All language subtitles for A.Travelers.Guide.to.the Planets.S01E06.Pluto.&.Beyond.2010.1080p.BluRay.DD5.1.x264-c0kE_track3_[eng]

MAN: T minus 40 seconds.
Everything looks good for launch.

NARRATOR: Want to get away
from it all?

Pluto is one of the loneliest
places you'll find.

Smaller than our own moon,

Pluto has never had
a single visitor from Earth...

until now.

WOMAN: We keep saying, "This is it,
this is humanity's trip to Pluto."

NARRATOR: For the first time
in human history,

Pluto is about to be revealed.

MAN: We can expect surprises.
It's almost guaranteed.

NARRATOR: Until then, we can
only guess what Pluto looks like.

And recently, astronomers decided
not to call it a planet anymore.

MAN: | will probably go down in history
as the guy who killed Pluto.

NARRATOR: Once thought to be
an isolated oddity,

Pluto now marks the beginning
of a whole new frontier.

WOMAN: It's as if the explorers
had climbed up to the top of the Rockies

and were looking over

and could see the lands
of California on the other side.

NARRATOR: And now, as we begin
to gaze beyond our own neighborhood,

the hunt is on for Earthlike worlds
around other stars.

MAN: | have no doubt that
within a few light years of our Earth

there are other life forms.

NARRATOR: There has never
been a better time to venture

where no human has gone before...

to follow in the footsteps
of our robot pioneers

and explore the planets
of our solar system.

MAN: T minus two minutes
and counting.

MAN: Go at throttle up.

NARRATOR: Ever wanted
to be an astronaut?

Imagine it was you who was heading
to the edge of our solar system.

Where would you go?

What would you see?

And how would you survive?

Recent discoveries have revealed
much more about these frozen depths.

Armed with this new knowledge,

think of this as your personal
travel guide to Pluto and beyond.

A fan of winter sports?

Like the feeling of isolation?

Don't mind the cold?

Welcome to ice land!

Out of sight--
and until now, out of reach--

Pluto is the solar system's
most puzzling world.

Why is it pink?

Where did it come from?

And how are we connected to it?

JOHN SPENCER: Pluto is such
a mysterious place,

we really have no idea what it's
going to look like when we get there.

And that really adds
to the wonder of it.

NARRATOR: Pluto is
uncharted territory.

We know so little about this place,
but it's not a complete mystery...

FRAN BAGENAL: Well, we know that
it's an object that is roughly round,

it has ice and a lot of dirt
on the surface.

HAL WEAVER: Pluto is a very cold world
for one thing, you know,

roughly minus 390 degrees Fahrenheit
on the surface.

KEVIN SCHINDLER: If you could
somehow have your hand exposed,

if you hit it, your hand would shatter
like an ice cube, it's so cold out there.

NARRATOR: To get a sense
of Pluto's scale,

imagine a world that's half
the width of North America,

sprinkle it with ice and toss it
3.7 billion miles into space.

Unlike the mostly circular orbits
of its big brothers,

Pluto's journey around the sun
is extremely elliptical and lengthy.

BAGENAL: Pluto's year
is 248 Earth years.

So it's a very, very long time
for Pluto to orbit the sun.

HAL LEVISON: And we really didn't know,
understand, how small Pluto really was

until 1977, when its satellite
was discovered.

NARRATOR: Charon, the largest
of Pluto's three moons,

isn't huge--
just 737 miles in diameter--

but compared to Pluto,
it's a whopper.

WEAVER: Charon is unusual

because even though we think of it
as a moon of Pluto,

it's really more of a companion object
that's almost the same size--

about half the size of Pluto.

NARRATOR: Named after the god
of the underworld,

for more than 70 years
school kids are taught

that Pluto is the ninth planet.

And it's a class favorite.

MIKE BROWN: Pluto has this place
in people's heart

that it's hard to understand,

except that even | sort of feel
it's the distant one,

it's the runty underdog,

it's the one that has a cartoon character
named after it.

