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NARRATOR: There's a
violent star at the center

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of our solar system.

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The immense power, the
roiling, boiling surface,

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the massive plumes.

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It's ridiculous.

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NARRATOR: And our
planet is at its mercy.

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There are explosions and
big giant eruptions of plasma

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that head straight to Earth.

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We have to understand these
better to protect ourselves.

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NARRATOR: The Sun is a churning
cauldron of nuclear reactions.

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Revealing its inner workings
was once mission impossible.

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But not anymore.

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We've recruited this
network of spies, if you will.

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We've built a fleet
of spacecraft that

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monitor the Sun 24 hours a day.

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NARRATOR: With the Sun
under close surveillance,

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we just might have what it
takes to defend our planet.

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[explosion]

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September 6, 2017.

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A flash of ultraviolet and
X-ray light erupts from the Sun,

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sending a burst of
radiation toward Earth.

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We call it a solar flare.

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Flares are huge explosions
on the surface of the Sun,

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throwing light out
into the solar system

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and absolutely baking
anything in its path.

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These are really powerful
events erupting from the Sun.

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And we are fundamentally
in the line of fire.

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NARRATOR: The flare
up is so intense it

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causes radio blackouts
across the side

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of the Earth facing the Sun.

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And the timing could
not have been worse.

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The problem was
at this time, there

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were hurricanes in the Atlantic
bearing down on the Caribbean.

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And there were people trying to
get in there and rescue folks.

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NARRATOR: Radio communication
between disaster relief teams

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goes down for most of the day.

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Space weather and Earth weather
combined to create chaos.

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HAKEEM OLUSEYI: It's not
just an academic exercise.

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Your very lifestyle
depends on understanding

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how the Sun behaves.

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We need to be able
to predict what

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the Sun is going to do next.

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And in order to do that, we
need to have eyes on the Sun,

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as many eyes as we can get.

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RADIO VOICE: 3, 2, 1.

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NARRATOR: That's why NASA has
put together an elite unit.

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RADIO VOICE: We have ignition.

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And we have liftoff.

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NEWSCASTER VOICES: Liftoff.

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And liftoff.

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On an international mission
of the solar physics.

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NARRATOR: A fleet of
daring spacecraft.

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We humans have come a long way.

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If you go back a
few thousand years,

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people were worshipping the Sun.

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And today, we've built
a fleet of spacecraft

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that monitor the
Sun 24 hours a day,

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observing it from
every angle, predicting

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what it's going to do next.

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That's nuts.

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NARRATOR: Leading
the pack is the Solar

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Dynamics Observatory, or SDO.

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It keeps a telescopic
eye on flares blasting

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out from the Sun's surface.

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24 hours a day, the
probe is on the lookout.

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It's constantly vigilant.

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PHIL PLAIT: It looks
at the Sun and a lot

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of different wavelengths
in exquisite detail

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so that we can see exactly
what sort of high-energy events

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are happening on the Sun.

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NARRATOR: The record
for the longest service

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goes to SOHO, our sentinel
monitoring the Sun

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and its faint outer atmosphere.

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PHIL PLAIT: The
Solar and Heliosphere

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Observatory, or SOHO, is the
old hand at studying the Sun.

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It's been up there for
25 years observing,

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not just the Sun itself, but
the environment around it.

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NINA LANZA: Instead of
looking directly at it,

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it actually blocks
out most of the lights

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that we can see all these
beautiful structures

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that surround the Sun.

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NARRATOR: And then
there's the new recruit...

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The Parker Solar Probe.

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Our scout going deep
behind enemy lines.

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PAUL M. SUTTER: The
Parker Solar Probe

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is going to give us the
closest look at the Sun

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that we have ever had in
the history of humanity.

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DAN DURDA: We're flying
so close to the Sun,

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we're flying through the
gases of its atmosphere.

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NARRATOR: 29 other
craft make up the fleet,

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each with their
own role to play.

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PHIL PLAIT: This
fleet of spacecraft

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that we have, the overall
mission is to observe the Sun

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scientifically, learn about its
behavior, but also importantly,

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to learn about the effects
that it has on Earth.

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NARRATOR: Our look-out
probe, the Solar

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Dynamics Observatory, or
SDO, spots something hellish.

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PHIL PLAIT: Today's
forecast for the Sun

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is predicted to be 10,000
degrees Fahrenheit with winds

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of up to 600 miles per second.

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And a pretty decent
chance of rain.

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You don't want to
be in this rainstorm

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because your umbrella
isn't going to help you.

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Solar rain isn't water.

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It's plasma.

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Hot plasma.

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NARRATOR: Rather than a
solid, liquid, or gas,

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the entire Sun is made up of a
strange fourth state of matter.

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Plasma.

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MICHELLE THALLER: Plasma is
just simply gas that's very hot.

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So hot it's lost
some of its electrons

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and become electrically charged.

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And the wonderful
thing about plasma

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is that once it has
that electric charge,

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you can direct it
with a magnetic field.

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NARRATOR: And the Sun has the
most powerful magnetic field

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in the solar system.

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It twists and flows
through the entire star.

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PHIL PLAIT: The
Sun's magnetic field

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is incredibly complicated.

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There are lots of loops
of magnetic lines coming

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out of the Sun's surface.

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GIBOR BASRI: As you
go above the surface,

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the magnetic field begins to
control where the gas can go,

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and you get these beautiful
loops and other structures

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above the Sun that
are just showing you

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where the magnetic field is.

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NARRATOR: The SDO spacecraft's
jaw-dropping videos

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of rain on the Sun show
plasma flowing along

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huge looping magnetic field
lines that have punched

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through the Sun's surface.

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PHIL PLAIT: Because the
surface of the Sun is a plasma,

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and these loops of magnetic
fields are coming out of it,

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it draws that plasma up
which then cools and rains

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down as a plasma rain.

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NARRATOR: Tracking these
loops of magnetic field

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and plasma could help
explain solar flares.

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And it could give
us some warning.

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September 2017.

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Minutes before the devastating
mid-hurricane radio blackout,

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our solar lookouts
spotted an explosion

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on the surface of the Sun.

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PHIL PLAIT: Suddenly you have
this tremendous flow of energy

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and an explosive release of it.

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And we call this a solar flare.

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This is SDO's specialty
of observation.

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NARRATOR: The craft
tracked the magnetic loops

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above the Sun's surface.

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They were highly unstable.

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SDO takes very detailed pictures

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of where the flows are.

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You can actually see gas
flowing from one place.

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You can see the magnetic loops.

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This magnetic flux loops
are kind of like wires

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carrying electricity.

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When they're on their
own they're fine.

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But if they get too close, they
can connect and short circuit.

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And then you get a
tremendous release of energy.

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The Ghostbusters were
really on to something.

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Don't cross the streams.

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NARRATOR: The contact between
magnetic loops released an epic

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explosion of high-energy light.

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This radiation altered
our planet's atmosphere.

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Radio waves jammed,
causing blackouts

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at the worst possible moment.

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PHIL PLAIT: Solar flares
are happening on the Sun

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90 million miles away.

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Who cares, right?

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Well, think of it this way.

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A really good solar
flare could be

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the equivalent of,
oh, say 10 million

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hydrogen bonds going off.

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How's that sound?

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Solar flares happen a lot.

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And they do affect us.

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They have affected
us in the past.

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And they will again
in the future.

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NARRATOR: But the Sun's
twisting magnetic fields

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do more than just disrupt
our communications.

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And when we see
flares, we've got

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to keep an eye out on those.

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But sometimes, there's
something even bigger.

