51x16 - Solar System: Wandering Worlds

[bunniefuu]

NARRATOR: Our solar system
is filled with mysterious worlds...

wandering between
and beyond the planets.

[collision pounds]

MALENA RICE: The objects
that lie between the planets

are actually the
key to understanding

how our solar system formed.

NARRATOR:
Imposters, and oddballs,

rewriting our understanding
of our place in space.

JESSICA SUNSHINE: It is two
pieces that are stuck together.

It was really quite remarkable.

[explodes]

QUEENIE HOI SHAN CHAN: It is
possible that after 30 million years,

Mars might have
a ring of its own.

♪ ♪

NARRATOR: Studying
these wandering worlds

allows scientists to explore
regions of the solar system

we have no chance of visiting.

WANDA DÍAZ MERCED: I
cannot go to the asteroid belt,

so when a meteorite
lands on Earth,

we will have a chunk of
history right in our hands.

ASHLEY KING: The
Winchcombe meteorite

was like a little treasure
box for planetary scientists.

[geyser bursts]

NARRATOR: And the
misfits of our solar system

are full of surprises.

VERONICA BRAY DURFEY: There
are many, many worlds out there

that we are yet to discover

and that we haven't
even imagined yet.

SCOTT SHEPPARD: It's
like a box of chocolates.

You never know what you're
gonna get in our images.

This model of the solar system,

it's missing all of the
most interesting bits.

NARRATOR: What secrets
do these wandering worlds

reveal about our solar system?

And what else is
lurking out there

in the dark?

[bursting]

"Solar System:
Wandering Worlds,"

right now on "NOVA."

♪ ♪

♪ ♪

NARRATOR: There's something
out there in the darkness.

We don't know for
sure where it came from

or how long it's been there.

But we know it's not alone.

It was discovered in 2018.

A world with no official name.

So distant, it has
been called simply

FarFarOut.

SHEPPARD: FarFarOut,

as its name implies,
is very far away.

So, it's just a, a
very faint point of light

that, uh, we discovered

with one of the largest
telescopes in the world.

JANE LUU: Its notoriety
comes from the fact

that it's the most
distant object

that we have found
in the solar system.

SHEPPARD: And the big question
is, what do we call the next one?

Do we just add
another "far" or not?

LUU: "ExtremelyFarOut,"
and then "StupendouslyFarOut,"

and it just keeps
going. [laughs]

♪ ♪

NARRATOR: 12 billion
miles from the sun,

FarFarOut is not alone.

Out here, there could
be countless other worlds

yet to be discovered,

wandering in the dark.

Even closer to home,
we are only just beginning

to explore the vast spaces
between the planets.

Home to a myriad of worlds,

many too small
or too dark to see.

NANCY CHABOT: When we
think about our solar system,

we think about the
sun, it's in the center,

everything else is
kind of going around it,

and we've got the big
planets, Jupiter and Saturn,

and the most
important planet, Earth.

But there are so many
more secrets and mysteries

than just these planets
that are shown in the model.

So, to me, the
most exciting thing

about studying the solar system
is not the planets themselves,

but it's all the bits in
between the planets.

NARRATOR: These worlds could
provide clues to our own planet's story.

RICE: In a lot of ways,
studying the solar system

is a way of trying to
understand ourselves.

How did we come
to be in the first place,

and what does it mean
that we're on this rock

that is sailing through space?

NARRATOR: With distances so
vast, there's still much to discover.

KING: There's so much stuff

that we just don't know
about our solar system,

and what we do know is, it
is constantly surprising us.

So we need to go out there,
look at these wandering worlds.

NARRATOR: And many
questions remain unanswered.

LYNNAE QUICK: Are these
lost and wandering worlds

worthy of exploration
in their own right?

CHABOT: How far do
these dark regions extend

beyond, to the edge
of our solar system?

Are there more planets
in the dark region

waiting to be discovered?

♪ ♪

[dog barking in distance]

NARRATOR: It was the
sound that most people noticed.

[expl*si*n echoing in distance]

A sonic boom in the night.

But this was no fighter jet.

Traveling at around


it tore through the atmosphere.

♪ ♪

Broke up.

And rained down
across the fields.

A visitor from a distant realm.

One of the biggest chunks

landed on a driveway
in front of a house.

