Nebula

A nebula was a cloud of cosmic matter. The Crab Nebula was once a star. (TV: Colony in Space) A spiral nebula was a gas cloud coalescing to form a star system. (TV: Underworld) Plasma storms could form in nebulae like the Horsehead Nebula. (TV: World War Three)

Some nebulae had habitable planets like the Cyclops Nebula, the Dragon Nebula, and the Scorpion Nebula. (TV: The Brain of Morbius, Warriors of Kudlak, Planet of the Dead)