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00:00There's a violent star at the center of our solar system.
00:07The immense power, the roiling, boiling surface, the massive plumes, it's ridiculous.
00:15And our planet is at its mercy.
00:18There are explosions and big, giant eruptions of plasma that head straight to Earth.
00:25We have to understand these better to protect ourselves.
00:30The sun is a churning cauldron of nuclear reactions, revealing its inner workings was once mission impossible, but not anymore.
00:42We've recruited this network of spies, if you will.
00:45We've built a fleet of spacecraft that monitor the sun 24 hours a day.
00:50With the sun under close surveillance, we just might have what it takes to defend our planet.
00:57A flash of ultraviolet and X-ray light erupts from the sun, sending a burst of radiation toward Earth.
01:27We call it a solar flare.
01:31Flares are huge explosions on the surface of the sun, throwing light out into the solar system and absolutely baking anything in its path.
01:40These are really powerful events erupting from the sun, and we are fundamentally in the line of fire.
01:45The flare is so intense, it causes radio blackouts across the side of the Earth facing the sun.
01:55And the timing could not have been worse.
01:58The problem was, at this time, there were hurricanes in the Atlantic bearing down on the Caribbean, and there were people trying to get in there and rescue folks.
02:12Radio communication between disaster relief teams goes down for most of the day.
02:17Space weather and Earth weather combine to create chaos.
02:24It's not just an academic exercise.
02:29Your very lifestyle depends on understanding how the sun behaves.
02:34We need to be able to predict what the sun is going to do next, and in order to do that, we need to have eyes on the sun, as many eyes as we can get.
02:43Three, two, one.
02:44That's why NASA has put together an elite unit.
02:46We have ignition, and we have liftoff.
02:47Liftoff, and liftoff on an international mission of solar physics.
03:00A fleet of daring spacecraft.
03:03We humans have come a long way.
03:05If you go back a few thousand years, people were worshipping the sun.
03:09And today, we've built a fleet of spacecraft that monitor the sun 24 hours a day, observing it from every angle, predicting what it's going to do next.
03:21That's nuts.
03:24Leading the pack is the Solar Dynamics Observatory, or SDO.
03:30It keeps a telescopic eye on flares blasting out from the sun's surface.
03:3424 hours a day, the SDO probe is on the lookout.
03:40It's constantly vigilant.
03:42It looks at the sun at a lot of different wavelengths in exquisite detail, so that we can see exactly what sort of high-energy events are happening on the sun.
03:52The record for the longest service goes to SOHO, our Sentinel monitoring the sun and its faint outer atmosphere.
04:01The Solar and Heliospheric Observatory, or SOHO, is the old hand at studying the sun.
04:07It's been up there for 25 years, observing not just the sun itself, but the environment around it.
04:14Instead of looking directly at it, it actually blocks out most of the light so that we can see all these beautiful structures that surround the sun.
04:21And then there's the new recruit, the Parker Solar Probe, our scout going deep behind enemy lines.
04:34The Parker Solar Probe is going to give us the closest look at the sun that we have ever had in the history of humanity.
04:42We're flying so close to the sun, we're flying through the gases of its atmosphere.
04:4929 other craft make up the fleet, each with their own role to play.
04:54This fleet of spacecraft that we have, the overall mission is to observe the sun scientifically, learn about its behavior, but also, importantly, to learn about the effects that it has on Earth.
05:11Our lookout probe, the Solar Dynamics Observatory, or SDO, spots something hellish.
05:16Today's forecast for the sun is predicted to be 10,000 degrees Fahrenheit, with winds of up to 600 miles per second.
05:27And a pretty decent chance of rain.
05:31You don't want to be in this rainstorm, because your umbrella isn't going to help you.
05:35Solar rain isn't water, it's plasma, hot plasma.
05:40Rather than a solid, liquid, or gas,
05:43the entire sun is made up of a strange fourth state of matter.
05:50Plasma.
05:58Plasma is just simply gas that's very hot.
06:01So hot it's lost some of its electrons and become electrically charged.
06:05And the wonderful thing about plasma is that once it has that electric charge, you can direct it with a magnetic field.
06:10And the sun has the most powerful magnetic field in the solar system.
