WEBVTT

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(SCIENCE TREK MUSIC)

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JOAN CARTAN-HANSEN, HOST: To
understand more about

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exoplanets, you first should
know what a planet is.

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You would think this is an easy
question to answer,

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but it isn't.

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Scientists have been arguing
about this for years.

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The current definition of a
planet is: A body or object that

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orbits a star and not a
different planet.

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It must be big enough to have
enough gravity to force it into

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a spherical shape and it must be
big enough that its gravity has

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cleared away any other objects
of a similar size

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near its orbit.

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Everything else in our solar
system except satellites are

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called small solar
system bodies.

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Our solar system has 8 planets.

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Dwarf planets like Pluto, dozens
of moons and millions of

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asteroids, comets and
meteoroids.

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Now an exoplanet is any planet
beyond our solar system.

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Most are tied to other stars but
there are free-floating or rogue

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exoplanets.

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We've learned some exoplanets
are a bit weird.

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Some are entirely covered by
water, some are covered by

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oceans of lava, and some may
have atmospheres that rain

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rubies or glass.

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For more information about
exoplanets, check out the

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Science Trek website.

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You'll find it at
ScienceTrek.org.