All language subtitles for How the Universe Works (2022) - S10E06 - Voyagers Ultimate Mission_track3_[eng]

[narrator] Voyager,

the most ambitious
space mission in history.

The two Voyager spacecraft
are iconic.

Iconic.

Iconic.

They're the first probes to
truly explore half the planets
in our solar system.

Jupiter, Saturn,
Uranus and Neptune.

These went from dots of light
in the sky,

to real worlds.

The Voyager missions have
ventured far beyond where other
probes have explored.

They are the most distant
emissary, representatives

of the human species.

They're the first spacecraft
to taste interstellar space.

[narrator] Exploring furthe
than any humanmade spacecraf
has gone before.

[narrator] These are
the logs of starships,
Voyager 1 and 2.

They have crossed
the final frontier

and are now
in interstellar space.

Almost a decade ago,

Voyager 1 achieved
something that had never
been achieved before.

It left our solar system.

When Voyager crossed
into interstellar space,

humans became
an interstellar species.

[narrator] 14 billion miles
from Earth,

their radio signals travelin
at the speed of light

still take 21 hours
to reach us.

The Voyagers are so far t

that when they look back
towards the sun,
it's just a pinprick of light.

And they would need
an exceptionally
powerful telescope

just to see the Earth.

[narrator] Their original
four-year mission has been
extended to 44,

and counting.

From their current
distant vantage point,

they look back
on strange new worlds

and bold new science
they've discovered.

August 20th, 1977.

[man] We have ignition,

and we have liftoff.

[narrator] The mission begin
when Voyager 2 blasts of

Followed two weeks later
by its twin, Voyager 1,

which will take a shorter
and faster route.

Their destination, Jupiter.

And then, Saturn.

When the time comes
that that mission is actually
ready to go to the launchpad,

it's a funny mixture of joy

and bittersweet loss.

[woman] They become like
your children.

And that launch is like
the birth of a baby.

I was standing there,
watching it climb up
into the sky.

We were cheering,
we were so happy.

Voyager was on its way.

[narrator] Though funded
to just explore
the two gas giants,

mission planners have a muc
bigger journey in mind.

To send the Voyager spacec

on a grand tour of
the solar system.

To the outermost planets,

Uranus and Neptune,

worlds that have
never been explored.

To visit each planet,

the probes must stick
to a strict schedule,

with only a quick flyby
of each world.

Once reaching Jupiter,

they must use every second
to complete close-up studie
of the planet

and its largest moons.

One of the biggest challenges
with flyby spacecraft is

it may have taken years
to get there,

but the actual time that
you're close to the planet

is remarkably short.

The Jupiter close-up data

occurred during just
three days.

[narrator] February 1979,

Voyager 1 begins beaming
pictures back to Earth.

It's an anxious wait.

[Cooper] This is pre interne

And so, when you look at
the data coming in,

it's coming in line by line,
pixel by pixel.

It was such an exciting time
it was hard to know
when to sleep.

I brought my sleeping bag
into my office

so I wouldn't miss
a single exciting picture.

[narrator] Both Voyagers
reveal an unbelievably
dynamic world.

Scientists were able to take
a sequence of images
of Jupiter

that they could put together
like a flipbook to get a sense
of motion.

And it was just astounding.

Now we can see things
moving within the atmospher
of Jupiter

in a way that we had
no sense of before.

[narrator] Together, the
spacecraft take over 33,000
images of the gas giant.

These pictures reshape
our understanding of Jupiter

Especially its largest moons

Ganymede,

Callisto,

Europa,

and Io.

We saw all sorts of different
kinds of landscapes on them

and each one had its own
individual type
of personality.

Of all the moons
around Jupiter,
and there are a lot,

Io is the one that
shocked everybody.

[Linda] We got back this
very unusual picture.

We saw this bright feature
on the dark limb of Io.

We wondered,
"What could it be?"

At first, they thought
that arc might be
another moon behind Io.

But the geometry was wrong.
There were no moons there.