06:16It twists and flows through the entire star.
06:20The sun's magnetic field is incredibly complicated.
06:26There are lots of loops of magnetic lines coming out of the sun's surface.
06:29As you go above the surface, the magnetic field begins to control where the gas can go.
06:38And you get these beautiful loops and other structures above the sun that are just showing you where the magnetic field is.
06:44The SDO spacecraft's jaw-dropping videos of rain on the sun show plasma flowing along huge, looping magnetic field lines that have punched through the sun's surface.
07:00Because the surface of the sun is a plasma and these loops of magnetic fields are coming out of it,
07:04it draws that plasma up, which then cools and rains down as a plasma rain.
07:13Tracking these loops of magnetic field and plasma could help explain solar flares.
07:18And it could give us some warning.
07:24September 2017.
07:28Minutes before the devastating mid-hurricane radio blackout,
07:33our solar lookout spotted an explosion on the surface of the sun.
07:37Suddenly you have this tremendous flow of energy and an explosive release of it.
07:44And we call this a solar flare.
07:46This is SDO's specialty of observation.
07:49The craft tracked the magnetic loops above the sun's surface.
07:55They were highly unstable.
07:59SDO takes very detailed pictures of where the flows are.
08:02You can actually see gas flowing from one place to another.
08:06You can see the magnetic loops.
08:10These magnetic flux loops are kind of like wires carrying electricity.
08:15When they're on their own, they're fine.
08:16But if they get too close, they can connect and short circuit.
08:19And then you get a tremendous release of energy.
08:24The Ghostbusters were really on to something.
08:26Don't cross the streams.
08:27The contact between magnetic loops released an epic explosion of high-energy light.
08:38This radiation altered our planet's atmosphere.
08:44Radio waves jammed, causing blackouts at the worst possible moment.
08:50Solar flares are happening on the sun 90 million miles away.
08:54Who cares, right?
08:55Well, think of it this way.
08:56A really good solar flare could be the equivalent of, oh, say, 10 million hydrogen bombs going off.
09:03How's that sound?
09:05Solar flares happen a lot.
09:07And they do affect us.
09:08They have affected us in the past, and they will again in the future.
09:12But the sun's twisting magnetic fields do more than just disrupt our communications.
09:17And when we see flares, we've got to keep an eye out on those.
09:22But sometimes there's something even bigger.
09:27The sun launches huge clouds of plasma across the solar system.
09:32All of that material can come to the Earth and really mess things up here.
09:37Blow out our power grid. Destroy our satellites.
09:40Even physically harm our astronauts in orbit.
09:44Can the solar fleet safeguard Earth?
09:58November 5th, 2018.
10:00An explosive cloud of plasma hits the Parker Solar Probe as it orbits just 15 million miles from the sun.
10:08We have this fleet of spacecraft out there viewing the sun, and they're also under attack by the sun.
10:17There are explosions coming from its surface.
10:22It's not just light, but explosions of hot plasma.
10:26And the Parker Solar Probe got blasted, and yet it survived.
10:30A huge blast of high-energy charged particles launches into the solar system at millions of miles an hour.
10:40A coronal mass ejection.
10:48But our solar scout is prepared for the onslaught.
10:52The Parker Solar Probe gets very close to the sun, and it has a heat shield to protect it.
10:56But if it gets hit by a coronal mass ejection, it has to be protected against that as well.
11:01And so it's been radiation-hardened to survive such an impact.
11:05Could these blasts pose a danger to our planet?
11:11A coronal mass ejection accelerates subatomic particles, and it's not a little bit of particles.
11:17It could be up to a billion tons of them screaming across the solar system at high speed.
11:22And this is something we need to take very seriously.
11:28To understand these dangerous blasts of plasma, we have to look at their source.
11:36An area around the sun known as the corona.
11:40The sun's corona is kind of like its atmosphere.
11:43You can think of the sun itself as being a ball of gas.
11:45And then outside of that is this ethereally thin gas stretching out for millions of miles.
11:52The corona is a difficult thing to study.
11:55Because the surface of the sun is so bright, it blocks our view.
12:00We can only see the corona during a total solar eclipse,
12:05when the moon blocks the sun's bright glare.