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NARRATOR: The Sun launches
huge clouds of plasma

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across the solar system.

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PHIL PLAIT: All of
that material can

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come to the Earth and
really mess things up here...

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Blow out our power grid, destroy
our satellites, even physically

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harm our astronauts in orbit.

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NARRATOR: Can the solar
fleet safeguard Earth?

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November 5, 2018.

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An explosive cloud
of plasma hits

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the Parker Solar Probe
as it orbits just

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15 million miles from the Sun.

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We have this fleet of spacecraft

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out there viewing the Sun.

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And they are also under
attack by the Sun.

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There are explosions
coming from its surface.

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Is not just light, but
explosions of hot plasma.

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And the Parker Solar
Probe got blasted.

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And yet it survived.

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NARRATOR: A huge
blast of high-energy

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charged particles launches
into the solar system

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at millions of miles an hour.

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A coronal mass ejection.

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But our solar scouts is
prepared for the onslaught.

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PHIL PLAIT: The
Parker Solar Probe

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gets very close to the Sun.

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And it has a heat
shield to protect it.

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But if it gets hit by a
coronal mass ejection,

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it has to be protected
against that as well.

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And so it's been
radiation hardened

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to survive such an impact.

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NARRATOR: Could these blasts
pose a danger to our planet?

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A coronal mass
ejection accelerates

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00:11:14,206 --> 00:11:15,373
subatomic particles.

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And it's not a little
bit of particles.

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It could be up to a
billion tons of them

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screaming across the solar
system at high speed.

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And this is something we
need to take very seriously.

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NARRATOR: To understand these
dangerous blasts of plasma, we

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have to look at their source...

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An area around the Sun
known as the corona.

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PHIL PLAIT: The Sun's corona
is kind of like its atmosphere.

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You can think of the Sun
itself as being a ball of gas.

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And then outside of that is this
ethereally thin gas stretching

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out for millions of miles.

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NARRATOR: The corona
is a difficult thing

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to study because the
surface of the Sun

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is so bright it blocks our view.

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We can only see the corona
during a total solar eclipse,

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when the moon blocks
the Sun's bright glare.

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Astronomers, though,
we're impatient.

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We don't want to have to wait
for a total solar eclipse,

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which only happens
once or twice a year.

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So we figured out a way
to make an artificial one.

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And it's really simple.

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NARRATOR: One member of the
solar fleet has it covered.

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Our solar sentinel, SOHO,
creates its own eclipse

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by obscuring the blinding
Sun with a circular plate

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in front of the probe's camera.

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Sometimes the best solution
is the simplest solution.

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You know, instead of trying
to make a sensor that could

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00:12:45,831 --> 00:12:49,534
actually see the full dynamic
range of the Sun's light,

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00:12:49,635 --> 00:12:51,936
why not just block out the
light that we don't need?

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NARRATOR: In July
2012, SOHO spotted

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00:12:57,743 --> 00:13:00,011
a huge chunk of
the corona blasting

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00:13:00,112 --> 00:13:01,646
off into the solar system.

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00:13:04,150 --> 00:13:08,486
Seconds earlier, another probe
monitoring the solar surface

249
00:13:08,587 --> 00:13:10,088
spotted a bright flare.

250
00:13:12,258 --> 00:13:14,893
Were these events connected?

251
00:13:14,994 --> 00:13:16,494
GIBOR BASRI: If
a flare goes off,

252
00:13:16,595 --> 00:13:18,329
it can disrupt those loops.

253
00:13:18,430 --> 00:13:20,632
And if you get the right
kind of disruption,

254
00:13:20,733 --> 00:13:22,967
the whole thing
can just blow open.

255
00:13:23,068 --> 00:13:25,036
And then you have
a tremendous amount

256
00:13:25,137 --> 00:13:28,606
of billions of tons
of hydrogen blown

257
00:13:28,707 --> 00:13:31,176
off into interplanetary space.

258
00:13:31,277 --> 00:13:33,011
And that's a coronal
mass ejection.

259
00:13:35,781 --> 00:13:39,050
NARRATOR: Coronal mass ejections
are solar flares on steroids.

260
00:13:40,653 --> 00:13:42,887
If a solar flare
was a firecracker,

261
00:13:42,988 --> 00:13:45,356
coronal mass ejection is
more like an atom bomb.

262
00:13:52,498 --> 00:13:56,100
NARRATOR: And if a coronal
mass ejection comes our way,

263
00:13:56,168 --> 00:13:58,036
it hits hard.

264
00:13:58,137 --> 00:14:00,471
The first thing it
does is it compresses

265
00:14:00,573 --> 00:14:02,006
Earth's magnetic field.

266
00:14:02,107 --> 00:14:04,308
And then it wraps
around the Earth.

267
00:14:04,376 --> 00:14:07,612
And this causes the magnetic
field itself to rearrange,

268
00:14:07,713 --> 00:14:10,415
reconnect, and
streams of particles

269
00:14:10,516 --> 00:14:13,618
travel down those magnetic
fields toward our poles

270
00:14:13,719 --> 00:14:15,353
and impact the atmosphere.

271
00:14:15,454 --> 00:14:16,688
Our shields are up.

272
00:14:16,789 --> 00:14:19,190
But they are able to
penetrate our shields.

273
00:14:19,291 --> 00:14:22,160
Our shield being our
own magnetic field.

274
00:14:22,261 --> 00:14:24,028
NARRATOR: Once they
breach our defenses,

275
00:14:24,129 --> 00:14:27,765
the particles of a coronal
mass ejection can wreak havoc.

276
00:14:30,669 --> 00:14:34,739
In August of 1972, tensions
were running high in Vietnam.

277
00:14:36,609 --> 00:14:40,912
[bombs exploding]

278
00:14:41,013 --> 00:14:43,915
Two dozen sea mines
detonated at the same time

279
00:14:44,016 --> 00:14:45,783
when their magnetic
sensors were tripped.

280
00:14:45,885 --> 00:14:49,387
A satellite was lost because
of the electromagnetic pulse

281
00:14:49,488 --> 00:14:50,989
that ripped through it.

282
00:14:51,090 --> 00:14:53,424
And an Air Force sensor detected

283
00:14:53,525 --> 00:14:55,693
what looked like a
nuclear explosion

284
00:14:55,794 --> 00:14:57,729
somewhere here on the planet.

285
00:14:57,830 --> 00:14:59,297
NARRATOR: Fortunately,
scientists

286
00:14:59,398 --> 00:15:00,932
quickly found the real culprit.

287
00:15:03,335 --> 00:15:05,370
A coronal mass
ejection had ripped

288
00:15:05,471 --> 00:15:07,338
through the Earth's
magnetic field

289
00:15:07,439 --> 00:15:08,806
and triggered magnetic sensors.

290
00:15:11,176 --> 00:15:13,511
The crisis soon de-escalated.

291
00:15:15,881 --> 00:15:18,616
PHIL PLAIT: The Sun is
an immense ball of plasma

292
00:15:18,717 --> 00:15:21,586
860,000 miles across.

293
00:15:21,687 --> 00:15:23,821
We are not going to be
able to stop it from doing

294
00:15:23,923 --> 00:15:25,356
whatever it wants to do.

295
00:15:25,457 --> 00:15:29,994
What we can do is learn to
predict what's going to happen.

296
00:15:30,095 --> 00:15:31,229
So we're doing that now.

297
00:15:36,201 --> 00:15:38,069
NARRATOR: Our new fleet
of solar observers

298
00:15:38,170 --> 00:15:39,537
are our first line of defense.

