Definitions for "Planetary Nebula"
Keywords:  ejects, nebula, glow, dwarf, giant
A type of nebula caused by an expanding cloud of gas ejected by a dying star. For cool pictures, check out HST's planetary nebula gallery. Hourglass Planetary Nebula
An expanding gas cloud that was created as the result of gas being expelled from a sunlike star in the later stages of its life. Ex. M57 - The Ring Nebula.
A bright cloud of dust and gas surrounding an old star, namely a red giant. Towards the end of its life the star ejects the dust and gas violently, losing most of its mass and becoming a white dwarf. The nebula disappears after approximately 100 000 years. They are called 'planetary' because originally astronomers thought they looked like planetary discs.
an astronomical object that appears nebulous and disk-like in low-resolution observations