KING: When I first saw
it, it was kind of a splat.

I mean, it's so soft, it
kind of just made a powder

and it threw fragments
all over the driveway.

SARA RUSSELL: The
Winchcombe meteorite fall

was the first U.K. meteorite
fall recovered for 30 years,

so we've been waiting
such a long time.

KING: I couldn't believe that we
had a new meteorite in the U.K.

Yeah, it was
incredibly exciting.

And all meteorites are
scientifically priceless.

RUSSELL: I feel
amazed and privileged

to be able to hold something

that may tell us
about the secrets

of the origins of
our solar system,

and how we got to be here.

NARRATOR: It's estimated as many
as 50 meteorites hit Earth every day.

Many burn up in our atmosphere,

creating sh**ting stars
and meteor showers.

But some of the largest
ones do make it to Earth.

In 2018, the Hamburg
meteor fireball

streaked across the
American Midwest sky.

WOMAN: What was that?

Did you see a light
flash out there?

It's particularly pristine,
because it landed

on a frozen lake, so that
keeps it in cold storage.

It was like the meteor
selected where to land,

because it wanted to be studied.

NARRATOR: A few years later,

a meteorite the
weight of a grand piano

exploded in the skies
near McAllen, Texas.

[expl*si*n pounds in distance]

MERCED: Ah!

It's like a, like an
expl*si*n of dynamite.

[expl*si*n echoes]

That big expl*si*n,
that was a sonic boom.

♪ ♪

NARRATOR: The cows
weren't the only witnesses

that night in Winchcombe.

Doorbell and CCTV
cameras never sleep.

And networks of
dedicated meteor cameras

captured it from
different angles.

That meant it was possible
to calculate its trajectory.

[cows mooing]

Back over the skies of England,

out of Earth's atmosphere,

past the orbit of Mars,

into the dark.

This is where the
meteorite's journey began,

a mysterious realm of
countless rocky worlds,

rubble left over from the
formation of the solar system:

asteroids.

There could be at
least a million out here.

But they're so dark,
reflecting little light,

they're incredibly
difficult to detect.

But asteroids don't always
stay in the asteroid belt.

[collision pounds]

When two collide,

they blast fragments
in all directions,

sending some out of
the asteroid belt forever.

Sometimes wreaking havoc
on planets they encounter.

♪ ♪

Including our own.

And asteroids
that leave the belt

can transform planets nearby.

♪ ♪

A planet covered in scars
from the asteroid belt is Mars.

Around 80 fresh impact sites
are found on Mars every year.

♪ ♪

And some amazing meteorites

have even been
snapped by NASA's rovers.

But there's another
dark rock here,

imaged by the
Perseverance rover,

not on Mars's surface,
but orbiting overhead...

♪ ♪

captured during an eclipse,

as it passed in
front of the sun.

This is Mars's moon Phobos.

Today, the orbiting
probe Mars Express

regularly flies between
Mars and Phobos.

♪ ♪

Its high-resolution camera

captured incredibly
detailed images of Phobos,

showing a surface
covered in strange grooves.

Phobos looks like someone
has ridden a giant bike all over it.

Astrophysicist Sean
Raymond is investigating

how objects like Phobos
could have formed.

Phobos is a
strange-looking moon.

Like this beach, it's
covered in grooves.

You might say it's

the grooviest moon
in the solar system.

NARRATOR: The magnificent
grooves here in Spain

are formed by
geological processes

and erosion from
relentless, crashing waves.

RAYMOND: It's so cool...
the grooves are amazing here.

NARRATOR: But Phobos
isn't anything like Earth,

so what's going on?

RAYMOND: Phobos
certainly looks like an asteroid.

It's covered in craters,
and it's dark in color.

So you might think it's
just an asteroid that got

too close to Mars and
then was captured in orbit.

NARRATOR: It turns
out it's not that simple.

Phobos orbits Mars in
an almost perfect circle,

right along Mars's equator,

and this makes us
question whether Phobos

is really the asteroid
it appears to be,

because captured
asteroids usually orbit planets

on very elliptical orbits

that sometimes take them
very far from their planet

and sometimes being much closer.

NARRATOR: So, if
it's not an asteroid,

where did this funny
little moon come from?