Everybody loved Pluto.

WOMAN: Pluto is a planet!

NARRATOR: But recently
this small-sized planet

has been the subject
of a neighborhood dispute

of cosmic proportions.

WOMAN: Pluto is a planet!
Size doesn't matter!

GEOFF MARCY: It's a highly controversial
topic, even today.

Poor little Pluto, of course,
being demoted.

And frankly, rightfully so.

NARRATOR: What on Earth caused Pluto
to be kicked out of the planet club?

Just what's going on at the end
of the solar system?

One mission is about to find out.

But to get there means setting out
on a three-billion-mile journey

to the edge of our neighborhood.

NARRATOR: Aiming for Pluto?

You'd better shoot straight.

Miss your target, and you could end up
a very long way off course.

It's something that Hal Weaver
thinks about often.

He's the Project Scientist
on NASA's current mission to Pluto,

New Horizons.

WEAVER: Oh, yes!

When you're shooting
a basketball,

you have to get the angle
and the speed just right

in order to get the ball
through the hoop.

And that's what we had to do
for the New Horizons spacecraft.

MAN: Two, one, zero,
ignition, liftoff.

NARRATOR: Launched in 2006,
New Horizons is set to become

the first visitor ever to Pluto,
due to arrive in 2015.

WEAVER: We had the most powerful rocket available
on the Earth,

the Atlas V 551.

It was the fastest spacecraft
ever to leave the Earth,

36,000 miles per hour.

It was screaming out.

WOMAN: We keep saying, "This is it,
this is humanity's trip to Pluto."

NARRATOR: Miss it, and we'll
miss the only opportunity

to explore Pluto in our lifetime.

WEAVER: Because it's heading
farther and farther away from the sun.

And if we didn't do this now,

we would have to wait probably
another 250 years.

We get one shot,
| have to get it right.

This is our one chance to go
to Pluto in my lifetime.

Whoa! There it goes.

And we made it!

WOMAN: Mon, this is
Pluto Ace, go ahead.

Station 43, Pluto Ace.

NARRATOR: Keeping vigil over
New Horizons' long, lonely journey

is the job of these flight controllers
at the Applied Physics Lab

at Johns Hopkins University
in Maryland.

WOMAN: Could you please tell us

what our current downlink
configuration is?

ALICE BOWMAN: Mission duration
for this mission is very long.

And so one of the things
we do to save costs

is to put the spacecraft into hibernation
a good portion of the year.

NARRATOR: Beyond the orbit of Saturn,

New Horizons awakes from its slumber
for its regular check-up.

WOMAN: That's affirmative,
we are go for command.

NARRATOR: Ever have problems
with your computer?

Try loading software to a hard drive
that's 1.4 billion miles away.

BAGENAL: The difficult thing about Pluto
is the fact that it's so far from the sun,

we're so far away from home.

We have to design and plan
a sequence of observations,

and they've got to work.

We don't get a second chance.

NARRATOR: Today's upload
goes without a hitch.

But as the spacecraft
travels farther away,

the communication times
get longer.

When New Horizons phones home
from Pluto in 2015,

its signal will take more than four hours
to reach Earth.

WEAVER: Encounter day is going to be
nerve-wracking and exhilarating.

You know, it's Bastille Day in 2015.

It will be roughly a day
after we fly by Pluto

that we should have our first glimpse
at what Pluto really looks like.

NARRATOR: And that glimpse
will be brief.

After ten years getting there,

New Horizons has only a few months
to explore Pluto in detail.

WEAVER: This is the model
of the New Horizons spacecraft,

one eighth of the actual size,
and it's about the size of a grand piano.

We have the long-range
reconnaissance imager,

our "eagle eyes" on
the New Horizons spacecraft.

This is the highest resolution
telescope that we have.

