Space's Deepest Secrets (2016–…): Season 8, Episode 1 - Mystery of the Dead Planets - full transcript

One day, future humans
must leave Earth

for a new home among the stars.

Finding another habitable world

is not just
a science-fiction dream.

It has to do with
the survival of humanity.

Today, astronomers
are laying the groundwork

for our move to a new Earth.

But the more alien worlds
they discover,

the more they learn how deadly
the cosmos really is.

The universe has this one rule

when it comes to life...
Kill it all.



To pinpoint our new home,

astronomers must unlock
why space is so savage.

What unleashed one of the most
powerful blasts of energy

ever seen to fry
a promising alien world?

You would be dead so fast,
you wouldn't even know it.

How did our cruel Sun
destroy Earth's sister planet?

It just didn't make it,

and it became
this inhospitable hellscape.

We dive through waves
of deadly radiation

and plunge into
suffocating atmospheres

to reveal the raw,
destructive power of the cosmos.

captions paid for by
discovery communications

Humanity's days on Earth
are numbered.

The Sun's brightness
will increase by 10%



over the next one billion years.

This extra heat will boil away
Earth's oceans

and incinerate
all life on our planet.

Our fate is written
in the stars,

we must leave
and find a new home

in another part of the galaxy,

To ancient people,

the Earth seemed
absolutely eternal.

It must have always been here
and always will be here.

We know planets change.

They live, and then they die.

Our galaxy stretches
100,000 light-years across.

Where in this huge expanse

is somewhere
that can support complex life?

Planets are formed
from the leftover debris

from star formation.

We have over 400 billion stars
in our galaxy.

That means we could have
trillions of planets.

Astronomers call these
alien worlds exoplanets.

In 2016, exoplanet hunters
make an exciting discovery.

They find a rocky planet that is
roughly the same size as Earth.

The planet orbits
Proxima Centauri,

the closest star to our Sun.

They named the planet Proxima B.

It is just 4.2 light-years
from Earth,

and it is in just the right spot

to potentially support
complex life, like humans.

Finding Proxima B
was a game changer,

because not only is it a planet
in the habitable zone

of its star,
it's the closest star to us.

So this means that we could
potentially go there.

This changes the future
directions of science on Earth.

The habitable zone
is the sweet spot around a star,

where temperatures are right
for liquid water to exist

on the surface of a planet.

If you're too close to the star,
that water is gonna boil away.

If you're too far,
it's going to freeze.

And if you're in that zone,

you can have liquid water
on your surface.

The signs
look good that Proxima B

might have what it takes to be
a home for humans in the future.

But what astronomers see next
puts the celebrations on hold.

2018, violent waves of radiation
slam into Proxima B.

The blast wipes out hopes that
the planet can support life.

This is one of the biggest
high-energy events

involving an exoplanet that
we've ever been able to witness.

What could have caused
such a huge release of energy?

Astronomers attempt
to unlock the mystery.

They examine
the prime suspect...

The star that Proxima B
orbits... Proxima Centauri.

Astronomers measure
the light output

from thousands of stars
in our galaxy.

A sudden increase in starlight
is evidence

that the star is releasing
a stellar flare.

A stellar flare is an explosion
of intense radiation

that erupts from
a star's outer layers.

Proxima Centauri
is a red dwarf star.

Astronomers discover
that this type of star

emits around 80,000 times
more flares

than a star like our Sun.

Observations also reveal
that each flare

is around a thousand times
more powerful

than the average type of flare
that our Sun emits.

Small red stars
have gigantic flares.

They're so huge,

they actually double
the brightness of the star.

That means the flare
is as bright as the star is.

So imagine if the Sun did that.

Imagine if the Sun doubled
its brightness right now.

That wouldn't be good.

The evidence is clear.

A super powerful flare
from Proxima Centauri

fried Proxima B.

Splitting open the star reveals
why it is so volatile.

Proxima Centauri is so small
that its core touches

the churning layer of hydrogen
that surrounds it.

The extreme heat in the core

drives streams
of superheated plasma

to the surface like a furiously
boiling pot of water.

Huge eruptions of plasma
spew from the star

with the force
of a billion hydrogen bombs.

The flares fan out
through space.

They slam into Proxima B

and extinguish any chance

that the planet
can support life.

Proxima Centauri discharges

mega flares like this
three times a year.

These extreme flares
will wipe out the ozone layer

of every planet in
the habitable zone of the star.

