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Crescent Nebula (NGC 6888)


Crescent Nebula
The Crescent Nebula. Image courtesy Richard Crisp
A rapidly expanding, luminous shell of gas that surrounds the Wolf-Rayet star WR 136 in the constellation Cygnus. The Crescent Nebula started to form about 250,000 years ago as the central star began shedding its outer envelope in a strong stellar wind. As this wind rammed into the surrounding interstellar medium, it compacted it and sent shock waves into it, resulting in a series of shells, which ultraviolet radiation from WR 136 subsequently ionized and made visible.


angular size 20'
distance 4,700 light-years
position R.A. 20h 12.0m, Dec. +38° 21'


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