NARRATOR: Other instruments
will peer at Pluto in ultraviolet light,

collect dust in its upper atmosphere

and measure charged particles
from the solar wind

to determine if Pluto
has a magnetosphere.

WEAVER: The New Horizons mission

is something that future generations
are going to look back on

and Say that this is one of the marks
that we made in civilization,

the initial exploration,
the initial reconnaissance

of this whole new region
of the solar system

that had never been
explored before.

BAGENAL: | have
a bumper sticker on my car

that says, "My other vehicle
is on its way to Pluto."

WEAVER: | love this thing!

NARRATOR: July 14, 2015,
is a date to remember--

when a tiny world
at the end of the solar system

finally gives up its secrets.

In 1930, a young American researcher,
Clyde Tombaugh,

scanned the skies for Planet X...

a world that was thought
to exist beyond Neptune.

CLYDE TOMBAUGH: It was
a very exciting time,

and | remember it
like it happened yesterday.

There was never another moment
in my life like that.

DAVID LEVY: | knew him very well.

He was a wonderful man
with a sublime sense of humor

and a lovely sense
of the ridiculous.

We had a lot of fun together.

SCHINDLER: Discovering Pluto
was very tedious,

| think that's the best word
to describe it.

During the nighttime
he would take pictures of the sky

on these photographic glass plates.

And then during the daytime

he would mount the plates
onto this machine,

look through this eyepiece.

And then, when you turn this on,
there's a mirror that flips back and forth.

And what you're doing is comparing
one picture to the other

to look for any changes.

NARRATOR: The machine
allowed Tombaugh

to flip between his time-lapsed
photographs of the night sky.

What he was searching for was
a single tiny pinprick of movement

against a sea of countless stars.

SCHINDLER: He would just
plug away at this, hours a day,

stare through this microscope eyepiece
looking at dots.

Hundreds of thousands of dots
he looked at.

LEVY: And on the 18th of February, 1930,
about four in the afternoon,

he saw the two images of the planet
appear and disappear alternately.

NARRATOR: These are the actual images
that show the discovery of Pluto:

First in one part of the sky...

And then another.

It's proof of a planet on the move.

TOMBAUGH: And | recognized it
immediately.

| knew instantly it was
beyond the orbit of Neptune

because of the small shift.

It made my day.

Ha!

NARRATOR: For the next 76 years,
Pluto is counted as the ninth planet.

But what does this tiny dot in the sky
really look like?

WILL GRUNDY: We do know
a lot about Pluto now,

a whole lot more than we knew,
say, 20 years ago.

And in large part that's driven
by the advance in technology

of telescope detectors
and telescopes.

NARRATOR: Peeling back
the layers of Pluto

is a little like solving
a cosmic whodunit...

and it's a mystery that stretches

back to the beginning
of the solar system.

GRUNDY: Kind of like
the crime scene photographer,

you see a few blood spatters
on the wall,

you've got to try to work out
what happened,

based on that little evidence
that's still left over.

NARRATOR: One clue
to unveiling Pluto

comes from NASA's
orbital telescope, Hubble.

These are some of the best images
we have of Pluto.

What the blotchy pixels show

is a world that's stamped
with light and shade.

What causes such
dramatic contrasts?

It could be that Pluto has
patches of ice and rock,

much like Colorado's
Rocky Mountains.

JOHN SPENCER: We do have
some idea what it looks like.

We know that it's
a very contrasty place.

There's black
or very dark brown areas.

And then there's some
extremely bright areas,

kind of like the snow
on the mountains here.

NARRATOR: As a member
of New Horizons' imaging team,

it's part of John Spencer's job
to guess what the surface of Pluto is like.

One piece of advice--
pack your snow boots.

SPENCER: Oh, dear. Ha ha!

So the snow on Pluto,

if you were to sit down
next to it like this,

would kind of look like this,
maybe, we don't really know.

It would be made
of nitrogen, not water.