Well, they figured out that
these were volcanic plumes.

And that bright feature
on the dark limb

was a volcano erupting on Io.

[narrator] Voyager 1 record
ash and lava

blasting 190 miles into spac

Eight times higher than
the largest eruptions
on Earth.

This is the first time
we'd ever seen another
volcanically active world

anywhere in
the solar system, right?

It really transformed
our ideas, our concept of
what a moon could be.

[narrator] But astronomers
were also baffled.

When scientists first saw
these images of Io,

they had to ask the question,
"How is this little moon
still so hot?"

On Earth, we know,
you know, it's a big planet,
it's volcanically active

because of plate tectonics,
and there's this,

you know, ancient heat system
inside the planet.

When you look at a little mo
like Io,

you expect, "Ah, it's gonna
be dead." RIght?

But instead, it's the most
volcanically active body
in the solar system.

[narrator] Io's volcanism
is powered by tidal heating

[Phil] As it orbits Jupiter

it gets stretched
and compressed by
the gravity of Jupiter

and the other moons
as they all pass by it.

[narrator] The compression
and expansion generates heat

melting Io's interior.

A planetary process

never before witnessed.

At Jupiter, the Voyagers
discover three new moons

and a ring system invisible
from Earth.

Not to be outdone,

the planet itself
has a few surprises.

The probes turn to
the gas giant's
most famous feature,

the Great Red Spot.

[Nina] Jupiter's red spot
is a feature

that has existed in
its atmosphere since we
began looking at Jupiter.

It's incredible.

What it turns out to be
is a storm

that has lasted centuries.

[narrator] The Voyagers re
a maelstrom of gas

swirling counterclockwise
between two bands
of high speed winds.

The red spot has been kept
in a single place

because it's kind of
sandwiched between these
two bands of atmosphere.

[Phil] Like a whirlpool or
an eddy in two currents

that are moving
next to each other.

that may have helped
promote its stability over
all these centuries.

[narrator] But Voyager's
closeup shots show

a far more complex structur
than we expected.

[Phil] It turns out,
the Great Red Spot
is not a single vortex.

It's more complicated
than that.

What you might expect from
a storm bigger than the Earth.

Voyager actually took
close up images of it and sa
several smaller vortices

spinning around inside of it

[narrator] These small
vortices are ten times large
than any hurricane on Earth

But the Voyagers
can't detect how they
interact with the spot.

It will take a new generatio
of space probes

to solve that mystery.

so, after Voyager had
flew past,

there were lots of questions
that went unanswered.

And Jupiter is a long way
from the Earth.

And really, the only way
to answer some of them
was to go back.

[narrator] 37 years after
the Voyager flybys,

the Juno probe
arrives at Jupiter.

[Carly] The Juno space probe
has a microwave radiometer.

That instrument is able
to detect microwave radiatio

coming from very deep
inside Jupiter.

And from that we're able to
determine things like
it's deep composition,

and its deep temperature.

[narrator] Juno finds
the Great Red Spot

stretches at least 200 mile
below the surface.

And in 2021,

a team combines Juno

with Hubble and
ground-based telescopes

to finally discover what
powers the gargantuan storm

These small storms that are
coming in

are rotating very quickly.

All of that feeds
the Great Red Spot
and keeps it spinning.

Gives it that spinning energ
that it used to survive.

[narrator] The Voyager pro
are ready for their
next destination, Saturn.

But to get there, they must
first fly dangerously
close to Jupiter.

[narrator] The next stop
on the Voyager probes'
grand tour of the solar system

is Saturn.

But the ringed planet is ove
450 million miles away
from Jupiter.

To get there,

the Voyagers will need
to perform a maneuver

known as
a gravitational slingshot,

which will catapult them
from one planet to the next

We allowed the large gravity
of Jupiter

to actually capture
the spacecraft

and start accelerating it
towards that massive planet.

But we did it
at just the right angle.

So we would move around it,
and then continue away from
the planet.

