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How to build a planet.

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Here we are, on the small,
water covered rocky planet,

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orbiting a medium-sized
yellow star.

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We're one of eight planets all
different from one another.

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The ones close to our sun
are small and made of rock.

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The ones farther out are
huge and made of gas.

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Orbiting the sun with
them are many other

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smaller objects, comets,
asteroids, lots of moons.

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Planetary rings, things we
used to think were planets.

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Vast fields of planet-sized ice
chunks and tiny speck of dust.

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All of these things make
up our solar system.

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And for a long time
we thought that's how

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all solar systems would look.

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But back in the '90s, we started
to find out that wasn't true.

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Astronomers found giant gas
planets so close to their stars

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that their atmospheres
boil away into space.

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They found planets orbiting
double star systems.

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They found super-earths 10
times our own planet's mass.

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Why are these planetary
systems so different?

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Is our little solar
system a cosmic oddball?

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To find out, we need to know
more about how planets form.

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And to do that, we need NASA's
James Webb Space Telescope.

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To study the formation
of stars and planets,

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astronomers look
at the giant clouds

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of molecular gas and dust,
where new stars are still

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being born today.

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But when we turn our most
powerful tool, the Hubble Space

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Telescope on these clouds,
we see mostly shadow.

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All that gas and
dust cloaks the stars

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blocking their light, but
not all of their light.

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Visible light, the kind
we see with our eyes

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can't get through.

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But infrared light is different.

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Its wavelength
penetrates gas and dust.

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Webb's infrared
detecting instruments

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will capture infrared light
as it emerges from the cloud,

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creating images that look
through the gas and dust

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to reveal the warm
bright objects within.

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With Webb's help, we
will be able to see

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both the newly forming stars
and the disks of debris

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around them that eventually
coalesce into planets

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where we'll even detect
newborn planets cocooned

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inside these disks.

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Normally, it's a real
challenge to see planets

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around other stars.

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This is the best picture we
have of one of these extrasolar

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planets taken by the
Hubble Space Telescope.

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No, not that.

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That's the star.

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The planet is are here.

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It's actually easier
to see the dust

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around planets than
the planets themselves

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since there's so
much dust spread out

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over such a vast area.

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This picture captures
visible light from the star

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as it reflects off
the planet and dust.

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But Webb's infrared vision
will detect the inherent glow

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of these objects as they shine
with their own infrared light.

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In fact, Webb will
observe both gas and dust

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in exquisite detail
around these young stars,

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studying and classifying
showers of tiny pebbles

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as they ride lofting
gaseous winds on a collision

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course with each other, and
eventually planetary destiny.

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Take a look at this animation.

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In the center is a heavy
ball of gas in the process

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of becoming a sun like star.

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Its gravity drags nearby
gas and dust toward it.

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But because that gas is also
zipping around the star,

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its motion balances
the sun's pole

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and keeps it in a stable orbit.

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This also explains why Earth
doesn't careen into the sun.

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Zooming into the disk, we
see small particles in orbit.

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Because the star has drawn
all this material together

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into the same space,
things start to collide.

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Some particles stick
together and develop

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a gravitational pull that
collects more particles.

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Gradually, they form bigger
and bigger objects, planets

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circling their own new sun.

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To identify the materials
around the stars that

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are forming into planets,
Webb uses a technique

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called spectroscopy.

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Webb captures the infrared
light from the star

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and breaks it into colors.

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By studying the way some
of the colors of light

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are blocked and filtered
by this material,

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Webb can tell what
the dust is made of.

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In fact, each atom and molecule
has a unique spectroscopic

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signature.

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Webb can even use spectroscopy
to look for water vapor,

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observing its presence
both in planetary disks

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and in the atmosphere
of existing planets.

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Astronomers are
particularly interested

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in water, because as
a requirement for life

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as we know it.

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They want to know which
planets have water vapor

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and how water is
carried to planets.

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By examining the birth of
solar systems similar to ours,

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we glimpse the ancient
history of our Earth.

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But Webb will do more
than help us understand

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how our planet came to be.

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Astronomers now think that
most of the stars in the Galaxy

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have planets around them.

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We can't possibly measure or
detect all of those planets.

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But by understanding
how they form,

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we can begin to predict
the diversity of planets

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out there, including how
many Earths we can expect

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to find orbiting other stars.

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