But you might expect
big banks of snow

left over from the previous season.

NARRATOR: Spectroscopy, or the analysis
of an object in different wavelengths,

has revealed that Pluto is made
of three types of ice...

mostly nitrogen, and a little
carbon monoxide and methane.

But less is known about Pluto's
large expanses of dark material.

SPENCER: The dark stuff on Pluto
is more mysterious.

We think it's probably some sort
of hydrocarbon gunk

from the methane that's
in the atmosphere

being processed
by ultraviolet light.

NARRATOR: Pluto's not alone
in having a mysterious dark coating.

When the Cassini spacecraft
flew past Saturn in 2004,

we saw something similar
on moon Phoebe.

Here, scientists believe, is a thin carpet
of carbon-bearing compounds...

the precursor for the evolution of life.

BAGENAL: If you take methane,

which is organic because
it's got carbon and hydrogen,

if you expose it to sunlight,
you expose it to energetic particles,

it goes a sort of pinkish color.

You have chemical reactions,

so it becomes a slightly
more complicated hydrocarbon.

NARRATOR: These slowly simmering hydrocarbons

could explain Pluto's other feature
that spectroscopy has revealed--

its color.

BAGENAL: Well, it has a bit
of a pink tinge to it.

| don't think it would be a flaming pink,
but a slight pink tinge.

SPENCER: It might even have
this kind of brownish color

that we have here on the snow
due to dirt mixed into it.

We do think the snow on Pluto
is kind of a creamy, browny color.

BAGENAL: Well, | wonder
what it would be like

to walk on the surface.

The ice--would it be crunchy,
or would it be soft?

Are there big cliffs?

Is the sort of snow just sort of
beautifully sitting on the surface

like a Christmas morning?

LEVY: Just an absolute cold,
sublime, terrible beauty out there

that | can't wait to see.

But | think it's going to be
one of the most spectacular things

humanity has ever gazed upon.

NARRATOR: And there is one tourist sight
you'll see nowhere else in the solar system--

Pluto's largest moon, Charon,
in a fixed position against the heavens.

BAGENAL: So we have Pluto and Charon,

each orbiting around the center of mass
between the two systems,

so this is the balance point right here
between the two objects,

and they orbit around that point.

So both Pluto revolves around Charon,
and Charon revolves around Pluto.

NARRATOR: The cause for this orbital ballet
is Charon's comparatively large size.

WEAVER: They're almost
like a double planet.

The only example of that kind of an object
that we know in the solar system.

SPENCER: On Pluto,
there's one side of Pluto

where you would
never see Charon

and one side where
you would always see it.

And they're rigidly locked.

You could build a bridge between
the two of them if you were so inclined.

So that's really a remarkable
and unique thing.

NARRATOR: So does the double planet
with three types of ice have four seasons?

We'll see, but it's best
to be prepared.

What we do know is that Pluto
has surprisingly complex weather.

Barely contained by its low gravity,

Pluto's whisper-thin atmosphere

is the first thing a visitor
will encounter here.

BAGENAL: Well, we think the atmosphere
is probably a bit like our atmosphere,

made out of nitrogen,

with some methane, and maybe
some carbon dioxide.

SPENCER: And then as you come
down towards the surface,

you'd probably encounter
some layers of haze.

NARRATOR: But watch
where you land.

On summer days, the Plutonian ice below
will literally vaporize into thin air.

BAGENAL: You can think of the atmosphere being a
bit like a frosty morning,

with evaporating stuff
coming off an icy surface.

NARRATOR: Come winter,
gentle Plutonian breezes

carry the atmosphere
to the dark side,

where it freezes and falls
to the ground again.

Camp out here, and you'll soon be covered
in a dusting of nitrogen frost.

SPENCER: The temperature there
in the icy regions,

which will be the coldest regions,

is probably only about 40 degrees
above absolute zero.