Jupiter itself is
barreling around the sun

at very fast velocities.

As you pull away from Jupite

you keep some of that
velocity with you.

[narrator] If it's successfu

the slingshot will knock yea
off the Voyager's journe

If things go wrong,
it's game over.

To do a
gravitational slingshot,

you need to do three things.

You need to have really
good calculations,

excellent planning
and perfect timing.

[narrator] Mission controlle
achieve all three.

And the maneuver works.

Voyagers 1 and 2 speed up
by 225,000 miles an hour

and race towards Saturn.

1980, right on schedule,

Voyager 1 arrives
at the ringed planet.

Its sensors probe
Saturn's atmosphere

and discover it's mainly
hydrogen and helium.

[Phil] Saturn has nearly
100 times the mass
of the Earth.

But it has so much more volu

that when you look at
its density, it's actually
less dense than water.

It's a very old joke
in astronomy

that if you put Saturn in
a bathtub, it would float.

But it would leave a ring.

[narrator] The most
striking discovery emerges
from the data

nine years after
Voyagers' flybys.

A bizarre cloud formation
at the north pole.

[Phil] A giant hexagon
over the north pole

with sides 9000 miles long

and it's 18,000 miles across.

Yeah, that's bizarre.

[Carly] We don't often
think about very stable
geometric shapes

like a hexagon. That feels
like it shouldn't happen,
right?

You don't get hexagon shaped
clouds on the Earth.

[narrator] What could possib
create a hexagon

more than twice
the size of Earth?

Voyager discovered
the hexagon.

But we didn't have
enough information to
truly understand it.

[narrator] Jump forward
24 years after Voyager,

and another probe arrives
at Saturn,

Cassini.

The main difference between
the Cassini mission
and the Voyager missions,

besides Cassini having more
cutting edge equipment on it,

is that it was an orbiter.

It orbited Saturn
for 13 years.

The Voyager missions just
flew past it.

[narrator] Cassini watches
the pole for several years,

capturing thousands of image
of the hexagon.

[Phil] The beauty of
the Cassini mission is th
it showed us what the hexago

looked like years later
after Voyager.

Didn't necessarily solve
the problem of why
this thing exists,

but it gave scientists
a lot of ammunition
to figure it out.

[narrator] Finally in 2020,

a team solves the mystery.

Many cyclones surround
a large jet stream of
the planet's north pole.

Where the two
weather systems meet,

a hexagon cloud forms.

Something we don't see here
on Earth.

[Carly] The trouble
with the Earth
is it has a lot going on.

We have oceans,
we have mountains,

all of that disrupts
the atmosphere.

On Saturn, there isn't
any of that.

So you're able to have thes
very stable airflows

that just wouldn't be possib
on the Earth.

[chuckles] Nature's
pretty wonderful.

[narrator] Next,
the Voyagers turn
their gaze to Saturn's rings

Their images are gamechanger

[Heidi] One of my colleague
in my undergraduate
planetary astronomy class

was a computer whiz.

And he managed to hack into
the NASA feed that was
going out.

We all piled into
his dorm room,

the professors, the students

seeing images coming from
the Saturn flyby.

[narrator] We thought that
Saturn had just a handful
of wide, flat rings.

Voyager's images reveal
thousands of separate rings

orbiting the planet.

But there's an even
bigger surprise.

An impossible ring.

When the F-ring of Saturn

close up image appeared
on the screen,

and instead of being sort o
a single ring,

it looked like multiple rings
that were braided together.

And my professor,
Irwin Shapiro,

famous planetary astronomer
professor said,

"That's not possible."

[narrator] Scientists pour
over the images

to figure out what's causin
the bizarre structure.

Our basic understanding of
rings back then,

was that they were collections
of little particles

that were all just following
the same orbit.

[Dan] You'd expect that syst
to have settled out into,

you know, all the traffic
on the highway,
driving in the same direction,

parallel lanes,
all nice and neat.