12:08Astronomers, though, we're impatient.
12:11We don't want to have to wait for a total solar eclipse, which only happens once or twice a year.
12:17So we figured out a way to make an artificial one.
12:20And it's really simple.
12:22One member of the solar fleet has it covered.
12:25Our solar sentinel, SOHO, creates its own eclipse by obscuring the blinding sun with a circular plate in front of the probe's camera.
12:38Sometimes the best solution is the simplest solution.
12:42You know, instead of trying to make a sensor that could actually see the full dynamic range of the sun's light,
12:49you know, why not just block out the light that we don't need?
12:51In July 2012, SOHO spotted a huge chunk of the corona blasting off into the solar system.
13:01Seconds earlier, another probe, monitoring the solar surface, spotted a bright flare.
13:10Were these events connected?
13:14If a flare goes off, it can disrupt those loops.
13:17And if you get the right kind of disruption, the whole thing can just blow open.
13:22And then you have a tremendous amount of billions of tons of hydrogen blown off into interplanetary space.
13:30And that's a coronal mass ejection.
13:35Coronal mass ejections are solar flares on steroids.
13:39If a solar flare was a firecracker, a coronal mass ejection is more like an atom bomb.
13:44And if a coronal mass ejection comes our way, it hits hard.
13:57The first thing it does is it compresses Earth's magnetic field.
14:00And then it wraps around the Earth, and this causes the magnetic field itself to rearrange, reconnect, and streams of particles travel down those magnetic fields toward our poles and impact the atmosphere.
14:15Our shields are up, but they are able to penetrate our shields, our shield being our own magnetic field.
14:20Once they breach our defenses, the particles of a coronal mass ejection can wreak havoc.
14:27In August of 1972, tensions were running high in Vietnam.
14:34Two dozen sea mines detonated at the same time when their magnetic sensors were tripped.
14:46A satellite was lost because of the electromagnetic pulse that ripped through it.
14:49And an Air Force sensor detected what looked like a nuclear explosion somewhere here on the planet.
14:57Fortunately, scientists quickly found the real culprit.
15:02A coronal mass ejection had ripped through the Earth's magnetic field and triggered magnetic sensors.
15:08The crisis soon de-escalated.
15:12The sun is an immense ball of plasma 860,000 miles across.
15:21We are not going to be able to stop it from doing whatever it wants to do.
15:25What we can do is learn to predict what's going to happen, so we're doing that now.
15:30Our new fleet of solar observers are our first line of defense.
15:43The sun is a little over 90 million miles from Earth.
15:46It takes light a little over eight minutes to get from there to here.
15:50As rapidly as a coronal mass ejection is traveling, it still takes a few days to get here.
15:55We can watch the sun to see, is there going to be an event?
16:01Or is an event starting?
16:03And these satellites can then tell us, hey, you better be careful.
16:06You might need to batten down the hatches on Earth.
16:11But there may be an earlier clue the fleet can watch out for.
16:15Vast, dark regions moving across the solar surface called sunspots.
16:21We know that this is the wind up before the release.
16:26This thing is getting ready to blow.
16:28In March of 1989, a solar eruption caused blackouts across Canada.
16:46And malfunctions onboard the space shuttle.
16:52We've been seeing some erratic pressure signatures out of Tank 3, as well as some manifold pressure spikes in that system.
16:59Eleven years later, the sun emitted a flare that was so powerful, it blinded the solar fleet's sensors.
17:07Eleven years after that, the Earth had a near miss with the most powerful coronal mass ejection ever recorded.
17:17The sun has a very predictable, but actually quite mysterious cycle of activity.
17:24It gets very, very active every 11 years, and then it settles back down to more of a peaceful existence.
17:29This 11-year cycle has astronomers scratching their heads.
17:36One thing we do know is that violent solar events seem to be preceded by dark patches on the solar surface.
17:45Sunspots.
17:46Sunspots are large areas on the surface of the sun, much bigger than the Earth, that are caused by incredibly strong magnetic fields disrupting the flow of plasma.
17:59And every 11 years, these dark spots grow in number.
18:04Like clouds gathering before a storm.