The Earth has a layer
of protective ozone

in its atmosphere

that absorbs ultraviolet light
from the Sun, which is great

because that kind of light
is harmful to life on Earth.

The problem with
Proxima Centauri

is that it is a flare star.

And if Proxima Centauri B
has an ozone layer,

it'll get destroyed
by this constant barrage

of high-energy radiation.

The destruction of
this layer ruins any chance

that humans could one day
live on Proxima B.

The kind of light
that these flares emit

is the kind of light that we use
to sterilize surfaces.

A DNA molecule would
just be completely destroyed.

A new Earth
must orbit a stable star

to support complex life.

The hunt for our next home
continues.

Can three newly
discovered planets

in the same system

sustain humans on a thin
boundary between fire and ice?

And can a Jupiter-sized
alien planet unlock the mystery

of why habitable worlds
are so hard to find?

Humans must leave Earth

before our Sun
incinerates our world

and forge a future on a planet
in another part of the galaxy.

Today, astronomers
lay the groundwork

for our eventual move
to a new planet.

In 2017, they discover
an extraordinary system

40 light-years away from Earth.

A dwarf star called Trappist-1

sits at the center
of the system.

Around it orbits
seven rocky planets

and all of them
are a similar size to Earth.

The planets are so close
to Trappist-1

that a year on these worlds

lasts between 2
and 19 Earth days.

Three of the planets fall inside
the habitable zone

of the system.

Could one of these worlds
be our future home?

There are times as a scientist

where you discover something
out there that, honestly,

if it wasn't right
in front of our eyes,

I would not believe
that it exists.

And the Trappist-1 system
absolutely blows me away.

Telescopes analyze
the system in more detail.

They reveal it is likely

that these planets
have unusual orbits.

They do not spin around
their star in the same way

as Earth
revolves around the Sun.

Instead, many astronomers think
that the same sides

of all seven planets
face their star.

They call this tidal locking.

You can witness an example
of tidal locking in action

really close to the Earth.

Just look up in the night sky
and look at the moon.

You only ever see
one side of it.

One face is always pointed
toward the Earth.

This is because the moon
is tidally locked to the Earth.

And what that means is that
the time it takes for the moon

to spin once
on its own rotational axis

is exactly equal to the time

that it takes to orbit
the Earth once.

The close proximity
of these planets to their star

unlocks why this happens
in the Trappist-1 system.

The star Trappist-1
is 20,000 times more massive

than its orbiting planets,

and its immense gravity grips
them as they huddle in close.

The star's gravity warps
each planet,

pulling out a huge bulge of rock
on the side facing the star.

The star tugs on the bulge
like a handle,

gently slowing the rotation
of the planet.

After millions of years,
the planet slows down so much

that one side remains locked,
always facing the star.

Living on a tidally locked world

in the Trappist-1 system

poses a big challenge
for future humans.

The rotation of Earth ensures
that no part of the planet

gets too hot
or too cold to support life.

It's the spin of our home planet

that allows it
to actually harbor life.

It's this spin that evenly
distributes thermal energy

across our planet's surface

and creates conditions
hospitable for life itself.

But tidal locking
turns the Trappist-1 planets

into super extreme worlds
of two halves.

It's likely that every planet
in the Trappist-1 system

is tidally locked.

Eternal darkness
shrouds one face,

the other is bathed
forever in starlight.

The star's powerful
radiation roasts

the surface of the dayside
and water evaporates away.

The nightside experiences
an endless cosmic winter.

Water freezes solid
as temperatures plummet.

In between these two hellish
half worlds

is a thin strip
where it is always dawn.

Temperatures here could be just
right to support complex life.

Any brave humans who do settle
this thin strip

will find themselves
living on a knife edge.

Huge mega storms
will engulf the areas

where the scorching winds
from one half of the planet...

...meet the frozen gases
of the other.

People here will live in
a never-ending super hurricane.

These mega storms raging inside
this potentially habitable band

make a Trappist-1 planet
too volatile

for humans to live on long term.

I don't want to say
that life can't exist

on a tidally locked planet,
but if our species were to have

its pick of a next planet
to move to,

we probably wouldn't pick
a tidally locked planet

as our new home.

Human space travelers
in the future

must search elsewhere
for a place to live,

but the odds of finding it
are stacked against them.

Just 2% of the over 4,000
exoplanets found so far

are in the sweet spot
of their star's habitable zones.

Why are rocky planets within
habitable zones so hard to find?

Astronomers believe
that a clue may lie

in where they find
another type of exoplanet.

