Planetary nebulae: ionized light-emitting shells shed by Asymptotic Giant Branch (AGB) stars.
M57—The Ring Nebula (NGC 6720)
M 97—The Owl Nebula (NGC 3587)
Abell 81—Planetary Nebula in Cepheus (IC 1454, PK 117+18 1, ARO 376)
Abell 50—Planetary Nebula in Draco (NGC 6742, PK 78+18.1).
Abell 61 is an old, evolved planetary nebula, about the size of the M97 – The Owl, although much fainter. […]