18:08When you start seeing more and more sunspots, there's an expectation that you're going to see more intense and more frequent solar flares.
18:19But what drives this 11-year cycle?
18:21It's kind of ironic that one of the most predictable things about the sun is also the most mysterious.
18:29We've been puzzling over the sunspot cycle for generations.
18:35And now, finally, we have spacecraft headed to the sun to try to give us some answers.
18:42The SOHO, SDO, and Stereo spacecraft monitor the sun's atmosphere using ultraviolet telescopes.
18:48They spot flashes of high-energy, ultraviolet light moving across the sun.
18:59These waves of light could be connected to the cycle of sunspots.
19:06And to the sun's outbursts.
19:09Because everything we see on the sun's surface is controlled by violent processes deep in its interior.
19:19The sun is a very simple onion.
19:24At the very, very center is the core, where the nuclear fusion happens.
19:29A layer surrounding that is known as the radiative zone, where most of the energy gets pushed out through radiation.
19:37Then surrounding that is something called the convective zone, where there's great plumes and chains of plasma moving up and down, up and down.
19:47But unlike an onion, the layers spin.
19:51There are currents inside the sun that we don't see from the surface.
19:57Layers of the sun deep down inside are rotating at different rates than the layers above.
20:01So it turns out the inner part of the sun is rotating at maybe three times more rapidly than the outer part of the sun.
20:11We also can see on the outer part of the sun that the equator is rotating more rapidly than the pole.
20:16These layers of plasma grinding against each other generate the sun's enormously powerful magnetic field.
20:26And give rise to sunspots, plasma loops and solar flares.
20:31This differential rotation takes the field and starts twisting it around the sun.
20:39So as the magnetic field gets too twisted, it starts knotting up and these knots start bubbling up to the surface.
20:45And that's what we're seeing actually with the sunspots.
20:47And that's why you see all these wonderful loops and prominences coming off the sun.
20:52Once the magnetic fields start twisting and interacting, they can direct the plasma into vast rivers and loops both above and below the surface of the sun.
21:00Why these events flare up every 11 years is a mystery.
21:09But now, new observations from the solar fleet could provide a clue about what triggers the solar cycle.
21:18Giant, moving magnetic fields beneath the sun's surface.
21:23We think that the ultraviolet light flickers are telling us where the magnetic field is.
21:32In the course of the 11-year cycle, the sun's magnetic fields begin to move down from the poles, closer and closer to the equator.
21:40As the magnetic field lines move through the star, they carry huge amounts of plasma with them.
21:46The magnetic field lines act like shepherds for the plasma underneath the surface.
21:55And they push plasma down to the equator of the sun.
21:59The magnetic fields trap enormous amounts of plasma, like water behind a dam.
22:06Until eventually, the floodgates open and the plasma comes rushing out.
22:11When the magnetic fields meet, they cancel each other out and release the plasma, which goes as a tsunami wave back to the poles.
22:23When that plasma rebounds from the equator and hits the magnetic field coming down from the poles at the mid-latitudes, you get a huge burst of magnetic activity.
22:32Magnetic activity that triggers sunspots and loops also explains the 11-year cycle.
22:38We think that this relationship between the magnetic fields, the ultraviolet flickers, and the plasma drives the 11-year cycle.
22:52We think this is what's actually doing the work.
22:55The solar cycle has wound down for now.
22:58But once the next plasma tsunami rushes through the sun, our star will kick-start into action again.
23:08Over the next few years, we're going to start to see more sunspots, more activity, more flares, more ejections, and more space weather that we have to deal with.
23:18Our fleet of solar spies is poised and ready.
23:28But flares and coronal mass ejections are not the only solar attacks we have to shield ourselves against.
23:35There's a strange, invisible force flowing through the entire solar system.
23:40There is this great wind of high-energy particles from the sun, a million-mile-an-hour wind.
23:46And it can be deadly.
23:49In November 2019, the solar fleet watched as Mercury sailed across the sun.
24:09Mercury is the closest planet to our sun in our solar system.
24:16So it's on the front line, receiving all of this radiation, an incredible amount of energy.
24:21And it's such a tiny planet.
24:23Temperatures on the innermost planet's surface reach 800 degrees Fahrenheit.