299
00:15:43,642 --> 00:15:44,819
PHIL PLAIT: The Sun
is a little over

300
00:15:44,843 --> 00:15:46,477
90 million miles from Earth.

301
00:15:46,578 --> 00:15:48,479
It takes light a little
over eight minutes

302
00:15:48,580 --> 00:15:50,148
to get from there to here.

303
00:15:50,249 --> 00:15:53,184
As rapidly as a coronal
mass ejection is traveling,

304
00:15:53,285 --> 00:15:55,987
it still takes a few
days to get here.

305
00:15:58,557 --> 00:16:01,993
We can watch the Sun to see
is there going to be an event,

306
00:16:02,094 --> 00:16:03,394
or is an event starting?

307
00:16:03,495 --> 00:16:05,229
And these satellites
can then tell

308
00:16:05,331 --> 00:16:06,798
us, hey, you better be careful.

309
00:16:06,899 --> 00:16:08,900
You might need to batten
down the hatches on Earth.

310
00:16:12,304 --> 00:16:13,944
NARRATOR: But there
may be an earlier clue

311
00:16:14,039 --> 00:16:15,373
the fleet can watch out for.

312
00:16:16,742 --> 00:16:21,012
Vast, dark regions moving
across the solar surface

313
00:16:21,113 --> 00:16:22,113
called sunspots.

314
00:16:23,582 --> 00:16:24,759
HAKEEM OLUSEYI: We
know that this is

315
00:16:24,783 --> 00:16:26,617
the wind up before the release.

316
00:16:26,719 --> 00:16:28,619
This thing is getting
ready to blow.

317
00:16:41,333 --> 00:16:45,069
NARRATOR: In March of
1989, a solar eruption

318
00:16:45,170 --> 00:16:50,641
caused blackouts across
Canada and malfunctions

319
00:16:50,743 --> 00:16:51,943
on board the space shuttle.

320
00:16:53,278 --> 00:16:55,090
RADIO VOICE: We've been
seeing some erratic pressure

321
00:16:55,114 --> 00:16:58,282
signatures out of tank 3, as
well as some manifold pressure

322
00:16:58,384 --> 00:16:59,517
spikes in that system.

323
00:17:01,453 --> 00:17:03,187
NARRATOR: 11 years
later, the Sun

324
00:17:03,288 --> 00:17:06,557
emitted a flare that was
so powerful it blinded

325
00:17:06,658 --> 00:17:07,759
the solar fleet's sensors.

326
00:17:10,462 --> 00:17:13,197
11 years after
that, the Earth had

327
00:17:13,298 --> 00:17:15,933
a near-miss with the most
powerful coronal mass

328
00:17:16,035 --> 00:17:17,335
ejection ever recorded.

329
00:17:21,073 --> 00:17:23,307
The Sun has a very
predictable, but actually quite

330
00:17:23,409 --> 00:17:25,343
mysterious cycle of activity.

331
00:17:25,444 --> 00:17:27,779
It gets very, very
active every 11 years.

332
00:17:27,880 --> 00:17:30,848
And then it settles back down
to more of a peaceful existence.

333
00:17:32,418 --> 00:17:34,419
NARRATOR: This 11-year
cycle has astronomers

334
00:17:34,520 --> 00:17:35,520
scratching their heads.

335
00:17:37,489 --> 00:17:40,525
One thing we do know is
that violent solar events

336
00:17:40,626 --> 00:17:44,595
seem to be preceded by dark
patches on the solar surface.

337
00:17:46,732 --> 00:17:48,199
Sunspots.

338
00:17:48,300 --> 00:17:50,535
HAKEEM OLUSEYI: Sunspots are
large areas on the surface

339
00:17:50,636 --> 00:17:52,537
of the Sun, much
bigger than the Earth,

340
00:17:52,638 --> 00:17:57,008
that are caused by incredibly
strong magnetic fields

341
00:17:57,109 --> 00:17:58,643
disrupting the flow of plasma.

342
00:18:00,245 --> 00:18:02,814
NARRATOR: And every 11
years, these dark spots

343
00:18:02,915 --> 00:18:08,052
grow in number like clouds
gathering before a storm.

344
00:18:10,689 --> 00:18:12,623
When you start seeing
more and more sunspots,

345
00:18:12,724 --> 00:18:14,044
there's an expectation
that you're

346
00:18:14,093 --> 00:18:16,761
going to see more intense and
more frequent solar flares.

347
00:18:20,632 --> 00:18:22,633
NARRATOR: But what drives
this 11-year cycle?

348
00:18:24,002 --> 00:18:25,547
It's kind of ironic
that one of the most

349
00:18:25,571 --> 00:18:28,439
predictable things about the
Sun is also the most mysterious.

350
00:18:30,342 --> 00:18:33,411
PAUL M. SUTTER: We've been
puzzling over the sunspot cycle

351
00:18:33,512 --> 00:18:35,446
for generations.

352
00:18:35,547 --> 00:18:39,283
And now finally we have
spacecraft headed to the Sun

353
00:18:39,384 --> 00:18:40,751
to try to give us some answers.

354
00:18:42,754 --> 00:18:45,456
NARRATOR: The SOHO, SDO,
and STEREO spacecraft

355
00:18:45,557 --> 00:18:49,227
monitor the Sun's atmosphere
using ultraviolet telescopes.

356
00:18:51,363 --> 00:18:54,832
They spot flashes of
high-energy ultraviolet light

357
00:18:54,933 --> 00:18:56,167
moving across the Sun.

358
00:19:00,339 --> 00:19:02,273
These waves of light
could be connected

359
00:19:02,374 --> 00:19:09,580
to the cycle of sunspots
and to the Sun's outbursts.

360
00:19:09,681 --> 00:19:11,649
Because everything
we see on the Sun's

361
00:19:11,750 --> 00:19:17,255
surface is controlled by violent
processes deep in its interior.

362
00:19:21,260 --> 00:19:24,762
The Sun is a very simple onion.

363
00:19:24,863 --> 00:19:27,198
At the very, very
center is the core where

364
00:19:27,299 --> 00:19:29,133
the nuclear fusion happens.

365
00:19:29,234 --> 00:19:31,469
A layer surrounding
that is known

366
00:19:31,570 --> 00:19:34,872
as the radiative zone, where
most of the energy gets

367
00:19:34,973 --> 00:19:37,108
pushed out through radiation.

368
00:19:37,209 --> 00:19:39,510
Then surrounding
that is something

369
00:19:39,611 --> 00:19:42,013
called the convective
zone, where there's

370
00:19:42,114 --> 00:19:45,416
great plumes and
chains of plasma moving

371
00:19:45,517 --> 00:19:48,286
up and down, up and down.

372
00:19:48,387 --> 00:19:51,422
NARRATOR: But unlike an
onion, the layers spin.

373
00:19:54,226 --> 00:19:56,137
MICHELLE THALLER: There
are currents inside the Sun

374
00:19:56,161 --> 00:19:57,962
we don't see from the surface.

375
00:19:58,063 --> 00:19:59,897
Layers of the Sun
deep down inside

376
00:19:59,998 --> 00:20:02,118
are rotating at different
rates than the layers above.

377
00:20:03,435 --> 00:20:05,903
GIBOR BASRI: So it turns out
the inner part of the Sun

378
00:20:06,004 --> 00:20:08,539
is rotating at maybe
three times more

379
00:20:08,640 --> 00:20:11,042
rapidly than the
outer part of the Sun.

380
00:20:11,176 --> 00:20:13,044
We also can see on the
outer part of the Sun

381
00:20:13,145 --> 00:20:16,714
that the equator is rotating
more rapidly than the pole.

