Daniel and Kelly’s Extraordinary Universe - Can the Parker solar probe shed light on the Sun?

Episode Date: February 21, 2023

Daniel and Jorge talk about the daring and dangerous mission of the Parker Solar Probe and what it might reveal about the Sun.See omnystudio.com/listener for privacy information.

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Monica Patton, Elaine Welteroth. Learn how to get comfortable pivoting because your life is going to be full of them. Listen to these women and more on She Pivot's now on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. It was basically staring up at the night sky and just wondering about the stars and everything out there. That's not really cliche. You know, I think that's what gets most people interested in physics. It doesn't make me wonder about something. You're wondering about my wondering?

Well, if everyone's wondering about stars, why don't they focus more on the star that's closest to us, the sun? I think it's a little bit more dangerous to stare at the sun than it is to stare at the night sky. Why? Didn't know physics was so dangerous? You're living on the edge, the edge of the solar system. I'm taking lots of risks, napping in my office every day. Sounds like a sunny job you got there.

Hi, I'm Jorge May a cartoonist and the creator of Ph.V. Comics. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine. And I'm a big fan of the sunshine. Oh yeah, you're a big sunbather. You like having a tan. You sit with those. reflective mirrors. I don't embody every Southern Californian stereotype, but I do enjoy a sunny day, you know, just sort of like lifts my mood. I've lived

in places where it's cloudy every day and it's just not as fun. Yeah, the sun is pretty warm out here in Southern California and it's interesting because it means we're getting bathed by science every day, almost. 75% of the time. It certainly affects our life. It grows all of our plants.

It controls the weather. It basically is in charge of everything. that happens on the surface of the earth. And so you think we might understand it a little bit better than we do. Are you saying we need to shed some sunlight on the sun? We need to illuminate those mysteries. Welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio. In which we try to shine a light on everything we do and don't know about the universe. Our curiosity knows no bounds as it flies from the surface of the earth down to the tiny particles all the way out to the workings of the sun at the heart of our solar system,

the fiery fusion engine that powers everything, including life on Earth and the sparkling stars in our sky. We dig into all of those mysteries and try to explain all of them to you as best we can. Yeah, because it is a bright and sunny universe, shining bright with amazing knowledge. We're ready for us to bathe in it and take it in and become and tan our brains, I guess, to make them more colorful and knowledgeable about how things work and why things are the way they are. I really like that picture of the universe as sending us information, as beaming us clues about how the universe works. Because as we've often lamented, we are trapped here on this little rock,

mostly unable to physically explore the universe, but we can decode those signals. The universe is zapping us information about what's going on elsewhere, letting us put the pieces together to try to build a mental model of what is happening. far, far away. Yeah, it is pretty amazing. We are in a little tiny corner of a galaxy, in a tiny corner of a super cluster of galaxies, in a tiny corner of the universe. And yet, just from the light we get from other suns out there in the universe, we're able to kind of piece together a huge picture of the entire universe. It really is incredible how much we do

know about things happening far, far away. We have models of little stars and big stars and star lifetimes and star deaths and star explosions and star implosion. all just from watching from this little rocky perch in the suburbs of the Milky Way. And that knowledge has been developed over many, many years. People staying up late at night, freezing their bones to look up in the night sky and take careful notes and developing fancy new technology to take better pictures of what's going on out there. And more recently, actually sending probes out to explore our neighborhood and try to learn a little bit closer up what's going on. Yeah, because we can learn a lot about stars and also about the star that's close.

closest to us the sun. It's kind of easy to forget that the sun is a star, you know, like if you're an alien in another planet and you look up at the sky and you see a tiny pinpoint shining bright in the darkness, that could be us. That could be our sun sending them information about the universe and us. Yeah. And I think the phrase solar system is sort of underappreciated. It's not just that we have a star and it's at the center of the system. We really are part of our star. In some sense, we are living in the atmosphere of our star. It really does dominate the solar system in a way I think people don't really understand. It's 99% of the mass of the solar system is in that star and it's sending out enormous waves of energy and particles all throughout the solar

system. So you could say we're just sort of like flying high in the very outskirts of the solar atmosphere. Yeah, we are a tiny little part of the solar system. It is basically the sun, the whole solar system. We're almost like little tiny moons on a giant exploding ball of fire. You could say that we live on the sun. In some sense, the edge of the sun is not really something that's well defined. You could say the whole solar system is basically just the sun and we are part of it.

Yeah. And even though it is the closest start to our system and it provides light for us and heat and which powers all of life on this planet, there's a lot that we surprisingly don't know about our own sun. It is fundamentally important to everything we do. It's the best example of a process that happens all over the universe and is really important for the universe looking the way that it does. And yet we still have basic questions about what's going on inside our star,

how it all works, and how it's even possible for it to get so hot. Yeah. And it seems like an important question, right, to understand this giant exploding ball of nuclear-powered fusion happening right next to us. You know, like, is it going to keep doing that? Is it going to go out? Is it going to explode? What's going to happen to it?