24:29But scientists discovered something unexpected on Mercury.
24:33Frozen pools of water hidden in its craters.
24:39It's one of the last places in the solar system you might expect to find ice on Mercury, one of the hottest planets in the solar system.
24:47Despite the overall really high temperatures across the whole planet, there are regions, typically deep within craters, that are permanently shadowed.
24:56So there's never direct sunlight on those regions of Mercury.
25:00And you can keep things as cold as ice in those craters.
25:04But where did the ice come from?
25:07When we first saw that there was ice on Mercury, we thought something must have brought it there.
25:12Something like a comet, which is made out of ice.
25:15But there's a new idea that maybe the materials that make this ice are actually coming from the sun.
25:23The sun creating ice sounds strange.
25:29But recent research shows it's not as crazy as it seems.
25:34We often think of space as being empty.
25:37But in fact, we are bathed in a wind, a million mile an hour wind of high energy particles from the sun all the time.
25:44The solar wind.
25:45A stream of subatomic particles called protons constantly flow out from the sun in all directions, bombarding the planets of our solar system.
25:58The solar wind is so strong when it hits Mercury that it can break down some of the minerals and rocks on its surface into their constituent parts.
26:10And those parts, especially if they have oxygen in them, can go to reform and form water, which if it forms in the right place can then stick around.
26:19Protons in the solar wind combine with oxygen to form water molecules.
26:27They condense and freeze in craters which never see sunlight.
26:32So even on the sun's closest neighbor, ice builds up.
26:38But the solar wind doesn't stop at Mercury.
26:42The solar wind has a tremendous impact on the worlds of our solar system.
26:51We think it's responsible for the planet Venus becoming this hell hole of heat.
26:56Up until as recently as 700 million years ago, Venus was a lush water world with conditions suitable for life.
27:05But the solar wind blasted away the water vapor and oxygen from Venus's atmosphere, leaving carbon dioxide to dominate.
27:16Trapping the sun's heat and causing surface temperatures to skyrocket.
27:21Mars was once habitable too.
27:26But the solar wind quickly took care of that as well.
27:30We believe that billions of years ago, Mars had an atmosphere and had oceans and rivers.
27:38It looked a lot like Earth. It was gorgeous.
27:41But that solar wind stripped away the Martian atmosphere and turned it into the barren wasteland that it is today.
27:49And Earth is in the line of fire too.
27:54It's bombarded every day with solar wind particles.
27:57So, how has life survived?
28:02One of the things we really take for granted is how well protected we are here on the Earth.
28:07The atmosphere absorbs a lot of harmful things from space and from the sun as well.
28:11But also our magnetic field deflects the solar wind around us and we still have an atmosphere.
28:16And when the charged particles come from the sun, the magnetic field lines trap those charged particles and redirect them to the poles of the planet.
28:25The physical effect, the direct physical effect of getting bombarded by these particles, they can generate the aurora borealis, the northern lights.
28:33And these are spectacular and beautiful.
28:36Auroras are beautiful.
28:38But they're also the front line in the battle between Earth and the solar wind.
28:46Without our protective shield, we'd suffer the same fate as Venus or Mars.
28:52But there is a mystery surrounding the solar wind.
28:55One of the things we know about the solar wind is that it is hugely energetic, a million miles an hour.
29:02What gives it that energy?
29:04Astronomers think the source of the solar wind lies in the inner corona.
29:09The atmosphere of the sun revealed by our solar sentinel, SOHO.
29:16SOHO's data shows that near the sun's surface, the wind speed is close to zero.
29:22But by the time the wind gets to the outer corona, it accelerates to 720,000 miles an hour.
29:32Something happens mysterious between the surface of the sun and the corona that gives a punch to the solar wind.
29:40To investigate, we need to visit the corona.
29:45So NASA sent a scout on a daring mission behind enemy lines.
29:53The Parker Solar Probe, that's a daredevil.
29:55This is designed to dive bomb the sun.
30:11The sun exerts a hostile influence on the planets of our solar system.
30:18The solar wind.
30:19It's fast, it's lethal.
30:23But we don't know how it works.