You don't expect these
weird, dynamic interactions
that are going on.

[narrator] Then, scientists
find two clues

to explain the interactions

And one of the things
that was discovered was
two satellites

that orbit inside and outside
of the F-ring.

Prometheus and Pandora.

It pointed to the idea that
the moons and the rings
were constantly interacting,

but it didn't really
tell us how.

[narrator] Voyagers' discove
of the moons doesn't solve
the mystery

of the braided F-ring.

But it does tell
the Cassini probe,

25 years later, where to loo

Cassini watches the tiny moo

looping and twisting
around each other

as they orbit the planet.

When you have two
little moons, sort of
co-orbiting with the ring,

there's a complex
gravitational dance
that happens

with the inner moon
wanting to speed up particle

the outer moon wanting to
slow them down.

And that interesting
gravitational dance

is what actually helps
confine the ring into

the narrow structure that
we actually see.

[Carly] By seeing these
moons either side,

there was an idea that
they could be shepherding,

they could be holding
the ring in place.

[narrator] Saturn's many moo
and complicated rings

are like a mini solar system

Now, the two
Voyager spacecraft separate

to carry out two
individual missions.

Voyager 1 heads off to explo
the edge of the solar system

and Voyager 2 flies int
the freezing cold

of Saturn's shadow.

For over two hours,

the giant planet blocks
all contact with
the space probe.

After a tense wait,

Voyager 2 emerges.

But something's wrong
with the spacecraft.

[Linda] Picture after pictur
of dark sky came back.

And we realized,
something had either happened
to the cameras,

or something had happened
to the scan platform.

[narrator] The scan platform

the vital rotating joint tha
points the probe's instrumen

isn't working.

But how can scientists
fix a probe

2 billion miles from Earth?

[narrator] August, 1981.

Pioneering space probe,
Voyager 2 , is in trouble.

Passing behind Saturn,

one of its key components,
the scan platform, jams.

[Linda] The scan platform
is kind of like your
head and neck.

Imagine the cameras
as your eyes.

And if you want to turn
to look at something,
you'd turn your head.

And your neck has to move.

[narrator] When Voyager 2
passed behind Saturn,

it ploughed through the ring
at 29,000 miles an hour.

Maybe a chunk of ice
damaged the platform.

Or maybe the maneuver
gave the probe whiplash.

We had been so ambitious
in looking at the moons
and the rings and Saturn,

that we had literally squeezed
the lubricant

out of the bearings
of the scan platform.

And it got stuck.

[narrator] The broken
scan platform could be fata

for the rest of the mission

[Linda] And so, we worried,
"Could we fix it?"

We had Uranus and Neptune
ahead of us with Voyager 2.

We wanted to be able
to fix the scan platform.

[narrator] To fix it,

the engineers employ some
space physiotherapy.

We slowly commanded it
from Earth and got it to move
a little bit at a time,

until finally we could get
those beautiful outbound
pictures of Saturn

that you see.

[narrator] With Voyager
operational again,

NASA agreed to fund
the next stage of the missio

[Heidi] I'm eternally gratef
that NASA did decide to

complete the grand tour.

It was tremendous
relief to know we had
a healthy spacecraft,

Voyager 2,

to go on to
Uranus and Neptune.

[narrator] 1986,

boosted by a slingshot
from Saturn,

Voyager 2 arrives at Uranus

After nine years in space,

the probe is now in
uncharted territory.

[Carly] Ahead of
Voyager's encounter,

Uranus was really
difficult to know much about

We knew what its color was,

but it didn't have any obvious
features from the Earth.

It looked sort of like
a generic green blob.

[narrator] We did know
a couple things.

Uranus has rings

and sits on its side.

[Dan] Unlike most of
the other planets,

whose spin axis are oriented
more or less perpendicular
to their orbital plane,

Uranus is tipped over
on its side,

it rolls around the sun
like a barrel at times.

There are other times when
the sun is shining right dow
the equator.

It's very unusual.