It seems like important to find out what's going on there. Yeah, if I lived right next to a fusion reactor, I'd want to understand pretty well if it was going to blow up or if it was going to fail or what it was going to do. And why is it suddenly so hot? There are lots of practical reasons to understand the sun. It's also just a great mystery. Like, it's doing so much cool, amazing, important stuff. Huge tubes of plasma superheated, incredibly powerful magnetic fields. It's just a great laboratory for understanding, like, what can the universe do after all?

How do all these forces come together in extreme environments to create such a dramatic and beautiful display? Yeah, I'm not sure I would call what the sun is doing cool. It's more like maybe lit. It's sizzlingly hot. Yeah, there's a lot we don't know about the sun. And so today on the podcast, we'll be asking the question. What will the Parker Solar Probe? teachers. I'm guessing things about the sun.

Yeah, the Parker Solar Probe is a really fun piece of technology that humanity designed, built, and launched out to go and explore, to visit up close the sun and to try to get some answers to some pretty basic questions about how the sun works. Yeah, it is a pretty cool NASA project, one which I made a comic about last year. I don't know if you know this for physics magazine. Oh, no, awesome. I didn't see that.

Yeah, I had to interview a bunch of scientists for it. And I put out a comic if you Google PhD comics and Parker Solar Prob, you'll find it. So in case you need a like a visual companion to this episode. Awesome. I encourage everyone to check that out. Jorge's cartoons explaining science are always super well done. And the visual is always very helpful. Yeah, it is a pretty interesting and fascinating project over at NASA there.

And so as usual, we were wondering how many people had heard about the Parker Solar Probe and what they know about it. So thank you very much to everybody who. volunteers for this segment of the podcast, we'd love to hear your voice as well. If you've been listening for a while but never screwed up to courage to write in, please don't be shy. Reach out to me at questions at danielanhorpe.com. So think about it for a second. Have you heard of the Parker Solar Probe? Here's what people had to say. I actually learned some things about the Parker Solar Probe recently and that it will study the outer atmosphere of the sun or the outer corona. And to learn why it is,

hotter actually than the surface of the sun. I believe the Parker Solar probe is designed to investigate some of the physics behind the fusion of our sun and perhaps try to explain why there is a temperature differential whereby the gases that are expelled or the atmosphere of the sun that is farther away from the surface actually heats up as it leaves the surface of the sun. So I guess it's going to the sun, the parker solar probe. So I feel like it could probably tell us about its magnetic field or maybe solar flares or on stuff like that. I have absolutely no idea speculating. I would imagine that it would be something that would go out into the solar system in order to collect information on things that we otherwise can't infer, such as particles in space, radiation from a point in space, or perhaps a different perspective that we can't.

get from Earth. I have no idea what the Parker Solar Probe is. I don't know. I would get something to do with like temperature radiation. I have no clue. Maybe solar flares. Not a lot of name recognition, but I think people sort of piece together that it's probing the sun. Yeah, but people seem excited to learn about what the Parker Solar Probe might teach us about the mysteries of the source of all energy and life on Earth. Yeah. And so let's dig into it or I guess let's go out into the sun with this idea first of all what is the parker solar probe so the parker solar probe is a really cool project it's a spacecraft launched from earth to go investigate the sun basically to do a bunch of really close flybys close sort of by solar standards and measure a bunch of things about the sun to try to get a handle on some

longstanding mysteries about how the sun works what's going on inside it how it gets so hot and the solar wind that flies out from it. And so in the end, it's just a satellite that we launched from here. It zooms around Venus a few times and makes a bunch of approaches to the sun and gathers a bunch of data about what's going on. Well, you can't just call it a satellite. It's more like a spaceship, right? A spacecraft.

That's right. It's not a satellite in the sense that it's orbiting the Earth. It will be orbiting the sun. So in that sense, it's a satellite of the sun. But yeah, spacecraft is definitely cooler. And this one contains a lot of really cool technological advances to let it like survive. getting so close to the sun, it's going to get closer to the sun than any human object ever has, and it's going to have a velocity with respect to the sun greater than any human object has achieved.

Super cool. But this is not the first spacecraft we sent to the sun, right? For the first spacecraft we used to study the sun, this is kind of the latest and most awesome, and the one that's going to get to the sun the closest. Yeah, the last spacecraft to go visit the sun before this was the Helios 2 in 1976. So it's been a few decades since we visited the sun. It's been a lot of planning, a lot of technological advancements, a lot of ideas, a lot of arguing at NASA budget meetings. So it's exciting to get to go back to the sun with new technologies and upgraded instruments and to get closer, as you said, than ever before. Yeah, it's a hot mission.

And it's a long mission too, right? It didn't just take decades to get it going, but the mission itself is several years. It was launched in August of 2018. And, you know, even when it launched, it was already unique for a couple of reasons. One is that it was named after a living person. Eugene Parker, who's a famous theorist about how the sun works, was alive at the time it was launched, even though he was 91 and he was on hand to observe the launch, which is really cool. Also, it contained the names of more than a million people who wanted their name to sort of touch the sun.

