One hundred and twenty
light-years away from us,
there's an exoplanet
that can potentially host life.
It's called K2-18b,
and it's a world you'd want to visit.
K2-18b isn't exactly like Earth.
It's more like a Super-Earth.
Yeah, it's 2.6 times larger
and almost nine times
more massive than our planet.
Scientists think it could be
a Hycean exoplanet.
Which is just a fancy way of saying
that it likely
has a hydrogen-rich atmosphere
and is covered in liquid ocean.
That means that K2-18b
could be home to alien life.
Only it would take a really
long time to get there.
If you were hurtling toward
this space rock from Earth,
you'd reach your destination
in about 1.3 million years.
Yeah, you heard right.
Million.
K2-18b has a lot of methane
and carbon dioxide in its atmosphere.
That's not exactly breathable air.
So you'd still need a spacesuit
to walk on this world.
And I wouldn't be too
hyped up about its ocean either.
If an exoplanet has liquid on it,
it doesn't mean that
the liquid is water.
It could be methane or ammonia,
even acid.
Even in our own Solar System,
there's a moon covered
in liquid lakes.
But these are methane
and ethane lakes
and I wouldn't recommend
swimming there.
K2-18b could have a pretty
mild temperature.
For an exoplanet,
that is.
At -100 °C (-148 °F),
you'd find this world
incredibly cold.
Now, the most exciting thing
we found out about this world
is that it could have traces
of dimethyl sulfide.
Woot, woot.
Well, on Earth,
this molecule can only be produced
by living things.
And that means K2-18b
could be home to alien life.
Now, it doesn't mean that
this life would be intelligent.
It could be aquatic or microbial.
Maybe even complex life
if the conditions for it
are just right.
We won't know for sure
unless we travel
to explore this interstellar world.
Now, how do we know all this?
Well, we had the James
Webb Space Telescope
look at this distant world
and take detailed
measurements of its atmosphere.
Most of the exoplanets
have been discovered using
what's called the transit method.
It's when a planet passes
in front of its star and blocks
its starlight.
That's when scientists study
the wavelengths around the planets.
And some of those wavelengths
can tell us
what kind of atmosphere
those distant planets have.
The problem is
exoplanets are really far away.
Trying to figure out
what their surfaces are like
just by peering through
even our most powerful telescopes
is not easy.
Some scientists will argue
that K2-18b
isn't a Super-Earth at all,
but a mini-Neptune.
And that's a bummer
because, as you know,
Neptune is an ice giant.
And if K2-18b is also an ice giant,
then the chances for alien
life on this planet
don't look so good.
Now, you don't have a million years
to travel to this world
to discover it for yourself.
So maybe we should look at a world
that's a lot closer to Earth.
Like Proxima Centauri b.
Proxima Centauri is the closest star
we've discovered.
Only 4.2 light-years away from Earth.
It's part of the Alpha Centauri
star system,
with not two,
but three stars orbiting each other.
The exoplanet Proxima Centauri b
orbits only one of these stars,
but you'll still see the other
two stars as bright dots in the sky.
This exoplanet is slightly larger than Earth
and revolves
uncomfortably close to its host star.
Luckily, that star is a red dwarf
and that's much cooler
and smaller than our Sun.
Which is good news
because that means this planet
isn't getting toasted like Mercury.
Scientists estimate Proxima Centauri b
has an average temperature
of about -39 °C (-38 °F).
That's pretty comfortable
as far as alien worlds go.
The bad news is
that we still don't know much
about the exoplanet’s
gravity or atmosphere.
It might be our best candidate
to set up an interstellar base,
but it also could have
a harsh environment
unsuitable for humanity's
future home.
It might even have an ocean.
Of acid.
Or something deadly like that.
The only way to find out
is to travel there.
And if Proxima Centauri b
doesn't work out, well, don't worry.
There are plenty
of potentially habitable
worlds out there.
Like this one.
Ross 128 b
is 11 light-years from Earth.
It's the second-closest
potentially habitable world
scientists have discovered.
And it's more promising
than Proxima Centauri b.
The thing is,
they both orbit red dwarf stars.
Only Proxima b's
host star is a lot more active
and violent.
It occasionally erupts
and bathes Proxima b in radiation.
Ross 128 b's star is nice and quiet.
And even though this world orbits
20 times closer to its star
than Earth is to the Sun,
it still lies in the habitable zone.
Because, like I said,
red dwarfs are way
cooler than the Sun.
And by cooler,
I just mean temperature.
This world could have a balmy average
temperature of 23 °C (73 °F).
That's only
slightly hotter
than the average temperature
here on Earth.
I don't know about you,
but I could settle there.
Now, we don't know
enough about this world
to call it our new home.
It likely has
lots of harmful radiation
reaching its surface
and its atmosphere
might not be breathable.
But hey,
that's not much worse than Mars.
With efficient life
support systems in place,
we could make it work.
Besides, this Super-Earth
might have its own life on it.
If Ross 128 b did have alien life,
it could be extremely different
from what you might imagine.
Just think about making
the first contact
with an alien species.
What would that be like?
I mean, it could go very wrong too.
For one,
we might not survive the trip
to any exoplanets,
even the nearest ones.
So far, we've discovered
and confirmed over 5,000 alien worlds.
63 of them are potentially habitable.
But we just can't know for sure.
Most planets
we've observed are extremely scary.
There's one exoplanet
that actually looks like Earth.
But this beautiful blue world
is not the kind of place
you could settle on.
If you tried,
you'd be dead within seconds.
But that's a story for another.
for another WHAT IF.