View source for NGC 2359

{{Short description|Emission nebula in the constellation Canis Major}}
{{ Planetary nebula |
| image = [[File:NGC 2359.jpg|300px]]
|caption= Thor’s Helmet Nebula imaged on the occasion of [[ESO]]’s 50th Anniversary.
| name = Thor’s Helmet Nebula
| type = Emission
| epoch = [[J2000]]
| ra = {{RA|07|18|30}}<ref name=simbad>{{cite simbad|title=NGC 2359|access-date=5 October 2012}}</ref>
| dec = {{DEC|-13|13.8|}}<ref name=simbad/>
| dist_ly = 11,960<ref name=zhekov/>
| appmag_v =
| size_v =
| constellation  = [[Canis Major]]
| radius_ly =
| absmag_v =
| notes = HII (ionized) region
| names = GUM 4, LBN 227.66-00.09, SH 2-298, GRS 227.80 -00.20, LBN 1041, RCW 5<ref name=simbad/>
}}

'''NGC 2359''' (also known as '''Thor's Helmet''') is an [[emission nebula]]<ref name="seds">[http://seds.org/~spider/ngc/ngc.cgi?2359 SEDS: NGC 2359] {{webarchive|url=https://web.archive.org/web/20100326114605/http://seds.org/~spider/ngc/ngc.cgi?2359 |date=2010-03-26 }}</ref> in the constellation [[Canis Major]]. The nebula is approximately 3,670 [[parsec]]s (11.96 thousand light years) away and 30 light-years in size.  The central star is the [[Wolf-Rayet star]] [[HD 56925|WR7]], an extremely hot star thought to be in a brief pre-[[supernova]] stage of evolution. It is similar in nature to the [[Bubble Nebula]], but interactions with a nearby large molecular cloud are thought to have contributed to the more complex shape and curved bow-shock structure of Thor's Helmet.

It is also catalogued as [[Sharpless catalog|Sharpless 2]]-298 and [[Gum catalog|Gum]] 4.<ref>{{cite web |url=http://galaxymap.org/cgi-bin/gum.py?s=1 |title=The Gum Catalog |publisher=Galaxymap.org |access-date=2013-10-06 |archive-date=2013-07-16 |archive-url=https://web.archive.org/web/20130716142645/http://galaxymap.org/cgi-bin/gum.py?s=1 |url-status=dead }}</ref>

The nebula has an overall bubble shape, but with complex filamentary structures.  The nebula contains several hundred solar masses of ionised material, plus several thousand more of unionised gas.  It is largely interstellar material swept up by winds from the central star, although some material does appear to be enriched with the products of fusion and is likely to come directly from the star.<ref name=cappa>{{Cite journal | doi = 10.1086/300995| title = A Study of Neutral and Ionized Gas of the Wolf-Rayet Ring Nebula NGC 2359| journal = The Astronomical Journal| volume = 118| issue = 2| pages = 948| year = 1999| last1 = Cappa | first1 = C. E.| last2 = Goss | first2 = W. M.| last3 = Niemela | first3 = V. S.| last4 = Ostrov | first4 = P. G.| bibcode = 1999AJ....118..948C| s2cid = 123709946| doi-access = free}}</ref>  The expansion rate of different portions of the nebula varies from 10&nbsp;km/s to at least 30&nbsp;km/s, leading to age estimates of 78,500 - 236,000 years.  The nebula has been studied at radio and x-ray wavelengths, but it is still unclear whether it was produced at the class O main sequence stage of development, as a [[red supergiant]], [[luminous blue variable]], or mainly as a Wolf-Rayet star.<ref name=zhekov>{{Cite journal | doi = 10.1093/mnras/stu1138| title = X-rays from wind-blown bubbles: An XMM-Newton detection of NGC 2359| journal = Monthly Notices of the Royal Astronomical Society| volume = 443| issue = 1| pages = 12–18| year = 2014| last1 = Zhekov | first1 = S. A.| doi-access = free| bibcode = 2014MNRAS.443...12Z|arxiv = 1406.2463 }}</ref>

'''NGC 2361''' is a bright knot of nebulosity on one edge of the central ring of NGC 2359.

==References==
{{Reflist}}

==External links==
{{commonscat}}
* [[Astronomy Picture of the Day]] - [http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?tquery=ngc+2359 Search for NGC 2359]
* [http://www.astrosurf.com/antilhue/ngc2359.htm astrosurf.com]
* [http://www.kopernik.org/images/archive/n2359.htm Kopernik image]
* {{WikiSky}}
* [http://www.daviddarling.info/encyclopedia/T/Thors_Helmet_Nebula.html Encyclopedia article]
* [http://www.eso.org/public/news/eso1238 ESO celebrates its 50th anniversary]
* [http://www.constellation-guide.com/thors-helmet-ngc-2359/ Thor's Helmet at Constellation Guide]

{{Sh2 objects}}
{{Gum catalogue}}
{{RCW}}
{{Ngc25}}
{{Canis Major}}
{{Sky|07|18|30|-|13|13|48|15000}}

{{DEFAULTSORT:NGC 2359}}
[[Category:Emission nebulae]]
[[Category:Wolf–Rayet nebulae]]
[[Category:Canis Major]]
[[Category:NGC objects|2359]]
[[Category:Sharpless objects]]
[[Category:Star-forming regions]]