0:03

This is NASA's Curious Universe. Our

0:06

universe is a wild and wonderful place.

0:09

I'm your host, Patty Boyd. And I'm

0:11

your co-host, Jacob Pinner. And in this

0:13

podcast, NASA is your tour guide. From

0:16

here on Earth, the sun can seem

0:18

a little boring, or at least predictable.

0:21

It's a big, docile yellow ball up

0:23

in the sky. It rises

0:25

and sets every day right on schedule. Well,

0:28

we're here to make you see the sun in

0:30

a whole new way. If

0:32

you zoom in closer, our nearest

0:34

star is an incredibly dynamic place. Full

0:37

of swirling magnetic fields and explosions

0:40

of plasma that rocket out into

0:42

space in all directions. And

0:44

right now, in 2024, the sun

0:46

is near solar maximum. Which

0:49

means it's at its most active and

0:51

stormy, sending explosions of space weather towards

0:53

Earth that can disrupt the technology that

0:55

we take for granted. Both up in

0:57

space and right here on the ground.

1:00

This year, the sun is making sure we

1:02

know it's the star of our solar system.

1:05

So we're bringing you something special in its honor.

1:08

A five-part Curious Universe miniseries

1:10

about all things solar. For

1:12

the next five weeks, we'll be bringing you

1:15

the stories of daring NASA missions like Parker

1:17

Solar Probe. Lift off of the mighty

1:19

Delta IV Heavy Rocket with NASA's

1:21

Parker Solar Probe. Which

1:23

is overcoming incredible odds to touch

1:26

the sun and unravel some of

1:28

its biggest mysteries. You'll

1:30

meet people obsessed with auroras and

1:32

eclipses, voyaging across the world,

1:34

braving icy blizzards and baking hot

1:36

deserts to catch fleeting glimpses of

1:39

our sun's power right here on

1:41

Earth. We'll take you

1:43

into the path of totality for the

1:45

otherworldly experience that is a total solar

1:47

eclipse. Wow, this is a gorgeous sight

1:50

to be home. And

1:52

inside the NASA control rooms

1:54

where heliophysicists, or sun scientists,

1:56

forecast space weather risks to

1:59

our astronauts. These

2:01

stories will change the way you think about

2:03

our nearest star, I promise. And

2:08

so to do all that, we're bringing the whole

2:10

team together. You'll hear from

2:12

me... Me... And me. That's

2:14

Christian Elliott, Taurus Universe producer. Hi

2:16

Patty, hi Jacob. In this episode,

2:19

Christian, you said you're bringing us the most important

2:21

story of all, our

2:23

Sun's superhero origin story. The

2:26

story of how a star is born, how

2:28

it shapes and molds the solar system and

2:30

planets, and how it makes life on Earth

2:32

possible. Christian, that is a lot

2:34

to cover. So where do we start?

2:37

Well how about the very basics? Sun

2:39

101. I mean, what exactly is the

2:42

Sun? Ooh, that's a... That's...

2:45

That's... What isn't the Sun, right?

2:48

For that hard-hitting question, I went right

2:50

to the top. Yeah, so my name

2:52

is Joe Westlake. I'm the division director

2:54

for heliophysics at NASA headquarters. So

2:57

you asked NASA's director of heliophysics what

3:00

the Sun is? Yes,

3:02

I did, Jacob. That's the great thing about

3:04

working at NASA. You get to ask very

3:06

smart people questions like that one. But

3:09

anyway, Joe is a great person to

3:12

explain the Sun to us. He's new

3:14

to the job at NASA, but he's

3:16

worked on nearly every aspect of space

3:18

science that you could think of. He

3:20

was on a team that helped discover

3:22

the Higgs boson, a new elementary particle

3:24

in physics at a laboratory in Europe.

3:26

He's studied Saturn's moons, tightens up our

3:28

atmosphere. It's a really fascinating place. Earth's

3:30

magnetosphere. The magnetosphere, our home here on

3:33

the Earth. So

3:35

anyway, back to the big question. At

3:37

the most basic level, the Sun is a

3:39

giant ball of gas and plasma that

3:42

is sort of the fundamental life

3:44

force or the fundamental source of

3:46

energy in our solar system.