NARRATOR: Absolute zero,
or minus 460 degrees Fahrenheit,

is as cold as it can
theoretically get.

Summer days
aren't much warmer.

But it's during this time when Pluto's
fragile atmosphere comes to life

and is eroded away by the solar wind.

WOMAN: It probably has lost
maybe up to half a mile of ice

over the age of the solar system,

which is kind of interesting.

It means that when New Horizons
flies by Pluto and takes close-up pictures,

we might see what we call
“sublimation scarps,"

so huge cliffs left from where the ice
has evaporated away.

NARRATOR: It could be that Pluto
has spectacular cliffs,

like those seen
on Uranus' moon Miranda...

carved by millions of years
of seasonal erosion.

WOMAN: We can actually
with a straight face

talk about trying to understand
weather on Pluto.

And that's one of the most fantastic things
for me in the last few years.

NARRATOR: Planetary scientist
David Jewitt couldn't understand

why the outer solar system
seemed so empty,

why Pluto seemed alone.

DAVID JEWITT: So the inner parts
of the solar system in the 1980s

were known to be full
of comets and asteroids

and all the planets and so on.

But the outer parts
basically had nothing.

And beyond Neptune
there was just Pluto.

And that seemed very strange.

NARRATOR: Then, in 1992,
he makes an extraordinary discovery:

the first of a vast army of frozen bodies
beyond the orbit of Neptune,

now known as the Kuiper belt.

JEWITT: The Kuiper belt is basically
a warehouse of icy bodies,

things that have been preserved
at temperatures

maybe 200 degrees colder
than the room I'm standing in right now.

NARRATOR: Out here
keeping Pluto company

is an immense ring of ice and rock

that redefines the backyard boundary
of our solar system.

BAGENAL: It's as if the explorers
had climbed up to the top of the Rockies

and were looking over

and could see the lands of California
on the other side.

NARRATOR: We now know
these Kuiper belt objects

number in the millions.

Many are the size of mountains...

some as large as Cities...

and some much larger, like Pluto.

JEWITT: We know there are
about 50,000 or more

larger than 60 miles in diameter.

And there's probably 100 million objects
bigger than a mile or so in this Kuiper belt,

and maybe even ten times that many.

So there's a huge number of bodies

that previously were
just completely unknown

in the outer parts
of the solar system.

NARRATOR: But what exactly
are these objects?

And where did they come from?

JEWITT: We think they formed
in the very early stages of the solar system.

NARRATOR: Dating back to the time
when the planets formed,

the objects of the Kuiper Belt
are what's left over,

planetary spare parts
that were hurled to the edge of space

to form an immense rubble pit.

JEWITT: And out in the Kuiper belt
it's really, really cold.

And so everything that was trapped
in the objects in the beginning

is still there.

It's all frozen in place,
in solid ice.

NARRATOR: For years, it seemed that Pluto
was the biggest object out here.

But some believed
there could be others...

even larger.

BROWN: | had actually
been wondering

about whether there was
another object out there

as big as Pluto, or bigger than Pluto,
or even much bigger than Pluto.

And for a long time
nobody had the technology

to really do the job right
to look for these.

And finally, when we got it,

we ran to the telescope
as fast as we could, basically,

and started scanning the skies.

NARRATOR: In the same way
that Clyde Tombaugh

searched the skies for Pluto
more than 70 years earlier,

Mike Brown hunted the heavens
for an even bigger prize.

BROWN: Our job is much easier
than Clyde Tombaugh's.

He did everything himself.

He did the telescope all by himself,
he developed the plates by himself.

| did almost none of it.

The telescope is run
by a robot and a computer.

And | only would come in
at the very end

and just double check
what the computer had done

and see what was really there
and what was really real.

NARRATOR: In 2003, this image
shows what could be a new planet.

But the movement is so tiny,
the computer misses it.

BROWN: So this is
the actual discovery image.

There it is.

To your eye it's really obvious,
and you can see it moving quite clearly.