[narrator] In a flyby lastin
just five and a half hours,

Voyager 2 discovers
11 new moons,

and two more ghostly rings
circling Uranus.

But Voyager 2's
strangest discovery

is the planet's freakish
magnetic field.

Voyager carried
a magnetic boom
that told us about

the magnetic field
of the planet.

And that turned out to be
really interesting.

[narrator] The strength
and direction of Uranus'
magnetic field

turns out to be unlike
any other planet.

[Phil] The Earth has
a magnetic field

and it's pretty complicated
how it behaves.

But you can think of it as if
there's a giant bar magnet
inside the planet.

There's a north magnetic pol
and a south magnetic pole,

and magnetic field lines
around them.

[narrator] On Earth,
the bar magnet lines up clos
to our planet's spin axis.

The Voyager probes foun
the same in Saturn
and Jupiter.

But Uranus'
magnetosphere is different.

The north and south axis
of the magnetic field
is tilted

by almost 60 degrees,

relative to the spin axis
of Uranus.

That's strange.

[Dan] If you imagine
transforming the Earth's
magnetic field to be like

the Uranus one,

you'd have the magnetic
north pole near
Miami someplace.

It's way out there
in left field.

[narrator] And the magnetic
field isn't just tilted.

[Dan] It's off center!
The center of
the magnetic field,

you think would be at
the center of the planet,

it's actually offset
by 5000 miles,

which is a lot.

We think it may be generated
in the mantle of Uranus,

where there is molten water,
not molten iron.

[narrator] Extreme heat
and pressure breaks
water molecules apart

and rearranges them into
a molten crystal structure,

an exotic state called
superionic ice.

When we talk about ice,

like, superionic ice
inside a giant planet,

we're not talking about
ice cubes. [chuckles]

Water has lots of
different ways of being.

And some of them
are really strange.

[narrator] The half liquid,
half solid ice

swirls around in the outer
layer of the planet,

moving like liquid metal.

Because the ice
conducts electricity,

this produces the offset
magnetic field around Uranus

Voyager 2 also uncovered
a gigantic magnetic glitch

but it remained hidden
in the data

until scientists discovered
in 2020.

[Phil] What they found
was a blip,

a strengthening of
the magnetic field,

and it was about
a million miles behind Uranus.

And whatever was causing this
was quite large.

[narrator] It's a giant
magnetic bubble,

250,000 miles across,

floating in space.

[Phil] This type of
magnetic bubble is called
a plasmoid,

and it happens when
the magnetic field lines ge
pinched off

and it can create, sort of
a self-contained shell.

This means that
the magnetic field
around Uranus

is dynamic

and can fracture and
interact with the solar win
in very interesting ways.

This can also have
some of the atmosphere
of Uranus in it.

So, it's literally leaking gas
into space.

Uranus is belching.

[narrator] It will take
another mission to Uranus

to truly understand
this strange world.

For now, Voyager 2
is the only spacecraft
to ever visit.

And what awaits the probe ne

could be Voyager's
greatest discovery yet.

[narrator] 1989,
Voyager 2 makes
one last flyby.

Neptune is the final stop
on the planet hopping tour

of the outer solar system.

It's once in
a lifetime opportunity

to study the blue ice giant
up close.

[Heidi] We had
these hints from our
ground-based telescopes

that there was activity
in the atmosphere.

But what its nature was,

what was it like?

There absolutely was
nothing we had to prepare us

for what we were going to see.

[narrator] Voyager 2 spots
four new rings
and six more moons.

It detects hydrogen,
helium and methane in
Neptune's atmosphere.

And it records the fastest
winds in the solar system,

pushing white clouds across
the planet

at up to 1500 miles an hour

And at their center,

a colossal dark storm.

[Heidi] There was a dark spo

A big, dark spot
on the disc of Neptune.

We hadn't seen anything
like that from the ground.
[laughing]

It was like, "What is that?

Uh, we called it
"The Great Dark Spot"
because...

that's all we could think of
at the time.

