Habitable zone

also called the Goldilocks zone

The band of orbits around a star where a rocky planet could hold liquid water on its surface, given the right atmosphere.

The habitable zone is the range of distances from a star where a planet gets about the right amount of light for liquid water to be stable on its surface: not so close that the water boils away, not so far that it freezes solid. Because a bright, hot star pours out far more energy than a dim red dwarf, the zone sits well out from big stars and hugs in tight around small ones.

Being inside the zone is a hint, not a promise. It says the sunlight is right; it says nothing about whether a world actually has water, an atmosphere, or a breathable sky. gravityfinder computes each planet's zone from its star's temperature and brightness (the Kopparapu 2013 boundaries) and marks worlds as in, near, or outside it. Venus and Mars both skirt the Sun's zone, and neither is a place you could take a drink.

See it in action

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