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Created page with "{{Night Sky | image = | designation =NGC 6369 | rightascension =17<sup>h</sup> 29<sup>m</sup> 20.45<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/..."
{{Night Sky
| image =
| designation =[[NGC]] 6369
| rightascension =17<sup>h</sup> 29<sup>m</sup> 20.45<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=little+ghost+nebula&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id NGC 6369] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref><ref name=2mass>Cutri, R. (2003). 2MASS All Sky Catalog of point sources. The IRSA 2MASS All-Sky Point Source Catalog. [http://adsabs.harvard.edu/abs/2003tmc..book.....C Online]</ref>
| declination =-23° 45′ 34.8″<ref name=simbad/>
| distance =5,053 ly<ref name=arxivDist>Schwarz, H. and Monteiro, H. (2006). 3D photoionization structure and distances of Planetary Nebulae III. NGC 6781. ''Exacta'', 4(2). [https://arxiv.org/abs/astro-ph/0604501 arXiv:astro-ph/0604501]</ref>
| constellation =Ophiuchus
| type =
| dimensions =0.467'<ref name=simbad/>
| magnitude =Apparent Mag: +12.0<ref name=simbad/>
| redshift =
| radvelocity =-106±5 km/s<ref name=simbad/><ref>Blaauw, A. (1954). General Catalogue of Stellar Radial Velocities. ''The Astrophysical Journal'', 119, p.689. [http://adsabs.harvard.edu/abs/1954ApJ...119..689B Online]</ref>
| propmotion =
| parallax =
}}
The '''Little ghost nebula''' (NGC 6369) is a [[planetary nebula]] in the [[constellation]] of [[Ophiuchus]].<ref name=esa>[https://www.esa.int/Our_Activities/Space_Science/Exploring_space/Little_Ghost_Nebula_NGC_6369 Little ghost nebula NGC 6369] from esa.int</ref> The nebula was first observed by [[William Herschel]] in the 18<sup>th</sup> century.<ref name=apod>[https://apod.nasa.gov/apod/ap120114.html NGC 6369: The Little Ghost Nebula] from apod.nasa.gov</ref> Images of the nebula taken by the [[Hubble Space Telescope]] have revealed the nebula to possess an extraordinarily intricate structure.
==Properties and Structure==
The nebula is situated around 5,000 [[light year]]s from [[Earth]] in the constellation of [[Ophiuchus]], though some estimates put it at only 2,000 ly.<ref name=arxivDist/><ref name=illinois>[http://stars.astro.illinois.edu/sow/n6369.html THE LITTLE GHOST NEBULA] from stars.astro.illinois.edu</ref> Its apparent size of 28 arcseconds therefore corresponds to a physical diameter of 0.3 ly.<ref name=illinois/> The nebula is a double-shelled planetary nebula meaning the [[gas]] and dust it is composed from is arranges in two shells as can be seen in images.<ref name=arxiv>Ramos-Larios, G., Guerrero, M., Vázquez, R. and Phillips, J. (2011). Weak and Extended H2 Emission in NGC 6369. ''Proceedings of the International Astronomical Union'', 7(S283). [https://arxiv.org/abs/1305.4211 arXiv:1305.4211]</ref> Its outer envelope has a filamentary structure as well as rather faint bipolar extensions. These knots are separated from the main nebula and have been observed in other planetary nebulae such as the [[Hourglass nebula]]. These are located upto 80 arcseconds from the main body of the nebula.<ref name=arxiv/> A [[white dwarf]] [[star]] can be found at the centre of the nebula.