CHABOT: So, in
planetary science,

the joke is that you
just add an impact event,

and an impact event
can explain everything.

That might actually be
true in this case, though.

It's this one-off event,
and it might have been

that an object hit Mars,

and Phobos is the result
of that impact collision

between those objects,
and that's what we're seeing.

♪ ♪

NARRATOR: Phobos may
not be a captured asteroid at all,

but formed from
debris thrown into orbit

after a massive asteroid impact.

However, this
still doesn't explain

why it's covered in grooves.

Phobos is about 3,700
miles from Mars's surface,

and every hundred years,
moves closer by about six feet.

And as it does, the tidal
forces caused by Mars's gravity

become stronger.

RAYMOND: So, just like
the moon pulls on the Earth,

dragging the oceans
and causing the tide,

Mars pulls on Phobos,
causing tides, as well.

So, as you can see
behind me right now,

the tide is coming in
as the moon is pulling on

the water on the Earth.

The same process happens
on Phobos, due to Mars,

except on Phobos, it's
sand and rock that's moving,

instead of water.

NARRATOR: Those tidal
forces are pulling Phobos apart.

And with every orbit, the
grooves widen and deepen.

Eventually, Phobos
will drift so close,

Mars's gravity will destroy it.

As Phobos breaks apart...

most of the debris will
fall to the surface of Mars.

♪ ♪

But the rest will
remain in close orbit,

spreading out to
encircle the entire planet,

giving Mars a wispy ring.

CHAN: It would
be quite impressive.

I love ring planets,
I love Saturn,

and it's not bad to have another
ring planet in our solar system.

NARRATOR: It seems Mars
will one day be transformed

by the asteroid belt.

But the asteroid belt
itself is still an enigma.

We've flown several spacecraft

through this mysterious region,

but only one has
orbited the rocks

in the asteroid belt itself:

NASA's Dawn probe.

Most of these ancient remnants
are misshapen boulders.

But one stands out.

Ceres is much
bigger than the others

and almost perfectly spherical.

QUICK: I joined the Dawn mission

right after it reached Ceres,

and it was so exciting.

Dawn collected thousands
of images of Ceres.

They showed us
areas of the surface

that we'd never seen before.

We thought that it's kind of

a dead planetary body.

Looking at those images,

we could not, basically,
believe our eyes,

and it was, like, "Uh,
what's going on over there?"

♪ ♪

NARRATOR: At first, it appears
dark and heavily cratered,

like its fellow asteroids.

But Ceres is different.

Its surface is peppered
with white crystals.

But what are they?

Clues come from another
planet in our solar system,

where white crystals are
also found on the surface.

Earth.

HAKEEM OLUSEYI: This mountain
is made up almost entirely of sea salt,

the exact same stuff
that you put on your food

at the dinner table.

NARRATOR: 40 million years ago,

this whole area was
under an ancient sea.

Over time, it dried out,

leaving behind a layer
of salt a mile thick.

Holy moly!

Whoa!

♪ ♪

It's definitely salty.

And the thing about
salt deposits like this

is that they're only formed
in the presence of water.

So, that raises an
intriguing possibility.

Could the white spots
on Ceres also be salts

that were deposited by water?

NARRATOR: Finding
water on Ceres today

would be an
astonishing discovery.

♪ ♪

Dawn made tight orbits of Ceres.

And by bouncing light
off the crystal deposits,

it determined what
they were made of:

sodium carbonate, a
common type of salt.

A tantalizing sign that Ceres,

which is 13 times
smaller than Earth,

had an ocean in the past.

Flying just over 20
miles from the surface,

Dawn finds something
else in the white spots:

hydrohalite crystals,

another salt found on Earth
in the presence of water.

Could Ceres still be
a water world today?

So, "hydro" is water
and "halite" is salt...

table salt.

So, if you imagine a table salt

that's got water
molecules in the structure,

that's what hydrohalite is.

It was very surprising
that there were hydrohalites

on the surface of Ceres.

CHAN: Hydrohalite
would be very unstable

at the surface of Ceres.

At that pressure,

the water molecule would
have been vaporized.

That implies that water was
recently emplaced on Ceres,

bound to salt crystals within
the past few hundred years.

This replenishment
of hydrohalite

at Ceres' surface
leads us to wonder

if Ceres might be an ocean world

that's masquerading
as an asteroid.