3:49

It's a great energy source because of

3:51

all that gas, mostly hydrogen, that's scrunched

3:54

together under the huge gravity of the

3:56

Sun. The hydrogen is

3:58

undergoing this like This fusion

4:01

to go into helium, so you're

4:03

fusing atoms together, creating

4:05

energy and doing that, that energy comes

4:07

out as light and the light that

4:09

we see, you know, when the sun

4:11

comes up. That's all true

4:13

for our sun, but it's actually true for

4:16

most stars most of the time. The important

4:18

point here is that the sun is a

4:20

star, just like any other. It

4:23

just happens to be our closest star. Right,

4:26

yes. When you look up at the

4:28

night sky, you're looking at a sky

4:30

full of faraway suns, of a vast

4:32

range of sizes and ages. Our sun

4:35

is a fairly average, you

4:37

know, main sequence star. You

4:40

can find a similar one in many places within

4:42

our galaxy. So what I'm hearing

4:44

here is that we aren't special? Well,

4:47

yes and no. It

4:49

might be an average star, but the sun

4:51

is just right for us. If

4:53

it was a much larger star, if it

4:56

was a much smaller star, if it had much

4:58

more mass, much less mass, we

5:00

might not have the same situation at

5:03

the Earth. It may not be as

5:05

habitable, might not be as unique

5:07

of an experience here for humanity, because our

5:09

sun may be more violent, maybe less violent,

5:12

things like that. Our sun is

5:14

definitely just right for us. But

5:16

since it is a star, just like all the others, just

5:18

light years closer to us, we

5:21

study it here at NASA to both better understand how

5:23

it affects us and

5:25

to better understand how stars elsewhere in the universe

5:27

work. Right, Patty, you're

5:29

an astrophysicist, and you're focused outward from

5:32

our solar system usually toward other stars

5:34

and exoplanets. But

5:36

it turns out we kind of have astrophysics here at

5:38

home too in our own backyard. We

5:40

just call it heliophysics. Huh. So

5:43

just to recap, we have this star, and

5:45

it's the same kind of star that we can see

5:47

all across the night sky that have planets

5:50

of their own, but it's right here in

5:52

the middle of the solar system, keeping Earth

5:54

nice and toasty and hospitable. I

5:56

guess my next question is, how did it all

5:58

start? How did we... get here? Well

6:01

that is a very good question and

6:03

to answer it we're gonna go way back.

6:09

Now imagine where our solar system, our

6:11

Sun, our Earth is now, it's just

6:14

completely empty, just the black void

6:17

of space. Well it's not

6:19

completely empty, there's some dust

6:21

and gases floating around. Well

6:24

what happens is is that you get sort of

6:26

collections of gas. These collections of

6:28

gas basically are gravitationally

6:30

bound to each other. So the

6:32

gravity pull of large masses of

6:35

gas is pulling

6:37

these particles together and

6:40

eventually you end up with enough to

6:42

where they're pulling in so much more

6:44

gas, so much more gas and

6:47

the things that are getting packed into

6:49

the inside are getting so close together

6:51

that they really can't

6:53

keep themselves apart and

6:55

then you start to do, undergo fusion and that

6:58

star is ignited. So

7:05

a star ignites in space, that's the beginning of

7:07

our solar system, but what about all

7:09

the other stuff that's around the Sun today? Like

7:11

when does Earth come into the picture? Well

7:14

in general once you have all the

7:16

mass of this star in one place, all the

7:18

leftover gas and bits and bobs start to orbit

7:20

around it and they pick

7:22

up speed and momentum. Yeah that's

7:24

exactly what Joe said, you get this

7:26

kind of disk of gas and dust

7:29

orbiting the Sun. As

7:31

this gas goes around and starts orbiting

7:33

the Sun, you end up

7:35

getting like clumps, right? Some of the

7:37

perturbations as they come together turn into

7:39

these larger perturbations,

7:42

you know larger fluctuations, larger

7:44

changes in that local

7:46

gravity, things start

7:48

to collect together and

7:50

stick. So

7:52

we're living on a, what was that word

7:55

he used? A perturbation? Like a clump of

7:57

matter? The third farthest

7:59

collection of matter. matter from the sun in

8:02

our solar system. Basically, yeah, those clumps

8:04

of gas and matter orbiting the sun

8:06

turn into Earth and into

8:08

all the planets. And there's a

8:10

lot that happens over billions of years to make

8:12

our Earth what it is today, of course. But

8:15

the biggest factor all along the way, the

8:17

reason why we're here at all, is

8:20

the sun. Obviously, you need

8:22

gravity. Otherwise, we would float off into

8:24

our own area and probably

8:26

not be near a star, be very cold. The

8:29

gravity of the sun that has kept the

8:31

Earth in close has created an

8:33

environment that's useful for us. And

8:37

again, the sun is putting off just the

8:40

right amount of energy, photons that bring light

8:42

and heat to Earth to keep our planet's

8:44

surface under the right conditions for life to

8:47

begin. And where a planet

8:49

is with respect to its star really matters.