But that was a little too slow
for the computer to get the first time.

That's the only little thing in there
that's moving across the sky.

NARRATOR: Mike Brown and his team
name the object "Eris."

1,500 miles across, it's nearly
a third more massive than Pluto...

and three times the distance
from the sun.

BROWN: First thing | did
is picked up my phone

and called my wife and said,
"| just found a planet!"

NARRATOR: No longer alone--
and now overshadowed by Eris--

Pluto's tenuous status as a planet
began to slip even more.

BROWN: My first thought was,
"| will probably go down history

as the guy who killed Pluto."

NARRATOR: In 2006,
the International Astronomical Union

asked an important question:

Just what is a planet?

For the first time ever, the rules
for being a planet are laid down.

BAGENAL: A planet has to be
big enough to be round.

Pull itself into a sphere.

It has to be in its own orbit
around the sun.

So we can't count moons
that orbit planets.

NARRATOR: Planets should also
have sufficient gravity

to spit out or suck up
all the debris around them.

LEVISON: Their definition is
if you put down a bunch of small objects

in an orbit similar to the orbit
of the planet,

if the planet either throws them
out of the solar system

or eats them in the age
of the solar system,

four billion years,
then it's a planet.

And if it doesn't,
it's not a planet.

NARRATOR: Surrounded by
the icy debris of the Kuiper belt,

Pluto is too small
to clear its orbital path.

MAN: Meeting in Prague Thursday,

the International Astronomical Union
voted it out.

NARRATOR: 76 years after its discovery,
the solar system loses a planet.

MAN: Pluto not a planet?
What on Earth is going on here?

BOY: Everyone grew up
thinking Pluto was a planet.

Because everyone was told that.

But now it's the other way around.

It will confuse people.

BAGENAL: | was pretty astounded
how the public responded.

Not only were all the young kids upset
that their favorite planet was demoted,

but there was a lot of debate
and discussion.

SPENCER: People learned at school
there were nine planets,

Pluto was the furthest from the sun,
and people are very comfortable with that.

And it's like someone rearranges
the furniture in your solar system

without your permission,

and that got people quite upset.

NARRATOR: So if Pluto is no longer
a planet, just what is it?

WOMAN: Members of the International Astronomical
Union

redefined the body as a "dwarf planet."

NARRATOR: Including Pluto and Eris,
there are now five official dwarf planets...

but perhaps there are hundreds more
waiting to be discovered in the ice.

BAGENAL: | don't think it really matters
whether we call it a planet

or whether we call it a dwarf object
or a Kuiper belt object,

in the same way it doesn't matter

whether we call a tomato
a fruit or a vegetable.

It could probably be
one or the other.

NARRATOR: Whatever we call Pluto
and its ring of icy neighbors,

one thing is becoming clear:

we have more in common
with these distant objects

than ever imagined.

LEVY: Welcome to my house of magic.

These are the telescopes
that | enjoy using to search for comets.

NARRATOR: Comet hunter David Levy
devotes his life to watching the skies.

LEVY: Comets are basically beautiful things
that are not dangerous at all.

But once in a long, long time,

a comet will threaten the Earth
or one of the other planets.

NARRATOR: But where do
these intruders come from?

Many comets originate
in the Kuiper belt,

where every so often
they're nudged out of orbit.

SPENCER: We have direct connections
to the Kuiper belt

because a lot of the comets that come
into our neck of the woods

here in the inner solar system

are originally derived
from the Kuiper belt.

NARRATOR: Even Pluto,

with its highly elliptical orbit
and streaming atmosphere

behaves more like a comet
than a planet.

BAGENAL: So we think of Pluto
as a colossal comet

because its atmosphere
is escaping.

But it's much, much, much bigger,
it's huge by comparison.

NARRATOR: Most of these visitors
from the Kuiper belt

harmlessly pass us by.

But others make a big impact.

