M57

The Ring Nebula in Lyra, a classic planetary nebula consisting of a shell of gas ejected from a dying star.   Recent research has confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell. We happen to view it from near one pole. The innermost region appears dark as it emits merely UV radiation, while in the inner visible ring, greenish forbidden light of ionized oxygen and nitrogen dominates the color, and in the outer region, only the red light of hydrogen can be excited. The central star is a faint white dwarf whose distance is uncertain, with estimates ranging from 1,000 to 5,000 light years. But recent studies by the US Naval Observatory have given a distance of 2,300 light years. This star is only planet-sized and shines at about 15th magnitude, while slowly cooling off over billions of years, eventually to end its life as a cold black dwarf. For amateurs, it is always a challenge to identify the faint central star of the Ring.

From the expansion rate of one arc second per century given above, the age of the nebula can be roughly estimated under the assumption of constant expansion. For its extension of 60x80 arc seconds, this yields a time of expansion of about 6,000 to 8,000 years.

Image is the result of stacking 5 separate photos taken through each of the color filters, over a period of 3 nights, beginning on July 9, 2009. Total exposure of each color is 25 minutes. Camera used is the ST-8 and the C-14 was operating at F:11

Taken summer, 2005, with the 402 camera on the C-14 operating at F:3.5 using a focal reducer.   Exposure was 5 minutes, from Carbon County.   Fastar image for comparison taken in Salt Lake several years earlier.