issues with naming stuff. bites about everything. Hmm. Okay. So then if we're asking how much metal is in the sun, what are we asking?

Like how much non-healium and hydrogen is in the sun? Or are we asking how much metallic, shiny stuff is in the sun? Well, I want to know everything about what's in the sun. Like how much iron is there anywhere? Where did it come from? How could iron get into the sun? But we don't even know very well the answer to the more basic question, which is how much non-hydrogen and helium is there in the sun?

How much astronomy metal is in the sun? Oh, okay. So we're really asking the question. question, how much of the sun is not hydrogen or helium? Yeah, exactly. Can we ask later how much of the sun is the shiny metallic stuff? I mean, you're very mercurious, so you're allowed to ask anything. A mercurious?

Is that what you said? Mercurius, yeah. Is that like a merman, but like a curious merman? Well, you know, I guess you can be bi-curious, you can be mur-curious. You know, I don't know what that means. I'll let you figure that out. You just want to dive into everything. Yeah, I want to know it all.

but only for a short amount of time. But anyways, how much metal is in the sun? That's an interesting question. How did you come up with this question? Well, I was reading some papers about the mysteries of how much metal is in the sun. I thought it was fascinating that we still don't know the answer

to this pretty basic question that influences like the most important thing in our neighborhood. Interesting. And I think also like what's in the sun sort of affects the kind of light that we get from the sun, right? Like you can tell,

what kinds of things are inside of a star by looking at its light. And it has really cosmic consequences because we use the sun to calibrate our understanding of what's in the rest of the universe. And the amount of metal in stars controls their fate, like whether they'll collapse into a black hole or not, and also how likely they are to have planets around them. And so if we revise our understanding of what's in the sun, it could change our understanding of what's out there in the universe, how long it will last. and the likelihood that there could be aliens.

So, yeah, in the end, it always connects to aliens. Whoa, where does that come from? Is this just a big excuse to talk about aliens again? That's what this whole podcast is. Are you just figuring that out? Yeah, well, a little bit. I thought we were explaining the universe. It's just a fun for talking about aliens.

I see. This is all just a ploy to, what, prepare us subconsciously for the imminent arrival of aliens? or the big reveal that you are an alien? No comment. Yeah, that's very suspicious. All right, so as usual, we were wondering how many people out there had thought about this question

and about the amount of metal in the sun. Thanks very much to everybody who answers these questions. I love hearing your thoughts on the question of the day. So please don't be shy if you would like to contribute. Write to me to questions at danielanhorpe.com and I'll get you on the air. So think about it for a second. How much metal do you think is in the same? sun. Here's what be bled to say.

I think the heavier elements only come out during supernovas, and so I would have to say no metal in the sun. I think that 99% of the solar systems metals are located in the sun itself, but with regards to the makeup of the sun, I think that only about 8% of it is metal, the rest of it is gas. Most of it is iron, I think. I want to guess not very much right now, like less than 1%, but as the sun grows older, maybe the amount of metal in the core will increase. until the mass becomes so great that the light cannot escape,

and then the sun will turn black. If we measure that diameter of the outer core, I would assume that the metal is less than like 10% of like the diameter width. But I feel like it's a trick question because don't cosmologists say anything above helium as a metal. So this might be a true question. I'm going to go 98% metal. The sun is totally metal, but I think if we're talking about actual composition, there's not all that much.

I'm going to guess that the sun has a lot. little bit of metal, like maybe one or two percent of its total composition. But that's actually considered a lot compared to other stars and that the stars that came before the sun had even less metal. All right. Like the person who said, the sun is totally metal. The sun has a good attitude. I think that's what he means. Yeah. Well, it is pretty hot, I guess. Intense. Yeah. It just not back down. It just keeps rocking on and on. Yeah, and it eventually burns up. So that kind of fits the heavy metal rock star trope.

Flaming out is a pretty metal thing to do. Mm-hmm, yeah. All right, well, Daniel, maybe start with the basics. How does a star even get metal in it? Because as we all know, stars are made out of hydrogen helium. Or hydrogen initially, right? All stars, or at least the original stars, were made out of hydrogen. Yeah, it's a cool question.

