A planetarium (plural planetaria or planetariums) is a theater built primarily for presenting educational and entertaining shows about astronomy and the nightsky, or for training in celestial navigation. A dominant feature of most planetaria is the large dome-shaped projection screen onto which scenes of stars, planets and other celestial objects can be made to appear and move realistically to simulate the complex "motions of the heavens".
Can also be used to describe an object that projects star-like lights on a surface (such as the ceiling).
