Editing Crescent Nebula (section)

{{Short description|Emission nebula in the constellation Cygnus}}{{More citations needed|date=May 2024}}{{Infobox nebula
| name = Crescent Nebula
| image = NGC 6888.png
| caption = The Crescent Nebula, captured with a color camera, narrowband filter, and high-speed amateur telescope
| type = Emission
| epoch = J2000.0
| ra = {{RA|20|12|7}}<ref name="simbad">{{cite simbad
  | title=NGC 6888
  | access-date=2007-04-23}}</ref>
| dec = {{DEC|+38|21.3}}<ref name="simbad"/>
| dist_ly = 5,000
| appmag_v = +7.4
| size_v = 18′ × 12′
| constellation  = [[Cygnus (constellation)|Cygnus]]
| radius_ly = 
| absmag_v = 
| notes = 
| names = [[New General Catalogue|NGC]] 6888,<ref name="simbad"/> [[Sharpless catalog|Sharpless]] 105, [[Caldwell catalogue|Caldwell]]&nbsp;27
}}
The '''Crescent Nebula''' (also known as '''NGC 6888''', '''Caldwell 27''', '''Sharpless 105''') is an [[emission nebula]] in the constellation [[Cygnus (constellation)|Cygnus]], about 5000 [[light-year]]s away from [[Earth]]. It was discovered by [[William Herschel]] in 1792.<ref name=ngcic>{{cite web |url=http://www.ngcicproject.org/ngcicdb.asp |title=NGC 6888 |work=The NGC/IC Project |last1=Erdmann |first1=Robert |url-status=dead |archive-url=https://web.archive.org/web/20120520010558/http://www.ngcicproject.org/ngcicdb.asp |archive-date=2012-05-20 }}</ref> 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<ref name="jumk">{{cite web|url=http://jumk.de/astronomie/big-stars/wr-136.shtml |title=WR 136 |access-date=25 March 2018 |website=jumk.de}}</ref> to 400,000{{citation needed|date=January 2013}} years ago. The result of the collision is a shell and two [[shock wave]]s, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to [[X-ray]]-emitting temperatures.