Planetary Nebula
An expanding shell of ionized gas ejected from a red giant star in the late stages of stellar evolution. Despite the name, it has no connection to planets. The glowing gas is illuminated by the hot core of the dying star.
Source: science.nasa.gov
APODs including "Planetary Nebula"
M27: The Dumbbell Nebula
29/07/1995
July 29, 1995 M27: The Dumbbell Nebula Credit: The Electronic Universe Project, Karen Gloria Explanation: The Dumbbell Nebula is a beautiful red and blue planetary nebula in the constellation of Vulpecula. It is the 27th object on Charles Messier's list of diffuse sky objects, and so is referred to as M27. Its high surface brightness makes it a good target for small telescopes. The term planetary nebula, used to describe this general class of objects, is misleading. Although these objects may appear round and planet-like in small telescopes, astronomers have determined them to be stars surrounded by cocoons of gas blown off in the late stages of evolution. For more information on M27 see The Electronic Universe Project's write-up. Many images of Messier objects can be found in The Electronic Universe Project's The Galaxy Gallery: Messier Objects.