382
00:20:19,651 --> 00:20:22,320
NARRATOR: These layers of plasma
grinding against each other

383
00:20:22,421 --> 00:20:27,525
generate the Sun's enormously
powerful magnetic field

384
00:20:27,626 --> 00:20:31,729
and give rise to sunspots,
plasma loops, and solar flares.

385
00:20:33,832 --> 00:20:36,601
This differential
rotation takes the field

386
00:20:36,702 --> 00:20:39,203
and starts twisting
it around the Sun.

387
00:20:39,304 --> 00:20:41,739
So as the magnetic
field gets too twisted,

388
00:20:41,840 --> 00:20:42,940
it starts knotting up.

389
00:20:43,041 --> 00:20:45,376
And these knots start
bubbling up to the surface.

390
00:20:45,477 --> 00:20:47,677
And that's what we're seeing
actually with the sunspots.

391
00:20:49,147 --> 00:20:51,082
And that's why you see
all these wonderful loops

392
00:20:51,183 --> 00:20:53,050
and prominences
coming off the Sun.

393
00:20:53,151 --> 00:20:55,853
Once the magnetic fields start
twisting and interacting,

394
00:20:55,954 --> 00:20:59,023
they can direct the plasma
into vast rivers and loops

395
00:20:59,124 --> 00:21:01,058
both above and below
the surface of the Sun.

396
00:21:05,397 --> 00:21:08,866
NARRATOR: Why these events flare
up every 11 years is a mystery.

397
00:21:10,902 --> 00:21:14,071
But now new observations
from the solar fleet

398
00:21:14,172 --> 00:21:17,341
could provide a clue about
what triggers the solar cycle.

399
00:21:19,378 --> 00:21:23,414
Giant, moving magnetic fields
beneath the Sun's surface.

400
00:21:26,285 --> 00:21:29,487
We think that the ultraviolet
light flickers are telling

401
00:21:29,588 --> 00:21:31,822
us where the magnetic field is.

402
00:21:33,258 --> 00:21:34,759
In the course of
the 11-year cycle,

403
00:21:34,860 --> 00:21:36,727
the Sun's magnetic
fields begin to move

404
00:21:36,828 --> 00:21:40,931
down from the poles closer
and closer to the equator.

405
00:21:41,033 --> 00:21:43,934
NARRATOR: As the magnetic field
lines move through the star,

406
00:21:44,036 --> 00:21:46,170
they carry huge amounts
of plasma with them.

407
00:21:48,774 --> 00:21:53,344
The magnetic field lines act
like shepherds for the plasma

408
00:21:53,445 --> 00:21:55,079
underneath the surface.

409
00:21:55,180 --> 00:21:58,182
And they push plasma down
to the equator of the Sun.

410
00:21:59,951 --> 00:22:02,953
NARRATOR: The magnetic
fields trap enormous amounts

411
00:22:03,055 --> 00:22:07,224
of plasma, like
water behind a dam,

412
00:22:07,326 --> 00:22:09,694
until eventually
the floodgates open,

413
00:22:09,795 --> 00:22:11,896
and the plasma
comes rushing out.

414
00:22:15,334 --> 00:22:17,802
When the magnetic fields
meet, they cancel each other out

415
00:22:17,903 --> 00:22:21,505
and release the plasma,
which goes as a tsunami wave

416
00:22:21,606 --> 00:22:22,606
back to the polls.

417
00:22:24,609 --> 00:22:25,929
MICHELLE THALLER:
When that plasma

418
00:22:26,011 --> 00:22:28,356
rebounds from the equator and
hits the magnetic field coming

419
00:22:28,380 --> 00:22:30,147
down from the poles
at the mid latitudes,

420
00:22:30,248 --> 00:22:33,818
you get a huge burst
of magnetic activity.

421
00:22:33,919 --> 00:22:37,421
NARRATOR: Magnetic activity that
triggers sunspots and loops.

422
00:22:37,522 --> 00:22:39,523
Also explains the 11-year cycle.

423
00:22:43,428 --> 00:22:45,696
We think that this
relationship between

424
00:22:45,797 --> 00:22:48,366
the magnetic fields, the
ultraviolet flickers,

425
00:22:48,467 --> 00:22:52,002
and the plasma drives
the 11-year cycle.

426
00:22:52,104 --> 00:22:55,039
We think this is what's
actually doing the work.

427
00:22:56,908 --> 00:23:00,344
NARRATOR: The solar cycle
has wound down for now.

428
00:23:00,445 --> 00:23:04,749
But once the next plasma
tsunami rushes through the Sun,

429
00:23:04,850 --> 00:23:07,785
our star will kick
start into action again.

430
00:23:09,187 --> 00:23:10,721
Over the next few
years, we're going

431
00:23:10,822 --> 00:23:15,092
to start to see more sunspots,
more activity, more flares,

432
00:23:15,193 --> 00:23:17,895
more ejections, and
more space weather

433
00:23:17,996 --> 00:23:19,036
that we have to deal with.

434
00:23:20,866 --> 00:23:24,068
NARRATOR: Our fleet of solar
spies is poised and ready.

435
00:23:28,573 --> 00:23:30,908
But flares and
coronal mass ejections

436
00:23:31,009 --> 00:23:33,177
are not the only
solar attacks we have

437
00:23:33,278 --> 00:23:34,478
to shield ourselves against.

438
00:23:36,214 --> 00:23:38,516
There's a strange,
invisible force

439
00:23:38,617 --> 00:23:41,886
flowing through the
entire solar system.

440
00:23:41,987 --> 00:23:43,654
There is this great
wind of high-energy

441
00:23:43,755 --> 00:23:44,622
particles from the Sun.

442
00:23:44,723 --> 00:23:46,123
A million mile-an-hour wind.

443
00:23:47,993 --> 00:23:49,393
NARRATOR: And it can be deadly.

444
00:23:53,465 --> 00:23:54,465
[explosion]

445
00:24:04,443 --> 00:24:09,213
In November 2019, the solar
fleet watched as Mercury

446
00:24:09,314 --> 00:24:10,548
sailed across the Sun.

447
00:24:13,819 --> 00:24:15,463
JESSIE CHRISTIANSEN: Mercury
is the closest planet

448
00:24:15,487 --> 00:24:17,021
to our Sun in our solar system.

449
00:24:17,122 --> 00:24:18,722
So it's on the
front line receiving

450
00:24:18,824 --> 00:24:19,957
all of this radiation.

451
00:24:20,058 --> 00:24:21,725
An incredible amount of energy.

452
00:24:21,793 --> 00:24:23,027
And it's such a tiny planet.

453
00:24:24,463 --> 00:24:26,831
NARRATOR: Temperatures on the
innermost planet's surface

454
00:24:26,932 --> 00:24:29,467
reach 800 degrees Fahrenheit.

455
00:24:30,902 --> 00:24:33,204
But scientists discovered
something unexpected

456
00:24:33,305 --> 00:24:34,305
on Mercury.

457
00:24:35,941 --> 00:24:39,009
Frozen pools of water
hidden in its craters.

458
00:24:41,813 --> 00:24:43,758
It's one of the last places
in the solar system you might

459
00:24:43,782 --> 00:24:45,983
expect to find ice, on
Mercury, one of the hottest

460
00:24:46,084 --> 00:24:47,852
planets in the solar system.

461
00:24:47,953 --> 00:24:49,820
KEVIN WALSH: Despite
the overall really

462
00:24:49,921 --> 00:24:52,056
high temperatures
across the whole planet,

463
00:24:52,157 --> 00:24:53,824
there are regions...

464
00:24:53,925 --> 00:24:55,559
Typically deep within craters...