Telescope observations
show that many exoplanets

are gas giants
made from hydrogen,

like our Jupiter.

When you look
at our own solar system,

there's one planet
that absolutely dominates,

and that's Jupiter.

Jupiter is actually large enough

that you could fit
1,000 Earths inside it.

And if you add up
all of the mass of the planets,

Jupiter would be about
70% of that.

So when you think about
what's really going on

in a solar system,

these giant planets
are the story you need to tell.

The Jupiter in our solar system

is almost 480 million miles
from the Sun.

But most Jupiter-like exoplanets
discovered so far

orbit less than 10 million miles
from their stars.

The super close proximity
to their stars

heats up the surface
of these gas giants

to over 7,700 degrees
Fahrenheit.

Why are these hot Jupiters
so near to their stars?

And does this closeness point
to why future space travelers

could find it hard to discover
habitable rocky planets?

One day, humans must leave Earth

to find a new home
among the stars.

Astronomers today find few
rocky planets with the potential

to support human life
in the future.

What they do find are many
gas giant worlds

that orbit close to their stars.

Do they unlock the mystery
of why astronomers find

so few Earth-like planets?

A clue comes from
special telescopes

that unlock what gas giant
exoplanets are made of.

Even though

most exoplanets
can't be seen directly,

we can figure out
what's in their atmosphere

because as they orbit the star

and pass directly in front of it

from our point of view,

that starlight passes
through their atmosphere.

Different constituents
in that atmosphere

absorb specific colors of light.

So by examining
the colors of light,

we can figure out
what's in its atmosphere.

The telescopes
discover something strange

about the atmosphere

of a hot Jupiter
called Wasp-39b.

The data reveals that
this planet contains water.

How can a planet that's hotter
than the surface of many stars

contain a liquid that should
vaporize in extreme heat?

Finding a planet with a lot
of water in its atmosphere

close to a star, there's no way
that planet formed there.

Astronomers think
the answer lies in the way

that many gas
giant planets evolve.

Planetary systems start life as
flat disks of gas and rock.

A star ignites at the center.

Its heat blows away
lighter elements

like water and hydrogen.

But millions of miles
further out from the star,

it is cold enough
to bind these materials

into gas giant planets
like Wasp-39b.

The huge gravity of the newly
forming star

pulls the gas giant closer
and closer

over millions of years.

Eventually, the gas giant
ends up so close

that it becomes a hot Jupiter.

Astronomers believe
that many of the hot Jupiters

they find in orbit around alien
stars made the same journey.

This death spiral could be
one reason

why future space travelers
might find few rocky planets

that could be our next home.

A Jupiter-sized gas giant

begins its journey
towards its star.

It steamrolls
everything in its path.

It's possible

that it swallows
smaller planets whole.

A Jupiter-like planet's
huge gravity

smashes other planets
together...

...and sometimes kicks them
out of the system entirely.

The planet eventually settles
into a close orbit

as a hot Jupiter.

But it leaves a trail
of destruction in its wake.

Runaway gas giants could be
responsible for the annihilation

of smaller rocky planets
and systems across the galaxy.

It might be one reason
why Earth-like exoplanets

prove hard to find.

A hot Jupiter migrating towards
its host star

could wreak absolute havoc
on the inner regions

of an early solar system.

Honestly, this ultimately
comes down to the universe

being a fairly
unforgiving place.

It's found many creative ways

to make a solar system
completely uninhabitable.

Jupiter smashed
potential future Earths

before they have
the chance to flourish.

But those planets that do escape
the destruction

can fall victim to other
world-killing phenomena.

Our own solar system shows
future space travelers

what disasters can ruin
promising rocky planets.

Venus is Earth's twin.

Both planets
are roughly the same size,

and they contain
almost identical elements

in the same proportions.

On paper, these characteristics
make Venus

a good candidate
to support life.

The reality is very different.

Venus is the hottest planet
in the solar system.

The surface temperature tops
a scorching

860 degrees Fahrenheit.

That's hot enough to melt lead.

And corrosive clouds
of sulfuric acid

blew through its atmosphere.

Have you ever had one
of those days

where it was just so hot
and humid

that you go outside

and it feels like
it's stinging your skin?

Well, Venus is a lot worse
than that.

Imagine that,
only you're in a fire

and people are pouring acid
on you.

Humans searching
for a new home in the future

could detect that
a Venus-like exoplanet

has many of
the right ingredients

to be a habitable world.