Stars can get metal in them in two ways. One is that they can be formed with metal in them. Stars come from a collapse of a big cloud of like gas and dust and other bits. So there's metal in the neighborhood when the star collapses, then that metal will become part of the star. But that depends, as you're alluding to, on what's around, what's been made, as something else out there made metal. And the only way that we know to make metal is in the hearts of stars.

So the second way that stars can get metal in them is they can make metal. They can fuse hydrogen and helium together to make heavier stuff, producing metal. Meaning like when a star was formed and it gathered all the gas to become a star, maybe there were metals floating around where all this stuff was. And that's how metal got inside the star. But were the first stars made out of pure hydrogen or did the universe make some metal at the Big Bang?

Yeah, great question. So about a millionth of a second after the sort of primordial goo, things were expanding and cooling. And you got quarks forming into protons and neutrons. And protons are hydrogen. So basically the first thing that was made was. hydrogen because protons form. Then you have a few minutes in which the conditions are ripe for fusion for those protons to bang together and make heavier stuff. And so that's when helium was made,

but you only had like three minutes where the universe was in the right conditions to make anything heavier. So you had huge amounts of hydrogen, made a little bit of helium, but almost nothing else. Basically after the big bang, you had vast quantities of hydrogen, trace amounts of helium and almost nothing else. Basically no metal was around after the Big Bang. Although I hear you saying almost, does that mean that there was

a little bit of the heavier metals in the universe right after the Big Bang before Stars got made? It's impossible to say that there was none, but it's very hard to make those heavier elements without the density and the time. Fusing helium together makes something very unstable. If you just

start with two helium nuclei, you really need three together to get to carbon and that's much harder to do without the density that you have in stars and the time to fuse them so it's possible you made a little tiny bit of carbon after the big bang but it's overwhelmingly hydrogen a little bit of helium and maybe tiny negligible amounts of carbon so the universe i guess was pretty pure hydrogen and helium and then those started to make stars and that's when the first metals really came into the universe exactly so those first stars were basically metal-free, just huge clouds of hydrogen with a little bit of helium in them. And they

produced the first metals, right? They didn't start with really any metal in them at all. But these were huge stars. Turns out if you form stars without any metal in them, you get much bigger globs. And those stars are really big, so they burn really hot and they burn really fast. So they don't last for very long. And then when they die, they spray their metals out into the universe to see the next stars. Right. And some of them burn and explode and collapse without having used up all of the hydrogen and helium, right? Oh yes, absolutely. Stars do not burn all of their hydrogen and helium before they end their lives. So like when those first stars exploded, how much of them was still hydrogen and helium and how much of the heavier metals had they made? Yeah, that's a cool question. We can answer that

by looking at how much metal is in the next generation of stars because those little bits of metal are excellent seeds for the next stars like metal is heavier than non-metal has more protons in it has more mass it's denser so it's more likely to form a seed of another star start that gravitational collapse so the next generation of stars the stars we call population two these are still really really low metal it's like less than a tenth of one percent of those stars is metal so it's still overwhelmingly hydrogen and helium even in the second generation of stars well So maybe paint a picture. So those first stars burned, they collapsed, they exploded, and then all that stuff

re-collapsed again. Yeah, exactly. But it didn't happen that quickly. Helium floats around for like hundreds of millions of years before the first stars are born. There's this period in the early universe called the Dark Ages, before there was any light in the universe, just these dark clouds of hydrogen and helium. And then those first stars burn for like just a few million years.

The larger the star is, the shorter its life. So those didn't burn for very long, but then the next generation, they're a little smaller and they can burn for a very, very long time. Why were they smaller? The more metal you have in the universe, the more likely it is that a big cloud of gas is going to break up into multiple stars rather than collapsing into one megastar because you have all these different places for it to seed. Remember that for a star to form, you need sort of special conditions. You need a big cloud of gas, but you need to also be cold enough so that it can collapse and you need some like gravitational sea. to get that runaway effect going. And so if you have a variety of different densities,

you're more likely to have smaller clumps than bigger clumps, and those smaller stars tend to burn colder, and then they last longer. So if you have a giant cloud of hydrogen, it doesn't break up as much. It just hangs around until it all condenses into a giant star. Exactly. And people might be imagining, like,

that one cloud makes one star, but it's more likely that a huge cloud makes multiple stars all simultaneously. And if that cloud has more metal in it, then you have more seeds for those stars. So you end up with more smaller stars rather than fewer megastars like you did in the first batch. Okay. So then that's the second generation of stars, right? Yeah, exactly. And those stars were formed like 13, 14 billion years ago.