465
00:24:55,660 --> 00:24:57,194
That are permanently shadowed.

466
00:24:57,295 --> 00:25:00,698
So there's never direct sunlight
on those regions of Mercury.

467
00:25:00,799 --> 00:25:05,169
And you can keep things as
cold as ice in those craters.

468
00:25:05,270 --> 00:25:07,071
NARRATOR: But where
did the ice come from?

469
00:25:08,406 --> 00:25:10,374
When we first saw that
there was ice on Mercury,

470
00:25:10,475 --> 00:25:12,355
we thought something must
have brought it there.

471
00:25:12,444 --> 00:25:14,745
Something like a comet,
which is made out of ice.

472
00:25:16,381 --> 00:25:18,349
But there's a new
idea that maybe

473
00:25:18,450 --> 00:25:21,552
the materials that
make this ice are

474
00:25:21,653 --> 00:25:23,454
actually coming from the Sun.

475
00:25:26,691 --> 00:25:28,859
NARRATOR: The Sun creating
ice sounds strange.

476
00:25:30,328 --> 00:25:34,098
But recent research shows
it's not as crazy as it seems.

477
00:25:35,734 --> 00:25:37,812
MICHELLE THALLER: We often
think of space as being empty.

478
00:25:37,836 --> 00:25:41,138
But in fact, we are bathed
in a wind, a million

479
00:25:41,239 --> 00:25:43,541
mile-an-hour wind of high-energy
particles from the Sun

480
00:25:43,642 --> 00:25:44,408
all the time.

481
00:25:44,509 --> 00:25:45,509
The solar wind.

482
00:25:48,179 --> 00:25:50,014
NARRATOR: A stream of
subatomic particles

483
00:25:50,115 --> 00:25:52,850
called protons
constantly flow out

484
00:25:52,951 --> 00:25:58,022
from the Sun in all directions,
bombarding the planets

485
00:25:58,123 --> 00:25:59,123
of our solar system.

486
00:26:03,228 --> 00:26:06,096
CARLY HOWETT: The solar wind is
so strong when it hits Mercury

487
00:26:06,197 --> 00:26:07,842
that it can break down
some of the minerals

488
00:26:07,866 --> 00:26:10,968
and rocks on its surface
into their constituent parts.

489
00:26:11,069 --> 00:26:14,405
And those parts, especially
if they have oxygen in them,

490
00:26:14,506 --> 00:26:17,508
can go to reform and
form water, which

491
00:26:17,609 --> 00:26:20,144
if it forms in the right
place, can then stick around.

492
00:26:22,614 --> 00:26:25,649
NARRATOR: Protons in the solar
wind combined with oxygen

493
00:26:25,750 --> 00:26:28,052
to form water molecules.

494
00:26:28,153 --> 00:26:30,521
They condense and
freeze in craters

495
00:26:30,622 --> 00:26:31,622
which never see sunlight.

496
00:26:34,626 --> 00:26:38,362
So even on the Sun's closest
neighbor, ice builds up.

497
00:26:40,899 --> 00:26:43,367
But the solar wind
doesn't stop at Mercury.

498
00:26:47,038 --> 00:26:49,139
The solar wind has
a tremendous impact

499
00:26:49,240 --> 00:26:51,809
on the world's of
our solar system.

500
00:26:51,910 --> 00:26:53,777
We think it's responsible
for the planet Venus

501
00:26:53,878 --> 00:26:55,512
becoming this hell hole of heat.

502
00:26:57,449 --> 00:27:01,719
NARRATOR: Up until as recently
as 700 million years ago,

503
00:27:01,820 --> 00:27:04,822
Venus was a lush water
world with conditions

504
00:27:04,923 --> 00:27:05,923
suitable for life.

505
00:27:07,959 --> 00:27:11,695
But the solar wind blasted
away the water vapor and oxygen

506
00:27:11,796 --> 00:27:17,167
from Venus's atmosphere, leaving
carbon dioxide to dominate,

507
00:27:17,268 --> 00:27:19,637
trapping the Sun's heat,
and causing surface

508
00:27:19,738 --> 00:27:21,138
temperatures to skyrocket.

509
00:27:23,608 --> 00:27:25,609
Mars was once habitable too.

510
00:27:27,312 --> 00:27:30,781
But the solar wind quickly
took care of that as well.

511
00:27:33,318 --> 00:27:34,929
PAUL M. SUTTER: We believe
that billions of years

512
00:27:34,953 --> 00:27:39,123
ago, Mars had an atmosphere,
and it had oceans, and rivers.

513
00:27:39,224 --> 00:27:40,267
It looked a lot like Earth.

514
00:27:40,291 --> 00:27:41,625
It was gorgeous.

515
00:27:41,726 --> 00:27:46,397
But that solar wind stripped
away the Martian atmosphere

516
00:27:46,498 --> 00:27:49,199
and turned it into the barren
wasteland that it is today.

517
00:27:51,302 --> 00:27:54,371
NARRATOR: And Earth is
in the line of fire too.

518
00:27:54,472 --> 00:27:58,208
It's bombarded every day
with solar wind particles.

519
00:28:00,178 --> 00:28:02,112
So how has life survived?

520
00:28:03,348 --> 00:28:04,558
MICHELLE THALLER: One
of the things we really

521
00:28:04,582 --> 00:28:06,250
take for granted is
how well protected

522
00:28:06,351 --> 00:28:07,651
we are here on the Earth.

523
00:28:07,752 --> 00:28:10,421
The atmosphere absorbs a lot
of harmful things from space

524
00:28:10,522 --> 00:28:11,655
and from the Sun as well.

525
00:28:11,756 --> 00:28:13,657
But also our magnetic
field deflects

526
00:28:13,758 --> 00:28:14,958
the solar wind around us.

527
00:28:15,060 --> 00:28:16,593
And we still have an atmosphere.

528
00:28:18,396 --> 00:28:21,098
And when the charged
particles come from the Sun,

529
00:28:21,199 --> 00:28:22,599
the magnetic field
lines trap those

530
00:28:22,701 --> 00:28:24,501
charged particles
and redirect them

531
00:28:24,602 --> 00:28:26,203
to the poles of the planet.

532
00:28:26,304 --> 00:28:28,549
PHIL PLAIT: The physical effect,
the direct physical effect,

533
00:28:28,573 --> 00:28:30,441
of getting bombarded
by these particles,

534
00:28:30,542 --> 00:28:33,610
they can generate the Aurora
borealis, the Northern Lights.

535
00:28:33,712 --> 00:28:36,447
And these are spectacular
and beautiful.

536
00:28:37,882 --> 00:28:40,584
NARRATOR: Auroras are beautiful.

537
00:28:40,685 --> 00:28:44,354
But they're also the front line
in the battle between Earth

538
00:28:44,456 --> 00:28:46,657
and the solar wind.

539
00:28:46,758 --> 00:28:49,093
Without our protective
shield, we'd suffer

540
00:28:49,194 --> 00:28:51,462
the same fate as Venus or Mars.

541
00:28:53,264 --> 00:28:56,867
But there is a mystery
surrounding the solar wind.

542
00:28:56,968 --> 00:28:58,768
One of the things we
know about the solar wind

543
00:28:58,803 --> 00:29:00,738
is that it is hugely energetic.

544
00:29:00,839 --> 00:29:02,339
A million miles-an-hour.

545
00:29:02,440 --> 00:29:03,540
What gives it that energy?

