NASA's Curious Universe - The Star in Our Backyard

Episode Date: May 17, 2020

Our Sun holds the solar system together and is responsible for life as we know it. Though it may seem calm and unchanging, the Sun is dynamic. Join NASA solar scientists on a trip around the Sun, our lively and mysterious neighborhood star.

We're very used to the sun. It's our star. We see it in the sky every day. We know that it has a lot of impact of what happens to us here on Earth. But of course, it's even more than that. The sun actually shapes our entire neighborhood as we orbit around the Milky Way. Understanding the sun and how it works is very, very fundamental to us. This is NASA's curious universe. Our universe is a wild and wonderful place. I'm Patty Boyd, and in this podcast, NASA is your tour guide. This week's adventure takes us to the very center of our solar system.

We're visiting our neighborhood star, the sun. For me, what makes the sun really cool is it's kind of like having a star in your backyard. Hi, I am Nikki Fox, and I am the director of NASA's. Heliophysics Division. You know, we're used to looking up at night and seeing all the beautiful stars, beautiful constellations, planets glowing, and it's all wonderful. And then you realize the sun is just like an average star, but it's very close to us. And so, number one, it means that we can study it in very, very, very detailed ways. But also because we live so close to it, we kind of live in the atmosphere of the sun. If we can understand our star, then it helps us understand stars

in other solar systems or stellar systems. So everything's happening in heliophysics. The sun is responsible for life as we know it. Its gravity holds the solar system together, keeping everything from the biggest planets to the smallest particles of debris in its orbit. But it also drives a vast space weather system of particles that weave through space. And that's what NASA's Heliophysics Division studies. The sun's outer atmosphere actually moves all the way out through the edge of our solar system. That's actually what's creating this boundary. And so we live in the atmosphere of the sun.

So when the sun is a very, very active star, that actually drives what we see here at Earth. Earth is orbiting through a space soup of solar particles. The interactions between the sun and Earth create a complex space environment. It drives effects from the beautiful to the detrimental. It creates aurora, but it also interferes with satellite electronics or GPS signals. That soup of particles also protects us. It extends billions of miles out, far past the last planets, and we wouldn't be here today without it.

The Sun creates this protective bubble that really protects us from all of the vagaries of interstellar space. interstellar space. So all the nasty things that are outside are kind of kept at bay by this atmosphere and this boundary that the sun creates for us. The sun is very dynamic. It's an exciting field to be in because the sun changes every day. So you always have something new to study. But for me, the big attraction about studying the sun is it's studying a star. And right now it's the only star that we can study up close. The sun is our closest star. It's our protector, our life giver, and it's also our only close-up and personal glimpse into star science overall.

Though we see the sun daily, there's a lot that would surprise you. I think a lot of people look at the sun and just think it's a bright, you know, ball of light, or some people think it's a bright ball of fire in the sky. But the sun is very complicated. Our star is actually a hot ball of glowing, electrically charged gas, and it's made up of many different layers. Let's break them down. Our star has a core.

It's not solid, and it works kind of like a nuclear reactor. Nuclear fusion happens there, producing all of the energy that eventually makes it out of the sun as light and radiation. After that, comes the radiative zone. It's the region where things literally radiate out of the core. Then there's the convective zone where the sun begins to act a bit like boiling water. Then there is the kind of visible, what we think of as the visible surface. We call it the photosphere.

It's not an actual surface. It's not solid. But it's what our eyes see as the kind of outermost region of the sun. However, there are two more layers. It's just we can't see them because this visible surface is so bright that you can't see those hazy layers. These layers are the chromosphere and the corona.

We can't see them because the visible light is so bright, making these layers seem hazy. The corona in particular is especially crucial. The most important thing for us here at Earth is the corona, which is that bright hazy atmosphere that you see during a total solar eclipse.

That's the only time you can see it, because finally the moon blocks out that bright point of light that we see, and you can see that beautiful corona around it. So the sun is a lot more complicated than you might think by just looking at it from here at Earth. That solar atmosphere, the corona, that's what's driving all the changes in space throughout the solar system. While the corona affects us the most, it's still the most mystifying part of our sun.

The corona, it is extremely hot. It's on average two million degrees. That's Alida Higginson. She's a heliophysicist at the Johns Hopkins University Applied Physics Lab. The weird part is that it's actually hotter than the surface of the sun. So colloquially, we all talk about how, oh, yeah, the surface of the sun, like that's some really hot, big number. And it is 6,000 degrees is really hot, but then you multiply that,

and that is what the atmosphere. of the sun actually, how hot it actually is. So that is something that you cannot have a physical grasp on as a human. The corona's high temperatures are a bit of a mystery to scientists. As you move away from the surface of the sun, the temperatures actually get hotter. Imagine sitting next to a campfire,

but then feeling warmer as you walk away. It may sound strange, but this is exactly what seems to happen in the sun. And heliophysicists have been trying to solve this mystery for a long time. The sun is incredibly violent. It's aggressive. So if you could fly next to the sun, you would be blinded by the amount of light that it's putting out. You actually probably wouldn't, if you could magically survive in a vacuum.