But they burn a long time because they're small. They're redder. They're colder stars. So we can still see some of those stars around in the universe, especially in globular clusters. Like around this or only far away or further back in time? They're also in like the heart of our galaxy. So Population 2 stars are all around. Did that generation of stars then eventually explode and make the next generation of stars?

That definitely happened. It's a little bit misleading to think about these as generations in a sort of crisp sense. It's not like all that first generation died and then there's only the second generation and there's only the third generation. Every star is formed from remnants of multiple stars and some of them. might have gone through one, two, three, four generations, maybe even more. It depends on the size of those stars. So this categorization is very rough. It's not super precise.

It's not like all the stars are in sync. But the latest generation of stars, which are called Population 1 stars, formed more recently in the universe when there's been more time to make metal in the universe. So these we call high metallicity stars, which means they have like between 1 and 4% metal. Wait, wait. The third generation of stars is called Population. Population one. Yeah, that's exactly right.

Population one are the ones made most recently. Population two is the previous generation. Population three is a still somewhat theoretical first generation of stars. And I know. The naming system is ridiculous, and I won't defend it even for a moment. What generation is our sun? Our son, we think, is a population one star. So it's part of the most recent generation.

All right. Well, then let's get to the question of how much metal is in our star, the sun, and whether it rocks or not? So let's dig into that. But first, let's take a quick break. I'm Dr. Joy Harden-Brand-Bradford, and in session 421 of Therapy for Black Girls, I sit down with Dr. Athea and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right, in terms of it can tell how old you are,

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All right, we're asking the question, how much metal is in the sun? And by metal, we mean elements that are not hydrogen or helium. Yeah, exactly. We want to know how much oxygen, carbon, neon, nitrogen, sulfur, iron, all that stuff, all added up. That's even like the first most basic question you want to know. like how much of that heavier stuff is in the sun. And then, of course, we want to know the proportions also.

But we first need to nail down the initial question. Well, why do you think astronomers call everything not hydrogen and helium metals? Because they couldn't come up with another name? Or is there a rationale there? Like, I would think metals, maybe in chemistry, has the connotation that it conducts electricity or is shiny. So what's the astronomers excuse? Well, I think there is this division between hydrogen and helium, of which there's so much in the universe and everything else.

And so you really need another category. I don't know if metal was the right way to describe it. But there definitely are two different categories. There really is hydrogen, helium, and all the other stuff in the universe. So it's more of a name just given by population or abundancy. Also, this is the stuff produced by stars. So it's sort of like the output of stars. It doesn't have to do as much with like the chemical properties or the behaviors or the appearance

the way it does in chemistry. It's more about the abundance in the universe and how it was made. All right. So then the latest generation of star has about 1.4 to 4% metals. Yeah, exactly. And so there's a variation there. Like depending on where you were when you were formed and also whether you can make metals inside you, there's a pretty big spread in how much metal there is in stars.

On the other hand, most stars still hydrogen and helium. Like we've been burning hydrogen for 14 billion years. we've hardly made a dent in the fraction of the universe that is hydrogen. You mean our star or in the universe in general? The universe in general, you know, the universe is still mostly hydrogen. Like 92% of the universe right now is hydrogen. So like our star right now is burning hydrogen. Were you saying like the amount of hydrogen it's burning or fusing together is super tiny, tiny?

