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Sun Series: The Sun, Our Star

Season 7Episode 2Mar 19, 2024

The Sun is our closest star. Billions of years ago, it shaped the formation of our home planet and the beginning of life on Earth. Today, it provides the heat and energy that powers our civilization, but it can also disrupt our technology and spacecraft through explosive outbursts of radiation. Join NASA Sun scientist Joe Westlake on a journey from the surface of Earth to the Sun’s core to learn how intricately we’re connected to our star and the progress we’ve made unraveling its mysteries. This is episode one of the Sun and Eclipse series from NASA's Curious Universe, an official NASA podcast.

The cover art display for the NASA's Curious Universe podcast.

About NASA’s Curious Universe Podcast

Come get curious with NASA. As an official NASA podcast, Curious Universe brings you mind-blowing science and space adventures you won’t find anywhere else. Explore the cosmos alongside astronauts, scientists, engineers, and other top NASA experts who are achieving remarkable feats in science, space exploration, and aeronautics. Learn something new about the wild and wonderful universe we share. All you need to get started is a little curiosity.

NASA’s Curious Universe is an official NASA podcast hosted by Padi Boyd and Jacob Pinter

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About the Episode:

The Sun is our closest star. Billions of years ago, it shaped the formation of our home planet and the beginning of life on Earth. Today, it provides the heat and energy that powers our civilization, but it can also disrupt our technology and spacecraft through explosive outbursts of radiation. Join NASA Sun scientist Joe Westlake on a journey from the surface of Earth to the Sun’s core to learn how intricately we’re connected to our star and the progress we’ve made unraveling its mysteries. This is episode one of the Sun and Eclipse series from NASA’s Curious Universe, an official NASA podcast.


[MUSIC: Dreaming Animation by Elliot Greenway Ireland]

HOST PADI BOYD: This is NASA’s Curious Universe. Our universe is a wild and wonderful place. I’m your host, Padi Boyd…

JACOB PINTER: And I’m co-host Jacob Pinter.

PADI: And in this podcast, NASA is your tour guide.

JACOB: From here on Earth, the Sun can seem… a little boring. Or at least, predictable. It’s a big, docile yellow ball up in the sky. It rises and sets every day, right on schedule. Well, we’re here to make you see the Sun in a whole new way.

[SFX: Buzzing solar wind data sonification]

PADI: If you zoom in closer, our nearest star is an incredibly dynamic place… full of swirling magnetic fields and explosions of plasma that rocket out into space in all directions. And right now, in 2024, the Sun is near Solar Maximum… which means it’s at its most active and stormy, sending explosions of space weather towards Earth that can disrupt the technology that we take for granted, both up in space and right here on the ground.

JACOB: This year, the Sun is making sure we know it’s the star of our solar system. So, we’re bringing you something special in its honor… a five-part Curious Universe miniseries about all things solar.

PADI: For the next five weeks, we’ll be bringing you the stories of daring NASA missions like Parker Solar Probe…

[Parker Solar Probe launch broadcast: Liftoff of the mighty Delta IV heavy rocket with NASA’s Parker Solar Probe…]

PADI: …which is overcoming incredible odds to touch the Sun and unravel some of its biggest mysteries.

JACOB: You’ll meet people obsessed with auroras and eclipses… voyaging across the world, braving icy blizzards and baking hot deserts to catch fleeting glimpses of our Sun’s power right here on Earth…

[SFX: Whistling wind]

PADI: We’ll take you into the path of totality for the otherworldly experience that is a total solar eclipse…

[2023 Ring of Fire annular eclipse broadcast: Wow, that is a gorgeous sight to behold, everyone is cheering…]

PADI: …and inside the NASA control rooms where heliophysicists forecast space weather risks to our astronauts…

JACOB: These stories will change the way you think about our nearest star… I promise.

[THEME MUSIC: Curiosity by SYSTEM Sounds]

PADI: And so, to do all that, we’re bringing the whole team together. You’ll hear from me…



PADI BOYD: That’s Christian Elliott, Curious Universe producer.

CHRISTIAN: Hi Padi, hi Jacob!

PADI: In this episode, Christian, you said you’re bringing us the most important story of all… our Sun’s superhero origin story. The story of how a star is born, how it shapes and molds the solar system and planets, and how it makes life on Earth possible. Christian, that’s a lot to cover. So where do we start?