[narrator] Five years later

when astronomers looked
for the Great Dark Spot wit
the Hubble Space telescope,

they get a surprise.

[Heidi] I was gonna look at
how it changed with time

and, you know,
where it was located,
things like that.

And I remember,
I got my first images
back from Hubble.

No Great Dark Spot.

It was gone.

It simply wasn't there.

[laughs] I'm like,
"What happened?"

How is this even possible?

The great Red Spot
on Jupiter's lasted for
hundreds of years.

This is only five years,
and this huge feature

was simply gone.

[narrator] Since Voyager,

we've seen seven different
dark spots on
Neptune's surface.

None lasting more than
a few years.

As to why that is
and what's driving that,

um, those are still mysteries
that we haven't fully solved.

[narrator] Before leaving
the Neptune system,

Voyager 2 turns its gaze
to Neptune's largest moon,

Triton.

It was sort of a bit like,
Voyager's last hurrah,

sort of one of the last things
that it showed us,
and it was just phenomenal.

[narrator] Voyager 2's
instruments reveal
a frozen world.

At 391 degrees below zero,

Triton is one of the coldes
objects in the solar system

[Linda] Here was a very
intriguing world.

We saw these dark streaks
on the surface

and realized that they were
actually sticking up above
the surface.

What they were seeing was
an active cryo volcano

jetting a jet of
black material,

something like eight miles
up above the surface
of Triton.

And then, the atmosphere
of Triton was sheering it ou
into a large cloud pattern.

That was one of
our first indications

of geyser-like activity on
a planet other than the Earth.

It was almost pandemonium

trying to figure out how
do you generate this kind
of activity

on a moon that should be
cryogenically frozen solid.

Where is the energy source
for this?

[narrator] In 2019,

scientists finally identify

frozen nitrogen
and carbon monoxide
in the streaks.

We think now what actually
is going on there is
it's the action of sunlight

shining in some of the darker
deposits on the surface
of the moon.

Just a little bit of
a temperature change

can take the nitrogen
and liberate it off
the surface.

[narrator] In their grand to
of the solar system,

the Voyager probes produ
an astounding number
of discoveries.

[Dan] Volcanoes on Io,
geysers on Triton,

and little weavy features
on the Rings of Saturn,

it all turned out to be
far, far more interesting
and alive

and dynamic than
we ever imagined.

[narrator] While Voyager 2
leaves the planets behind,

its twin, Voyager 1,
heads to the edge of
the solar system.

But not before taking
one last snapshot of home.

A family portrait.

[Phil] This idea by Carl Sag
to take this family portrai

is just magnificent.

And the scientific need
for it may be limited

but the appeal to our sense
of beauty,

is staggering.

[narrator] This shot isn't
in pursuit of a new discover

It's about finding
a new perspective.

[Phil] This family portrait
is a series of 60 images

put together into a mosaic.

And in it you can see
the sun and six planets,

Venus, Earth, Jupiter, Satur
Uranus and Neptune.

As we're sending the images,
we noticed along
one of these sunbeams,

there was the Earth.

That pale blue dot,

which contains every
single person.

We realized just how tiny
our planet is.

And how very special.

It's one of the most
amazing and beautiful things
I've ever seen.

[narrator] February 1990,

the cameras power down
for the last time.

But this mission isn't over

The Voyager probes
are about to reach the edge
of the solar system,

a region no spacecraft
has been to before.

[narrator] Far from the sun

at the very edge
of the solar system,

lies a vast expanse

where no human-made object
has ever entered.

Until the Voyagers.

This is like early explorers
leaving sight of land.

They are just surrounded by
a vast ocean of night.

They are all alone.

It's sort of like the boat
going from the bay,
out into the open ocean.

It's a whole
different environment.

[narrator] The Voyager pro
are about to leave the calm
of the solar system

and enter the stormy waters
of the galaxy.