I'm saying we've been burning it for 14 billion years and we've hardly made a dent. Yeah. Stars are the universe's mechanism. them for like turning light stuff like hydrogen into heavier stuff and you might think wow we've been burning for a long time we must have plowed through it all but there's still vast vast quantities of hydrogen out there now why is that just because there's so much hydrogen and helium in the sun but really the part that's fusing it's only at the very tiny center of it or why isn't it burning up faster the reason you suggested is totally accurate like fusion happens mostly at the core

where things are dense and things are hot, at least in the initial stages. Then when the core of the sun fills with ash or fills with heavier metals, then the sun can fuse, then the fusion moves outwards. But also remember, fusion is hard. Even if you have an enormous pile of hydrogen, you squeeze it to the right pressure and density and temperature, it's not like all the hydrogen is instantly just going to fuse into helium. You need a lot of hydrogen and a lot of time to get any fusion happening.

So it's a very low probability thing, which is why you need an enormous pile of very high temperature, high density gas to get any of it to happen. All right. So then that's kind of the general picture. But what about our sun? How much of our sun is still hydrogen and helium and how much of it is badly named metals? So about 20 years ago, we thought we had this settled. We had studied the sun and looked at the light that comes from the sun, the spectrum of it, like how much red light is there, how much green light, how much blue light. And use that to try to figure out what was in the sun. And we thought, thought we had it nailed down. We thought the answer was about 1.8% metal. Meaning, like,

if you look at the light from the sun, the spectrum of the light from the sun sort of can tell you what the sun is made out of, or we thought it could. Yeah, exactly. The sun is really fascinating because on one hand, a lot of the light comes from just the sun being hot. Everything out there in the universe that's made of charged particles will glow based on its temperature. And the hotter things are, the higher energy, the photons will be released. So a lot of the light from the is what we call just black body radiation, something hot, giving off light. The way like, I give off light and you give off light. We don't give off light in the visible spectrum the way the sun does because we're not white

hot, the way the sun is, but that's where a lot of the light from the sun comes from. Where does the other light come from? The other light comes from specific atoms in the sun emitting light or absorbing that light. So if it's like an oxygen atom in the atmosphere of the sun and it gets hot, its electrons jump up a couple of energy levels, then they jump down, they relax. they emit a photon. And that photon, it's very specific energy. It corresponds to the difference in the energy levels of that electron around the oxygen atom. Every atom out there can emit and absorb light in very specific wavelengths. So if you look at the spectrum from the sun,

this is overall black body radiation. Then are these spikes where certain atoms are emitting light that correspond to their energy levels and there are dips where other atoms are absorbing light that's produced by the sun at the energy levels that they can do it. So you look at all those wiggles in the spectrum and you can tell what's in the sun. Or at least it seems like we thought we could. So we did that for our sun and we thought it had a certain amount of metals in it. But then what happened? So people thought, okay, that's cool 1.8%.

That makes total sense. But then people thought, well, let's cross check it. Let's see if we can measure what's in the sun using another technique and come up with the same answer. Another way to figure out what's in the sun is to watch it boil is to look for waves in the surface of the sun because that tells you

how thick the sun is the viscosity of the sun which depends on what's in there what's sort of mucking around wait what do you mean like as you look at the surface of the sun you see it churning it's like super hot plasma right

and the way the plasma churns tells you how goofy it is yeah they call it heliolesysmology And it's sort of similar to the way you can use earthquakes to understand what the earth is made out of. Like an earthquake shakes the earth and then that shaking travels through the earth and it reflects at boundaries. Like that's how we know where that boundary is between various layers of the earth. We can also deduce things about like what's there because how it bounces and reflects depends on the relative density of things at those layers.

So just by measuring earthquakes at the surface, you can get a pretty good picture for what's in the earth. In the same way, we can look at ripples on the surface of the sun, heliocysmology, they call it, to get a picture for what's in the sun. We don't have earthquake measuring devices on the sun. How do we know the shaking of the surface of the sun? So we don't need a complete picture of what's in the sun, but we can watch waves move across the surface of the sun. You know, we have a lot of telescopes that can look at the sun