NASA let people submit their names. And they wrote down more than 1.1 million submissions, put it on a memory. card and slapped it on the outside of the probe so those people could sort of ride along and go visit the sun with them. No kidding. For real? They just like duct tape a little flash drive to the outside. Yeah, there was a memory card mounted on the plaque so that all those people could feel like they went to visit the sun. Pretty cool. But you're right, there's going to be like 24 solar orbits in a seven year mission. So it's going to zip around the sun a bunch of times. And it goes sort of between the sun and Venus and the sun and Venus. And some of those visits are

closer to the sun. Some of them are further from the sun. Also remember that the sun has a weird cycle of its own. It's about 11 years. So the mission lasts long enough to allow us to sample the sun several times in different places in its own internal cycle. What do you mean the sun has a cycle? Like it's not moving. I mean, it's moving through space, but it's not wiggling with respect to the solar system. It's more like it has cycles of its temperature and size, right? Yeah, people have been noticing over the last few hundred years that there's an 11-year cycle. of the sun. Over 11 years, you see like the number of sunspots rise and then fall. And people have been recording this for hundreds of years. It's something we've known about for quite a while.

And so the number of like solar flares and corona loops increase and then fall. And actually they think that this cycle has been pretty stable for like hundreds of millions of years. They see evidence of this going back to like the impact on ancient tree rings that have they have dung up like fossilized tree rings from hundreds of millions of years ago show these same kind of cycles. Are you saying the trees are the original scientist, solar scientists of Earth? It's incredible how sensitive life on Earth is to like the mood of the sun. As the sun gets hotter, it changes the weather on Earth in a way that we can measure hundreds

of millions of years later because of the impact on the trees. And it's not just the sun's weather. The sun's magnetic field also flips every 11th. years. Remember, the Earth's magnetic field also flips, but it's very irregular. Sometimes it flips every 50,000 years, sometimes every million years. The sun's magnetic field flips every 11 years. So that's all part of the solar cycle that people want to understand. And so the mission is like seven years long to try to gather data from different parts of that solar cycle. Yeah, super interesting. Now for the probe, one thing that I found interesting when I talked to scientists about

this was that it's actually really hard to get close to the sun. Like you would have thought that sending something to the sun, you just kind of put it in space and then the gravity makes it fall towards the sun. But actually, you need a lot of energy to slow down your spacecraft in order to get close to the sun. Yeah, as you fall towards the inner solar system, you speed up because you're trading gravitational potential energy for kinetic energy. And so you're likely to sort of like whizz around the back of the sun. That's true because you have angular momentum and it doesn't go away, right? And so you need to like use some energy to basically lose angular momentum if you want to actually fall into the sun.

And that's why it goes around Venus, right? It kind of uses Venus's gravity to slow itself down. Exactly. It uses Venus as like a gravity assist. And it's going to do like five different flybys of Venus to try to shed some of that energy so we can get closer to the sun. They were previous designs for this mission back in earlier iterations when it was going to use Jupiter as a gravity assist and also have like a bunch of nuclear power on board to

try to help it get even closer. So previous designs were going to get even more. closer to the sun than the actual spacecraft that they launched, but it wasn't going to be near the sun as long. It was going to be like a very fast, close flyby. So they opted for this approach, which is cheaper, didn't require nuclear power and give them a longer visit to the sun, even though it's a little bit further than the original design. Yeah. And so it's on this kind of elliptical orbit where it's kind of swinging between Venus and the sun. You can imagine like in the ellipse, like one end of the ellipse is really close to the sun. And that's the flyby they do

close to the sun to take data from the sun. Exactly. So it's going around. Remember, this is like a multi-year mission. It's going to be like 24 solar orbits. As of October 2020, it's done 13 of those so far. And so it's like more than halfway through its life. But there's a lot more coming. And we're all looking forward to it getting closer to the sun. It hasn't yet reached its closest approach. And also it's sampling the solar maximum, which is going to happen in around 2025. That's when the sun is. like at its peak of solar activity. Yeah, because every time it goes near the sun,

it gets a little bit closer each time, right? Like the orbits are getting smaller and smaller. Yeah, if you look at a map of the orbits, you see it's sort of corksqueering around in this elliptical path, as you say, between the sun and Venus. So it's sort of like zooming in on the sun. Yeah, it's pretty cool that we can like navigate a spacecraft around the solar system like that,

like swing it between the sun and then on the planet. Yeah, it requires really precise knowledge of where everything is in the solar system. And also a really detailed understanding of gravity. You know, these are also really exquisite tests of our understanding of how gravity works. Because you're talking about throwing a rock and basically predicting where it's going to be in 10 years, right, as everything is flying around the solar system. So it's incredible precision and really awesome sort of control over the physics of the solar system and gravity. Yeah, you don't want to fall short on that knowledge of gravity when you're sending something close to the sun.

Yeah. And so this thing is going to get closer than anything has ever gotten to the sun before by a factor of seven. Though when you say the number, it doesn't actually sound that impressive. It's going to get within four million miles of the sun. It's like just under 5% of one AU, the distance from the sun to the earth. But that is seven times closer than any previous mission. And it's going to be within 10 times the radius of the sun. Yeah, it sounds like a lot, but it's actually super duper close to the sun.

sun and super dangerous. And in fact, people, I think one of the ways they described it is that it's actually going to touch the sun in a way. And we'll talk about that later about what that means. Yeah, it's cool to think about touching the sun, though we can, of course, argue about what it means to touch it because like, where is the edge of the sun? In some definitions, we're already in the sun. But it's definitely fascinating to get nearer to the sun and to study up close what's going on with its magnetic fields and its corona and the solar wind and maybe even understanding what's going on inside it to generate all these cycles. Yeah, NASA sent

this probe to the sun to learn about its mysteries. There are still a lot of things we don't know about the sun, and so we'll get into those. But first, let's take a quick break. Adventure should never come with a pause button. Remember the movie pass era?

