- [Narrator] You've seen weird,
wonderful worlds in science fiction.
We don't yet know what sorts of life might exist out there.
But some of the planets not unlike the ones
in your favorite stories are real.
At NASA we're studying them.
They're called exoplanets.
The term exoplanet means a planet outside our solar system,
a planet that doesn't orbit our sun.
Most orbit other stars,
but some are just sunless wanders
out in the space between the stars.
Now, just the fact that they orbit other stars
means exoplanets are extremely far away.
Most are too far to even dream
of sending space probes to explore them.
So we study them in other ways, like with telescopes
on the ground and in space that can observe
these far off planets from right here in our solar system.
Here's the thing about exoplanets.
They are everywhere.
In fact, from our observation so far,
we know there are more planets than stars.
So there's our solar system.
Then there are all the billions
of planetary systems in our galaxy, the Milky Way.
Then there are all the billions of other galaxies.
Basically, there are a lot of exoplanets out there.
Each of the stars you see in the night sky is the sun
for any planets that orbit around it.
But not all stars are created equal.
Bigger stars burn way brighter and hotter
and don't last as long.
Smaller, fainter stars like our sun
and red dwarf stars last much longer.
But even nice cool red dwarf stars can have powerful flares
that blast their planets with radiation.
We're still trying to understand which kinds
of stars provide long lasting stable conditions
that could allow life a chance to take hold
and evolve like it did here on Earth.
Exoplanets are super hard to see both because
they're so far away and because
they're so much fainter than their stars.
But we've worked out some clever methods to detect them
and even take pictures of some.
So what can we observe?
Well, for many, we can determine their size,
their mass, how much they weigh,
and how far away from their stars they orbit.
From these and a few other clues,
we can infer a bunch of other qualities
like how hot or cold it might be on their surfaces
or if they even have surfaces.
We can tell that some are gas giants like Jupiter
while others are like bigger bulkier versions of Earth.
For some, we can determine they have atmospheres
and even some of the gases in those atmospheres.
Most exoplanets are very different from our planet.
They have a lot of weird wild variety with gas giants
much bigger than our own Jupiter and other planets
with oceans of lava or rainy glass or even gemstone.
Funny thing is looking at how they're arranged
as families of planets, we don't see a lot
of exoplanet systems that look like ours so far.
Many are arranged quite differently.
So we might actually be the weird ones.
Some planets are closer to their stars.
Some are super far.
Some even orbit multiple stars.
Imagine having two or three suns in the sky.
So why do we study exoplanets?
Well, our interest in finding worlds
with life on them is a big factor.
We want to know more about what makes a planet a place
with all the right ingredients and conditions for life,
what scientists refer to as habitability.
How does it happen?
How common is it?
We think the most life-ready planets are the ones
most similar to Earth with a range of qualities
that include similar size and composition to our planet
and being at the right distance from their stars
to have liquid water on the surface.
These qualities are really challenging to observe
from so far away, but we're working on it.
Exoplanets teach us a bunch of other things too.
Studying other planetary systems helps us better
understand the story of our own planet family
including Earth.
Scientists detected the first exoplanets in the 1990s.
But now we're finding tons more, thousands so far.
We're studying their atmospheres
and even making weather maps for some.
We're surveying exoplanets to understand all their variety.
And the more we learn, the more it powers our curiosity,
the more we want to explore exoplanets,
planets outside our solar system.