They start to exit
the heliosphere,

a protective bubble around
the whole solar system

and cross into a combat zon

that hosts a cosmic battle
between the sun
and interstellar space.

Inside the heliosphere,

waves of particles
from the sun,

called the solar wind,
push outward.

Outside, an ocean of gas
and particles

pushes back.

As the solar wind is
expanding away from the sun,

it's pushing against this
thin stuff between the stars

the interstellar medium.

[Paul] That's the last
influence that the sun has

in the bubble surrounding it.

Once you cross that,
you are in interstellar space.

[narrator] The heliosphere'
frontline protects us

from one of the galaxy's
deadliest weapons,

high energy particles
called cosmic rays.

Cosmic rays are like
tiny bullets

and they travel at
close to the speed of light.

[narrator] December 2004,

Voyager 1 detects a sudden
drop in the solar wind,

evidence that the space prob
is nearing the heart
of the battlefield,

a region known as
the Termination Shock.

[Paul] The Termination Shoc
is the region

where the solar wind
starts to meet resistance,

starts to run into something.

And that causes it
to slow down.

[narrator] Voyager 1 picks u
surges from both
opposing forces,

blasts of cosmic rays,

followed by waves
of the solar wind.

The instruments
onboard Voyager didn't just
suddenly change from

sun space to galaxy space.

It actually kind of went
back and forth several times

as it was measuring
the energies of the particle
at that region.

[narrator] This suggests tha
the edge of the heliosphere

is not a single battlefront

but rather, a complex regio
of skirmishes.

A sea of gigantic,
magnetic bubbles

created by the sun's
magnetic fields.

The sun's magnetic field
rotates with the sun,
physically.

But this far out, billions of
miles from the sun,

those magnetic field lines
get dragged by particles

and there's a lot of different
effects on them.

And they can get tangled up
and loose.

This creates bubbles,

and some of these bubbles
are a hundred million
miles across.

[narrator] The magnetic bubb
boundary is not watertight.

Some cosmic rays
blast through.

[Paul] This heliosphere
is much more foamy
than we had thought.

There are gaps in our defens

where deadly cosmic rays
can find their way through

into the inner solar system

[narrator] The foamy defensi
line blocks 90 percent
of cosmic rays

but allows 10 percent throug

As Voyager 1 passes throu
the battlefield,

it detects fewer and fewer
solar particles.

Eventually, there are only
cosmic rays

and interstellar space.

In 2012, the probe becomes
humankind's first object

to leave the solar system,

followed in 2018 by Voyager.

It's been 50 years since
the first satellite

poked their way out of
the Earth's atmosphere.

And now,
both Voyager spacecraft

have poked their heads out
of the sun's atmosphere,

are outside the solar system

and exploring the galaxy.

[narrator] The Voyagers cr
the final frontier

and sail the ocean
between the stars.

They don't see
their first discovery,

they hear it.

In space, no one can
hear you scream.

There is no actual soundwaves
moving around.

But there are waves of plasma.

Of electrons.

[Phil] So, as Voyager pas
through this, we can transla

these changes in
the plasma density
to soundwaves.

[deep space sounds]

[narrator] This is the soun
of interstellar space.

Poetically, I kind of like
to think of it as the song
the galaxy is singing,

welcoming Voyager
to interstellar space.

[Paul] Some of the sounds
may even come from
distant supernovas.

Think about that, a star dyi

tens of thousands
of lightyears away

and here's an echo of it,
here.

[narrator] The sounds of
deep space tell us more abou
our part of the galaxy.

[Paul] As Voyager travel
through the interstellar
medium,

we can use these sounds to
map out its local environment.

And since 2017, we've been
mapping how these sounds
get higher,

and lower and higher,
louder and softer,

and it's telling us that
the interstellar medium
is not uniform at all.

[narrator] Built to last
five years,

Voyager 1 and 2 are now
more than 40 years old.

Only one final
mission remains,

perhaps the most
important mission.

To let the rest of the galax
know we're here.

