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The Crescent Nebula NGC 6888 in Cygnus

At the heart of this nebula is a Wolf-Rayet star near the end of its life-cycle. W-R HD 192163 is shedding its mass in the form of a stellar wind.moving at 3.8 million mph. At this rate, it loses matter equal to that of our Sun's every 10,000 years. This will eventually result in a supernova explosion. We've seen several planetary nebulae with W-Rs at their center but 6888 is considered an emission nebula, as it fluoresces hydrogen and helium. The surrounding nebulosity is associated with the field around Sadr, the middle star of Cygnus' wing.