Ring Nebula (M57)

This image was captured on May 14, second clear sky night in a row.  The image is composed of 15 4-minute exposures with my normal set up (see preceding post).  The Ring Nebula is very tiny - 1.4X1 arc minute but still visible through the eye piece as a faint grey ring.  It is located in the constellation Lyra, south of Vega.  The Ring is a Planetary Nebula.  In this case a torus of bright light-emitting gas surrounding its central star (at 15th magnitude to faint to be seen by my 115 mm telescope).  The inner ring of green is light emitted from exited oxygen and the red outer ring from excited hydrogen.  Its distance and age is estimated at 2,300 ly and 6,000 to 8,000 years respectively.  The Ring is the remainder of a Sun-like star which has blown away its outer envelope of gas after its hydrogen fuel has been exhausted in its inner core.