File:M57, NGC 6720, Ring Nebula (noao-02678).jpg

English: The Ring Nebula, M57, NGC6720 This true color picture was taken using Ektachrome film at the prime focus of the Kitt Peak 4m telescope on September 1st 1973. This is unusual: normally color images are made by combining black and white images taken through different colored filters. The Ring Nebula, also known as M57 or NGC 6720, is found in the constellation Lyra. A spherical shell of glowing gas surrounds a central hot star. The nebula was formed when the central star ejected perhaps as much as ten percent of its mass, over a period of some millions of years. Initially slow mass loss creates a surrounding shell of material which is later ionized by hotter, faster ejecta, which can result in quite complex structures. The Ring Nebula was the first planetary nebula discovered, so called because of its visual spherical appearance through telescopes in the past. It has a diameter a little under one light-year and is 3000 light-years from Earth (angular size 1.2 arc minutes). Location: 18 hrs 53.6 min +33 deg 02 min (2000) Photograph by Bill Schoening.