C27 · nebula

Crescent Nebula

The Crescent Nebula is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth.

RA20h 12m 06sDec+38° 21' 16"

Image: Chuck Ayoub. CC0, via Wikimedia Commons.

Identity & coordinates

Identification

Primary designation: C27
All designations: C27 · NGC 6888 · Crescent Nebula
Object type: Nebula
Constellation: Cygnus
Best viewing: Summer · Autumn

Coordinates & physical

Right ascension (J2000): 20h 12m 06s
Declination (J2000): +38° 21' 16"
Apparent magnitude (V): —
Distance: —

III

Visibility tonight

The science

The Crescent Nebula is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. It was discovered by William Herschel in 1792. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 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.

Summary adapted from Wikipedia · CC-BY-SA-4.0