It's believed that a large comet

ended the reign of the dinosaurs
65 million years ago.

LEVY: This is maybe
a once in 100,000-year event,

or even a million-year event,
that a comet is likely to hit the Earth.

But it has happened before.

And believe me,
it will again at some point.

NARRATOR: In recent years we've taken
a good hard look at these tourists

as they come in from the cold,

hoping to find out
what they're made of.

NARRATOR: In 1986,
the European Space Agency's Giotto

made a brave rendezvous with one
of the most famous comets of all--Halley.

DAVID SOUTHWOOD: We did
the most challenging thing,

which was to fly very close
to the cometary core

to see the nucleus, an environment
that was really unknown.

NARRATOR: In 2005, NASA made
an even more daring mission

with Deep Impact--

deliberately smashing
into a speeding comet.

MAN: Oh, yeah!

Oh, my God, look at that!

[applause]

NARRATOR: And in 2014,
Europe's Rosetta mission

will be the first to make
a long-term study of a passing visitor

by landing on its surface and then
surfing it around the sun.

SOUTHWOOD: At the same time

we will actually land something
down on the surface

to really, truly scratch and sniff
what the comet is made of.

NARRATOR: So what secrets
have these comets been hiding?

It now seems that the outer solar system
is flooded with carbon-bearing molecules,

which are also found in the DNA
of every living creature on Earth.

WEAVER: It turns out
that the outer solar system

is one of the most prodigious sources
of organic material in the solar system,

as well as plain old water ice.

SOUTHWOOD: Once you start
discovering organic material

sitting on something like a comet,

you've got to really ask, well,

to what degree did the Earth
just pick up life?

NARRATOR: What does all this mean?

The makings for life on Earth,
and even its water,

may have originated
in the Kuiper belt.

WEAVER: And fortunately nature
has provided a way

to transport that rich, organic material
from the outer solar system

into the inner solar system
through the comets.

And we think that that
may have been a significant source

of the seeds for life
that we have here on the Earth.

NARRATOR: And if water
and pre-organic molecules

came to Earth this way,

there's every chance they were delivered
elsewhere in the solar system, too.

MARCY: There's no doubt that there are
some lovely environments suitable for life,

right in our own backyard,
the solar system.

The aquifers under the surface of Mars,
the ocean under the ice crust of Europa,

the reservoirs of water on the moon
around Saturn called Enceladus,

not to mention Titan
with its liquid methane.

Some exquisite destinations

where we humans will be
searching for life on them

| suspect for the upcoming
hundred years and beyond.

NARRATOR: It could be that
our own backyard is abundant with life.

We just need to go find it.

CHRIS McKAY: Finding evidence
of a second type of life

on a nearby planet

would have broad implications,
first just philosophically.

We would now know that life
is common in the universe.

If it started right here
in our little solar system twice,

then certainly the universe
is full of life.

NARRATOR: And if we ever do find life
in our solar system,

we can probably thank the vast army
of ancient bodies in the Kuiper belt.

But where exactly does
our neighborhood end?

And what lies beyond it?

NARRATOR: One mission that began
more than 30 years ago is about to find out.

Launched in 1977,
the twin Voyager spacecrafts

were the first to visit the gas giants
of the outer solar system.

And now, after powering down
their cameras, they're still traveling.

EDWARD STONE: Well, Voyager 1
is about 110 times

as far from the sun as the Earth.

And Voyager 2 is about 90 times
as far from the sun as the Earth.

Neptune's at 30.

So you can see, we are many times
as far away as Neptune is,

the outermost planet.

NARRATOR: Although flying blind,
both spacecrafts can still hear.

And on December 15, 2004, Voyager 1
recorded something never heard before.

[chirping and hissing]

NARRATOR: This is the sound
of the solar wind

as it abruptly slows down
from the pressure of interstellar gases--

8.7 billion miles from the sun.