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Listen to no such thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right. It's a sunny day here in Southern California, and we're talking about the sun and the probe that NASA has sent to study it. The Parker Solar probe launched in August 2018, and it's been making closer and closer passes to the sun, getting us closer to what's going on there inside of the sun and in its atmosphere to learn about some of the deep mysteries we still have about how it works and what's going on inside there and outside of it. Yeah, you think that after studying the sun for hundreds or thousands of years that we might understand better this fusion engine at the heart of our solar system, the thing that's basically making all life on Earth possible. And while we do have some understanding of how stars work in general, there are a lot of big mysteries remaining about basic facts about the sun. Yeah, like why don't my kids like to put on sunblock? It's a huge mystery to me. The fight to the death.

Maybe you should move somewhere less sunny. Maybe I should get them into the habit of wearing hats, perhaps. But the sun does have a lot of interesting and pretty deep mysteries about it that we still don't know. And so let's dig into those. Daniel, what are some of the unknowns about the sun? Or the sun unknowns. One of my favorite mysteries about the sun is just why the outside of it is so hot. You know, the sun is, of course, very, very hot.

It's thousands of degrees sort of at its surface. And that's where the light that you see is generated. Remember we talked on the podcast several times about the connection between temperature and wavelength everything in the universe radiates light and the light that it radiates depends on its temperature and the sun is several thousand degrees Kelvin and at that temperature you tend to radiate in the visible spectrum and it's no coincidence of course that the sun tends to give off light in the visible spectrum our eyes evolved in this environment in order to see the light typically given off by the sun and so the sun itself is several

thousand degrees Kelvin but around the sun is something called the corona which is much, much hotter than the sun itself. And that's a really big mystery, how that gets so hot and how it stays so hot. Yeah, it's a really weird thing. It's a little bit hard to wrap your head around because the sun itself is not one temperature, right? Like the core of the sun is super duper, duper, duper hot because that's where all the fusion is going on.

But as you get closer to the surface, it sort of cools off, right? Like the surface of the sun is much cooler than the center of the sun. But then if you keep going out further past the sun, surface, it actually starts to get hotter again. It's like having a light bulb where the air around the light bulb is hotter than the surface of the light bulb itself. You expect the hottest point to be to center. This is the source of the heat where most of the fusion is happening until the star gets

much, much older, of course. But in a star that's at the age of our sun, mostly you have hydrogen fusion at the core, which is driving it. And then it cools off, as you say, as you get to the outer regions. But then it weirdly spikes again. So this part, the corona is hotter than the actual surface of the surface of the surface of sun itself it can be like hundreds of times hotter the corona is like millions of degrees Kelvin yeah it's super weird it's like you said it's like you can imagine the air around a light

bowl hotter than the actual surface of the light bulb like what's going on there how is that possible it's a big mystery and it's been a mystery for more than a hundred years people have been studying the sun like in the 1800s we're looking at the light that comes from the sun and they notice something really weird when they looked at the spectrum like they took the light from the sun and they asked what is the wavelength of all the photons that we get that's sort of the spectrum and it peaks in the visible range as you expect but there's also a one particular line this green line from the sun at a very strange wavelength that they couldn't explain the only way to explain this line the only thing that tends to give off light at this particular frequency is a weird form of iron iron

Iron that's been ionized 13 times. So iron has like 26 protons and 26 electrons. And in extremely hot situations, it can get so ionized that it loses 13 of its electrons. So this is iron 13 plus. And this is capable of making that green line, but it only exists in situations that are super duper hot, like multi-million degree plasmas. So they spotted this in 1869 and it was a real puzzler. Yeah, it tells us that the corona of the sun is a lot harder than the surface of the sun. And now, to give people some context, I think you maybe mentioned that the corona is, it's like the sun is about 1.4 million kilometers wide.

But the corona extends 8 million kilometers around the sun, right? It's like a much wider circle that they call the corona of the sun. That's right. And if you just like had a hot blob of gas around the sun that was hotter than the sun, then that heat would flow in. would cool down. This is not like an equilibrium situation. In order for this to persist, you need some source of heat. But if the source of heat is the sun itself, you would expect it to be hotter in the core. So really nothing about this makes sense. There needs to be some way to heat the corona. And it doesn't seem like it can come from the inside, right? And so it's a very strange

situation. Somehow heat seems to be flowing out, violating the second law of thermodynamics from something cooler, which is the surface of the sun, to the corona, which is hotter, right? He doesn't usually flow from a cooler surface to a hotter surface. Right. Well, there's some subtleties, I think, then maybe we need to go over. Like, for example, you're talking about temperature, not overall energy. Like, the corona is hotter than the surface of the sun, but it's a lot sparser. So this is one of those situations where it's like, it's not like there's more energy

outside of the sun. It's just that the particles that are there are moving faster than the particles at the surface of the sun, right? That's exactly right. It's much less dense than the surface of the sun, but the temperatures are higher. In the same way that you can have very high temperature plasmas between galaxies, places where if we dropped you without a space suit, you would instantly freeze, though technically you're in a very high temperature plasma. It's just very dilute. So there are fast moving particles, just not very many of them. So I think the same thing is true here. The corona is definitely hotter than the surface of the sun.