8:51

The Earth is in like this perfect position

8:53

with respect to the sun, something we call

8:55

the habitable zone or Goldilocks zone. And

9:00

what that means is that once life got

9:02

a foothold here on Earth, it could spread

9:04

and thrive and evolve. So

9:07

at this point in the story, we've got Earth, we've

9:09

got life, which is starting up because of the

9:12

sun's warmth and light. And

9:14

then humans show up and we start to

9:16

build civilizations, right? Right.

9:19

And we've been looking up at the sun and

9:21

wondering about it and thinking about it ever

9:23

since. It's pretty wild

9:25

if you think about it, just how impactful the

9:28

sun has been. It's

9:30

made agriculture possible for one, which

9:32

let us settle in cities and develop

9:35

civilizations all around the world. And

9:37

at the same time, we have the sun

9:39

to thank for calendars, our sense of time

9:42

and seasons, basically all the

9:44

rhythms of our life here on Earth. And

9:47

wherever you look, the sun shows up over and over

9:49

again in literature, music,

9:51

religion. By

9:53

looking at the sun through telescopes and observing

9:56

its influence on us through the aurora, eclipses

9:58

and more, we We as humans

10:00

learned more and more about how it works

10:02

over the centuries. And

10:06

our understanding of the sun really advanced

10:08

when NASA came into the picture. All

10:11

at once Americans were interested in the oncoming

10:14

age of space. And with

10:16

the curiosity came a mounting swelling demand

10:19

to get a satellite into the air on

10:21

the double. So to set the

10:23

scene, it's the 1950s, it's the space

10:25

age, we've got rockets and satellites and

10:27

we can go into space and

10:30

scientists are eager to study all the bodies

10:32

in our solar system and beyond. cosmic

10:35

ray intensity, meteor impact, solar radiation,

10:37

these are the dry facts that

10:39

will help carry man ever farther

10:42

into the age of space. We've

10:45

had a long history of observing the sun. It

10:48

dates back, you know, before the United States

10:50

was formed, right? We've observed the sun. But

10:52

observing the sun from the space has

10:55

happened really since the beginning of the space

10:57

age. And there's been

10:59

a lot of discoveries that have happened since

11:01

the beginning of our space fairing, you know,

11:04

race. Studying

11:06

the sun has sort of defined NASA's history.

11:10

Understanding our star was a goal for

11:12

space science even before NASA formed. So

11:14

there have been a lot of missions.

