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Universe of the Hubble Space Telescope 2001 Calendar

The Ring Nebula (or M 57) is the most famous of all the planetary nebulae. Named because they look like planets when viewed with small telescopes, planetary nebulae are actually spherical shells of gas that are cast off by aging giant stars late in life. The spherical shells look like rings because they are seen in projection. The Ring Nebula was first cataloged by the French astronomer Charles Messier (1730­­1817) and is sometimes designated M 57. In this image, blue represents very hot helium, green represents ionized oxygen, and red represents ionized nitrogen. The hot central star that produced the nebula is visible at the center of the ring. The Ring Nebula is about one light year in diameter and is about 2000 light years distant, toward the constellation Lyra.