They're faster moving particles, but they're not as many of them. is less energy. Yeah, but it's still kind of a, I guess, the mystery is like, why are these particles around the sun moving faster than the particles just coming off of the sun, right? That's kind of the mystery. Yeah, exactly. Where do they get this energy? Because by standard heat diffusion process, that shouldn't happen.

You shouldn't get this weird spike where things suddenly get hotter further from the source of the heat. Now, could this just be like a situation where it's just the gas around the sun is absorbing the heat from the sun and getting that heat building up, you know, kind of like if I put a black blanket around a light bulb, it's going to get hot. It is going to get hot, but it's not going to get hotter than the light bulb, right? That's the weird thing that's happening here. The air is already a blanket around the light bulb and it doesn't get hotter than the light bulb. The heat diffusion equations tell you that the heat flows from the higher temperature to the lower temperature. So you need

something else to explain this. You need some way to like pump energy out from the sun, some other kind of process, not just diffusion of energy. All right. So that's a huge mystery. There are also other mysteries about the solar wind. Yeah, this is sort of connected in the sense that there are mysterious high speed particles. The solar wind is something that actually is kind of well named because when you think about a wind on earth, you thinking about like high speed particles pushing on you, bouncing off

you, transferring their momentum. Well, the solar wind is sort of similar. The sun doesn't just put out photons. It also puts out particles. protons, electrons, all these things moving at very, very high speeds, like hundreds of kilometers per second. So this is what we call the solar wind. And it flies out through the whole solar system, right? You get the solar wind even out here on Earth and it's far out at Jupiter and Neptune. It's like it's not just light. It's actual like stuff flying from the sun, right?

Yeah, the sun is sort of throwing itself at us. This is one reason people say that we're sort of in the atmosphere of the sun because we are in this envelope of gas that the sun is basically produced and it's sitting in the middle of. Yeah. So then what's the mystery about the solar wind? The mystery is how the solar wind gets so fast. Like a 400 kilometers per second is very, very high speed for these particles. If you build a model of the sun and just think about like particles at the edge of the sun boiling off based on the temperature of the sun, then you don't get particles this high speed. Like the Earth has an atmosphere, right? And

it's losing its atmosphere because things at the very top of the atmosphere, sphere are moving at high speeds and gravity gets lower and they just sort of like fly off. They reach escape velocity. So the earth is boiling off hydrogen. The same way, the sun is boiling off particles of itself. But if you do the calculations and predict how fast those particles should boil off, you get like 150 kilometers per second. But what we see are things like 400 kilometers per second. So there's some mechanism we don't understand.

It's like accelerating these particles over a really short distance, just from like the surface of the sun, boom, out through the corona and out into the rest of the solar system. You're saying the solar wind is faster than what you would expect. Now, is that related to also why the corona is hotter? Because the corona being hotter also means that the particles there are moving faster than what we expect. Yes, we think that these might all be connected mysteries. And the answer to them might lie somehow in the magnetic fields.

Because sun isn't just a hot ball of gas the way the Earth is. It has very, very powerful magnetic fields that are. driving what's happening inside of it and also that are driven by what's happening inside of it. And these magnetic fields contain a lot of energy. And so if essentially you're getting little pumps or these magnetic fields are breaking, then those are various theories we have about how these particles might get accelerated really fast. And it also might explain how the corona is getting heated so much. Cool. Now, you mentioned solar cycles before the cycles that the sun goes through. There are some mysteries about that too. Yeah, I think this is one of the most incredible

mysteries in the solar system, which is that the sun's magnetic field flips, right? I mean, it blew my mind when I learned that the Earth's magnetic field flips. First of all, that it isn't just static. It doesn't just like point the same direction and like wanders around a little bit, but that every 50,000 years or million years, it changes direction. North becomes south, south becomes north. If that's not weird enough for you, the sun does that also, but it does it like clockwork. Every 11 years, it flips. I can't overstate how much energy is involved here. And because the sun is enormous and whatever is causing its magnetic fields

are very, very powerful. For that entire thing to flip over, it's like turning a football stadium upside down, right? And it does it every 11 years. Yeah, it's pretty amazing. And so you're saying we don't quite know why they flip or we don't know what's causing it to flip every 11 years?

