Crescent Nebula


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. It was discovered by William Herschel in 1792.[2] It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000[3] to 400,000[citation needed] 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.

Crescent Nebula
Emission nebula
The Crescent Nebula, as taken by an amateur astronomer
Observation data: J2000.0 epoch
Right ascension20h 12m 7s[1]
Declination+38° 21.3′[1]
Distance5,000 ly
Apparent magnitude (V)+7.4
Apparent dimensions (V)18′ × 12′
DesignationsNGC 6888,[1] Sharpless 105, Caldwell 27
See also: Lists of nebulae

It is a rather faint object located about 2 degrees SW of Sadr. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity. Larger telescopes (20 cm or more) reveal the crescent or a Euro sign shape which makes some to call it the "Euro sign nebula".

Image galleryEdit

See alsoEdit


  1. ^ a b c "NGC 6888". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2007-04-23.
  2. ^ Erdmann, Robert. "NGC 6888". The NGC/IC Project. Archived from the original on 2012-05-20.
  3. ^ "WR 136". Retrieved 25 March 2018.

External linksEdit

  • "Crescent". National Optical Astronomy Observatory.
  • "Crescent Nebula: Live Fast, Blow Hard and Die Young". Chandra X-Ray Observatory. 14 October 2003.
  • Crescent Nebula on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
  • Nemiroff, R.; Bonnell, J., eds. (11 November 2007). "NGC 6888: The Crescent Nebula". Astronomy Picture of the Day. NASA. Retrieved 25 March 2018.