546
00:29:05,210 --> 00:29:08,512
NARRATOR: Astronomers think
the source of the solar wind

547
00:29:08,646 --> 00:29:13,617
lies in the inner corona, the
atmosphere of the Sun revealed

548
00:29:13,718 --> 00:29:15,586
by our solar sentinel, SOHO.

549
00:29:17,555 --> 00:29:20,491
SOHO's data shows that
near the Sun's surface,

550
00:29:20,592 --> 00:29:22,593
the wind speed is close to zero.

551
00:29:25,130 --> 00:29:28,031
But by the time the win
gets to the outer corona,

552
00:29:28,133 --> 00:29:33,904
it accelerates to
720,000 miles-an-hour.

553
00:29:34,005 --> 00:29:36,774
Something happens mysterious
between the surface of the Sun

554
00:29:36,875 --> 00:29:39,409
and the corona that gives
a punch to the solar wind.

555
00:29:41,246 --> 00:29:44,548
NARRATOR: To investigate,
we need to visit the corona.

556
00:29:46,050 --> 00:29:50,420
So NASA sent a scout on a daring
mission behind enemy lines.

557
00:29:53,424 --> 00:29:55,993
The Parker Solar Probe,
that's a daredevil.

558
00:29:56,094 --> 00:29:58,962
This is designed to
dive bomb the Sun.

559
00:30:03,701 --> 00:30:04,701
[explosion]

560
00:30:12,110 --> 00:30:14,344
NARRATOR: The Sun exerts
a hostile influence

561
00:30:14,445 --> 00:30:16,280
on the planets of
our solar system.

562
00:30:18,983 --> 00:30:19,983
The solar wind.

563
00:30:21,152 --> 00:30:22,186
It's fast.

564
00:30:22,287 --> 00:30:23,921
It's lethal.

565
00:30:24,022 --> 00:30:27,157
But we don't know how it works.

566
00:30:27,258 --> 00:30:29,098
MICHELLE THALLER: We have
spacecraft between us

567
00:30:29,160 --> 00:30:31,238
and the Sun that can actually
see what's coming towards us

568
00:30:31,262 --> 00:30:32,596
and how it will impact us.

569
00:30:32,697 --> 00:30:35,032
But what scientists have
never been able to explain

570
00:30:35,133 --> 00:30:39,069
is what actually accelerates
the wind away from the Sun.

571
00:30:39,170 --> 00:30:41,570
This has been one of the biggest
mysteries of the Sun so far.

572
00:30:43,741 --> 00:30:45,943
NARRATOR: For decades, we
had no way of solving it.

573
00:30:47,812 --> 00:30:48,812
Until now.

574
00:30:50,582 --> 00:30:52,259
There really are some
of these wonderful moments

575
00:30:52,283 --> 00:30:53,517
when you're a scientist.

576
00:30:53,618 --> 00:30:56,720
And I was actually at the launch
of the Parker Solar Probe,

577
00:30:56,821 --> 00:30:58,856
standing right next
to Dr. Eugene Parker,

578
00:30:58,957 --> 00:31:00,424
who the probe is named after.

579
00:31:00,525 --> 00:31:03,427
NEWSCASTER VOICE: Liftoff
of the Parker Solar Probe.

580
00:31:03,528 --> 00:31:05,039
MICHELLE THALLER: Long
ago, he had proposed

581
00:31:05,063 --> 00:31:06,830
the Sun probably had
a wind of particles

582
00:31:06,931 --> 00:31:08,131
that affected the Earth.

583
00:31:08,233 --> 00:31:10,100
And people basically
laughed at him.

584
00:31:10,201 --> 00:31:11,869
But he was proven
right over time.

585
00:31:11,970 --> 00:31:15,472
And as that giant delta rocket
slowly went up from the pad,

586
00:31:15,573 --> 00:31:18,475
he and I both got to be bathed
in that light, and smile.

587
00:31:21,646 --> 00:31:24,348
There has been
no spacecraft ever

588
00:31:24,449 --> 00:31:27,484
in human history to
fly through the corona,

589
00:31:27,585 --> 00:31:30,520
the very atmosphere of the Sun.

590
00:31:30,622 --> 00:31:32,299
GIBOR BASRI: Didn't work
out well for Icarus.

591
00:31:32,323 --> 00:31:34,758
And we hope it works
out well for Parker.

592
00:31:34,859 --> 00:31:36,360
The thing about
going near the Sun

593
00:31:36,461 --> 00:31:40,564
is, the closer you go to it,
the closer your temperature gets

594
00:31:40,665 --> 00:31:42,366
to its surface temperature.

595
00:31:42,467 --> 00:31:44,801
And its surface temperature
is 6,000 degrees,

596
00:31:44,903 --> 00:31:46,637
which vaporizes metal easily.

597
00:31:49,440 --> 00:31:52,075
NARRATOR: Surviving close
to the Sun is a big ask.

598
00:31:53,645 --> 00:31:54,978
But reaching the Sun?

599
00:31:55,079 --> 00:31:57,915
That's an even bigger challenge.

600
00:31:58,016 --> 00:31:59,116
It's very hot.

601
00:31:59,217 --> 00:32:01,485
It tends to melt
your spacecraft.

602
00:32:01,586 --> 00:32:02,953
That's the obvious problem.

603
00:32:03,054 --> 00:32:06,189
A less obvious problem is
it's just hard to get there.

604
00:32:06,291 --> 00:32:08,669
This is something I think that
it's very hard for most people

605
00:32:08,693 --> 00:32:10,560
to grasp.

606
00:32:10,662 --> 00:32:11,972
There have been
suggestions of, you

607
00:32:11,996 --> 00:32:14,197
know, let's send all our
nuclear waste into the Sun,

608
00:32:14,299 --> 00:32:15,999
or our trash, or whatever.

609
00:32:16,100 --> 00:32:18,535
And it turns out to be
very difficult to drop

610
00:32:18,636 --> 00:32:19,636
anything into the Sun.

611
00:32:21,506 --> 00:32:23,006
NARRATOR: The
reason is the Earth

612
00:32:23,074 --> 00:32:28,378
is circling around the Sun
at 67,000 miles-an-hour.

613
00:32:28,479 --> 00:32:31,815
That's good because that means
we don't drop in to the Sun.

614
00:32:31,916 --> 00:32:33,517
We stay at the same distance.

615
00:32:33,618 --> 00:32:35,285
But if you do want
to drop into the Sun,

616
00:32:35,386 --> 00:32:36,820
you'd have to lose
that velocity.

617
00:32:36,921 --> 00:32:38,155
And that's a lot of velocity.

618
00:32:40,591 --> 00:32:43,093
NARRATOR: To lose speed
the Parker Solar Probe

619
00:32:43,194 --> 00:32:48,432
swings by Venus, performing
a gravitational slingshot

620
00:32:48,533 --> 00:32:49,533
in reverse.

621
00:32:50,935 --> 00:32:53,047
MICHELLE THALLER: Now usually,
a gravitational slingshot

622
00:32:53,071 --> 00:32:54,771
gives us more velocity.

623
00:32:54,872 --> 00:32:57,040
So if we're flying out
to Pluto, for example,

624
00:32:57,141 --> 00:32:59,576
we might whip the spacecraft
around the planet Jupiter.

625
00:32:59,677 --> 00:33:02,879
It actually takes the spacecraft
and gravitationally slingshots

626
00:33:02,981 --> 00:33:05,282
it forward, making go faster.

627
00:33:05,383 --> 00:33:07,094
The thing that we have to
do with Parker Solar Probe

628
00:33:07,118 --> 00:33:08,251
is the opposite.

629
00:33:08,319 --> 00:33:10,079
We're going to use a
gravitational slingshot,

630
00:33:10,121 --> 00:33:11,355
but not to speed it up...

