Image of the Day: The Red Giant Nebula

6a00d8341bf7f753ef0120a8babf12970b.jpg The Crescent Nebula (NGC 6888 or Caldwell 27) is a ring nebula of breathtaking beauty in the Cygnus constellation, about 5000 light years away. It is formed by the fast stellar wind from a  massive Wolf-Rayet star colliding with and energizing the slower moving wind ejected by the star when it became a super red giant around 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.

Image Credit: NASA/Chandra


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