30:26We have spacecraft between us and the sun that can actually see what's coming toward us and how it will impact us.
30:32But what scientists have never been able to explain is what actually accelerates the wind away from the sun.
30:38This has been one of the biggest mysteries of the sun so far.
30:43For decades, we had no way of solving it.
30:45Until now.
30:48There really are some of these wonderful moments when you're a scientist.
30:52And I was actually at the launch of the Parker Solar Probe.
30:56Standing right next to Dr. Eugene Parker, who the probe was named after.
31:00Lift off of the Parker Solar Probe.
31:03Long ago, he had proposed the sun probably had a wind of particles that affected the Earth.
31:08And people basically laughed at him.
31:09But he was proven right over time.
31:11And as that giant Delta rocket slowly went up from the pad, he and I both got to be bathed in that light and smile.
31:21There has been no spacecraft ever in human history to fly through the corona, the very atmosphere of the sun.
31:28Didn't work out well for Icarus, and we hope it works out well for Parker.
31:34The thing about going near the sun is the closer you go to it, the closer your temperature gets to its surface temperature.
31:42And its surface temperature is 6,000 degrees, which vaporizes metal easily.
31:46It's very hot. It tends to melt your spacecraft.
31:49That's the obvious problem. A less obvious problem is, it's just hard to get there.
32:05This is something I think that is very hard for most people to grasp.
32:10There have been suggestions of, you know, let's send all our nuclear waste into the sun or our trash or whatever.
32:16And it turns out to be very difficult to drop anything into the sun.
32:21The reason is, the Earth is circling around the sun at 67,000 miles an hour.
32:28That's good, because that means we don't drop into the sun. We stay at the same distance.
32:33But if you do want to drop into the sun, you have to lose that velocity, and that's a lot of velocity.
32:40To lose speed, the Parker Solar Probe swings by Venus,
32:43performing a gravitational slingshot in reverse.
32:49Now, usually, a gravitational slingshot gives us more velocity.
32:54So if we're flying out to Pluto, for example, we might whip the spacecraft around the planet Jupiter.
32:59It actually takes the spacecraft and gravitationally slingshots it forward, making it go faster.
33:03The thing that we have to do with Parker Solar Probe is the opposite.
33:08We're going to use a gravitational slingshot, but not to speed it up.
33:11To slow it down.
33:13Parker's gravitational maneuvers send the craft on a trajectory inside the sun's extended corona.
33:22Closer to the sun than any spacecraft before it.
33:25This probe actually dives really deep toward the sun, so it's actually going through some of this coronal material and can actually observe it directly in a way that other probes can't.
33:38Using its extreme ultraviolet telescope, Parker spots vast, dark regions below.
33:46There's really interesting regions called coronal holes where you can see, literally, deeper into the sun.
33:56Coronal holes are areas of the sun's corona where the atmosphere is cooler and less dense.
34:05And when the probe passes over a hole in the corona, it gets more, it gets a bigger blast of the solar wind.
34:11These coronal holes appear to be the source of the solar wind.
34:16We think it's through these holes that the solar wind is able to escape the sun.
34:22The big question is, how does the solar wind actually accelerate away from the sun?
34:28It seems to defy logic.
34:31You would think that as something leaves the source, it would probably start to slow down, or at least stay the same speed.
34:38But this doesn't. It gets faster.
34:42Something is accelerating the solar wind.
34:44It gets faster and hotter as it moves away from the surface of the sun, and the mechanism is a mystery.
34:50To solve the mystery, our solar scout dives close to the sun.
34:55Not to see what's going on, but to listen.
34:59That sounded spooky. That sounded really spooky.
35:19You know, for something that's so big and powerful, it's very gentle sounding.
35:23It really, you know, disguises the fact that it's incredibly destructive and would kill me in an instant.
35:31These strange sounds could actually reveal what gives the solar wind its destructive power.
35:39Fluctuations in the sun's magnetic field generate waves that roll through the particles of the solar wind.
35:45These acoustic waves transport particles with them. They give them energy.
35:52Think about a surfer actually going down the surface of a wave, going faster and faster all the time.
35:57These waves could be what accelerates the particles in the solar wind from zero to 720,000 miles an hour.