♪ ♪

NARRATOR: Scientists suspect
that pools of salty water exist

about 25 miles underground,

raising another question:

how did these salts
end up on the surface?

A clue lies in Ceres' location,

right in the heart
of the asteroid belt,

where collisions are common...

[collision pounds]

and incoming asteroids
can form cracks in the surface

reaching the pools below.

Exposed to the vacuum of space,

the water vaporizes,

leaving its cargo of salt behind

and peppering Ceres
with white spots.

QUICK: There's
still one big twist

to the story of Ceres' past.

The Dawn spacecraft found
ammonia salts on the surface.

NARRATOR: Ammonia salts
could be traces of ammonia ices

that once covered
Ceres' surface.

Frozen ammonia is
common in colder parts

of the solar
system, but not here.

CHAN: Ammonia doesn't really
exist as ice at where Ceres is now.

It has to be formed
at a distance

further away from the sun,

where the distance
is cold enough

for ammonia to exist as ice.

This suggests that
Ceres didn't form

where it stands currently
in our solar system.

NARRATOR: Instead, scientists
think it formed much farther out,

and as it wandered
towards the sun,

the ammonia ices melted,

leaving behind the
ammonia salts we see today.

An imposter lurking
in the asteroid belt,

exposed by its salty secrets.

Ceres has a
journey of relocation

just written all
across the surface.

NARRATOR: But just how did
Ceres end up where it is today?

OLUSEYI: The best
explanation is that it wandered.

Well, actually, it was pulled.

So let's say this is Ceres.

Okay?

We think that Ceres
formed beyond

what is known as the ice line

for ammonium ices.

NARRATOR: Beyond this ice line,

ammonia freezes,

and this is where Ceres
likely started forming,

alongside Neptune and Uranus.

OLUSEYI: And here we
have Saturn and Jupiter.

Now, normally, these planets

aren't lined up like this.

They're moving
around the solar system.

And what happens is, as Ceres

orbited the solar system,

Jupiter tugged on
it with its gravity,

and Ceres ended up right there,

in the asteroid belt,
where we find it today.

NARRATOR: In the
heart of the asteroid belt,

Ceres, once a much icier world,

has migrated far
from where it formed,

evidence that our solar
system is ever changing.

♪ ♪

Ceres isn't the only
displaced world.

Farther from the sun,
there is another icy world

that doesn't seem to
belong where it's found today.

Beyond Jupiter,

the space between
the planets gets wider

and wider.

And temperatures plummet.

♪ ♪

And a billion miles past Uranus,

we finally reach the
farthest planet from the sun.

Neptune.

♪ ♪

Wrapped in a dense blue blanket,

Neptune has no
detectable surface,

with clouds of
methane and ammonia.

But there are
rocky worlds nearby.

Neptune has at least 16 moons.

And one is very unusual.

Triton is the largest
of Neptune's moons.

Its surface is coated with ice.

And, unlike the other moons,

Triton is an active world.

[geyser bursts]

Geyser-like plumes
of gas and dust

stretch five miles high
into Triton's atmosphere...

which flattens them abruptly

by 90 degrees,

creating a vista so strange,

it's hard to believe it's real.

How did a moon 2.8
billion miles from the sun

become so active?

A clue lies with how
the planets and moons

move around each
other in the solar system.

CARLY HOWETT: Every
day, the sun rises in the east

and sets in the west.

And the moon follows
the same course.

And there's a reason for that.

NARRATOR: To understand why,

we need to go all the way back.

To the birth of
the solar system.

DURFEY: In the beginning
of our solar system,

the sun was surrounded

by a disc of dust and gas.

And it was within
this spinning disc

that the planets formed.

PAREKH: So that's the reason

the planets and
the moon continued

orbiting also in
the same direction

around the sun.

NARRATOR: Moons that
form around their planets

tend to follow this pattern,

orbiting and spinning
in the direction

of the planet's rotation.

But while the inner moons orbit
Neptune in the same direction,

Triton goes the other way,

suggesting it didn't
form alongside Neptune,

but came from elsewhere.

HOWETT: What a
planet's made from

can tell you where it
formed in our solar system.