CHRISTIAN: Well, how about the very basics… Sun 101. I mean, what exactly is the Sun?


Oooh, that’s a, that’s… what, what isn’t the sun? Right? [Laughs]

[Music: Idle Thumbs by Thomas Ellis}

CHRISTIAN: For that hard-hitting question, I went right to the top.


Yeah, so my name is Joe Westlake. I’m the Division Director for heliophysics at NASA headquarters.

JACOB: So, you asked NASA’s director of heliophysics what the Sun is?

CHRISTIAN: Yes, I did Jacob. That’s the great thing about working at NASA… you get to ask very smart people questions like… that one. But anyway, Joe is a great person to explain the Sun to us. He’s new to the job at NASA, but he’s worked on nearly every aspect of space science that you could think of. He was on the team that helped discover the Higgs Boson, a new elementary particle in physics…


At a laboratory in Europe…

CHRISTIAN: He’s studied Saturn’s moons…


Titan’s upper atmosphere, it’s a really fascinating place…

CHRISTIAN: Earth’s magnetosphere…


The magnetosphere, our home here on the Earth.

CHRISTIAN: So anyway, back to the big question…


At the most basic level, the sun is a giant ball of gas and plasma, that is sort of the fundamental life force or the fundamental source of energy in our solar system…

CHRISTIAN: It’s a great energy source because of all that gas, mostly hydrogen, that’s scrunched together under the huge gravity of the Sun.


The hydrogen is, you know, undergoing this, like, this fusion to go into helium. So you’re fusing atoms together, creating energy and doing that, that energy comes out as light, and the light that we see, you know, when the sun comes up…

[SFX: Humming/rumbling Sun sonification]

PADI: That’s all true for our Sun, but it’s actually true for most stars most of the time! The important point here is that the Sun is a star, just like any other. It just happens to be our closest star!

CHRISTIAN: Right, yes! When you look up at the night sky, you’re looking at a sky full of faraway “Suns” of a vast range of sizes and ages.


Our Sun is a fairly average, you know, main sequence star… you could find a similar one in many places within our galaxy.

JACOB: So, what I’m hearing here is that we aren’t special?

CHRISTIAN: Well, yes and no… it might be an average star, but the Sun is just right for us.


If it was a much larger star, if it was a much smaller star, if it had much more mass, much less mass, we might not have the same situation at the Earth. It may not be as habitable, might not be as unique of an experience here for humanity. Because our Sun may be more violent, may be less violent, things like that.

PADI: Our Sun is definitely just right for us, but since it is a star just like all the others… just lightyears closer to us… we study it here at NASA to both better understand how it affects us, and to better understand how stars elsewhere in the universe work.

CHRISTIAN: Right, Padi you’re an astrophysicist, and you’re focused outward from our solar system usually, toward other stars and exoplanets. But it turns out we kind of have astrophysics here at home too, in our own backyard. We just call it heliophysics!

JACOB: Huh. So, just to recap, we have this star, and it’s the same kind of star that we can see all across the night sky that have planets of their own, but it’s right here in the middle of the solar system keeping our Earth nice and toasty and hospitable. I guess my next question is, how did it all start? How did we get here?

[Music: Light Warp by Elliot Greenway Ireland]

CHRISTIAN: Well, that is a very good question… and to answer it, we’re going to go wayyy back… imagine where our solar system, our Sun, our Earth is now, is just completely empty, just the black void of space. Well, it’s not completely empty, there’s some dust and gasses floating around.

[SFX: Whooshing gasses, bouncing sounds]


But what happens is that you get sort of collections of gas, these collections of gas, basically, are gravitationally bound to each other. So, the gravity pull of large masses of gas is pulling these particles together. And eventually, you end up with enough to where they’re pulling in so much more gas, so much more gas, and the things that are getting packed into the inside, are getting so close together, that they really can’t keep themselves apart. And then you start to do, undergo fusion, and that star is ignited.

[SFX: Echoing explosion]

JACOB: OK so a star ignites in space, so that’s the beginning of our solar system, right? But what about all the other stuff that’s around the Sun today, like when does Earth come into the picture?

PADI: Well, in general, once you have all the mass of the star in one place, all the leftover gas and bits and bobs start to orbit around it, and they pick up speed and momentum.

