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The crescent Nebula, against a back drop of vast clouds of hydrogen gas
About the image:
This image is a true colour image shot in RGB on the ZWO ASI 533 MC Pro Cooled astronomy camera using the Optalong L-pro light pollution filter. C27, known as the Crescent Nebula, is a faint HII Emission nebula in the constellation of Cygnus, located not too far from the star Sadr. Surrounding the Crescent nebula are vast clouds of faint hydrogen gas and interstellar dust. A distinct greenish blue shell of ionised oxygen gas surrounds the nebula.
The nebula's shape is formed by fast interstellar winds from the Wolf Rayet star WR136,, which is colliding with and also energising an earlier and slower moving stellar wind that where the gases of the star were ejected when it was a Red Giant around 300,000 years ago. The result is a shell and two shock waves moving outwards and inwards, which heats the gases in the stellar wind to temperatures so high they emit X-rays. The nebula is approx 25 light years in diameter and lies 5,000 light years from earth.
Where in the sky is it?
The Crescent Nebula can be found in the constellations of Cygnus, check the sky map below (click to expand).