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CrescentNebula
The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth.

HistoryEdit

It was discovered by Friedrich Wilhelm Herschel in 1792.

It is formed by the fast stellar wind from the Wolf-Rayet-class star Hathor (WR 136) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 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.

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