Ring Nebula, M57 (NGC 6720)

This is a two-minute exposure taken on the night of September 26th 1994 (UT of observation 27/09/94:04:21). This photograph shows a region 150 arc seconds square. The black-and-white images have been compressed in brightness (approximately a double logarithm) to show both bright and faint features. Alternatively, the pseudo-color version of the same original is used to show more of the fainter features while not saturating the bright regions. Although sky conditions were not the best that Kitt Peak can offer, this image has a "seeing" measurement (average FWHM of several stars) of about 0.8 arc seconds. The image has not been re-oriented to remove either the CCD orientation or the field rotation of the altitude-azimuth design of the WIYN telescope, and is therefore shown with E up and S to the left. About this object 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 some 3000 light-years from Earth (angular size 1.2 arc minutes). Location: 18 53.6 +33 02 (2000)