11:17

Right, studying the sun has been a huge

11:19

focus for NASA for decades. There's

11:22

a whole fleet of heliophysics spacecraft

11:24

and they're spread out in strategic

11:26

places between the sun and earth

11:28

and even into the interstellar medium

11:30

beyond our solar system. So

11:33

from all of these missions, we've learned that

11:35

the sun and its relationship with the earth

11:37

is more complicated than we thought. Hmm,

11:40

complicated how? Well first we

11:42

really have to understand the sun. It's

11:45

got layers, literally. So let's start by

11:47

zooming all the way in. At

11:49

the very center of our sun is its

11:52

core, where those nuclear reactions happen. That

11:54

fusion that releases the sun's energy. Then

11:57

we've got the radiative zone and the convection

11:59

zone. Two layers where the plasma

12:01

and magnetic fields are swirling around and

12:03

up toward the photosphere, where the sun's

12:06

light comes from. If you

12:08

were to stand on the surface of

12:10

the Earth and with your protective eclipse

12:12

glasses on, look up at the sun,

12:15

you see the photosphere. You see where the photons

12:17

are coming from. That's

12:19

relatively cold. Cold, yes,

12:21

but still pretty hot compared to Earth, coming

12:23

in at over 6,000 degrees

12:26

Fahrenheit. Right, but

12:28

that photosphere is actually not the sun's

12:30

outermost layer or its hottest. That

12:33

honor goes to the corona, the sun's

12:35

crown, its outer atmosphere. And

12:38

the corona is a really wild and

12:40

mysterious place. It's way, way

12:42

hotter than the photosphere. What happens is

12:44

that as you come from this photosphere

12:46

out into the corona, you

12:48

get this intense warming,

12:51

intense heating of the particles and

12:53

plasma. Yeah,

12:56

that seems like a puzzle. I mean, if the

12:58

core is the hottest part, as you move further

13:00

away from that, you would expect it to get

13:02

cooler, right? I'm picturing when you make a campfire

13:05

and you sit too close to it and you

13:07

get hot, and so what do you do? You

13:09

walk away from the campfire, right? Yeah,

13:12

it doesn't make sense to heliophysicists either,

13:14

but it's true. How it

13:16

gets so, so hot is one of the

13:18

sun's biggest mysteries. And

13:20

a big reason why it's mysterious is that you

13:23

can't see the corona with your naked eye. From

13:25

Earth, we can only see and study it during

13:28

eclipses when the moon blocks off our view of

13:30

most of the sun or through

13:32

the eyes of spacecraft or telescopes. Yeah,

13:35

but we can see some of the

13:37

stuff the corona does because this outer

13:39

atmosphere of the sun is so hot

13:41

and has so much activity, it has

13:43

these huge explosions, these outbursts that we

13:46

can detect. It's really

13:48

like the atmosphere of the sun is blowing

13:50

off into space, and that

13:52

atmosphere is so hot, so incredibly

13:54

hot, that it then ejects itself

13:56

off into space, sometimes violently, sometimes

13:58

with these coronal mackerels. ejections and

14:00

things like that. So coronal

14:02

mass ejections, what are those? Good

14:05

question. There's actually a couple kinds of

14:07

explosions or eruptions that come off of

14:10

the Sun. Now a coronal mass ejection

14:12

is something where you're seeing basically a

14:14

big parcel of gas, a big parcel

14:16

of hot gas being blown off of

14:18

the surface of the Sun. So

14:21

there's this explosion on the Sun that

14:23

actually sends material from the Sun flying

14:25

off into space, like an

14:27

ejection of coronal mass I

14:29

guess. Yes it's well

14:31

named but it actually gets even

14:33

wilder than that. The second kind

14:35

of eruption is called a solar

14:38

flare. A flare is a

14:40

very explosive event that basically sends

14:42

off all this energy very very fast

14:44

in the form of high-energy light to

14:46

the Earth. And coronal mass

14:49

ejections and solar flares can even happen

14:51

at the same time. And

14:53

sometimes you get it where there's a

14:55

coronal mass ejection that has flares within

14:58

it, okay? But that coronal mass ejection

15:00

travels much slower to the Earth a

15:02

few days. So you've got

15:04

flares, these quick flashes of energy radiation

15:07

that hit the Earth, and then these

15:09

coronal mass ejections which are big chunks

15:11

of plasma that come our way a

15:13

lot more slowly because they have mass?

15:16

Yeah exactly. Now remember you

15:18

can really just see the photosphere from

15:20

here on Earth unless there's an eclipse.

15:23

All this wild chaotic activity in

15:25

the Sun's atmosphere is basically invisible.

15:28

But NASA has satellites like the

15:30

Solar Dynamics Observatory floating

15:32

out in space looking at the Sun

15:34

that can zoom in close on that violent

15:36

activity. So you can see it for yourself

15:38

in imagery. That satellite is

15:40

part of a program NASA calls

15:42

Living with a Star because it's

15:44

about learning to live next to

15:47

such an explosive neighbor. Yeah I think

15:49

I have an explosive neighbor at my

15:51

house too so I get that. Yeah

15:53

I think we all do. It's very true. Anyway

15:56

in the imagery you can see sunspots,

15:58

these dark cooler airy areas of the

16:00

surface where magnetic fields are just going

16:03

crazy. And of course, coronal

16:05

mass ejections and flares. It

16:07

almost looks like, to me, volcanic

16:09

eruptions, right? But Joe said, unlike

16:12

a volcano, there's more order to

16:14

it, because it's all controlled by

16:16

the sun's electricity and magnetism. So

16:18

you see particles. You see what

16:20

looks like plasma, this really bright

16:23

stuff being blown off of the surface.

16:26

But then it follows these paths,

16:28

beautiful paths, across the surface where

16:30

you see, you know, sinews, like these

16:32

really, like, beautiful little traces of particles

16:34

going across and lighting up. Joe told

16:36

me it's kind of like watching a

16:39

pot of boiling water. You

16:41

get this hot water that's constantly

16:43

rising up to the surface and

16:45

going back down and churning around

16:47

in the pot's convection zone, sometimes

16:49

bursting out, just like the

16:51

plasma and magnetic fields do in the

16:53

sun's convection zone. Now,

16:59

there's another NASA mission I have to

17:01

mention. It's called Parker Solar Probe. We

17:04

mentioned it at the top of this episode, and

17:06

we'll talk about it a lot more a little

17:08

later in this miniseries, because it's just so cool.

17:11

It's NASA's mission to touch the sun's

17:13

corona. And as it gets

17:15

closer and closer to the sun with

17:18

every orbit, it's starting to actually fly

17:20

through these explosions. Like,

17:22

there's this one time where this huge

17:24

coronal mass ejection hit the spacecraft, and

17:26

it was so powerful. It rattled it.