Both. We don't even know why it flips. We don't know why the Earth's magnetic field flips either, but we definitely don't know why the sun's magnetic field flips and we don't know why it's so regular. We have a bunch of different theories for why the Sun's magnetic field flips, some of which are pretty awesome and hilarious. Is it like an 11-year-old kid at the switch just going click, click, click, click, click, click, click. I don't think 11-year-old

kids are that regular over a 700 million year timeline. It's amazing. The first thing to understand is how you get a magnetic field anyway. For the earth, we think it comes from like motion of fluid metals inside the Earth, right? Essentially, you're having the flow of charged particles creates a magnetic field that pushes the charged particles. You get more flow, which gives you more magnetic field. It's called a dynamo. We have a whole podcast episode about where the Earth's magnetic field comes from. It might be that the Sun's magnetic field also comes from something similar, but these dynamos, these flows of plasma within the Sun could be affected by other things. Like, for example, it could be that gravity from the other planets like

Jupiter and Saturn and even the Earth are tugging on these things. And as they move around the sun, their collective gravity could, like, create an instability which flips the whole thing over. Yeah, it's like a giant generator basically inside of the sun and the Earth where you have like all these kind of like magnetic materials kind of swirling around and creating things. And so I guess if the overall flow changes, then the overall magnetic field changes too. Another possibility is that it could be due to differential rotation. Like the sun rotates, but it doesn't rotate the same speed all over.

It's not a firm object the way the Earth is, right? And so, for example, at the equator, it takes about 35 days for the sun to rotate, and it's 25 days to rotate closer to the poles. And so the magnetic field lines might be getting, like, twisted and pinched, and it might take like 11 years for enough tension to build up, for everything to sort of like snap and reassemble upside down. That's another possibility. And there's a third possibility.

for what might be explaining the sun's weird magnetic field, which is that the plasma currents inside the sun that are generating these magnetic fields might be moving sort of like in a huge donut of plasma. Like imagine not just a donut, but a donut now with layers in it. Like what do they call that when you have a croissant and a donut together, a cronut, right? So imagine a donut with all these layers in it. And every 11 years, instead of these plasma currents going sort of around the outside of the donut,

they flip. So now they're going like around the short side. of the donut briefly before it's flipping around and going the other direction. So we have lots of very different weird ideas about what's going on inside the sun. And the problem is we just haven't gotten close enough to make the measurements we need to understand what's going on. Yeah, because it is pretty hard to get close to the sun. As I think Icarus and his father learned, it's hard to touch the sun and obviously also

a little bit dangerous because the sun is so hot and putting out so much radiation and light and heat. And so let's get into what it takes to build a spacecraft to get that close to the sun to solve some of these mysteries. But first, let's take another quick break.

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I'm looking at this thing. Listen to no such thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, we're talking about the Parker Solar Probe, which is the fastest, or it's going to be the fastest moving spacecraft that humankind has ever built. And it's also going to get closer to the sun than anything we've ever built. Some say it made, it sort of, in a way, touches the sun. That makes me think of that kid on a Christmas story who puts his tongue on the light post and gets it stuck. Yeah, it does sound like a cautionary tale. The people who try to touch the sun.

Yeah, and I love this description of it as the fastest thing ever built. And that sounds really impressive until you kind of hear the number. It's going to go 0.064% of the speed of light relative to the sun. And that's really, really fast. It's like 690,000 kilometers per hour. 690 kilometers per hour? 690,000 kilometers per hour. That is insane, right?

Because as you go down the highway, you're going at like, 100 kilometers per hour. This is 600,000 kilometers per hour. Yes, it's much, much faster than I hope any of our listeners are traveling on their commute, but it's also such a tiny fraction of the speed of light. Just another sense for like how vast the universe is and how extreme the conditions are out there and how like quiet and cozy things are in our neighborhood. It's still a pretty amazing achievement and it's also a huge achievement to sense something that close to the sun because the sun is hot like it's hot here on earth like if you stand in the sun in the desert maybe you're going to get heat stroke but we're millions of kilometers away from the sun imagine being like super close to the sun

you're just getting so much more of that radiation and heat and particles trying to kill you right yeah it's a very intense environment and as you say an incredible technological achievement to build a spacecraft that can survive these visits yeah do you know how they did it yeah they have a bunch of like really cutting edge thermal engineering advances. They have a complex solar shield. Basically, the thing is diving towards the sun, but most of the instruments are protected by a shield. So the thing is like diving towards the sun,

but it's doing its sort of shield first. Behind that shield are a bunch of instruments, and the shield itself is very fancy and very technological. It's made of two panels of reinforced carbon composite with like a carbon core foam. And a lot of really complicated, engineering and modeling went into like how to bleed this energy off, how to make sure that the stuff behind the shield doesn't get fried. Yeah, I think if you look at a picture of the Parker

solar probe, you'll see that like half of it is basically the heat shield. It's almost like, you know, like when Captain America jumps out of a building and he's, you know, it's covered behind his shield. That's kind of what this probe is doing. It's not that it's covered all the way around. It just has a one shield in front. And so it's always going to be facing the sun with the shield otherwise it's going to get fried yeah and the shield can withstand temperatures up to like 13 or 1400 Celsius but the instruments have to be kept at like 30 Celsius otherwise they'll get fried and you know this is a complicated maneuver it's not just diving towards the sun and done as you said it's orbiting the sun a bunch of times so has to orient itself to always keep the shield between the

instruments and the sun so that means like turning right if these things are exposed to the intense radiation near the sun for like tens of seconds, they're fried. So over like a 10 year mission, you can't have 10 seconds of exposure to the sun. So this thing has a lot of computing on board to make sure that the shield is always in place. They call it one of the most autonomous spacecraft ever flown because it's so far away that like nobody on Earth can drive it in real time. It would take too long for the signals to get back and forth. So basically has to fly itself.