[SFX: Whooshing sounds increasing in speed]

CHRISTIAN: Yeah, that’s exactly what Joe said. You get this disk of gas and dust orbiting the Sun.


As this gas goes around and starts orbiting the sun, you end up getting like clumps, right, some of the perturbations, as they come together, turn into these larger perturbations, you know, larger fluctuations, larger changes in that local gravity, things start to collect together and stick.

JACOB: So, we’re living on a … what’s that word he used? A perturbation? Like, a clump of matter?


The third farthest collection of matter from the sun, [Laughs] in our solar system.

CHRISTIAN: Basically yeah, those clumps of gas and matter orbiting the Sun turn into Earth, and into all the planets. And there’s a lot that happens over billions of years to make our Earth what it is today of course. But the biggest factor all along the way, the reason why we’re here at all, is the Sun.


Obviously, you need gravity, otherwise, we would float off into, into our own area, and probably not be near a star, be very cold. So, the gravity of the Sun that has kept the Earth in close, has created an environment that’s useful for us.

CHRISTIAN: And again, the Sun is putting off just the right amount of energy, photons, that bring light and heat to Earth, to keep our planet’s surface under the right conditions for life to begin.

PADI: And where a planet is with respect to its star really matters. The Earth is in like, this perfect position with respect to our Sun, something we call the habitable zone, or goldilocks zone.

[MUSIC: Harmonic Echo by Ella Ryan]

PADI: And what that means is that once life got a foothold here on Earth, it could spread and thrive and evolve.

JACOB: So at this point in the story we’ve got Earth, we’ve got life, which is starting up because of the Sun’s warmth and light, and then humans show up, and we start to build civilizations, right?

[SFX: Animal noises, children playing at a playground]

CHRISTIAN: Right, and we’ve been looking up at the Sun, wondering about it, thinking about it… ever since.

[SFX: Wind through tree branches, bird song]

PADI: It’s pretty wild if you think about it… just how impactful the Sun has been… it’s made agriculture possible, for one, which let us settle in cities and develop civilizations all around the world. And at the same time, we have the Sun to thank for calendars, our sense of time and seasons. Basically all the rhythms of our life here on Earth. And wherever you look, the Sun shows up over and over again… in literature, music, religion… By looking at the Sun through telescopes and observing its influence on us through the aurora, eclipses and more, we as humans learned more and more about how it works over the centuries.

CHRISTIAN: And our understanding of the Sun really advanced when NASA came into the picture.

[Explorer 1 satellite video: All at once, Americans were interested in the oncoming age of space. And with the curiosity came a mounting, swelling demand to get a satellite into the air, on the double…]

CHRISTIAN: So, to set the scene… it’s the 1950s, it’s the space age, we’ve got rockets and satellites, and we can go into space, and scientists are eager to study all the bodies in our solar system and beyond.

[Explorer 1 satellite video: Cosmic ray intensity, meteor impacts, solar radiation. These are the dry facts that will help carry man ever farther into the age of space…]

We’ve had a long history of observing the Sun. It dates back, you know, before the United States had formed. But observing the sun from space has happened really since the beginning of the space age. And there’s been a lot of discoveries that have happened since the beginning of our spacefaring, you know, race.

[MUSIC: Veronique by Benjamin James Parsons]

CHRISTIAN: Studying the Sun has sort of defined NASA’s history… understanding our star was a goal for space science even before NASA formed. So, there have been a lot of missions.

PADI: Right, studying the Sun has been a huge focus for NASA for decades. There’s a whole fleet of heliophysics spacecraft! And they’re spread out in strategic places between the Sun, and Earth, and even into the interstellar medium beyond our solar system.

CHRISTIAN: So, from all these missions, we’ve learned that the Sun, and its relationship with the Earth, is more complicated than we thought.

JACOB: Hmm. Complicated how?

CHRISTIAN: Well, first we have to really understand the Sun. It’s got layers, literally. So, let’s start by zooming all the way in… at the very center of our sun is its core, where those nuclear reactions happen, that fusion that releases the Sun’s energy. Then we’ve got the radiative zone and the convection zone, two layers where the plasma and magnetic fields are swirling around and up towards the photosphere, where the Sun’s light comes from.