and they can see the behavior and the churning on the surface. And there's a lot of stuff going on there, but we only need a sort of rough picture of what's in the sun because it turns out there's one very particular thing that's controlled by the metals that we're trying to get a sense of it's a balance between two processes that are trying to move the heat out of the sun the sun has sort of two parts to it is like the outermost part and the innermost part and the innermost part a lot of heat is being created it's radiating out so that radiation comes out from the core and hits the outer part of the sun. But that outer part can be kind of opaque because of like oxygen or heavy elements can

absorb those photons. So that means that that energy can't be radiated out from the core of the sun. Instead, you need to get that energy out using another method we call convection, basically just like hot stuff rising up the way it does in a pot of water. So there's sort of two parts to the sun, one where photons can bring the energy out and the other where you have to rely on convection. And there's a boundary between these two regions. And that depends a lot on like how much oxygen is there in the sun. And that's what we're trying to measure with this heliocysmology. We're trying to figure out like where's the threshold between these two parts of the inside of the sun.

And we do this by just looking at the flow that you can see in the picture of the sun? Or do we have like an x-ray way to look inside the sun? No, we have no x-ray, unfortunately. It's just effectively sound waves in the sun. And of course, nobody's hearing these things. When we say sound waves, we just mean pressure waves moving through the sun. But just the same way that earthquakes make effectively sound waves through the earth. And you can listen to the earth ringing just by seeing the earth shake.

If we watch the surface of the sun, we don't have like instruments on the surface to measure the actual shaking. But you can see these ripples in the plasma on the surface. You can effectively see sound moving through the sun and bouncing back. And this boundary between the two parts of the sun, one that's opaque to photons and one that is shows up as like a glitch in the sound waves. It changes how those sound waves move through the sun. Wait, are you saying there's sort of like two kinds of sun surfaces? Yeah, there's like a surface within the surface.

The same way that like the earth has multiple layers to it. You know, there's the mantle and the outer core and the inner core, et cetera. The sun also has these regions. And there's this boundary. They think it's like 70-ish percent of the solar radius. Within that, photons can like fly free and you have this radiative train. for where photons can move heat out from the center. The outer part is more opaque and photons can't really get through it.

So the only way to get heat out from the sun there is more like convection, like hot gas rising up. But then what are you basically saying that looking at these sound waves tells us a different number for what the sun is made out of? Exactly. Looking at the sound waves tells us something about where this balance is between the two different parts of the sun. And that depends on how much metal is in the sun. because the metallicity of the sun controls whether it's opaque or transparent.

We have more oxygen, more carbon, more neon that makes the sun more opaque, which changes how far the photons can get. So if we can use sound waves on the surface of the sun, figure out where is this transition within the sun between opaque and transparent to these photons, then we could figure out how much metal is in the sun because the metallicity controls where that transition is. But then why do metals make the sun more opaque? These heavy elements like oxygen, they like to absorb these photons. Like more than hydrogen? Yeah, more than hydrogen. You know, every atom likes to absorb photons of a certain energy.

And so the kinds of energy that tend to be produced in fusion tend to also be the kind that oxygen likes to gobble up, for example. So if you do all these calculations, you figure out, well, where is this threshold, where is the sun become opaque inside of it? And what does that mean about the amount of metal inside the sun? you get a different number. So from helioseismology, from these sound waves, we get the number 1.8%.

Whereas we look at the spectrum of light from the sun, we got the number 1.3%. So we thought, oh, this would be a great way to cross-check and to just make sure we understand what's in the sun. And then it turns out, oops, the numbers don't agree. Now, is that, do you think maybe because looking at the spectrum of the sun only kind of maybe tells you what's in the surface of the sun?

It is possible, but they've accounted for that. They have models for where these things are distributed. in the sun and how much they would radiate. So there are definitely questions there and things people are trying to drill down on, but they do think they've accounted for that. But the second one that way seems a little bit more circumspect, I guess, or more indirect than actually just looking at the light from the sun. It does.

