What is a planet?
The International Astronomical Union defines a planet as a celestial body that:
- It must orbit a star
- It must have enough mass to generate so that its self-gravity draws it into a (nearly) spherical
- It has enough gravity to have cleared smaller objects out of its orbit
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In case you ever feel lost, or want to jump, here’s a map.
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Welcome to the Greenhouse
Earth’s atmosphere works like a greenhouse, trapping heat from the sun to turn our planet into the brown-green-blue-white Earth it...