[SFX: Rumbling Sun sonification, swirling, whooshing]


If you were to stand on the surface of the Earth, and with your protective Eclipse glasses on, look up at the sun, you see the photosphere, you see where the photons are coming from, that’s relatively cold.

PADI: Cold yes, but still pretty hot compared to Earth, coming in at over 6,000 degrees Fahrenheit!

CHRISTIAN: Right. But that photosphere is actually not the Sun’s outermost layer, or its hottest! That honor goes to the corona, the Sun’s crown, its outer atmosphere. And the corona is a really wild and mysterious place. It’s way, way hotter than the photosphere…


What happens is, as you come from this photosphere, out into the corona, you get this intense, you know, warming, intense heating of the particles and plasma.

JACOB: Yeah, that seems like a puzzle. I mean, if the core is the hottest part, as you move further away from that, you’d expect it to get cooler, right? Like, I’m picturing when you make a campfire and you sit too close to it and you get hot, and so, what do you do, you walk away from it, right?

CHRISTIAN: Yeah, it doesn’t make sense to heliophysicists either, but it’s true! How it gets so, so hot is one of the Sun’s biggest mysteries.

PADI: And a big reason why it’s mysterious is that you can’t see the corona with your naked eye! From Earth, we can only see and study it during eclipses, when the moon blocks off our view of most of the sun… or through the eyes of spacecraft or telescopes.

CHRISTIAN: Yeah, but we can see some of the stuff the corona does. Because this outer atmosphere of the Sun is so hot and has so much activity, it has these huge explosions, these outbursts that we can detect.

[SFX: Explosive solar storm sonification]


It’s really the, like, the atmosphere, the sun is blowing off into space. And that atmosphere is so hot, so incredibly hot, that it then ejects itself off into space, sometimes violently, sometimes with these coronal mass ejections and things like that.

JACOB: So, coronal mass ejections… What are those?

CHRISTIAN: Good question. There’s actually a couple kinds of explosions or eruptions that come off of the Sun.

[MUSIC: Hip Flop by Thomas Ellis]


Now, coronal mass ejection is something where you’re seeing, basically a big parcel of hot gas being blown off of the surface of the sun…

JACOB: So, there’s an explosion on the Sun that actually sends material from the Sun flying off into space? Like, an ejection of coronal mass, I guess?

CHRISTIAN: Yeah, it’s well-named. But it actually gets even wilder than that. The second kind of eruption is called a solar flare.


A flare is a very explosive event that basically sends off all this energy very, very fast in the form of generally light and high energy light to the Earth.

CHRISTIAN: Coronal mass ejections and solar flares can even happen at the same time!

And sometimes you get it where there’s a coronal mass ejection that has flares within it. Okay, but that coronal mass ejection travels much slower to the Earth, a few days.

JACOB: So, you’ve got flares, these quick flashes of energy, radiation, that hit the Earth, and then these coronal mass ejections, which are big chunks of plasma that come our way a lot more slowly, because they have mass?

CHRISTIAN: Yeah, exactly. Now remember, you can really just see the photosphere from here on Earth, unless there’s an eclipse. All this wild, chaotic activity in the Sun’s atmosphere is basically invisible. But NASA has satellites like the Solar Dynamics Observatory floating out in space, looking at the Sun that can zoom in close on that violent activity so you can see it for yourself in imagery. That satellite is part of a program NASA calls “Living with a Star,” because it’s about learning to live next to such an explosive neighbor.

[MUSIC: Heat Seeking by Benjamin James Parsons]

JACOB: Ah yeah, I think I have an explosive neighbor at my house too, so I get that.

CHRISTIAN: Yeah, I think we all do, it’s very true. Anyway, in the imagery you can see sunspots, these dark, cooler areas of the surface where magnetic fields are going crazy, and of course coronal mass ejections and flares.


You know, it almost looks like, to me like volcanic eruptions, right?

CHRISTIAN: But Joe said, unlike a volcano, there’s more order to it, Joe said, because it’s all controlled by the Sun’s electricity and magnetism.

[SFX: Gurgling, bubbling lava]


So you see particles, you see what looks like, you know, plasma, this really, you know, bright stuff being blown off of the surface, but then it follows these paths, beautiful paths, across the surface, where you see, you know, sinews like these really like, beautiful little traces of particles going across and lighting up.