And that's because, in
our early solar system,

the ingredients that a
planet could be built from

varied as the
distance from the sun.

So if we take
Earth, for example,

it's got a lot of rocks
and metals, too:

aluminium and iron.

And Mars is pretty similar.

Iron, metals, and other rocks.

So these can be paired together.

If we do the same thing

for the ice giants,
Neptune and Uranus,

with big atmospheres
made of hydrogen,

helium, and a bit of methane,

they're huge, too.

So we can pair those together.

So how does Triton fit in?

Well, its surface is
mainly nitrogen ice,

and it's much smaller.

It doesn't fit with either
of these two groupings.

To understand
where it could fit,

we have to look at Pluto.

Pluto has a, a nitrogen
ice surface with methane,

carbon monoxide, and water ice.

And it's about the
same size as Triton, too.

These are a good pairing.

NARRATOR: With
such similar ingredients,

Triton and Pluto could've
formed in the same place,

but they aren't anywhere
near each other today.

HOWETT: Triton's located
one billion miles from Pluto.

So how did that happen?

NARRATOR: Neptune might be
the farthest planet from the sun,

but it's not the edge
of our solar system.

Not even close.

Almost a billion
miles farther out

lies Pluto.

And it's not alone.

There are hundreds of
thousands of other worlds out here.

This is the Kuiper Belt,

a vast, doughnut-shaped
ring of icy bodies

billions of miles wide.

So dark and distant,

it remained
undiscovered until 1992.

LUU: We had been searching
for, uh, the Kuiper Belt

for, uh, for five years
before we finally found it.

So when we spotted
the first Kuiper Belt object,



there was jumping up
and down, and there was...

I think we gave each
other a high five. [laughs]

The discovery of the Kuiper Belt

helped us to better
understand our solar system

as it is now, and
also its history.

LUU: The Kuiper Belt
is really the frontier

if you want to understand
the solar system.

But it is very
difficult to study it,

because it is so far away.

NARRATOR: Despite
the challenges,

more than 4,000
Kuiper Belt objects

have been discovered to date.

And scientists estimate

there may be 200 dwarf planets.

Some have rings and moons.

Some are bizarre and misshapen.

But they all share
one thing in common.

They're made of icy
materials, similar to Triton.

This is where Triton belongs.

So how did it end up
around a billion miles away,

in orbit around Neptune?

♪ ♪

HOWETT: So, to
understand Triton,

you have to understand
the Kuiper Belt.

If this is our sun,

the one population
of Kuiper Belt objects

orbit it in a nice circle.

Another population
of Kuiper Belt objects

have a highly elliptical orbit.

So the question is, why
are these so different?

What caused them to
be in this weird orbit?

Well, the answer is,
some of these objects

are in resonance with
another planet, Neptune.

Resonance is when
two objects have paths

that meet up occasionally.

And we see this
throughout the solar system.

If you look, for
example, at Pluto,

it'll go around

on this elliptical orbit twice

in the same time Neptune
has gone around three times.

And this resonance
is an important clue

in understanding how disruptive

Neptune is to
Kuiper Belt objects.

♪ ♪

NARRATOR: Scientists
think Neptune formed

much closer to the sun,

then slowly drifted out.

Its huge gravity
disrupted the orbits

of the Kuiper Belt
worlds it encountered,

kicking them into
the elliptical orbits

we see today.

DURFEY: The early solar
system was complete chaos,

filled with small
bodies growing larger

and smashing into each other,

sometimes destroying.

Complete chaos.

NARRATOR: During
all the commotion,

Triton became trapped
by Neptune's gravity,

slipping into its
backward orbit.

And being this close to a
giant has consequences.

Just as our moon
raises tides on Earth,

Neptune raises tides on Triton,

stretching and squashing
it like a stress ball,

heating it up.

HOWETT: Triton being
captured by Neptune

fundamentally
changed how it works.

On Earth, we experience
energy every day.

You might be able
to hear it in the roar

that comes from the tide
coming in underneath us.

[waves pounding]

Tidal energy can force
water up through cracks

in the Earth, like
the one in front of us,

creating plumes
erupting up to the sky.

NARRATOR: On Triton, the
plumes are even more spectacular.

HOWETT: The plumes on Triton
would be magnificent to behold.

Erupting from the
surface, cracks like this,

but going five
miles into the sky.

