Crescent Nebula
Crescent Nebula
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| Emission nebula | |
|---|---|
 | |
| Observation data: J2000.0 epoch | |
| Right ascension | 20h 12m 7s[1] |
| Declination | +38° 21.3′[1] |
| Distance | 5,000 ly |
Apparent magnitude (V) | +7.4 |
| Apparent dimensions (V) | 18′ × 12′ |
| Constellation | Cygnus |
| Designations | NGC 6888,[1]Sharpless 105, Caldwell 27 |
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 Friedrich Wilhelm 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.
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".
Contents
1 Image gallery
2 See also
3 References
4 External links
Image gallery[edit]
Crescent Nebula in H-alpha and OIII. Imaged with a 715mm focal length telescope. The hydrogen gas is red. The oxygen is blue.
Image of NGC 6888 using H-alpha filter.
Picture of NGC 6888 captured in narrowband by amateur astronomer Luca Moretti
See also[edit]
- Cygnus Bubble
References[edit]
^ abc "NGC 6888". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2007-04-23..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
^ Erdmann, Robert. "NGC 6888". The NGC/IC Project. Archived from the original on 2012-05-20.
^ "WR 136". jumk.de. Retrieved 25 March 2018.
External links[edit]
 | Wikimedia Commons has media related to Crescent Nebula. |
"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.
Caldwell catalogue | |
|---|---|
| List |
|
| See also |
|
| |
Book:Caldwell catalogue
Category:Caldwell objects 
Portal:Astronomy
Commons:Caldwell objectsCategories:
- NGC objects
- Wolf–Rayet nebulae
- Cygnus (constellation)
- Sharpless objects
- Caldwell objects
- Astronomical objects discovered in 1792
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