[SFX: Bubbling, boiling water]

CHRISTIAN: Joe told me it’s kind of like watching a pot of boiling water… you get this hot water that’s constantly rising up to the surface and going back down, churning around in the pot’s convection zone, sometimes bursting out, just like the plasma and magnetic fields do in the Sun’s convective zone.

[MUSIC: Earth Shine by Arun Ganapathy]

CHRISTIAN: Now there’s another NASA mission I have to mention, it’s called Parker Solar Probe. We mentioned it at the top of this episode, and we’ll talk about it a lot more a little later in this miniseries, because it’s so cool. It’s NASA’s mission to “touch” the Sun’s corona. And as it gets closer and closer to the Sun with every orbit, it’s starting to fly through these explosions! Like there was this one time where this huge coronal mass ejection hit the spacecraft, and it was so powerful it rattled it, you can see things move on it as it gets hit.

[SFX: Coronal mass ejection explosion hits Parker Solar Probe]


But you could see, it almost looked like a bubble, you know, coming onto it, and then nothing. And so, you know, you saw, you saw this big, burst of gas go across the spacecraft, and then the stars came out, because all of a sudden, the gas that was there, the atmosphere that was there, has been blown off. And there’s this huge vacuum behind it, which is just incredible.

CHRISTIAN: So, all that to say…


As you get closer and closer to the sun, it goes from being this beautiful, you know, timid, yellow ball of gas to being this very exciting, very powerful, very chaotic surface, where something’s always going on, something’s always happening.

PADI: And that activity is not always the same, right? We’ve mentioned early on that the sun is near Solar Maximum, right now in 2024. So, it’s at its peak activity, and we’re seeing more sunspots, coronal mass ejections and flares than usual!

[MUSIC: Speaking in Riddles by Zachary Scott Lemmon]

JACOB: So, I’m thinking, if parts of the Sun’s atmosphere are exploding away, and they’re just getting blown off into space through coronal mass ejections, where do those go?


As those go out into space, you know, it’s expanding into this sort of void between the Sun and the Earth. And as it expands, there’s not a lot of particles in between there. But there’s this constant sort of solar wind, that’s moving from the Sun to the Earth.

[SFX: Whistler waves detected by satellites]

JACOB: So, we essentially live in that solar wind here on Earth, right? In the atmosphere of our star? Being in the crosshairs of that steady stream of particles from the Sun sounds… not optimal.

CHRISTIAN: Yeah, it can definitely be bad! and there’s a lot more on that to come later in this series. But what you need to know right now is that here at NASA we try to keep an eye on the Sun’s activity, because it can be hazardous.

PADI: Right… In really extreme cases, space weather can even affect us here on Earth’s surface! In 1859, the most intense solar storm in history hit Earth. It was called the Carrington Event. It released solar flares so bright that astronomers observed them from here on the ground… for the first time ever. When all that energy reached Earth, it set telegraph lines on fire!

JACOB: And I’m thinking something like that would have to be way worse today, right? I mean in 1859 it’s telegraph lines, but today we have way more electrical infrastructure that could be in danger from that kind of event, right?

CHRISTIAN: Yeah, I mean, there’s the potential for things to be pretty bad. But don’t worry, luckily, we have this built-in shield that protects us from all but the worst storms here on Earth.

[SFX: Earth’s magnetosphere rebounding from solar wind data sonification]


So, as you move as you get closer and closer to the Earth, you come upon this obstacle, which is the Earth’s magnetic field. It’s created by, you know, the rotation of the metallic core of the Earth, that sets up this magnetosphere, that’s our protective shield. You come up to that, and all of a sudden, you’re blocked. You, as the solar wind, you’re pushed off to the northern and southern regions of the Earth and brought down into the poles where the sort of the field lines reconnect and then funnel particles down onto the earth in sort of those polar regions, which creates the aurora.

PADI: You can actually see visual evidence of our magnetosphere’s protection at work if you’re far enough north or south and catch a glimpse of the aurora, the northern and southern lights!


Particles, they come down, they hit our atmosphere on Earth. And when they hit the atmosphere, the colors that you see in the Aurora are the different composition of both the particles but also of the atmosphere lighting up as these particles hit.

CHRISTIAN: Right now, in 2024, the northern lights are going crazy up at the poles, because the more radiation coming from the Sun, the more particles our magnetic shield has to funnel down into the poles. When the Sun’s activity is really high, you can actually even see the aurora further south.


The aroura, the northern lights are just these beautiful displays in the sky, but beautiful displays of both the power of the sun, but also of our Earth’s protective magnetosphere. The protection is at work, right? It’s keeping those solar particles away from our, the surface of the Earth.

PADI: So, to recap, the Sun makes life possible here on Earth through the light and heat it provides us. But it also releases powerful storms and radiation that can disrupt our technology. And so, we have a quirk of planetary geology, our Earth’s metal core, to thank for the shield that protects us.

JACOB: That’s pretty cool… I still have one more question though. I mean, if the Sun is sending out the solar wind in all directions, all the time, I mean—only a tiny fraction of that is going to hit Earth. So, what happens to the rest of it?

PADI: Well, as the solar wind expands out past Earth and through our solar system, it creates this big, protective bubble around us. We call that bubble the heliopshere! It keeps out most of the galactic cosmic rays from elsewhere in the universe that otherwise would hit us on Earth and damage our DNA.

[MUSIC: New Beginning by Lincoln Jaeger]


That bubble that the sun creates, this protective bubble, is really one of the things that has allowed humanity, the habitability of the Earth to exist, because it’s protected us from this, the harsh interstellar environment.

JACOB: So, I’m picturing those Russian nesting dolls, you know? Like we have a bubble here on Earth that protects us from the Sun, and then we’re within this larger bubble that the Sun creates that protects us from stuff coming from outside the solar system, right?

CHRISTIAN: Exactly! And, if you’re like me, you might be wondering how on Earth we know that.

PADI: Yeah, it’s a good question! We’ve studied the heliosphere in a lot of ways, but one of the things we’ve done is actually sent spacecraft out there, like the famous Voyager missions that launched back in 1977. Voyager 1 and 2 were the first NASA spacecraft to leave our solar system and the first to directly explore the heliopshere.

JACOB: The Voyager missions have the golden record on them, right? That mixtape of information about Earth and humanity for potential life in other parts of our own galaxy could maybe someday find.

CHRISTIAN: Yeah, it’s pretty wild to think about. Near the beginning of the space age, we’re sending this message in a bottle out into the universe, expanding our horizons, way before all our modern Sun-studying spacecraft…

[Voyager 1 launch broadcast: …the first of two Voyager spacecraft to extend Man’s senses farther into the solar system than ever before…]

CHRISTIAN: …and decades later it leaves the solar system, and it detects the boundary of the heliosphere, this bubble that allowed humanity to flourish on Earth in the first place, that’s given us this habitable planet that we can use to build spacecraft like the Voyager probes!

PADI: Ooh.


So, the Voyagers moved out. And they punched out through the heliosphere in two locations, roughly 100 times the distance between the Sun and the Earth. So, at about 100 astronomical units is roughly where they punched out.

[Voyager 1 milestone broadcast: The most distant human-made object, NASA’s Voyager 1 spacecraft, is in interstellar space, the space between the stars…]

PADI: Even though they’re out in interstellar space now, the space between the stars, this wild west without the heliosphere’s protection, they’re still sending us back valuable data!


It was the first mission for us to really understand the interstellar medium. It still had the instruments available, it still had the observations available, to punch out of our heliosphere and start to understand what that local interstellar medium is, what the gasses between the stars are.

JACOB: I’m still not over that distance… 100 times the distance between the Sun and the Earth? I mean that’s pretty far itself if you think about how we have Mercury and Venus between us and the Sun! What does the heliosphere look like? I mean if it’s a heliosphere, is it just a big sphere all the way around the solar system?

CHRISTIAN: We still really don’t know… there have been other missions that tried to detect its shape through remote sensing and there’s another interstellar mapping probe planned. But right now, we just have theories…


And, and it’s interesting to think about, just like the structure, what does our heliosphere really look like?

[MUSIC: Phony Friends by Daniel Marantz]

CHRISTIAN: OK so, there are basically two theories. There’s the banana slash croissant theory, that has to do with how the solar wind comes off the Sun’s poles, which we still don’t know about, since we haven’t really seen the Sun’s poles.


You know these sort of theories say like, maybe there’s two jets that go off the two poles, and they wrap around sort of making this banana or croissant-shaped kind of thing…

CHRISTIAN: I like the banana slash croissant theory, but…


There’s theories that say well, maybe it’s just sort of a bubble and you know, it sort of terminates somewhere a little farther back and things like that. We really don’t understand that at all. We haven’t sent a spacecraft down the tail of our heliosphere.

CHRISTIAN: There are also other forces beyond our solar system acting on the heliosphere, kind of affecting its shape. It’s not all determined by the Sun’s activity.


Because if you think about, you know, how the Sun has evolved and how things have evolved over time, you know, we’re not, we’re not the only star in the neighborhood. And there’s lots of stars and gas in the neighborhood that affects how big that heliosphere is, the bigger the heliosphere, so the more powerful the sun is, the less radiation you get that comes in from outside. The smaller it is, the more radiation you get to come in from outside.

CHRISTIAN: All that other stuff, these clouds of interstellar gas, change our heliosphere over time, at the same time as our Sun changes its activity on its 11-year cycle.


We’ve seen the heliosphere breathe, it expands right? The solar wind is dynamic, it changes how that interaction is. It’s a huge object, just a huge object.

JACOB: So, you need a star that’s powerful enough to create a protective heliosphere but not so strong it cooks you on your planet with radiation?

CHRISTIAN: Exactly. Our relationship to our nearest star is a lot more complex than you might think.

[MUSIC: Deepen the Mystery by Espen Fahlen]

It’s really both our nearest protective neighbor, but also can be, I guess, a little bit of an ornery neighbor at times. And has these sort of, these real explosive events that can affect our critical infrastructure and things like that. So, you really need both, you know, you need the solar wind to create this protective bubble around the Earth. But you also need the Earth’s magnetosphere to protect us from that solar wind that’s also protecting us. It’s sort of circular in that way.

PADI: It’s like this beautiful balance.

JACOB: It’s a lot to think about. Because so much of our life depends on the sun being the stable partner that we have come to know not just through our lives but through humanity’s time on Earth. But there’s a lot of ways that’s not always the case, right? It sounds like it’s important to keep understanding how it all works.

CHRISTIAN: Yeah, it really is. And it’s all just a little mind blowing to me. But that’s just the start. We’re going to get into so much more in the coming episodes.

JACOB: OK, so what do we have to look forward to, can we get a little hint for now?

CHRISTIAN: Yes, I will give you a hint! A mysterious pink line in the sky called STEVE, petroglyphs carved into a desert cliff a thousand years ago that might help us understand our upcoming total solar eclipse in a new way, and the story of a spacecraft lost spinning in space for months that, once it recovered, had an ability to discover new things close to the Sun that nobody expected! The Sun is just such a mysterious place, full of new things to discover. But you don’t have to take my word for it.


Heliophysics is sort of at this really bright time in its path, where we’re building upon the knowledge that we’ve gained about the Sun…and we’re really turning it into a well-refined scientific topic…about really something that’s so fundamental in our lives. Every day you wake up you see the Sun, hopefully, depending on where you live. And it’s an amazing thing that we take for granted. And it’s so incredibly ingrained in what we do. And it’s a place where great discoveries are still to be made.

PADI: We’ll have all that and more right here on Curious Universe.

JACOB: And before we go, we have a special new segment for you…

[MUSIC: Sound Design Digital Uplifting Texture by David Thomas Connelly]

PADI: What are you still curious about? We ask that question to every single person we interview for this show. And we want to know what you’re curious about too. In this segment we’ll take a question from a curious listener and track down the answer. Today’s question comes from Dallas Taylor. He’s a sound design and audio expert, and he’s the host of the podcast Twenty Thousand Hertz, which explores the stories behind the world’s most interesting and recognizable sounds. Dallas, it’s great to have you with us.

DALLAS TAYLOR: The feeling is mutual because I am so excited to talk to you.

PADI: You’ve produced quite a few episodes about space, right?

DALLAS: Yeah. So usually, I do shows all about very recognizable sounds, like the Netflix ta-dum sound or the Wilhelm scream. But we sometimes dabble in brain science and all sorts of things. But what I spend a lot of my own free time on is just thinking about space and the unknown and all of that.

PADI: Let’s hear a clip from one of those episodes, “Space Remix”, which is all about what other planets might sound like.


