Gravity Well

Suns
Updated 1/21/2015

One to three suns exist in each solar system.

Energy output of suns varies by spectral type and size of the star. The amount of energy decreases with distance from the sun. The amount of energy to strike each world orbiting a sun determines its orbit zone.

A world's orbit zone is solely determined by the sun that it orbits. Other suns in the same solar system are not considered when determining orbit zone or habitability of a world, no matter how close they pass to the world.

Inferno

Inferno zone worlds are constantly bathed in the fiercest heat of the sun.
Inferno zone worlds never have hospitable environments.

Inner
Inner zone worlds are hot but not too hot.
Inner zone worlds sometimes have habitable environments but they never have an indigenous population.
Inner zone worlds are not counted toward winning the game, even if the environment is habitable.

Habitable
Sometimes called the Goldilocks Zone, energy output from the sun is just right at this distance.
Habitable zone worlds usually have habitable environments, though not always.
Habitable zone worlds with habitable environments should be colonized to win the game.

Outer
Outer worlds are cold but not too cold.
Outer worlds sometimes have habitable environments but they never have an indigenous population.
Outer worlds are not counted toward winning the game, even if the environment is habitable.

Frigid
Forever in dim darkness, frigid zone worlds receive feeble energy from the sun.
Frigid zone worlds never have hospitable environments.