And it doesn't just have to fly by itself because it's far away. Because at some point it goes behind the sun, right? Like at some point it's on the other side of the sun and there's like no way it can send a signal to us or we can send a signal to it. So it has to be pretty much autonomous and always face the shield towards the sun. Yeah, that's a really good point. We cannot control anything on the other side of the sun. No signals we send could be received there.

So every time it goes behind the sun, we just sort of sit and wait and hope that it comes back. around the other side in good condition. Yeah, they told me that apparently there are three computers on board. And the way that the probe makes decisions is that the three computers are independent and they vote on what the probe should do at any point when it's independent. And then they take a vote and whichever decision wins gets the most votes is what the probe does. That's awesome. Are they all running Windows?

No, I think one of them is like iOS, one of them is PC, the only one is Linux or Unix, just to be safe. I would download the Windows computer. But it's also interesting because like the probe needs to shield itself from the sun when it's closed because the sun is so hot. But when it's far away from the sun, it needs the sun's energy to power and its batteries. So it has like these retractable solar panels that when it's far away from the sun, it like puts out these panels. But when it's getting closer, it tucks them in kind of like one of those jets that tucks its wings in. Yeah, it's like a hawk diving, right? as it gets to very high speeds, it tucks itself in.

It's really very awesome. And my applause to everybody who worked on this project and designed it. And it must be really nail-biting to see it actually out there and flying and implementing the programming that you put into it and trusting these autonomous systems to make these decisions with your baby. I mean, you work on this project for like a career. This is, you know, not a one project you work on and then you move on to another one the next week.

This is a decades-long project. So these people are biting their nails every time. goes around the sun. Yeah, it's a lot of trust to put into democracy for a majority vote. But you know, to get answers to the physics questions that we want, you really do have to get near the sun. Sometimes you can learn things about what's happening really far away just by sampling the photons I get here, but sometimes they're scrambled. And that's the case here. To understand what's going on in the sun's corona and the acceleration of the solar wind and the magnetic field, you have to get as close as possible to the sun because things tend to get scrambled by the time

they're already here on Earth. Yeah. And so part of what the probe is doing is getting those measurements really close to the sun, which we know is really hard, but they seem to be doing it. And so the idea is to, as you said, to study the electromagnetic field to the sun because maybe that's where a lot of these mysteries can be explained. Yeah, they have a bunch of instruments on board. One of them measures the electromagnetic fields.

Another one measures the velocity of the particles of the solar wind. And there's also a camera. They can just like take pictures of solar activity. But it's this one that like measures the electromagnetic fields that I think is really going to provide the clues that help us understand and build it like a deeper model of what's going on inside the sun. Because fundamentally the sun is a ball of plasma. And remember a plasma is just a gas that's so hot that the electrons are free. They're flying around. So everything in the plasma has an electric charge.

So instead of just being like any other blob of hot gas now affected by electromagnetic fields and it generates electromagnetic fields. fields. So it's very chaotic. It's very difficult to understand. This is part of why fusion is so hard to do here on Earth because plasmas are chaotic and very intense. And so measuring those electromagnetic fields close up will give us a sense for like what's going on inside the sun. How are these things flipping? Are these magnetic tubes like reconnecting and snapping to accelerate particles? That really is part of the core of the mission of this spacecraft. Yeah, because as you mentioned before, maybe the sort of two big mysteries about the sun that we don't know right now, why the outside of the sun, the solar corona is hotter than the surface of the sun.

And also, what is making the solar wind so fast, faster than it should be if it was just coming off of the sun. And so it seems like maybe a big explanation is what's going on with the magnetic fields outside of the sun, right? Exactly. And it might be connected to another mystery, which is the mystery of these solar flares. You know, the sun is bright and hot, but it's not always static, right? There are sun spots. And sometimes it ejects a lot of energy. and even like huge blobs of plasma. These things are called coronal mass ejections and solar flares and something we want to understand

because it affects life on Earth because these particles sometimes even reach Earth and can damage our electronics. And they think that these solar flares might be caused by disruptions in the magnetic field of the sun. Like when these magnetic tubes get pinched off and collapse, it can cause a little eruption.

That's an idea for what might be explaining these solar flares. And a related idea might solve these questions of the solar winds and the heat of the corona, as you were saying. There's this theory of like nano flares. And instead of like always having huge big flares, maybe the sun is constantly having a lot of these little magnetic disruptions

that cause nanoflares that dump out energy from the surface of the sun to the solar wind and to the corona. Yeah, because I think an interesting concept here is that the sun isn't just the gas that's on fire. It's not just a circle that's shining bright. Kind of like part of the sun is also. the invisible magnetic fields that the sun is creating and that it's that are extending out past the visible surface right because these magnetic fields are huge right they are there are millions of

kilometers more wider than the actual visible width of the sun like it has invisible fingers right yeah and it's sort of like a duet right or like a dance there's two partners there the magnetic fields push on the particles and change how they behave and where they go and how much energy they have. And the particles, because they have charges, also generate electric fields. It's this very non-linear behavior that can easily generate runaway effects. They can get very, very extreme. And they power each other like these dynamos inside the sun or inside the earth that generate our magnetic field. And so as you say, there's like one partner in that dance that we can't always see directly with our eyes, but it plays a really big role in what's happening.