Just like Earth,

it might have
the correct elements

to support liquid water,
an oxygen-rich atmosphere,

and potential life-forms.

Venus is in many ways
much like the Earth.

It's about the same size.
It's a rocky planet.

Billions of years ago,
it probably looked a lot

like the Earth.

It had
an atmosphere like we did.

It may have even had
liquid water on its surface.

Why did Venus transform

from a potentially
habitable planet

into a scorching hell?

A clue lies in the data

that the Venera missions
beamed back to Earth.

The Venera landers captured
the only photographs

ever taken
of the surface of Venus.

These images show the hellish,
baked planet up close.

The instruments on board
the landers

record that the atmosphere
of Venus

is 95% carbon dioxide.

It is the quantity of this gas

that explains why the planet
is so hot.

Carbon dioxide
is a greenhouse gas.

Light from the Sun
can warm the surface,

but the carbon dioxide
absorbs that warmth

and won't let it
escape back into space.

So it's insulating the planet,

and the planet just gets hotter
and hotter and hotter.

Carbon dioxide makes up

just 0.04%
of Earth's atmosphere.

This small amount
of carbon dioxide in the air

allows our planet to radiate
excess heat into space

and stay cool.

If Venus and Earth
are twin planets

born with almost
identical elements

in roughly the same proportions,
then how did Venus end up

with so much carbon
in its atmosphere?

And what turned the once
vast oceans of Mars

into frozen deserts?

Our days on planet
Earth are numbered.

A billion years from now,

humans must find a new home
in another part of the galaxy.

But how will future space
travelers make the right choice

when selecting the next planet
to move to?

Today, astronomers learn
a valuable lesson

from Earth's twin, Venus.

Venus and Earth were born
with the same elements

in roughly the same proportions,

but unlike Earth,
Venus is now a burning hell

with a suffocating
carbon dioxide rich atmosphere.

How did two planets
that started out so similar

end up so different?

A clue lies in where
Earth stores its carbon.

Four billion years ago,

mega volcanic eruptions release
huge amounts of carbon dioxide

into Earth's atmosphere.

Water droplets inside clouds
dissolve this carbon dioxide

and carry it back
to the surface as rain.

Rivers flow to the oceans

and some of the dissolved
carbon dioxide reacts

with other elements
to make calcium carbonate.

Solid calcium carbonate
rains down on the ocean floor

and helps to form
limestone rocks

that lock away
the carbon dioxide.

This cycle over
many millions of years

packs almost all Earth's carbon
into the planet's crust.

But Venus turns this process
on its head.

What triggers a planet like this
to release so much of its carbon

from its rocks
into the atmosphere?

Astronomers believe that a clue
lies in the light

from groups of thousands
of stars called open clusters.

Telescopes measure
the brightness

of the different stars
in these clusters.

These observations reveal

what could bake
an Earth-like planet to death?

The light from middle-aged stars
is much brighter than the light

from young stars
of the same size and type.

Scientists think that the reason
why these stars get brighter

as they age...

Lies deep
inside their super hot cores.

A star heats up
and gets brighter

as it burns through
its nuclear fuel supply.

Astronomers calculate

that our Sun was both 30% cooler

and dimmer 4 billion years ago.

Our understanding of stars
tells us that in the past,

the Sun was not as bright
as it is today.

That means that the planets
would have been bathed

in less radiation.

So Venus probably
would not have been as hot.

It may have had rivers
and oceans,

and it may have been a place
that could harbor life.

Venus shows future humans

how an aging star like our Sun
can wreck a promising planet.

Over the Sun's lifetime,

nuclear fusion inside its core
generates more and more energy,

which builds up in
the surrounding hydrogen shell.

The star heats up.

This extra heat warms
the surface of Venus

125 million miles away.

The oceans on
the planet evaporate

and the atmosphere
fills with water vapor.

This traps heat
that bakes the rocks

and forces them
to release their carbon.

This triggers a runaway
greenhouse effect

that pushes surface temperatures
to over 860 degrees Fahrenheit.

Venus shows how an aging star
can transform the atmosphere

of a habitable-candidate planet

into a thick,
suffocating nightmare.

Our solar system contains
one more example

of what a rocky planet

in the habitable zone
of a distant star might be like.

And it serves as another warning
to future humans

looking for their next home.

Mars is around 75 million miles
further away

from the Sun than Venus.

Probes and rovers sent
to the red planet confirm

that it appears
to be a dead, frozen world.