In the end, we're always just getting information from far away and using that to try infer what's going on. And what's happening here is something I love in science. It's like, well, let's cross-check our understanding by seeing if we can do this two different ways. could do this two different ways, making different assumptions or probing our model in different ways to see whether it breaks. And this kind of detailed work has led to crazy discoveries in the past, you know, when we, for example,

predicted how many neutrinos would be coming from the sun versus how many neutrinos we saw from the sun. We saw a huge difference that led to understanding neutrino oscillations and neutrino masses. So not every way is going to be as precise, but it's important to have different ways to cross-check each other and to try to get some hints about what's really going on inside the sun. Well, it sounds like we've measured how much metal is in the sun in two different ways, and they disagree by a pretty big amount. And so let's get into what that difference means, who's right, who's wrong, and how metal is the sun. So let's dig into that. But first, let's take

another quick break. I'm Dr. Joy Harden Bradford. And in session 421 of therapy for black girls, I sit down with Dr. Ophia and Billy Shaka to explore how our here. hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right? In terms of it can tell how old you are, your marital status, where you're from, you're a spiritual belief. But I think with social media, there's like a hyperfixation and observation of our hair, right?

That this is sometimes the first thing someone sees when we make a post or a reel is how our hair is styled. You talk about the important role hairstylist play in our community. the pressure to always look put together and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying, don't miss Session 418 with Dr. Angela Neil Barnett,

where we dive into managing flight anxiety. Listen to therapy for black girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Get fired up, y'all. Season two of Good Game with Sarah Spain is underway. We just welcomed one of my favorite people and an incomparable soccer icon,

Megan Rapino to the show, and we had a blast. We talked about her recent 40th birthday celebrations, co-hosting a podcast with her fiancé Sue Bird, watching former teammates retire and more. Never a dull moment with Pino. Take a listen. What do you miss the most about being a pro athlete? The final, the final, and the locker room.

I really, really, like, you just can't replicate, you can't get back. Showing up to the locker room every morning, just to shit talk. We've got more incredible guests like the legendary Candice Parker and college superstar A.Z. Fudd. I mean, seriously, y'all.

The guest list is absolutely stacked for season two. And, you know, we're always going to keep you up to speed on all the news and happenings around the women's sports world as well. So make sure you listen to Good Game with Sarah Spain on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Presented by Capital One, founding partner of IHeart Women's Sports. I'm Dr. Scott.

Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills, and I get eye rolling from teachers or I get students who would be like, it's easier to punch someone in the face. When you think about emotion regulation, like, you're not going to choose an adapted strategy which is more effortful to use unless you think there's a good outcome as a result of it, if it's going to be beneficial to you. Because it's easy to say, like, go you go blank yourself.

right? It's easy. It's easy to just drink the extra beer. It's easy to ignore, to suppress, seeing a colleague who's bothering you and just like walk the other way. Avoidance is easier. Ignoring is easier. Denials is easier. Drinking is easier. Yelling, screaming is easy. Complex problem solving, meditating, you know, takes effort. Listen to the psychology podcast on the Iheart radio app, Apple Podcasts, or wherever you get your podcast. Have you ever wished for a change what weren't sure how to make it. Maybe you felt stuck in a job, a place, or even a relationship. I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken

big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten. Monica Patton. Elaine Welteroff. I'm Jessica Voss. And that's when I was like, I gotta go. I don't know how, but that kicked off the pivot of how to make the transition. Learn how to get comfortable pivoting because your life is going to be full of them. Every episode gets real about the why behind these changes and gives you the inspiration and maybe the push to make your next pivot listen to these women and more on she pivots now on the iHeart radio app apple podcasts or wherever you get your podcasts all right we're asking how much metal is in the sun and it sounds like we have two answers one way by looking at the light from the sun

tells us that it's 1.3% non-hydrogen and helium. But looking at the flow of the plasma and how the sound waste travel across the surface of the sun, that tells us that maybe the sun is 1.8% non-hydrogen and helium. So who's right and who's wrong? We don't know yet. But we have a third answer. People came up with yet another way to try to figure out how much metal is in the sun. Just asking the sun.