It controls how all this plasma flows and where the energy is deposited. And so, So instead of just thinking about the sun as like a hot ball of gas where the energy is diffusing out from the second law of thermodynamics, instead now we're imagining like all these little magnetic tubes that are like leaching energy out from the sun more intensely. And those could be like heating up the particles and speeding them away in the solar wind to get them really, really fast and making the corona hot as well. Yeah, because the other thing is that it's kind of like a dynamic environment around the sun, right? like the sun is churning, things are moving. Like you said before, there are flows inside of the sun of these particles and the stuff in the sun is changing and flowing and churning. And so these magnetic fields outside of the sun are also moving and changing

and sometimes they crash into each other. And that's kind of, I think, one of the other explanations for maybe what makes the corona so hot is that these magnetic fields are basically crashing and exciting the corona more than you would think. Yeah, and it's Eugene Parker who sort of came up. up with this idea. Before him, people thought about the Sun's atmosphere sort of like static the way the Earth's is. It's, you know, maybe boiling off a little bit at the top, but it's basically just floating there held by gravity. But he wrote the first paper suggesting that the Sun's atmosphere is sort of dynamic and has all these magnetic components and generates this really

powerful wind to explain these high-speed particles. And his original paper was like rejected a million times sort of like the way like the Harry Potter manuscript was rejected by dozens of people before it was published. But he was right and it was confirmed later by like the Mariner mission that measured the solar wind to be these really high speed. And so yeah, the sun's atmosphere is much more complex than the Earth's atmosphere because it's a big magnetic ball of hot plasma and there's lots of crazy things happening. These magnetic tubes are breaking and clipping and reversing and smashing into each other. It's like magnetic weather. Yeah, it's good that his theory finally saw the light of day. But I think also that could also maybe explain the solar wind, right? It could be these

like thrashing, moving magnetic fields around the sun that are maybe causing or accelerating particles in the solar wind. Yeah, these are all mechanisms for taking energy from the inside of the sun and dumping it out into the corona, accelerating those particles into the solar wind and heating up the corona. Remember to solve this mystery, we need something other than just the second law thermodynamics, we need some pump that's like pulling energy from the sun and accelerating these particles. And as you say, these magnetic fields and their crazy behavior might just do that. And early results from the Parker Solar probe are suggestive. They've made a bunch of measurements of these magnetic switchbacks, like sudden reversals in the magnetic field, much more dramatic

than anything you would expect otherwise. They're like frequent and short-lived changes in the magnetic field that's suggesting that it's sort of like a chaotic magnetic and environment and these magnetic pumps, these nano flares of the surface of the sun caused by this crazy magnetic behavior could be with heating up the corona and accelerating the solar wind. Yeah, I think that was the whole point of the Parker solar probe is to get in there in those magnetic fields and measure what's going on in there. And that's kind of what they mean when they say that probe kind of touches the sun because it's sort of in there.

It actually gets to the point where it's right in the middle of those magnetic fields, which in a way are kind of the sun itself, right? I mean, it's not touching the visible surface of the sun, but it is touching its magnetic fingers. Well, yeah, when you're building a model of the sun, you have to match the data you see from the outside. But there's always ambiguity about what's going on inside. So what you really want is data from the inside, from where all the action is happening, right, from the inside out. As you say, Parker is going to give us this measurement of what's going on very, very close to the sun and can help us constrain these models. Tell us which ideas are wrong and which ideas do actually describe what's happening in the sun.

So that's pretty exciting. Yeah, in a way, it's sort of like the probe is not really touching the sun. It's more like it's getting to a point where the sun touches it. Touched by the sun. That's going to be the name of its memoir when it's done with this trip. And hopefully it didn't make its heat shield out of wax and feathers. Because we know that's a bad idea. And there's also exciting room for surprises, right?

We have these ideas about what might be happening inside the sun and near its edge. But remember that every time we send something out into the universe or develop a new kind of eyeball, We're surprised by what we learn. The universe doesn't just say yes or no to our theories. It says yes, but or actually something totally different is happening. And so the Parker Solar Probe is going somewhere nobody's gone before and might discover things that totally surprise us. The universe is not big into improv theory.

It's not a yes and kind of thing. It's a yes but. It's a sorry about the theory you've been developing for decades, but you were totally wrong. Well, that's when we have to improvise, I guess. All right. Well, the probe is out there. It's flying close to the sun. There's data coming in all the time now and new papers coming out of it. And so as it gets even closer to the sun, we'll learn more and more about what's going on in there. And so stay tuned for more news about the sun. I'm saying the probe has a lot of sunny days ahead of it. Exactly. And so thank you to everybody at NASA who developed this thing and sweated over it and launched it so that we could all learn more about what's going on at the heart of our. solar system. Yeah, and thanks to the scientists who talked to me to make my comic about the Parker Solar Probe

and all of this solar science. Again, if you want a visual companion to this episode, just Google PhD comics and Parker Solar Probe. You'll see it on Physics Magazine's website. All right, well, we hope you enjoyed that. Go out there and get some sun if you can. Thanks for joining us. See you next time.

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