[narrator] The Voyager
spacecraft are now outside
the solar system.

Our sun is just
the brightest star among man

How much longer can the prob
keep going?

[Linda] A limiting factor
on the mission has
turned out to be power.

And every year there are
four watts less power

to run each of
the Voyager spacecraft.

There are no service stations
out there, no way to,

you know, repair things
that go wrong.

And it's really remarkable,
the fact that they're still
out there,

in the cryogenic cold,

you know, operating,
they're still working.

They're still alive.

[narrator] In just five year
there may be too little powe

to transmit signals to Earth

After a final message home,

the Voyagers will
fall silent forever.

This part of
the Voyager mission,

flying in interstellar space,

is the long goodbye.

[Dan] They're gonna become
our messages in a bottle.

Little bit of humanity,

you know, representing us
when we're long gone.

[narrator] The two probes
could survive for
billions of years.

They could be not only,
you know,
interstellar voyagers,

they could turn into
intergalactic voyagers,
ultimately.

[narrator] Maybe the Voyages
won't just drift forever.

Maybe they'll be found.

[Michelle] It was kind of
a wonderful little jaunt
of imagination.

that maybe some alien
civilization with incredibly
powerful telescopes

might notice that there's
a little artificial object

flying through space
and be curious about it.

[narrator] Strapped to each
Voyager is an aluminum case

On the outer side,
is a map of how to find Eart

with directions from
different pulsars.

[Michelle] So why use
pulsars to direct
the aliens to our location?

These are the dead cores
of stars after
a supernova explosion.

Well, amazingly,
pulsars all spin
at slightly different rates

So, if you can actually
triangulate your location,

based on the rates of
different pulsars
in the sky,

you can actually have
sort of a galactic GPS system.

You can show the aliens
where we are with
incredible accuracy.

[narrator] Inside each case

a gold plated copper disc.

[Michelle] Looking back on i

it's really kind of
this wonderful part
of humanity.

We sent aliens out there,

unimaginably, technologically
advanced aliens,

we sent them, basically,
a vinyl record.

[Paul] Yeah, the golden disc
are literally discs.

They actually are records
with grooves.

You can play them.
You can jam out to them.

It's got a soundtrack
of our species.

[Beethoven's
'Fifth Symphony' plays]

[narrator] The records have
tracks by Beethoven,

Blind Willie Nelson
and Chuck Berry,

the sound of surf, of thunde
of birdsong,

and a human heartbeat.

So, will aliens ever find
the records and give them
a spin?

[Phil] The Golden Record is
a lovely idea.

Especially to energize
and excite the public
about this.

Will it ever be found?

There's a reason
we call it space.

[narrator] A tiny,
cold spacecraft

is a difficult target to fin

Any species capable
of detecting them,

would have a better chance
of spotting our planet.

But the Voyagers will
long outlive Earth.

[Michelle] It's possible tha
they will find it millions,

or even billions of years
in the future.

Long after we are gone.

When there really
aren't humans anymore.

Or is there even a possibility
that when we start traveling
to the stars

in the far future,
we'll find them.

[narrator] Awaiting discover

or doomed to drift alone,

the Voyager probes have
already inspired
one civilization,

ours.

Calling these " Voyager "...
[kisses] ...it's perfect.

Because that's what
they are doing.

They are voyaging out
to the outer solar system
and beyond

and showing that there is
no end to our desire
to explore.

[narrator] They've shown us
countless wonders of
the solar system

and a glimpse of
what lies beyond.

[Heidi] We, as a species,

can build ships

that not only sail
the oceans of our Earth,

but that can sail outwards,

to the other planets
in our system

and reveal new worlds.

[narrator] They are the
greatest space mission ever

[Paul] The legacy of Voyagr
is our remnant.

It is our memory.

It is a sampling of humanity

that is out there now
among the stars.

[narrator] And if they last
until the death of
the Universe,

as the final stars fade,

and everything goes dark,

they will be humanity's
final statement,

"We were here."