17:28

Like, you can actually see things move

17:30

on it as it gets hit. It

17:32

almost looked like a bubble, you know,

17:34

coming onto it, and then nothing. And

17:37

so, you know, you saw this

17:39

big burst of gas go across

17:41

the spacecraft, and then the stars came

17:43

out, because all of a sudden,

17:45

the gas that was there, the atmosphere that

17:47

was there, has been blown off, and there's

17:49

this huge vacuum behind it, which is just

17:51

incredible. So

17:54

all of that to say, as you

17:56

get closer and closer to the sun, it

17:58

goes from being this. beautiful,

18:01

timid, yellow ball of gas to

18:04

being this very

18:06

exciting, very powerful, very

18:09

chaotic surface where

18:11

something's always going on, something's

18:13

always happening. And that activity

18:15

is not always the same, right? We've

18:18

mentioned early on that the sun is near solar

18:20

maximum right now in 2024. So

18:23

it's at its peak activity and we're

18:26

seeing more sunspots, coronal mass ejections, and

18:28

flares than usual. So I'm

18:30

thinking if parts of the sun's atmosphere

18:32

are exploding away and they're just getting

18:35

blown off into space through coronal mass

18:37

ejections, where do those go? As

18:40

those go out into space, you know,

18:42

it's expanding into this sort of void between

18:44

the sun and the earth. And

18:47

as it expands, there's not a lot of

18:49

particles in between there, but there's this constant

18:51

sort of solar wind that's moving from the

18:53

sun to the earth. So

18:55

we essentially live in that solar wind here on

18:57

earth, right? Like in the atmosphere of our star.

19:00

I'm just thinking being in the crosshairs

19:03

of a steady stream of particles from

19:05

the sun sounds not optimal. Yeah,

19:08

it can definitely be bad. There's

19:10

going to be a lot more of that to

19:12

come later in this series. But what you need

19:14

to know right now is that here at NASA,

19:16

we try to forecast and keep an eye on

19:18

the sun's activity because it can be hazardous. Right.

19:22

In really extreme cases, space weather can even

19:24

affect us right here on Earth's surface. In

19:27

1859, the most intense solar storm

19:29

in history hit Earth. It

19:32

was called the Carrington event. The

19:34

sun released solar flares so bright that

19:36

astronomers observed them from here on the

19:38

ground for the first time ever. When

19:40

all that energy reached Earth, it set telegraph

19:42

lines on fire. And I'm

19:44

thinking something like that would have to be way

19:46

worse today, right? I mean, in

19:49

1859, it's telegraph lines, but today

19:51

we have way more electrical infrastructure

19:54

and it would be in danger from that kind of event, right?