I mean, it'd just be
absolutely phenomenal.

[geyser bursts]

NARRATOR: What creates
Triton's plumes is a mystery.

But one theory lies
in its unusual orbit.

HOWETT: It's highly tilted,
and Triton orbits backwards.

Meaning as it goes
around Neptune,

its pull and push
that it receives

from Neptune and
its moons changes.

This creates a kind of friction,

similar to the one that you get

when you rub your hands
together on a cold day.

Your hands warm up,
and so might Triton.

We call that kind of
energy tidal heating.

NARRATOR: As Neptune's
gravity stretches and squashes

its giant moon...

[plume roaring]

the tidal heating produced

melts Triton's
frozen interior...

♪ ♪

powering its spectacular plumes.

DURFEY: Triton
is a great example

of how interconnected
our solar system is.

And it also serves
as a good example

of how a large, giant planet

straying into a belt of objects

can really mess up your system.

NARRATOR: Triton was
plucked from the Kuiper Belt,

a distant realm filled
with mysterious worlds

so far away

we can't make them
out in much detail.

But we have sent one spacecraft.

It took over nine years for
New Horizons to get here

and home in on
its primary target.

♪ ♪

The tiny spacecraft captured
the first close-up images

of this Kuiper Belt world,

revealing unexpectedly complex

and dynamic surface features:

mountains as high as
the Alps, made from water,

frozen as hard as granite.

But there's something
else odd out here.

Another world close by.

How did Charon and Pluto
end up almost touching?

Charon orbits about 12,000 miles

from the surface of Pluto,

which sounds like a
really large number,

but is actually really close

for the scale of
the Kuiper Belt.

It's very common
in our solar system

for moons that are close
enough to their parent body

to become tidally locked.

And that is where one orbit

will also be one spin,

so that the same
face of that moon

is presented to the
planet at all times.

NARRATOR: All large
moons in the solar system,

including our own,
are tidally locked,

only showing one face
to their parent planet.

But in the case of
Pluto and Charon,

it isn't just Charon that
is tidally locked to Pluto.

Pluto is also tidally
locked to Charon.

Both worlds constantly
face each other at all times.

RICE: And what that means
is, if you're on the side of Pluto

where you're able to see Charon,

then it'll look like it's just
hanging there all the time.

It's not going to rise,
it's not going to set.

It's just going to
constantly be in your sky.

♪ ♪

NARRATOR: This isn't just
a dwarf planet and its moon,

but a binary pair.

♪ ♪

New Horizons is still studying
Kuiper Belt worlds today.

During the most
distant fly-by in history,

it encountered Arrokoth,

a bizarre snowman-shaped object.

SUNSHINE: It is two
pieces that are stuck together,

and those two pieces must
have come together very gently.

To actually see it was
really quite remarkable.

Any time you see a new
world, it's remarkable.

NARRATOR: Why do the
worlds out here in the Kuiper Belt

form these partnerships?

LUU: Things become
slower and slower

as you go further
away from the sun.

In the Kuiper Belt,
things might collide

at the speed of a few
hundred feet per second.

They occur at such
low-impact velocity

that a lot of the
collisions are constructive

rather than destructive.

NARRATOR: At some point in their
history, Pluto and Charon collided.

But their slow movements

meant this was less of an impact

and more of an embrace.

The Kuiper Belt is so
vast and far from the sun

that many
mysteries still remain.

I am often pretty amazed
that we're actually able

to study things
like the Big Bang

and the early universe
and distant galaxies,

and yet we still actually
don't know everything

that there is to know
about our own solar system

and our own backyard.

I'm very confident that
there are many, many worlds

out there that we
are yet to discover,

and that we haven't
even imagined yet.

♪ ♪

NARRATOR: We can see
distant stars in the night sky

because they burn so bright.

Telescopes can detect planets

as they pass in front
of their parent stars.

Seeing worlds in
our own solar system

is much harder,

but not impossible.

♪ ♪

In 2018,

a faint point of
light was detected

about 12 billion
miles from the sun.

It's thought to
be a dwarf planet

nicknamed FarFarOut.

This is the most distant object
yet seen in our solar system

by some of our most
powerful telescopes.

But it's not the limit of
what could be out there.

