shapley1 NASA APOD 16 Aug 2011

Shapley 1: An Annular Planetary Nebula
Image Credit: ESO

Explanation: What happens when a star runs out of nuclear fuel? For stars about the mass of our Sun, the center condenses into a white dwarf while the outer atmospheric layers are expelled into space and appear as a planetary nebula. This particular planetary nebula, pictured above and designated Shapley 1 after the famous astronomer Harlow Shapley, has a very apparent annular ring like structure. Although some of these nebulas appear like planets on the sky (hence their name), they actually surround stars far outside our Solar System.