19:56

Yeah, I mean, there's the potential for things to be

19:59

pretty bad. But don't worry,

20:01

luckily we have this built-in shield that

20:03

protects us from all but the

20:05

worst storms here on Earth. So

20:07

as you move, as you get closer and

20:10

closer to the Earth, you come upon this

20:12

obstacle, which is the Earth's magnetic field. It's

20:14

created by the rotation of the metallic core

20:16

of the Earth that sets

20:18

up this magnetosphere that's

20:20

our protective shield. You

20:23

come up to that and all of a sudden you're blocked. You

20:26

as the solar wind are pushed off to the

20:28

side or you're pushed off to the northern and

20:31

southern regions of the Earth and brought

20:33

down into the poles where

20:35

the field lines reconnect and

20:37

then funnel particles down onto the Earth

20:40

in that sort of those polar regions, which creates

20:42

the aurora. You

20:44

can actually see visual evidence of our

20:46

magnetosphere's protection at work if you're far

20:49

enough north or south and catch a

20:51

glimpse of the aurora, the northern

20:53

and southern lights. As

20:55

they come down, they hit the atmosphere

20:57

on Earth and when they hit the

20:59

atmosphere, the colors that you

21:01

see in the aurora are the different

21:03

composition of both the particles but also

21:05

of the atmosphere lighting up as

21:08

these particles hit. Right

21:10

now in 2024, the northern lights are

21:12

going crazy up at the poles because

21:14

the more radiation coming from the sun,

21:16

the more particles our magnetic shield has

21:18

to funnel down into the poles. When

21:21

the sun's activity is really high, you can

21:23

actually even see the aurora further south. The

21:26

aurora, the northern lights, are just these

21:28

beautiful displays in the sky but beautiful

21:30

displays of both the power of the

21:32

sun but also of our

21:35

Earth's protective magnetosphere. The

21:37

protection is at work, right? It's keeping

21:39

those solar particles away from the

21:42

surface of the Earth. So

21:44

to recap, the sun makes life possible here

21:46

on Earth through the light and heat it

21:48

provides us but it also

21:50

releases powerful storms and radiation that

21:52

can disrupt our technology. And

21:55

so we have a quirk of planetary geology, our

21:57

Earth's metal core, to thank for the

22:00

shield that protects us. That's

22:02

pretty cool. I still have one more

22:04

question though. I mean if the Sun is sending

22:06

out the solar wind in every direction all

22:09

the time, I mean only a tiny

22:11

fraction of that is gonna hit Earth,

22:13

right? So what happens to the

22:15

rest of it? Well as the

22:17

solar wind expands out past Earth and

22:19

through our solar system, it creates this

22:21

big protective bubble around us. We

22:24

call that bubble the heliosphere. It

22:26

keeps out most of the galactic cosmic rays

22:28

from elsewhere in the universe that otherwise would

22:31

hit on Earth and damage our DNA. That

22:34

bubble that the Sun creates, this protective

22:36

bubble, is really one of the

22:38

things that is allowed. Humanity

22:41

has allowed the habitability of

22:43

the Earth to exist because

22:45

it's protected us from the

22:48

harsh interstellar environment. So I'm picturing those Russian

22:50

nesting dolls, you know? We have a bubble

22:52

here on Earth that protects us from the

22:54

Sun and then we're within this

22:57

even larger bubble that the Sun creates and

22:59

that protects us from stuff coming from outside the

23:01

solar system, right? Exactly. And

23:04

if you're like me, you might be wondering

23:06

how on Earth we know that. Yeah,

23:08

it's a good question. We've

23:11

studied the heliosphere in a lot of ways,

23:13

but one of the things we've done is

23:15

actually send spacecraft out there, like

23:17

the famous Voyager missions that launched back in 1977.

23:21

Voyager 1 and 2 were the first

23:23

NASA spacecraft to leave our solar system

23:25

and the first to directly explore the

23:27

heliosphere. The Voyager missions, they

23:29

have that golden record on them, right? The

23:31

mixtape of information about Earth and humanity, that

23:34

potential life and other parts of

23:36

our own galaxy could maybe someday find.

23:40

Yeah, it's pretty wild to think about. Near

23:43

the beginning of the space age, we're

23:45

sending this message in a bottle out

23:48

into the universe, expanding our horizons, way

23:50

before all our modern Sun-studying spacecraft, and

23:59

decades later it leaves the universe. the solar system and

24:01

it detects the boundary of the heliosphere,

24:03

this bubble that has allowed humanity to

24:05

flourish on Earth in the first place

24:08

and that's given us this habitable planet that

24:10

we can use to build spacecraft like the

24:12

Voyager probes. So

24:14

the Voyagers moved out and they punched

24:16

out through the heliosphere in two locations,

24:20

roughly a hundred times the distance between the

24:22

Sun and the Earth. So

24:24

at about a hundred astronomical units is

24:26

roughly where they punched out. The

24:29

most distant human-made object, NASA's

24:31

Voyager 1 spacecraft, is

24:33

an interstellar space, the space

24:36

between the stars. Even

24:38

though they're out in interstellar space

24:40

now, the space between the stars,

24:42

this wild west without the heliosphere's

24:44

protection, they're still sending us back

24:46

valuable data. It was

24:49

the first mission for us to

24:51

really understand the interstellar medium. It

24:53

still had the instruments available, it

24:55

still had the observations available to

24:57

punch out of our heliosphere and

24:59

start to understand what that local

25:02

interstellar medium is, what the gases

25:04

between the stars are. I'm

25:08

still not over that distance, a hundred times

25:11

the distance between the Sun and the Earth.

25:13

I mean that's pretty far itself. If you

25:15

think about how we have Mercury and Venus

25:17

between us and the Sun, what

25:20

does the heliosphere look like? I mean if

25:22

it's a heliosphere, is it just

25:24

a big sphere all the way

25:26

around the solar system? We

25:29

still really don't know. There have been

25:31

other missions that have tried to detect

25:33

its shape through remote sensing and there's

25:35

another interstellar mapping probe planned, but

25:38

right now we just have theories. And

25:41

it's interesting to think about, just like

25:43

the structure, what does our heliosphere really

25:45

look like? Okay, so there are basically

25:47

two theories. There's the banana slash croissant

25:49

theory that has to do with how

25:51

the solar wind comes off the Sun's

25:53

poles, which we still don't know about

25:55

since we haven't really seen the Sun's

25:57

poles. You know, these sort of theories.

26:00

say like maybe there's two jets that go off

26:02

the two poles and they wrap around sort of

26:04

making this banana or croissant

26:06

shape kind of thing. Now

26:08

I like the banana slash croissant theory

26:10

but there's theories that say well

26:13

maybe it's just sort of a bubble and it

26:15

and it you know sort of terminates somewhere a

26:17

little farther back and things like that. We

26:20

really don't understand that at all.

