Planet

Planets are bodies that meet several conditions.

They must:
 * Orbit a star
 * Have sufficient mass to be round, or nearly round
 * Not be satellites (moons) of another planetary objects
 * Have strong enough gravity to remove debris and small objects from the area around orbits

There are five planets in Spaceflight Simulator, Mercury, Venus, Earth, Mars, and Jupiter. The latter four have atmospheres, though of their moons only Europa has.