STONE: The sun has a solar wind

blowing radially outward from it
in all directions

at about 1.5 million kilometers per hour,

and that wind creates a bubble
around the sun.

NARRATOR: This bubble,
called the heliosphere,

marks the end of our sun's reign.

NARRATOR: Both Voyager spacecrafts
have now crossed into this invisible region.

STONE: We are now on the final
outer layer of that bubble

where the supersonic wind from the sun
has finally slowed down

as it turns around and meets
the interstellar wind.

NARRATOR: So what's there to see
beyond the heliosphere?

Out here there is believed to be
another field of ice.

Not a disk, but a huge sphere
known as the Oort cloud.

LEVISON: Probably one with 12 zeros
is the number of objects in the Oort cloud.

And it's a circular structure that extends
10% of the way to the nearest star.

It's huge.

NARRATOR: If a traveler makes it
this far out,

they will be teetering on the brink
of interstellar space.

Because the outer edge of the Oort cloud

marks the city limits for our tiny patch
of the universe.

From here, you can look back and see
what makes for a good home...

A star that's not too big
and not too hot.

You'll want a rocky planet with liquid water
and protected by a magnetic field.

And a good home should have
at least one giant gas neighbor,

whose immense gravity
can vacuum up rogue comets.

You wouldn't want to live
anywhere else, or would you?

Because it now seems
that beyond our solar system

is a whole universe of possibilities.

MARCY: There's a wild
international competition,

a race, if you will, to find
the first planets around other stars.

By far the most successful technique

is something called
the wobble technique.

It's very simple.

We can't see the planet
going around the star,

so instead we watch
the star itself.

And a star, of course,
will wobble, move in space,

because it's yanked on gravitationally
by the unseen planet.

NARRATOR: Using this method,
we've found more than 400 exoplanets--

alien worlds around other stars.

But can these worlds support life?

McKAY: If we find such a planet,
we'll want to zoom in

and look to see if we can detect
key molecules in the atmosphere,

like oxygen or ozone.

Almost certainly that is evidence
of life on that world.

MARCY: | have no doubt that
within a few light years of our Earth

there are other life forms.

The much more difficult
and daunting question

is whether or not intelligent life is common
in our galaxy and in our universe.

NARRATOR: So how will we know
if intelligent life exists

on other Earthlike worlds?

What will be the telltale signs?

MARCY: You'll point your radio telescope
at that Earth,

to try to pick up the radio waves,
the television transmissions,

any other transmissions that intelligent species
might be broadcasting,

perhaps serendipitously.

NARRATOR: Trying to tune into ET's TV
may sound far-fetched...

but who knows, maybe they've
been watching ours all along.

ANNOUNCER: You are there!

NARRATOR: Whether
a human traveler

will ever make it to the edge
of the solar system

remains to be seen.

But one man has begun the journey.

On board New Horizons
is a small urn

holding the cremated remains
of Clyde Tombaugh,

the man who discovered Pluto.

SPENCER: He died in the late '90s,

and it's very cool
that some of his ashes

are now onboard that spacecraft
on their way out to Pluto.

And who could have predicted
when he discovered Pluto in 1930

that part of him could have actually
gone there in person?

And | think that's
a really wonderful tribute

to the person who made
this whole thing possible.

NARRATOR: But Clyde Tombaugh
will not rest here.

After flying past Pluto in 2015,
New Horizons will keep going.

WEAVER: The spacecraft
will continue moving.

Newton's laws tell us that,
you know,

the spacecraft is just going
to keep heading out.

It won't be operating, we won't be communicating
with it.

So it will just be another piece
of space junk.

We'll just, we'll say goodbye.

NARRATOR: Clyde Tombaugh
may be disappointed

to learn that Pluto is no longer
regarded as a planet...

but to become humanity's
longest ever space traveler

would surely make up for it.

And with an estimated
1,000 billion billion stars in the universe,

where he travels to we can only imagine.