♪ ♪

OLUSEYI: How far do you
expect the solar system to extend?

You may imagine that it ends

at the last major
planet, Neptune.

However, that's
not exactly the case,

and let me show you why.

Here I'm gonna make a
model of the solar system.

This rock is my sun,

and I'm gonna
place it right there,

and an inch away, I'm
gonna place the Earth.

And so this will be my
scale, one inch equals

the average distance
between the Earth and the sun.

So now, if I go a second inch,

I arrive at the asteroid belt.

And to get to the most
distant major planet, Neptune,

that's gonna be about 30 inches.

Now, we have to
keep going and going,

because out here is

the most distantly
observed object ever

in the history of
our solar system,







is FarFarOut.

NARRATOR: But the solar
system doesn't end here.

OLUSEYI: I have to
walk another 50 paces...

another 186 billion miles,

and now we've
reached our destination,

a vast region known
as the Oort Cloud.

♪ ♪

NARRATOR: Clinging
on at the very edge

of the sun's
gravitational influence,

the Oort Cloud is our
solar system's largest

and most mysterious realm.

It's so deep into the darkness,

it's almost
impossible to imagine,

let alone see,

filled with billions
upon billions

of strange worlds.

Most are thought
to be icy objects

the size of mountains.

But it's likely some
are made of rock.

And if we were able to go there,
we'd discover they are pristine.

♪ ♪

Barely changed since the
dawn of the solar system.

It's thought some could
be older than the sun.

The Oort Cloud's
existence is hypothetical,

but science doesn't
deal in fairy tales,

so how do we know it's actually
there if we've never seen it?

♪ ♪

NARRATOR: For as long as
we've been looking into the night sky,

we've seen signs that
the Oort Cloud is real.

And this is one of them.

For hundreds of years,

it's been locked in a
deep, frozen slumber.

♪ ♪

But now it stirs.

♪ ♪

As it nears the sun,

warm rays bathe its surface...

and it begins to thaw.

[hissing]

♪ ♪

So much debris is
torn from the surface,

it stretches out,
forming a tail...

around 14 million miles long.

This is the comet Nishimura.

It's visible from Earth
for just a few weeks,

before eventually heading
back into the darkness,

just the latest in a
long line of icy visitors.

Hale-Bopp.

Neowise.

They lit up our skies for
weeks, or even months, on end.

Humans have been
captivated by comets

because, frankly,
they're spectacular.

CHABOT: And the
fact that they do wander

around the solar
system from time to time

really is a unique
scientific opportunity.

NARRATOR: When scientists
followed the trajectories

of these comets back,

they discovered they
came from the same region,

more than 200 billion
miles from the sun.

SUNSHINE: If you calculate

where the orbit
took you back to,

it was way out,

unbelievably far out, what
we now call the Oort Cloud.

NARRATOR: It's thought the
gravity of other objects in the galaxy

can occasionally knock
these icy objects inwards.

SUNSHINE: But the
really interesting thing

was that they were coming
from all directions in space,

and there had to be a cloud.

♪ ♪

NARRATOR: Although
we can't see this far out,

comets with orbits
starting in the Oort Cloud

streak across our skies.

RICE: The Oort Cloud
is kind of incredible.

No one's actually been there,

no one's actually observed
anything within the Oort Cloud.

They've only seen the
wanderers that have escaped

from the Oort Cloud
for a brief moment,

which I think is what makes it

so spectacular and
so exciting to me.

CHABOT: If I could visit
one of those dark regions,

I would have to
choose the Oort Cloud.

We don't know
that region at all,

we haven't ever
explored it, so for me,

that would be the most
exciting place to go.

♪ ♪

NARRATOR: We
think of the solar system

as the sun and all the planets.

But that's just
what's close to Earth.

As wandering worlds
give us rare glimpses

into what is beyond

and technology improves,

we're discovering more and more.

RUSSELL: We're really
only scratching the surface,

so there are millions of
these tiny bodies out there,

and we still have so many
secrets to unlock from them.

MERCED: There is so
much information in darkness.

If we pay more attention

and we trust what we perceive

with all our senses,

we will gain
much more information

from those dark regions
of not only our solar system,

but of the universe.

This model of the solar system,

it's missing all of the most
interesting bits.

♪ ♪

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