But new evidence reveals
that Mars

was a very different place
billions of years ago.

The Mars reconnaissance orbiter

takes super detailed images
of the martian geology.

These photographs reveal
the telltale signs

that water shaped
much of the landscape of Mars.

At one time,
Mars had river valleys

that were full,
lakes that were full.

It was raining.
It was snowing.

It was very much like Earth.

Over time,
this wonderful Earth-like world

that was friendly to life
turned into a dead, cold desert.

What happened to Mars?

NASA's maven spacecraft

uncovers a clue in 2017.

Maven monitors
the atmosphere of Mars.

The probe discovers that each
year, around 35,000 tons of gas

escapes into space from the
atmosphere of the red planet.

Every single second
that ticks by,

Mars is shedding a little bit
of its gaseous atmosphere

into the void of space,

and that's like stealing coins
from a cash register

every single day.

Each individual theft
is pretty small,

but the amount really
adds up over time.

The thinning atmosphere of Mars

lowers the planet's
atmospheric pressure

and liquid water boils away.

The atmosphere cannot trap heat
to warm the planet.

In the past,
Mars has what it takes

to be a viable, habitable world.

What is robbing
the red planet of its gas?

And can mysterious mega geysers
millions of miles from Earth

redefine the search
for a habitable planet?

Humans in the future
must find a new home

in another part of the galaxy.

Astronomers today scour
the cosmos for planets

that can support complex life.

But our solar system
contains a warning

about how the galaxy
can wreck habitable worlds.

What transformed the oceans
on Mars into barren deserts?

The data from NASA missions to
the red planet reveals a clue.

It shows that the magnetic field
of Mars is 40 times weaker

than that of Earth.

A planet's magnetic field

is its protective armor
against the Sun.

The Sun blasts
the inner solar system

with an intense stream
of radiation.

The weak magnetic field of Mars

cannot withstand
this punishment.

The Sun's radiation rips away
the martian atmosphere,

one molecule at a time.

Astronomers think they know
why the magnetic field of Mars

is failing.

The super hot metal ball at the
center of the planet is cooling.

We think that
the magnetic field of a planet

is generated by its rotating,
hot, molten core.

So the bigger the planet,
the bigger the core,

and the longer it takes
to cool down.

The mass of Mars is
around 10 times smaller

than that of Earth.

This difference in size

unlocks why the magnetic field
of the red planet is so weak.

And it shows future humans
looking for our next home

what can happen if they settle
a rocky planet

that is too small.

One billion years
after Mars forms,

the planet is a water-rich world
covered in rivers and oceans.

Around it is a protective
magnetic field

that emanates from its
churning molten-metal core.

But Mars is so small
that it loses heat quickly

and solidifies
from the outside in.

The core hardens
and the flow of metal slows,

disturbing and weakening
the magnetic field.

When this planetary
shield fails completely,

it exposes Mars
to the scorching solar wind.

Energy from the Sun strips
away the martian atmosphere,

and the liquid water
on the surface of Mars

evaporates into space.

If you would have
visited our solar system

billions of years ago,

both Earth and Mars
would have been

these beautiful blue planets.

But then if you came back today,

you realize that something
really changed.

Mars had gone all wrong.

And the difference between
the two planets, one habitable

and one probably not,
is the mass.

Mars warns humans
searching for a second Earth

how the galaxy
can wreck viable planets

in the habitable zones
of stable stars.

We look around our
galaxy and our solar system,

we see that the ingredients
for life are everywhere,

but you need more
than just the ingredients.

You also need
the right conditions.

The universe is a violent place.

So being in a habitable zone
does not guarantee your safety.

Liquid water is the key

to sustaining complex life
long term on another planet.

But where outside the habitable
zone of an alien star

can humans in the future
find water in its liquid form?

When scientists

first came up with the term
"habitable zone,"

they were thinking about
how close a planet

had to be to its star to be
warm enough for liquid water.

But perhaps we need
to look farther out.

Perhaps we've missed something.

NASA's Cassini probe
uncovers a clue.

Cassini studies the giant planet
Saturn and its moons.

In 2015,

the probe takes this photograph
of a frozen moon

called Enceladus.

It shows mysterious plumes
blasting out

at over 750 miles per hour

from icy cracks
in the moon's crust.

Cassini grabs a sample
from one of the plumes.

Analysis reveals
that it contains

tiny grains of water ice

and salty water vapor.

This evidence leads scientists
to a startling conclusion.

