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Created page with "{{Night Sky | image = | designation =Sharpless 276 | rightascension =05<sup>h</sup> 27<sup>m</sup> 30<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/si..."
{{Night Sky
| image =
| designation =Sharpless 276
| rightascension =05<sup>h</sup> 27<sup>m</sup> 30<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=sh2-276&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id Barnard's Loop] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref>
| declination =-03° 58′ 00″<ref name=simbad/>
| distance =1,600 ly<ref name=seds>[http://www.messier.seds.org/xtra/ngc/b-loop.html Barnard's loop] from messier.seds.org</ref>
| constellation =Orion
| type =Diffuse nebula
| dimensions =>20°<ref name=seds/>
| magnitude =
| redshift =
| radvelocity =
| propmotion =
| parallax =
}}
'''Barnard's loop''' (Sharpless 276, part of the Orion-Eridanus Bubble) is a [[diffuse nebula]] in the [[constellation]] of [[Orion]], the hunter.<ref name=seds/> The nebula was discovered by E. E. Barnard in 1895 utilising long exposure photographic methods.<ref name=apod>[https://apod.nasa.gov/apod/ap050420.html Barnard's Loop Around Orion ] from apod.nasa.gov</ref> However it may have been observed by [[William Herschel]], one of the great nebula discoverers, in February 1786.<ref name=seds/> Unsurprisingly it is therefore far too faint to be observed with the naked eye. The nebula can be seen as a ring of bright [[gas]] surrounding Orion's belt. The [[Orion nebula]] along with the famous [[horsehead nebula]] are situated within Barnard's loop.
==Properties and Structure==
At 1,600 [[light year]]s away, the nebula's apparent size of over 20° corresponds to a physical size of at least 582 light years.<ref>By direct calculation using values given here.</ref> The segment that is visisible is believed to be part of a larger shell of material, with only the easternmost segment being visible in optical light.<ref name=arxiv>O'Dell, C., Ferland, G., Porter, R. and van Hoof, P. (2011). Physical Conditions in Barnard’S Loop, Components of the Orion-Eridanus Bubble, and Implications for the Warm Ionized Medium Component of the Interstellar Medium. ''The Astrophysical Journal'', 733(1), p.9. [https://arxiv.org/abs/1103.2789 arXiv:1103.2789]</ref> The nebula is expanding at around 15-23 km/s.<ref name=arxiv/> The nebula contains several O and B [[Stellar Classifications|type]] [[star]]s.
Even this nebula may be the inner surface of an even larger nebula that is at least 30 degrees in diameter.<ref>[http://www.daviddarling.info/encyclopedia/B/Barnards_Loop.html Barnard's Loop] from daviddarling.info</ref> As only the inner suface is [[ionization|ionized]], only this is visible. The enveloping nebula would be truly vast and comprise of very hot, low [[density]] [[gas]].<ref name=seds/> Observations of the nebula in [[ultraviolet|ultraviolet light]] have suggested the existence of this larger nebula.
==References==
{{reflist}}
{{Nebulae}}
[[Category:Astronomy]]
[[Category:Nebulae]]
| image =
| designation =Sharpless 276
| rightascension =05<sup>h</sup> 27<sup>m</sup> 30<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=sh2-276&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id Barnard's Loop] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref>
| declination =-03° 58′ 00″<ref name=simbad/>
| distance =1,600 ly<ref name=seds>[http://www.messier.seds.org/xtra/ngc/b-loop.html Barnard's loop] from messier.seds.org</ref>
| constellation =Orion
| type =Diffuse nebula
| dimensions =>20°<ref name=seds/>
| magnitude =
| redshift =
| radvelocity =
| propmotion =
| parallax =
}}
'''Barnard's loop''' (Sharpless 276, part of the Orion-Eridanus Bubble) is a [[diffuse nebula]] in the [[constellation]] of [[Orion]], the hunter.<ref name=seds/> The nebula was discovered by E. E. Barnard in 1895 utilising long exposure photographic methods.<ref name=apod>[https://apod.nasa.gov/apod/ap050420.html Barnard's Loop Around Orion ] from apod.nasa.gov</ref> However it may have been observed by [[William Herschel]], one of the great nebula discoverers, in February 1786.<ref name=seds/> Unsurprisingly it is therefore far too faint to be observed with the naked eye. The nebula can be seen as a ring of bright [[gas]] surrounding Orion's belt. The [[Orion nebula]] along with the famous [[horsehead nebula]] are situated within Barnard's loop.
==Properties and Structure==
At 1,600 [[light year]]s away, the nebula's apparent size of over 20° corresponds to a physical size of at least 582 light years.<ref>By direct calculation using values given here.</ref> The segment that is visisible is believed to be part of a larger shell of material, with only the easternmost segment being visible in optical light.<ref name=arxiv>O'Dell, C., Ferland, G., Porter, R. and van Hoof, P. (2011). Physical Conditions in Barnard’S Loop, Components of the Orion-Eridanus Bubble, and Implications for the Warm Ionized Medium Component of the Interstellar Medium. ''The Astrophysical Journal'', 733(1), p.9. [https://arxiv.org/abs/1103.2789 arXiv:1103.2789]</ref> The nebula is expanding at around 15-23 km/s.<ref name=arxiv/> The nebula contains several O and B [[Stellar Classifications|type]] [[star]]s.
Even this nebula may be the inner surface of an even larger nebula that is at least 30 degrees in diameter.<ref>[http://www.daviddarling.info/encyclopedia/B/Barnards_Loop.html Barnard's Loop] from daviddarling.info</ref> As only the inner suface is [[ionization|ionized]], only this is visible. The enveloping nebula would be truly vast and comprise of very hot, low [[density]] [[gas]].<ref name=seds/> Observations of the nebula in [[ultraviolet|ultraviolet light]] have suggested the existence of this larger nebula.
==References==
{{reflist}}
{{Nebulae}}
[[Category:Astronomy]]
[[Category:Nebulae]]