nobody thought of that oh my gosh you know if the sun really isn't a rock band it's going to love doing interviews but this third way actually does use neutrinos because fusion at the heart of the sun produces vast vast quantities of neutrinos these tiny little ghostly particles that are everywhere but we can't feel them because they only have weak interactions they have no electric charge they have no strong force charge they're very difficult to spot but we have technologies neutrino eyeballs we've invented to be able to pick out a few of these neutrinos. We can also measure the energy of those neutrinos. And the neutrinos are produced by fusion in the sun. And how much metal you have in the sun affects the rate at which

that fusion happens and also affects the energy of the neutrinos that's produced. We're trying to fuse protons and protons together. If there's a bunch of heavy metal around that actually interferes with the fusion, makes it less likely. It makes it more important to have higher energy on those protons, et cetera. So the neutrino energy energy spectrum you expect depends on how much metal is in the sun, but it's a bit of a weak effect. It's not a very strong way to measure this quantity. Well, also, what do you compare it to? Like, how do you know what the right amount of neutrinos should be for a certain amount of metals?

Yeah, great question. We have a really detailed model of the fusion and how it produces neutrinos, and that's been the subject of decades of study. And of course, first, there were big mysteries. We predicted a huge amount of neutrinos. We only saw a third of them. Later, we discovered that's because those neutrinos are changing into another kind of neutrino as they travel through space. Check out our episode on neutrino oscillation, if you want to understand that more. But yeah, there are definitely uncertainties there. These are models we have of how the diffusion is happening and how the neutrinos are being created. So we don't have an absolute calibration of that either.

We just have these calculations we've done that predict the spectrum. And then those calculations depend also on the metals. So you tweak the metals up. You get one spectrum. You tweak the metals down. You get another spectrum. so we can tweak the amount of metals we put into these calculations to match what we see

and then we think, well, that's the most likely value of the metal in the sun. So then what does this neutrino method say about the metals in the sun? So unfortunately, this method isn't super precise. It slightly favors the higher metal scenario, so like 1.8%. But it can't rule out the 1.3%.

It's just sort of more like a hint. It's a little bit of a vote towards heavy metals. So then we have three competing methods. And they all say something slightly different. How are we going to figure out which one's right? We're going to dig in and question all of our assumptions, understand where we might have overlooked something. We're going to do more experiments, collect more data.

These neutrino experiments specifically, this is sort of like the first run, the first gasp of the data. As that runs longer and longer, it'll get more and more precise and maybe sharpen our understanding. But this is really crucial that we figure this out because the sun is sort of like our yardstick for the rest of the universe. For other stars, we have no hope at like looking at sound waves on the surface

we can only look at the light from those stars and we compare the light from those stars to the light we get from the sun and we use that to infer what's in them. Our whole estimate for what's out there in the universe is based on what's in the sun. If we were wrong about what's in the sun, then we were wrong about the whole universe.

Well, unless it turns out that these other ways to measure what's in the sun are wrong and making the one that you can apply to other stars is right. Yeah, absolutely. It could be. Or it could be that we don't understand what's inside the sun and how this all works. And they're both wrong. Either way, we'd love to understand better what's in the sun because it helps us understand what's out there in the universe. It also really helps us understand the fate of all of those stars. Even though the stars are mostly not metal, those metals can really influence whether those stars have planets around them, how long those stars will live, and how they will die. Ooh, wait, what's the connection between the metals in a star and their planets? I knew you wanted to talk about aliens, right?

No, no, I just asked about the planets. I didn't say anything about aliens. Don't project your alien fetish on me, man. Who do you think is living on those planets, man? Nobody, maybe, algae, plants? Heavy metal bands. Nobody said anything about aliens, Daniel. All right, well, I'm about two.

Okay, get ready. Well, the more metal there is in the initial cloud that forms that solar, system, the more metal there's going to be for making planets. And the more metal there is, the more likely you are to seed something that's not just a star. You have this huge collapsing cloud. Why isn't it all just become a star? If some little seed near the star can form fast enough to make its own little gravitational well, it can gather up a bunch of stuff and get into orbit and avoid collapsing into the star. To do that, you need a little density seed. So stars with more metal in them tend to have more planets around them as well, rocky planets and giant planets.