You might not feel the heat from the material. surrounding you as much as you would just feel the heat from the radiation of the sun. So the front of you would be really hot and the back of you would be really cold because even though we have all that material in space next to the sun surrounding the sun, it's not very dense. Our star is not a burning ball of fire. It's plasma. A soupy mixture of electrically charged gases, mostly hydrogen and heat. The Sun is made of 90% plasma.

Its unique makeup means that the laws of gravity, the force we experience most on Earth, is only one of the forces driving how particles move. So all that plasma moves around unlike anything we have normally experienced on Earth. Our Sun is an active star. It releases a constant stream of that solar material, the plasma, in all directions at all times. Our star's activity creates what we call space weather. Space weather is the term that we use to define all of the dynamic activity. The sun's activity makes its way through space and then impacts the Earth system.

NASA cares a lot about understanding space weather because it can be very disruptive. It can trigger power outages and disrupt GPS signals. It can also affect astronauts and spacecraft in space. It also can change in a really large way, really suddenly. So you can have several days of just kind of background, low-level variation in the space weather activity, and then suddenly there'll be a huge eruption on the surface of the sun. And then that can, within a matter of minutes, cause all kinds of interference here at Earth just from the radiation from the sun. The sun impacts us here on Earth.

And it's also a laboratory for understanding the stars far beyond our solar system. Scientists like Nikki and Aleda are working to unravel the mysteries of our star. There are a couple of mysteries we've known about for well over 100 years. The corona, this hazy atmosphere, it's hotter than the surface of the sun by about 300 times. And that doesn't make sense. We call it the coronal heating mystery. What is it that's happening that's actually causing this heating? And we've known about these questions, but you know, you can study the sun from all different kinds of wavelengths, which we have done.

We've sent spacecraft in as far as the planet Mercury. And we've done amazing science, but we've never really been able to go and visit exactly where this heating is happening. In 2018, NASA launched a mission to touch the sun. Three, two, one, zero. Lift-off of the mighty Delta 4 heavy rocket with NASA's Parker Solar Probe. Parker Solar Probe, a mission headed to explore the unknown. It's on a voyage of discovery, and it's looking for some answers to those big questions. Parker Solar Probe is actually flying in to the Sun's Corona, making cuts through the Sun's Corona, very close to the Sun's Corona,

and is already returning amazing data to us. It's getting closer to the sun than humankind has ever sent a probe before, and it's actually going to be touching the very outer layers where the corona transitions to the solar wind and studying the mysteries that are there and trying to understand why is the corona so hot? Why is the sun's atmosphere so hot? We think we know where the energy is coming from, but we just don't know how it's getting. there. So that is something that we're hoping Parker Solar Probe will be able to shed light on and is one of the biggest questions that will probably have some important implications for physics

in general as well, not just for space weather and the sun. There's a lot to study with heliophysics. There's many, many different aspects of it that you can study. And it's a great time to be a heliophysicist. We're launching great missions to all these key locations. Some people say, say, you know, it's a new discipline of science. I would say it's the original discipline of science. Everybody looked up at the sun at some point and wondered what it was and how it affected us. And that's what we study in heliophysics.

There are billions of stars like ours scattered throughout the Milky Way. But the sun is incredibly important to us. It's ours. And it affects so much of what we experience here on Earth. We still have plenty of questions about the star in our backyard. With each day, NASA's sun scientists gain a new understanding of it and get a little closer to unraveling its mysteries.

This is NASA's Curious Universe. The Curious Universe team includes Elizabeth Tammy and Michaela Sosby. Our executive producer is Katie Atkinson. Special thanks to Karen Fox, Sarah Frazier, and the Johns Hopkins University Applied Physics Lab. If you liked this episode, please let us know by leaving a review, tweeting about it at NASA, and sharing it with a friend. You can also tag along on more solar adventures

by following at NASA's sun on social media. Thank you for listening to the first season of NASA's curious universe. Our universe is a wild and wonderful place, and we've enjoyed exploring it with you. We're taking a break now, but we'll be born. back before you know it. Until then, you can continue exploring the universe and discovering our home planet with NASA by visiting nassah.gov. You can also follow NASA on Twitter, Instagram, and Facebook. And find more NASA podcasts in your app or at nassah.gov slash podcasts.