26:22

We haven't sent a spacecraft down the tail of

26:24

our heliosphere. There are also

26:27

other forces beyond our solar system

26:29

acting on the heliosphere, kind of

26:31

affecting its shape. It's not

26:33

all determined by the Sun's activity. Because if

26:35

you think about you

26:37

know how the Sun has evolved and how things

26:39

have evolved over time, you know we're not we're

26:42

not the only star in the neighborhood and

26:45

there's lots of stars and gas in the neighborhood

26:47

that affects how big that

26:49

heliosphere is. The bigger the

26:51

heliosphere, so the more powerful the Sun

26:53

is, the less radiation you

26:55

get that comes in from outside. The smaller

26:58

it is, the more radiation you get to

27:00

come in from outside. All of

27:02

that other stuff, these clouds of

27:04

interstellar gas, change our heliosphere over

27:06

time at the same time as

27:08

our Sun changes its activity on

27:10

its 11-year cycle. We've

27:13

seen the heliosphere breathe. It

27:15

expands, right? The solar wind is dynamic.

27:18

It changes how that that interaction is.

27:21

It's a huge object, just a huge object.

27:26

So you need a star that's

27:28

powerful enough to create a protective heliosphere,

27:30

but not so strong that it

27:32

cooks you on your planet with

27:34

radiation? Exactly. Our

27:36

relationship to our nearest star is a

27:38

lot more complex than you might think.

27:41

It's really a both our nearest

27:43

protective neighbor, but also can

27:45

be I guess a little bit of an ornery neighbor at times,

27:49

and has these sort of these

27:51

real explosive events that can affect

27:53

our critical infrastructure and things like

27:55

that. You know, you need the

27:57

solar wind to create this protective bubble around the Earth.

28:00

But you also need the Earth's

28:02

magnetosphere to protect us from

28:04

that solar wind that's also protecting us.

28:08

It's sort of circular in that way. It's

28:10

like this beautiful balance. It's

28:12

a lot to think about because so much of our life depends

28:14

on the sun being the stable partner

28:17

that we have come to know throughout,

28:19

you know, not just our lives, but

28:21

humanity's time on Earth. But

28:23

there's a lot of ways that that's not always the case,

28:25

right? It sounds like it's important to keep understanding how it

28:27

all works. Yeah, it really

28:30

is. And it's all just a little mind

28:32

blowing to me. But this is all just

28:34

the start. We're going to get into so

28:36

much more in the coming episodes. Okay,

28:39

so what do we have to look forward to? Can we

28:41

get a little hint for now? Yes,

28:43

I will give you a hint. A mysterious

28:45

pink line in the sky called Steve. Petroglyph

28:48

carved into a desert cliff a thousand years

28:51

ago that might help us understand our upcoming

28:53

total solar eclipse in a new way. And

28:56

the story of a spacecraft lost, spinning

28:58

in space for months, but once it

29:00

recovered, had an ability to discover new

29:02

things close to the sun that nobody

29:05

expected. The sun is

29:07

just such a mysterious place full of new

29:09

things to discover. But you don't

29:11

have to take my word for it. Heliophysics

29:13

is sort of at this really

29:15

bright time and it's in

29:17

its path, right? Where we're building

29:20

upon the knowledge that we

29:22

have that we've gained about the sun. And

29:24

we're really turning it into a

29:27

well refined scientific topic about

29:30

really something that's so fundamental in our lives,

29:32

the sun, right? Every day you wake up,

29:34

see the sun, hopefully, depending on where you

29:36

live. And it's an amazing thing

29:38

that we take for granted. And

29:40

it's so incredibly ingrained in what we do.