631
00:33:11,456 --> 00:33:12,456
To slow it down.

632
00:33:13,725 --> 00:33:15,726
NARRATOR: Parker's
gravitational maneuvers

633
00:33:15,827 --> 00:33:18,962
send the craft on a
trajectory inside the Sun's

634
00:33:19,063 --> 00:33:24,001
extended corona,
closer to the Sun

635
00:33:24,102 --> 00:33:27,137
than any spacecraft before it.

636
00:33:27,238 --> 00:33:31,074
This probe actually dives
really deep toward the Sun.

637
00:33:31,175 --> 00:33:34,945
So it's actually going through
some of these coronal material

638
00:33:35,046 --> 00:33:37,047
and can actually observe
it directly in a way

639
00:33:37,148 --> 00:33:38,148
that other probes can't.

640
00:33:41,152 --> 00:33:44,221
NARRATOR: Using its extreme
ultraviolet telescope,

641
00:33:44,322 --> 00:33:46,857
Parker spots vast,
dark regions below.

642
00:33:50,028 --> 00:33:51,305
There's really
interesting regions

643
00:33:51,329 --> 00:33:53,397
called coronal holes
where you can see

644
00:33:53,498 --> 00:33:55,265
literally deeper into the Sun.

645
00:33:56,901 --> 00:34:00,037
NARRATOR: Coronal holes are
areas of the Sun's coronavirus

646
00:34:00,138 --> 00:34:02,773
where the atmosphere is
cooler and less dense.

647
00:34:05,576 --> 00:34:09,980
And when the probe passes over
a hole in the coronavirus it

648
00:34:10,081 --> 00:34:11,648
gets a bigger blast
of the solar wind.

649
00:34:13,184 --> 00:34:14,728
NARRATOR: These coronal
holes appear to be

650
00:34:14,752 --> 00:34:16,153
the source of the solar wind.

651
00:34:18,322 --> 00:34:19,762
And we think it's
through these holes

652
00:34:19,857 --> 00:34:21,792
that the solar wind is
able to escape the Sun.

653
00:34:23,194 --> 00:34:24,728
NARRATOR: The big
question is, how

654
00:34:24,829 --> 00:34:28,198
does the solar wind actually
accelerate away from the Sun?

655
00:34:29,667 --> 00:34:31,001
It seems to defy logic.

656
00:34:33,271 --> 00:34:35,739
You would think that as
something leaves the source,

657
00:34:35,840 --> 00:34:37,874
it would probably start
to slow down, or at least

658
00:34:37,975 --> 00:34:39,076
stay the same speed.

659
00:34:39,177 --> 00:34:40,077
But this doesn't.

660
00:34:40,178 --> 00:34:41,178
It gets faster.

661
00:34:42,513 --> 00:34:44,758
MICHELLE THALLER: Something is
accelerating the solar wind.

662
00:34:44,782 --> 00:34:46,850
It gets faster and
hotter as it moves away

663
00:34:46,951 --> 00:34:48,151
from the surface of the Sun.

664
00:34:48,252 --> 00:34:49,686
And the mechanism is a mystery.

665
00:34:51,489 --> 00:34:53,623
NARRATOR: To solve the
mystery, our solar scout

666
00:34:53,724 --> 00:34:55,158
dives close to the Sun...

667
00:34:57,095 --> 00:35:00,530
Not to see what's going
on, but to listen.

668
00:35:00,631 --> 00:35:01,965
[strange noises]

669
00:35:15,780 --> 00:35:18,281
That sounded spooky.

670
00:35:18,382 --> 00:35:20,083
That sounded really spooky.

671
00:35:20,184 --> 00:35:22,129
You know, for something
that's so big and powerful,

672
00:35:22,153 --> 00:35:23,320
it's very gentle sounding.

673
00:35:24,922 --> 00:35:27,991
It really, you know,
disguises the fact

674
00:35:28,092 --> 00:35:29,470
that it's incredibly
destructive and would

675
00:35:29,494 --> 00:35:30,494
kill me in an instant.

676
00:35:32,597 --> 00:35:34,564
NARRATOR: These
strange sounds could

677
00:35:34,665 --> 00:35:37,767
actually reveal what
gives the solar wind

678
00:35:37,869 --> 00:35:39,636
its destructive power.

679
00:35:39,770 --> 00:35:42,739
Fluctuations in the
Sun's magnetic field

680
00:35:42,840 --> 00:35:45,342
generate waves that roll
through the particles

681
00:35:45,443 --> 00:35:46,443
of the solar wind.

682
00:35:48,613 --> 00:35:51,248
These acoustic waves
transport particles with them

683
00:35:51,349 --> 00:35:52,482
that give them energy.

684
00:35:52,583 --> 00:35:53,984
Think about a surfer
actually going

685
00:35:54,085 --> 00:35:55,552
down the surface
of a wave, going

686
00:35:55,653 --> 00:35:57,120
faster and faster all the time.

687
00:35:58,956 --> 00:36:01,958
NARRATOR: These waves could be
what accelerates the particles

688
00:36:02,059 --> 00:36:07,964
in the solar wind from 0
to 720,000 miles-an-hour,

689
00:36:08,065 --> 00:36:10,300
giving them the momentum
they need to reach

690
00:36:10,401 --> 00:36:11,902
far into the solar system.

691
00:36:13,905 --> 00:36:17,007
The solar winds travel
just incredible distances.

692
00:36:17,108 --> 00:36:19,676
You know, they go past
the Earth, past Jupiter.

693
00:36:19,777 --> 00:36:22,212
They've even been
seen past Pluto.

694
00:36:24,348 --> 00:36:26,527
MICHELLE THALLER: It really does
pack a wallop, even all the way

695
00:36:26,551 --> 00:36:27,831
at the edge of our solar system.

696
00:36:29,253 --> 00:36:31,588
One of the things that really
surprised me is that Pluto...

697
00:36:31,689 --> 00:36:33,990
There are bits of its
atmosphere being blasted off

698
00:36:34,091 --> 00:36:35,825
by the solar wind all the time.

699
00:36:35,927 --> 00:36:38,662
Tons of atmosphere a day
are being lost from Pluto.

700
00:36:40,097 --> 00:36:41,777
NARRATOR: The solar
wind is powerful enough

701
00:36:41,866 --> 00:36:47,571
to blast past the planets to the
very edges of our solar system.

702
00:36:50,174 --> 00:36:53,944
When we sent members of the
solar fleet to investigate,

703
00:36:54,045 --> 00:36:58,048
we witnessed a battle between
the Sun and interstellar space.

704
00:37:00,051 --> 00:37:03,453
A battle that could decide
the fate of our planet.

705
00:37:06,524 --> 00:37:07,524
[explosion]

706
00:37:15,366 --> 00:37:18,735
The Sun blasts the solar system
with a storm of particles.

707
00:37:20,271 --> 00:37:21,271
The solar wind.

708
00:37:22,640 --> 00:37:24,207
But how far does
that wind reach?

709
00:37:26,644 --> 00:37:29,512
For 40 years, the oldest
members of the solar fleet

710
00:37:29,614 --> 00:37:31,648
have been on a
long-range reconnaissance

711
00:37:31,749 --> 00:37:33,316
mission to find out.

712
00:37:35,586 --> 00:37:38,355
The Voyager program,
it was a wonderful idea.

713
00:37:38,456 --> 00:37:41,491
A grand tour of the outer
solar system in the latter part

714
00:37:41,592 --> 00:37:43,193
of the 1970s.