36:06Giving them the momentum they need to reach far into the solar system.
36:11The solar winds travel just incredible distances. You know, they go past the Earth, past Jupiter.
36:19They've even been seen past Pluto.
36:23It really does pack a wallop even all the way at the edge of our solar system.
36:28One of the things that really surprised me is that Pluto, there are bits of its atmosphere being blasted off by the solar wind all the time.
36:36Tons of atmosphere a day are being lost from Pluto.
36:38The solar wind is powerful enough to blast past the planets, to the very edges of our solar system.
36:48When we sent members of the solar fleet to investigate, we witnessed a battle between the sun and interstellar space.
36:57A battle that could decide the fate of our planet.
37:04The sun blasts the solar system with a storm of particles.
37:18The solar wind.
37:21But how far does that wind reach?
37:25For 40 years, the oldest members of the solar fleet have been on a long-range reconnaissance mission to find out.
37:32The Voyager program was a wonderful idea, a grand tour of the outer solar system in the latter part of the 1970s.
37:43In fact, both Voyagers have traveled so far now that they've effectively reached the outer edges of our solar system.
37:48That boundary zone where the sun's influence wanes and the stars take over.
37:54Over 11 billion miles away, the Voyager probes cross over into interstellar space.
38:01But have they reached the edge of the solar wind?
38:06Voyager 2 was able to sample the environment around it and found the usual mix of solar wind particles give way to a different flavor of particles with different energies.
38:18The general interstellar mix of particles that are just hanging out in our galaxy.
38:24The solar wind actually smashes into and shocks up against the gas of the interstellar medium.
38:31We had discovered the edge of our solar system and it was much more dramatic, much more active than we anticipated.
38:39Interstellar space is violent and dangerous, teeming with lethal radiation.
38:44Supernova blasts and colliding neutron stars send cosmic rays across the galaxy straight toward our solar system.
38:56But these deadly threats are stopped in their tracks.
39:02We really do live inside kind of a protective bubble that's being blown by the solar wind.
39:08You see, as the solar wind moves out into our solar system, it carries with it the sun's magnetic field.
39:13That magnetic field protects us from the highest energy particles the universe can come up with, cosmic rays.
39:19In some cases, a single proton can have as much energy as a 100-mile-an-hour fastball.
39:25Without this protective bubble, called the heliosphere, cosmic protons would smash through your cells, damaging your DNA.
39:34Ironically, the solar wind is deadly, but without it, we wouldn't be here.
39:40Like we saw with Mars, the solar wind has the ability to wipe out life on Earth.
39:48But out there in the furthest reaches of our solar system, it's defending life on Earth.
39:53So in a way, it's a giver of life and it takes life, a yin and a yang.
40:01And now, for the first time, the Voyager probes have looked back at the heliosphere from the outside,
40:09revealing what our solar system looks like as it moves through space.
40:14Something that we lose sight of, sitting here on Earth, watching the sun go around, watching the planets go around,
40:22is that the sun itself is actually hurtling through space really, really fast on an orbit around the center of our galaxy.
40:29If our sun were perfectly stationary, then the heliosphere would be a perfect sphere.
40:38But because it's moving, it's plowing through that interstellar medium.
40:44And so that makes one end shorter and the other end longer.
40:48And new research is showing it's even more complicated than that,
40:51where we might have like a double tail, almost like a buttery croissant surrounding the sun.
41:00Our sun shapes our world and protects us from the dangers of interstellar space.
41:09It's the engine that drives the entire solar system.
41:12And now, for the first time, our fleet of solar spacecraft shows us how it works.
41:22We're pretty familiar with the sun, right?
41:24You see it all the time during the day, lights up the Earth, provides us with heat.
41:28But observing it with all these other satellites, all these observatories,
41:32has shown us a side of the sun that we knew nothing about.
41:35We have this whole fleet of spacecraft orbiting the sun, taking observations,
41:41in all of these different wavelengths, X-ray, ultraviolet, optical, infrared.
41:46They tell us about the functioning of the sun from its outer atmosphere down to its deep core
41:52and give us a window into its functions and its evolution.
41:57Put them all together and we finally have an understanding of our source of life itself.
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