29:44

And it's a place where great discoveries are still

29:46

to be made. We'll

29:48

have all that and more right here on

29:51

Curious Universe. And

29:53

before we go, we have a special new segment

29:55

for you. still

30:00

curious about. We

30:03

ask that question to every single person

30:06

we interview for this show and we

30:08

want to know what you're curious about

30:10

too. In this segment

30:12

we'll take a question from a curious listener

30:14

and track down the answer. Today's

30:20

question comes from Dallas Taylor. He's

30:23

a sound design and audio expert and he's

30:25

the host of the podcast 20,000 Hertz

30:28

which explores the stories behind

30:30

the world's most interesting and

30:32

recognizable sounds. Dallas it's great

30:34

to have you with us. The feeling

30:36

is mutual because I am so excited to

30:39

talk to you. You've produced

30:41

quite a few episodes about space right? Yeah

30:43

so usually I do shows

30:46

all about very recognizable sounds

30:48

like the Netflix to Doom sound or

30:50

the Wilhelm scream

30:53

but we sometimes dabble in brain science and

30:55

all sorts of things but what I spend

30:57

a lot of my own free time on

31:00

is just thinking about space and the unknown and

31:02

all of that. Let's hear a

31:04

clip from one of those episodes, Space Remix,

31:07

which is all about what other planets

31:09

might sound like. Let's

31:16

go from planet to planet in our solar system

31:18

to find out what each surface would sound like

31:20

to our ears. Let's start closest to

31:22

the Sun. Places like Mercury

31:24

and these rocky bodies with no atmospheres

31:26

or would be similar to being in

31:29

space. There would not be much sound

31:31

if any. Well Mercury

31:33

is an airless body so you

31:35

know we're back to listening for

31:37

Mercury quakes. That

31:40

would be really the only source of

31:42

sound. And

31:46

you could only hear these Mercury quakes if your

31:49

head was pressed up against the rock because there's

31:51

no atmosphere for traditional sound to travel through. Next

32:02

up, Venus. In

32:05

my mind, what sound would be like

32:07

on the surface, because you have this

32:09

really dense atmosphere, much denser than Earth,

32:12

the sound would be more like or

32:14

tend toward what things sound like when

32:16

you're underwater. If you

32:18

could imagine something in between air and water, that

32:21

kind of density, you're running your hand through that

32:23

and you would feel that. One

32:30

thing we do know about Venus is that it

32:33

has lightning, so you might hear thunder. I

32:39

wonder what other things, like my voice might sound

32:41

like. I'm

32:44

on Venus in this ethereal world that's

32:46

a mix between a gas-like atmosphere and

32:48

water. I'm

32:51

almost floating, but yet it's not as

32:53

restrictive as being submerged in water. My

32:57

voice, the thunder, it's

33:00

all slightly muffled and distorted as

33:02

it travels through the thick atmosphere. I

33:07

recognize some of those voices, and it's cool that

33:09

you feature NASA scientists in your show. So,

33:12

what are you still curious about when it comes

33:14

to space? So we

33:16

went through every planet in the solar system, but

33:19

we never talked about the sun.

33:23

I have no idea what it

33:25

would be like on the sun. It's more

33:27

of a thought experiment, but I'd love to know if

33:30

you don't immediately burn up and

33:33

if you're in some aspect

33:35

of what you would call a surface, just

33:38

let your mind go. What

33:40

would it sound like on the so-called

33:42

surface of the sun? that

34:00

we actually can listen to the Sun, but

34:02

it's a little complicated. Our

34:04

star is a really active place.

34:06

It emits this constant stream of

34:08

particles called the solar wind, and

34:11

in that solar wind, in space, plasma

34:14

waves can travel full of electric and

34:16

magnetic fields. You can't hear those

34:18

waves in the same way you can hear sound

34:20

waves in the air on Earth because

34:22

space just isn't dense enough. We

34:25

can detect them with satellite instruments, especially

34:28

when they collide with Earth's magnetic field lines

34:30

and vibrate them like giant space guitar

34:32

strings. Then we can play those

34:34

waves aloud here on Earth in a range our

34:37

ears can hear. But if we were actually

34:39

standing on the surface, would it just be like a loud

34:41

roar? Would it just be like... That's

34:44

a great question, and we have a

34:46

whole division here at NASA called heliophysics

34:48

that is focused on learning more about

34:51

the Sun from space. And

34:53

one of the most exciting missions that's active

34:55

now is called the Parker Solar Probe. One

34:58

of the things that Parker Solar Probe is going to

35:00

do is touch the Sun. And so

35:02

it's a man-made spacecraft that will get the

35:04

closest to the Sun that we've ever come.

35:07

So we'll be able to answer these questions with like real

35:10

scientific data. Oh, I love it.

35:12

Well, if you ever want to make any sound

35:14

shows that are very romantic about space, you know

35:17

who to turn to. It was great to

35:19

talk to you, Dallas. Great to talk to you

35:21

too. Thanks again

35:23

to Dallas from 20,000 Hertz for

35:25

his question. Expect more answers

35:27

to curious questions in the coming episodes.

35:32

This is NASA's Curious Universe. This

35:34

episode was written and produced by

35:36

Christian Elliott. Our executive producer is

35:38

Katie Conance. The Curious Universe team

35:40

includes me, Jacob Penner, Matti Olson,

35:42

Michaela Sosby, and of course, Patty

35:44

Boyd. Christopher Kim is our show

35:47

artist. Our theme song

35:49

was composed by Matt Russo and Andrew

35:51

Santaguida of System Sounds. Special

35:53

thanks to NASA's Heliophysics team. If you

35:56

enjoyed this episode of NASA's Curious Universe, please let

35:58

us know by leaving us a review and

36:00

sharing the show with a friend. And remember,

36:02

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36:14

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