It is likely that
only liquid water under pressure

inside Enceladus could blast out
these plumes

from the surface of the moon.

And the huge quantity of water
in each plume

is evidence that they could come
from a giant saltwater ocean

locked inside Enceladus.

When you stand on the beach

or take a boat
out into the ocean,

it seems like it's vast,

just a huge amount
of water out there.

But in fact, it's only a tiny
percentage of the total amount

of mass of the Earth.

On Enceladus,
liquid water makes up a quarter.

A quarter of that moon's
total mass.

Enceladus is around
750 million miles

outside the habitable zone
of our solar system.

How is it possible for this moon
to be warm enough

to contain liquid water?

And how does this heat

transform the search
for our next home world?

Humans in the future must search

beyond our solar system
for a new home world.

The galaxy stacks the odds
against the existence

of a second Earth

in the habitable zone
of an alien star.

Today, scientists hunt
outside the habitable zone

for signs of liquid water,

the key for sustaining
complex life long term.

They find a secret ocean
hidden below the icy shell

of Saturn’s moon, Enceladus.

How is it possible for a moon
over 900 million miles

from the Sun
to contain liquid water?

Astronomers believe
that the answer

lies with the huge gravitational
power of Saturn.

Saturn's immense gravity
squashes and stretches Enceladus

as the moon orbits
on an elliptical path.

This constant warping
of the moon's rocky core

creates friction

and a huge amount of heat.

As this heat radiates outwards,

it melts the lower layers
of the moon's icy shell

to create a subsurface ocean.

Cracks appear in the seafloor.

Hydrothermal vents form
in these gaps

and pump minerals
from the core into the ocean.

It's pretty amazing
when you think about it.

Being way
out of a habitable zone,

having a completely
frozen surface,

and yet still having a warm,
salty ocean?

That is cool.

Astronomers believe
that our galaxy could contain

100 times more moons
than planets.

It is likely that there are
trillions of moons

in the Milky Way.

A watery moon heated by
the gravity of a huge planet

could be a viable new home
for humans in the future.

I remember when the idea came up

that there could be undersurface
oceans on these icy moons

and how amazing that was,
but the thing is,

there are more icy moons
out there

than there are rocky planets.

If we're looking for
liquid water worlds,

maybe we should be looking
for icy moons of gas giants.

If a giant alien planet

is close enough to its star

and its water-rich moon
has a thick atmosphere

to protect against radiation,
then it is possible for the moon

to have liquid water
on its surface.

This moon could look like Earth.

The moons in our solar system
that have liquid-water oceans

are all in the outer part
of our planetary system.

They're very, very cold.

But what if we find
a system out there

that has a massive planet
closer into the star?

Now its moons are warmer.

They actually could be
Earth-like.

There could be atmosphere.
There could be oceans.

There could even be life
on an exomoon.

This isn't science fiction.

This is actually
entirely possible.

Imagine standing
on this lush world

and looking up into the sky

and seeing not only your Sun
but this enormous planet

that you're orbiting,
filling half the sky.

NASA's new James Webb
space telescope

promises to revolutionize
the search for alien worlds.

This next-generation observatory

will help astronomers
study distant planets

and their moons in more detail
than ever before.

It is possible
that the discovery

of a habitable Earth-like planet

could be just around the corner.

Just a few decades ago,
we didn't know of any planets

around other stars,
and someday in the future,

people will talk about this time
and say they didn't even realize

there were other Earths
out there.

Things change fast.

It's wonderful to be along
for the ride.

Today's astronomers see a galaxy

that is a violent,
unpredictable place.

Flares from super huge stars
fry planets instantly.

Gas giants smash smaller,
rocky worlds to pieces.

Solar radiation
bakes planets alive

and strips them
of their atmospheres.

What is for sure
is that the universe

does not make it easy
for life to thrive.

Some of these so-called
habitable exoplanets

might actually be these totally
uninhabitable alien hellscapes.

But today's astronomers

think that the galaxy
contains many viable planets

that future human travelers
can make their homes.

Even though we know
of a lot of exoplanets

and very few of them
are potentially Earth-like,

that doesn't mean there aren't

lots of Earth-like planets
out there.

There are hundreds of billions
of stars in the galaxy.

And planets with conditions
like our own

are hard to detect
for us right now.

So there could still be billions
of Earths out there.

Our future home could
be a rocky planet

around a sunlight star.

It could be an ocean moon
orbiting a gas giant.

There are trillions
of candidates in our galaxy,

our next home is out there
just waiting for us to find it.