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NGC6888, THE CRESCENT NEBULA, on 2023-07-31_116 subs x 180 sec

The Crescent Nebula (also known as NGC 6888, Caldwell 27, and Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light-years away from the Earth. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving stellar wind ejected by the star when it became a red giant 250,000 to 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures.