Original subtitles

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.

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

It just didn't make it and 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.

Humanity's days on Earth are numbered.

The sun's brightness will increase by 10% over the next 1 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 it 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.

You can imagine any kind of world, water worlds, fire worlds, ice worlds, and you

can be pretty sure that they exist in great numbers.

Astronomers call these alien worlds exoplanets.

Finding a habitable exoplanet out of the trillions that probably exist in our

galaxy, is a huge challenge.

Imagine looking out into the sky where our telescopes don't even have the power

to truly resolve the stars.

All we see is their brightness.

And now try to see something that's a millionth the size of that. It's nearly

impossible.

How do we pinpoint a planet that is like the one we inhabit now?

The answer...

lies in measuring the effect that planets have on the stars they orbit.

When planets pass in front of their star they block out a fraction of its light.

The more the light drops, the bigger the planet.

A large planet tugs on its star as it orbits, making the star wobble.

The bigger the wobble, the more massive the planet.

The size and mass of a planet reveals its density and if it's made of gas,

ice, or rock like the Earth.

And by timing a planet's orbit, they can figure out its distance from the star

and its surface conditions.

In 2016,

Exoplanet hunters using this technique 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 name 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's going to 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.

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 a 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 a 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?

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 orbit 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.

The star is cooler than many similar stars of its type.

This means that three of the planets fall inside the habitable zone of the

system.

Could one or even all three of these planets 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 sites 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.

It's a different story for the planets in the TRAPPIST-1 system.

Tidal locking turns them 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 day side.

and water evaporates away.

The night side 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.

The brave humans who do settle on this thin strip will find themselves living

on a knife edge.

Huge megastorms 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 spots

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 a thousand Earths inside

it. And if you added 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 800 million kilometers from the

Sun.

Most Jupiter-like exoplanets discovered so far orbit less than 15 million

kilometers from their stars.

That's closer than the planet Mercury is to our Sun.

This super close proximity to their stars heats up the surfaces of these gas

giants to over 4,300 degrees Celsius.

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 find habitable rocky 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 that we see from that planet, 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 the moment it's exposed to 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 all the lighter elements like water and hydrogen.

Millions of kilometers away from the star, it is cold enough for hydrogen,

water and ice to exist in large quantities.

These materials bind together to build immense gas giant planets like WASP-39b.

The huge gravity of the newly forming star holds 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 explain 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 steamrollers everything in its path.

It's possible

that it swallows smaller planets whole.

The 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 in systems across the galaxy.

It might be one reason why Earth-like planets prove hard to find.

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.

Hot Jupiters smash 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.

Why did the once temperate climate of Venus change and transform the planet

into a roasting hellhole?

And what turned the once vast oceans of Mars into frozen deserts?

A billion years from now, humans must reach for the stars and find a new home

planet in another part of the galaxy.

Today, powerful telescopes are laying the groundwork.

They pinpoint rocky planets that orbit distant stars But how Earth-like are

these worlds?

What will humans in the future find when they arrive?

A clue lies in the habitable zone of our own solar system 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 460 degrees Celsius.

That's hot enough to melt lead.

and corrosive clouds of sulfuric acid blow 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 carbon-based 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.

that had an atmosphere like we did. It may have even had liquid water on its

surface. But something happened to change it very drastically.

Why did Venus transform from a potentially habitable planet into a

scorching hell?

A clue lies in the data that the Venera missions beam back to Earth.

The Venera landers capture 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?

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 of 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 searching

for a new home what happens to a promising planet in a habitable zone if

it is too close to an aging star like our sun

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.

The sun's extra heat warms the surface of Venus 200 million kilometers 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 460 degrees Celsius.

Venus shows how an aging star can transform the atmosphere of a

potentially habitable 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 120 million kilometers 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 30,000 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 its atmospheric pressure.

Liquid water boils away.

The atmosphere cannot trap heat to warm the planet.

In the past, Mars has what it takes to be a habitable world like Earth.

So, what is robbing it of its gas?

The data from NASA missions to Mars reveals a clue.

It shows that the magnetic field of the red planet 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 on 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'd 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 and Venus warn humans searching for a second Earth how the galaxy can wreck

viable planets in the habitable zones of stable stars.

The quest for a new home continues.

Can mysterious mega geysers billions of kilometers from Earth redefine the

search for a habitable planet?

And is humanity's next home not a planet close to a star, but a completely

different type of world?

Everywhere that today's astronomers look, they discover how our galaxy

blasts.

roasts, strips, and smashes all the candidates that are close enough to

stars to support life.

When 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.

Liquid water exists on Earth thanks to the perfect combination of temperature

and atmospheric pressure.

Astronomers today know that water exists elsewhere in the universe.

Telescopes and space probes discover vast reserves of frozen water locked

inside planets and asteroids.

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 1200 kilometers per hour from

icy cracks in the moon's crust.

Cassini grabs a sample from one of these 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

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 1.2 billion kilometers 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 could this heat transform the search for our next homeworld?

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 sea floor.

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 the habitable zone,

having a completely frozen surface, and yet still having a warm, salty ocean.

That is cool.

Missions to the outer solar system find evidence that a total of six moons of

Jupiter and Saturn could have oceans beneath their icy shells.

The presence of liquid water in the outer solar system transforms the search

for a second Earth.

It explodes the standard definition of the habitable zone.

The discovery of these warm salty water flows on these distant icy worlds is

completely upending our understanding of what the habitable zone might actually

be.

Astronomers believe that our galaxy could contain a hundred 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 ocean. 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 sun-like 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.