715
00:37:43,294 --> 00:37:45,929
In fact, both Voyagers
have traveled so far now

716
00:37:46,030 --> 00:37:48,131
that they've effectively
reached the outer edges

717
00:37:48,232 --> 00:37:50,233
of our solar system,
that boundary

718
00:37:50,334 --> 00:37:53,036
zone where the Sun's influence
wanes and the stars take over.

719
00:37:55,072 --> 00:37:57,741
NARRATOR: Over 11
billion miles away,

720
00:37:57,842 --> 00:38:01,278
the Voyager probes cross
over into interstellar space.

721
00:38:03,114 --> 00:38:05,248
But have they reached the
edge of the solar wind?

722
00:38:06,617 --> 00:38:10,153
Voyager 2, it was able
to sample the environment

723
00:38:10,254 --> 00:38:13,156
around it and found the usual
mix of solar wind particles

724
00:38:13,257 --> 00:38:16,626
give way to a different
flavor of particles

725
00:38:16,727 --> 00:38:20,697
with different energies,
the general interstellar

726
00:38:20,798 --> 00:38:24,000
mix of particles that are just
hanging out in our galaxy.

727
00:38:25,403 --> 00:38:27,003
The solar wind actually smashes

728
00:38:27,104 --> 00:38:31,274
into and shocks up against the
gas of the interstellar medium.

729
00:38:31,375 --> 00:38:33,410
We discovered the edge
of our solar system.

730
00:38:33,511 --> 00:38:35,645
And it was much more
dramatic, much more active

731
00:38:35,746 --> 00:38:36,880
than we anticipated.

732
00:38:39,383 --> 00:38:41,918
NARRATOR: Interstellar
space is violent

733
00:38:42,019 --> 00:38:44,888
and dangerous, teeming
with lethal radiation.

734
00:38:47,591 --> 00:38:51,594
Supernova blasts and
colliding neutron stars

735
00:38:51,696 --> 00:38:54,831
send cosmic rays across
the galaxy straight

736
00:38:54,932 --> 00:38:56,032
toward our solar system.

737
00:38:58,769 --> 00:39:01,271
But these deadly threats
are stopped in their tracks.

738
00:39:03,941 --> 00:39:05,452
MICHELLE THALLER: We
really do live inside kind

739
00:39:05,476 --> 00:39:08,745
of a protective bubble that's
being blown by the solar wind.

740
00:39:08,846 --> 00:39:11,281
You see, as the solar wind
moves out into our solar system,

741
00:39:11,382 --> 00:39:14,017
it carries with it the
Sun's magnetic field.

742
00:39:14,118 --> 00:39:16,319
That magnetic field
protects us from the highest

743
00:39:16,420 --> 00:39:19,622
energy particles the universe
can come up with... cosmic rays.

744
00:39:19,724 --> 00:39:22,525
In some cases, a single
proton can have as much energy

745
00:39:22,626 --> 00:39:24,060
as a 100 mile-an-hour fastball.

746
00:39:25,696 --> 00:39:27,664
NARRATOR: Without this
protective bubble, called

747
00:39:27,765 --> 00:39:32,402
the heliosphere, cosmic protons
would smash through your cells,

748
00:39:32,503 --> 00:39:33,503
damaging your DNA.

749
00:39:35,172 --> 00:39:38,508
Ironically, the
solar wind is deadly.

750
00:39:38,609 --> 00:39:40,643
But without it, we
wouldn't be here.

751
00:39:42,880 --> 00:39:44,447
PHIL PLAIT: Like
we saw with Mars,

752
00:39:44,548 --> 00:39:48,585
the solar wind has the ability
to wipe out life on Earth.

753
00:39:48,686 --> 00:39:52,122
But out there in the furthest
reaches of our solar system,

754
00:39:52,223 --> 00:39:54,524
it's defending life on Earth.

755
00:39:54,625 --> 00:39:56,593
So in a way, it's
a giver of life.

756
00:39:56,694 --> 00:39:57,560
And it takes life.

757
00:39:57,661 --> 00:39:58,661
A yin and a yang.

758
00:40:01,766 --> 00:40:04,401
NARRATOR: And now
for the first time,

759
00:40:04,502 --> 00:40:07,971
the Voyager probes have
looked back at the heliosphere

760
00:40:08,072 --> 00:40:12,976
from the outside, revealing
what our solar system looks

761
00:40:13,077 --> 00:40:14,944
like as it moves through space.

762
00:40:17,748 --> 00:40:20,316
Something that we lose sight
of sitting here on Earth,

763
00:40:20,418 --> 00:40:23,286
watching the Sun go around,
watching the planets go around,

764
00:40:23,354 --> 00:40:27,424
is that the Sun itself is
actually hurtling through space

765
00:40:27,525 --> 00:40:29,826
really, really fast on an
orbit around the center

766
00:40:29,927 --> 00:40:30,927
of our galaxy.

767
00:40:32,363 --> 00:40:34,631
If our Sun were
perfectly stationary,

768
00:40:34,732 --> 00:40:38,101
then the heliosphere
would be a perfect sphere.

769
00:40:38,202 --> 00:40:41,204
But because it's
moving, it's plowing

770
00:40:41,305 --> 00:40:43,640
through that
interstellar medium.

771
00:40:43,774 --> 00:40:45,875
And so that makes
one end shorter

772
00:40:45,976 --> 00:40:47,777
and the other end longer.

773
00:40:47,912 --> 00:40:51,548
And new research is showing it's
even more complicated than that

774
00:40:51,649 --> 00:40:54,150
where we might have
like a double tail,

775
00:40:54,251 --> 00:40:57,787
almost like a buttery
croissant surrounding the Sun.

776
00:41:00,458 --> 00:41:03,593
NARRATOR: Our Sun
shapes our world

777
00:41:03,694 --> 00:41:06,896
and protects us from the
dangers of interstellar space.

778
00:41:09,667 --> 00:41:12,302
It's the engine that drives
the entire solar system.

779
00:41:15,039 --> 00:41:19,275
And now, for the first time,
our fleet of solar spacecraft

780
00:41:19,376 --> 00:41:21,344
shows us how it works.

781
00:41:22,847 --> 00:41:24,547
We're pretty familiar
with the Sun, right?

782
00:41:24,648 --> 00:41:26,159
You see it all the
time during the day.

783
00:41:26,183 --> 00:41:26,950
Lights up the Earth.

784
00:41:27,051 --> 00:41:28,251
Provides us with heat.

785
00:41:28,352 --> 00:41:30,954
But observing it with all
these other satellites, all

786
00:41:31,055 --> 00:41:33,790
these observatories, has
shown us a side of the Sun

787
00:41:33,891 --> 00:41:35,191
that we knew nothing about.

788
00:41:37,261 --> 00:41:39,539
JESSIE CHRISTIANSEN: We have
this whole fleet of spacecraft

789
00:41:39,563 --> 00:41:41,931
orbiting the Sun taking
observations in all

790
00:41:42,032 --> 00:41:43,243
of these different wavelengths.

791
00:41:43,267 --> 00:41:45,902
X-ray, ultraviolet,
optical, infrared.

792
00:41:46,003 --> 00:41:48,705
They tell us about the
functioning of the Sun

793
00:41:48,806 --> 00:41:51,474
from its outer atmosphere
down to its deep core

794
00:41:51,575 --> 00:41:54,978
and give us a window into its
functions and its evolution.

795
00:41:56,914 --> 00:41:59,883
Put them all together, and we
finally have an understanding

796
00:41:59,984 --> 00:42:02,552
of our source of life itself.

797
00:42:02,576 --> 00:42:04,576
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