View source for IC 2118

{{Short description|Reflection nebula in the constellation Eridanus}}
{{Infobox nebula
| name = IC 2118
| image =Starless_witch_head_stack_ks_Final_4.jpg
| caption= IC 2118
| type = Reflection
| epoch = [[Epoch (astronomy)#Julian years and J2000|J2000]]
| ra = {{RA|05|02|00.0}}{{cn|date=June 2023}}
| dec = {{DEC|-07|54|00}}{{cn|date=June 2023}}
| dist_ly = 1,000{{cn|date=June 2023}}
| appmag_v = 13{{cn|date=June 2023}}
| size_v = 3 × {{val|1|ul=°}}{{cn|date=June 2023}}
| constellation  = Eridanus
| radius_ly = 
| absmag_v = 
| notes = 
| names = Witch Head Nebula, Cederblad 41, NGC 1909{{cn|date=June 2023}}
}}
'''IC 2118''' (also known as '''Witch Head Nebula''' due to its shape) is an extremely faint [[reflection nebula]] believed to be an ancient supernova remnant or gas cloud illuminated by nearby [[supergiant]] star [[Rigel]] in the constellation of [[Orion (constellation)|Orion]]. The nebula lies in the [[Eridanus (constellation)|Eridanus]] Constellation,<ref>{{cite web |title=Witch Head Nebula |website=[[NASA]] |archive-url=https://web.archive.org/web/20230622155656/https://www.nasa.gov/multimedia/imagegallery/image_feature_1209.html |archive-date=2023-06-22 |url-status=live |url=https://www.nasa.gov/multimedia/imagegallery/image_feature_1209.html}}</ref> about 900 [[light-year]]s from [[Earth]]. The nature of the dust particles, reflecting blue light better than red, is a factor in giving the Witch Head its blue color. Radio observations show substantial carbon monoxide emission throughout parts of IC 2118, an indicator of the presence of molecular clouds and star formation in the nebula. In fact candidates for pre-main sequence stars and some classic [[T Tauri star|T Tauri stars]] have been found deep within the nebula.<ref>{{cite journal
 | doi=10.1051/0004-6361:20034510
 | author=Kun
 | last2=Prusti
 | first2=T.
 | last3=Nikolić
 | first3=S.
 | last4=Johansson
 | first4=L. E. B.
 | last5=Walton
 | first5=N. A.
 | title=The IC 2118 association: New T Tauri stars in high-latitude molecular clouds
 | journal=[[Astronomy and Astrophysics]]
 | year=2004 | volume=418
 | issue=1 | pages=89–98
 | bibcode=2004A&A...418...89K|arxiv = astro-ph/0402353 | s2cid=15970267
 }}</ref>

The molecular clouds of IC 2118 are probably juxtaposed to the outer boundaries of the vast [[Orion-Eridanus Superbubble|Orion-Eridanus bubble]], a giant supershell of molecular hydrogen blown by the high mass stars of the [[Orion OB1 association]]. As the supershell expands into the interstellar medium, favorable circumstances for star formation occur. IC 2118 is located in one such area. The wind blown appearance and cometary shape of the bright reflection nebula is highly suggestive of a strong association with the high mass luminous stars of Orion OB1. The fact that the heads of the cometary clouds of IC2118 point northeast towards the association is strong support of that relationship.

==See also==
* [[New General Catalogue#Index Catalogue]], IC is acronym for Index Catalogue

==References==
{{Reflist}}

== External links ==
{{Commons category|IC 2118}}
*  [https://web.archive.org/web/20050825030101/http://www.seds.org/~spider/ngc/ngcic.cgi?IC2118 http://www.seds.org/]
*  {{APOD |date=29 December 2009 |title=Image of IC 2118}}
*  [https://web.archive.org/web/20150110045934/http://www.constellation-guide.com/witch-head-nebula-ic-2118/ Witch Head Nebula at Constellation Guide]
{{Orion (constellation)}}
{{sky|05|04|54|-|07|15|00|1000}}

{{DEFAULTSORT:Ic 2118}}
[[Category:IC objects|2118]]
[[Category:Orion (constellation)]]
[[Category:Emission nebulae]]