We think or we know this for sure? Like, have we measured this out there? We've measured this out there because we've seen planets around other stars. And so we've seen this correlation. Stars whose light indicates more metal in them also tend to have more planets around them. So there's a correlation between metallicity and number of planets, potentially. No, that's something we've measured. Of course, we have a biased view of all the planets out there. We can't see all the kinds of planets. We're not great at seeing some kinds of planets. We can only see planets under certain conditions, et cetera, et cetera.

So this is sort of an initial thing. But it's a correlation that we've noticed. And also one that makes sense, right? It fits in with our model for how solar systems form. All right. Well, I guess how are we going to figure out what's in our sun then? Is there going to be like conclusive proof at some point? Like, are we going to be able to maybe dip into the sun and get a scoop of it?

That would be awesome. We were thinking about sending your band over to visit the sun. Are you guys available? Who's your agent? Well, it depends how much are you paying. What's the budget? Will there be green M&Ms in the green room? Oh, I thought it was brown M&Ms in the green room.

Well, I mean, I think the whole point is that we get to choose what kind of NMs are in the waiting room. All right, we'll work on the budget. But this is not something that we are likely to figure out directly. It's always going to be a game of improving our models, comparing the models' predictions to what we see out there in the universe and then seeing if we get it to tell a coherence story. Could we send something into the sun, like have something fall into the sun and as it falls and gets destroyed, it maybe tells us what's in the sun? Potentially with some technological advances.

As I know, you know, our recent Parker Solar Probe got pretty close to the sun, but almost got toasted. It's very difficult to even get that close to the sun, and it was nowhere near being able to like actually sample something. On the other hand, we're sort of already in the sun in one sense, because we're in is the edge of the sun. The sun starts out very dense and then it gets more and more dilute. Then it's got this huge extended corona and the wind.

So we're already sort of sampling stuff from the sun. So it's possible that like the solar wind itself might have clues we can use to figure out what's in the sun. The energy of those particles could potentially be sensitive to the metallicity of the sun. Well, it's kind of interesting that like we only have one star close to us. We able to run these experiments and verify our models. of what goes on in any star. And so we're sort of hoping that our sun

is not super atypical or weird. Yeah, exactly. We know that our star is unusual in some sense. It's more massive than your typical star. Most of the stars out there are red dwarfs. But it's also in a sort of unusually good position to sample the average kind of stuff in the Milky Way. We're like halfway from the Milky Way center

to the edge of the disk of stars. And most stars out there in the universe are in big galaxies like the Milky Way. So the sun is sort of a scoop of typical material we think. So understanding what's in the sun will really help us understand what's in the universe. And how heavy metal aliens might be. Isn't that the whole point of this episode, Daniel? Yes, exactly.

We were just working up to that one joke the whole time. All right. Well, another example of how there are still big mysteries. Even in our own heart of the solar system, the sun, And we sort of don't really know what it's actually made out of. And even though it's so close, we can't actually go in there and figure it out ourselves directly. We have to find all these clever ways to infer what's inside the sun. These basic questions about what's in our own backyard affect the whole universe.

They tell us what's likely to be out there in the universe and also how it all will end. Stars with more metal in them are more likely to form neutron stars rather than black holes. And so the fate of all those stars we see up there in the night sky could depend on these measurements of what's in our backyard. We hope you enjoyed that. Thanks for joining us. See you next time. For more science and curiosity, come find us on social media

where we answer questions and post videos. We're on Twitter, Discord, Insta, and now TikTok. Thanks for listening. And remember that Daniel and Jorge Explain the Universe is a production of, IHartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app,

Apple Podcasts, or wherever you listen to your favorite shows. Why are TSA rules so confusing? You got a hood of you. I'll take it off. I'm Manny. I'm Noah. This is Devin. And we're best friends and journalists

with a new podcast called No Such Thing, where we get to the bottom of questions like that. Why are you screaming? I can't expect what to do. Now, if the rule was the same, go off on me. I deserve it. You know, lock him up. Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast.

No such thing. 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 Nielbornet and I discuss flight anxiety. What is not normal 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. It's important that we just reassure people that they're not alone and there is help out there. The Good Stuff podcast, season two, 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. One Tribe saved my life twice. 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 podcast. This is an IHeart podcast.