Let’s go from planet to planet in our solar system to find out what each surface would sound like. To our ears. To be clear though, you’d pretty much die instantly everywhere, except for here. But, for these examples we’re going to pretend to have superhuman powers that will keep us alive. So, with that disclaimer out of the way, let’s start closest to the Sun.


Places like… Mercury and these rocky bodies with no atmospheres would be similar to being in space. There would not be much sound if any.


Mercury is an airless body, so we’re back to listening for Mercury quakes, essentially. That would be really the only source of sound.

[SFX: Rumbling Mercury quake]


And you could only hear these Mercury quakes if your head was pressed up against the rock, because there’s no atmosphere for traditional sound to travel through. Next up, Venus.


In my mind, what sound would be like on the surface, because you have this really dense atmosphere, much denser than Earth’s, the sound would be more like or tend toward what things sound like when you’re underwater.

[SFX: Bubbling underwater sound]


If you could imagine something in between air and water, that kind of density, you’re running your hand through that, and you would feel that.


One thing we do know about Venus is that is has lightning, so you might hear thunder.

[SFX: Muffled underwater thunder sound]


I wonder what other things, like my voice, might sound like. I’m on Venus in this ethereal world that’s a mix between a gas-like atmosphere and water. I’m almost floating, but yet it’s not as restrictive as being submerged in water. My voice… the thunder… it’s all slightly muffled and distorted as it travels through the thick atmosphere.

PADI: I recognize some of those voices, and it’s cool that you feature NASA scientists in your show. So, what are you still curious about when it comes to space?

DALLAS: So, we went through every planet in the solar system. But we never talked about the Sun. And I have no idea what it would be like on the Sun. And it’s more of a thought experiment, but I would love to know if you don’t immediately burn up and if you’re in some aspect of what you would call a surface, just let your mind go. What would it sound like on the so-called surface of the Sun?

[MUSIC: Collective Conscious by Aron Wright and Florian Moenks]

PADI: Right, another thought experiment, similar to what you did with Venus there, we can do it with the Sun. And you’re in luck, because in our last season of Curious Universe we took a deep dive into that very question in an episode we called “Hum of the Sun.” It turns out that we actually can listen to the Sun, but it’s a little complicated. Our star is a really active place. It emits this constant stream of particles called the solar wind, and in that solar wind in space, plasma waves can travel, full of electric and magnetic fields. You can’t hear those waves in the same way you can hear sound waves in the air on Earth because space just isn’t dense enough. But we can detect them with satellite instruments, especially when they collide with Earth’s magnetic field lines and vibrate them like giant space guitar strings. Then we can play those waves aloud here on Earth in a range our ears can hear.

DALLAS: But if we were actually standing on the surface, would it just be like a loud roar? Would it just be like, Krrrrghhh?

PADI: So that’s a great question, and we have a whole division here at NASA called heliophysics that is focused on learning more about the Sun from space. And one of the most exciting missions that’s active now is called the Parker Solar Probe. One of the things the Parker Solar Probe is going to do is touch the Sun, and so it’s the manmade spacecraft that will get the closest to the Sun that we’ve ever come. So, we’ll be able to answer these questions with real scientific data.

DALLAS: Ooh, I love it. Well, if you ever want to make any sound shows that are very romantic about space, you know who to turn to.

PADI: It was great to talk to you, Dallas.

DALLAS: Great to talk to you too.

PADI: Thanks again to Dallas from Twenty Thousand Hertz for his question. Expect more answers to curious questions in the coming episodes.

[THEME MUSIC: Curiosity by SYSTEM Sounds]

JACOB: This is NASA’s Curious Universe. This episode was written and produced by Christian Elliott. Our executive producer is Katie Konans. The Curious Universe team includes me, Jacob Pinter, Maddie Olson and Micheala Sosby… and of course, Padi Boyd. Krystofer Kim is our show artist.

PADI: Our theme song was composed by Matt Russo and Andrew Santaguida of SYSTEM Sounds. Special thanks to NASA’s heliophysics team.

CHRISTIAN: If you enjoyed this episode of NASA’s Curious Universe, please let us know by leaving us a review and sharing the show with a friend. And remember, you can “follow” NASA’s Curious Universe in your favorite podcast app to get a notification each time we post a new episode.

[NASA Podcasts stinger: 3, 2, 1. This is an official NASA podcast]