The nebula is composed of a variety of different [[element]]s, the most abundant being [[helium]], [[nitrogen]], [[oxygen]], [[neon]], [[sulphur]] and [[argon]].<ref>Girard, P., Köppen, J. and Acker, A. (2006). Chemical compositions and plasma parameters of planetary nebulae with Wolf-Rayet and wels type central stars. ''Astronomy & Astrophysics'', 463(1), pp.265-274. [https://arxiv.org/abs/astro-ph/0611149 arXiv:astro-ph/0611149]</ref> Evidence for H<sub>2</sub> molecules as well as polycyclic [[Aliphatic and aromatic compounds|aromatic]] [[hydrocarbons]] has been observed.<ref name=arxiv/> The nebula is expanding, as is seen in most other planetary nebulae, at 41 km/s.<ref name=illinois/> The central white dwarf is cool compared to most planetary nebulae and has a [[luminosity]] 1,000 greater than that of the [[Sun]]. However it is still very hot by everyday standards at 58,000 k.<ref name=illinois/> As a result it emits vast quantities of [[ultraviolet]] radiation. This [[ionization|ionizes]] the enveloping gas causing it to glow. However the in the outer region, this radiation is not as intense so does not fully ionize (strip the [[atom]]s of all their [[electron]]s) as it does in the inner regions. Consequently the nebula can be seen to be green/blue (due to hydrogen and oxygen) in the centre but red (due to nitrogen) in its outer region.<ref name=esa/>
==References==
{{reflist}}
{{Nebulae}}
[[Category:Astronomy]]
[[Category:Nebulae]]
| image =
| designation =[[NGC]] 6369
| rightascension =17<sup>h</sup> 29<sup>m</sup> 20.45<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=little+ghost+nebula&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id NGC 6369] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref><ref name=2mass>Cutri, R. (2003). 2MASS All Sky Catalog of point sources. The IRSA 2MASS All-Sky Point Source Catalog. [http://adsabs.harvard.edu/abs/2003tmc..book.....C Online]</ref>
| declination =-23° 45′ 34.8″<ref name=simbad/>
| distance =5,053 ly<ref name=arxivDist>Schwarz, H. and Monteiro, H. (2006). 3D photoionization structure and distances of Planetary Nebulae III. NGC 6781. ''Exacta'', 4(2). [https://arxiv.org/abs/astro-ph/0604501 arXiv:astro-ph/0604501]</ref>
| constellation =Ophiuchus
| type =
| dimensions =0.467'<ref name=simbad/>
| magnitude =Apparent Mag: +12.0<ref name=simbad/>
| redshift =
| radvelocity =-106±5 km/s<ref name=simbad/><ref>Blaauw, A. (1954). General Catalogue of Stellar Radial Velocities. ''The Astrophysical Journal'', 119, p.689. [http://adsabs.harvard.edu/abs/1954ApJ...119..689B Online]</ref>
| propmotion =
| parallax =
}}
The '''Little ghost nebula''' (NGC 6369) is a [[planetary nebula]] in the [[constellation]] of [[Ophiuchus]].<ref name=esa>[https://www.esa.int/Our_Activities/Space_Science/Exploring_space/Little_Ghost_Nebula_NGC_6369 Little ghost nebula NGC 6369] from esa.int</ref> The nebula was first observed by [[William Herschel]] in the 18<sup>th</sup> century.<ref name=apod>[https://apod.nasa.gov/apod/ap120114.html NGC 6369: The Little Ghost Nebula] from apod.nasa.gov</ref> Images of the nebula taken by the [[Hubble Space Telescope]] have revealed the nebula to possess an extraordinarily intricate structure.
==Properties and Structure==
The nebula is situated around 5,000 [[light year]]s from [[Earth]] in the constellation of [[Ophiuchus]], though some estimates put it at only 2,000 ly.<ref name=arxivDist/><ref name=illinois>[http://stars.astro.illinois.edu/sow/n6369.html THE LITTLE GHOST NEBULA] from stars.astro.illinois.edu</ref> Its apparent size of 28 arcseconds therefore corresponds to a physical diameter of 0.3 ly.<ref name=illinois/> The nebula is a double-shelled planetary nebula meaning the [[gas]] and dust it is composed from is arranges in two shells as can be seen in images.<ref name=arxiv>Ramos-Larios, G., Guerrero, M., Vázquez, R. and Phillips, J. (2011). Weak and Extended H2 Emission in NGC 6369. ''Proceedings of the International Astronomical Union'', 7(S283). [https://arxiv.org/abs/1305.4211 arXiv:1305.4211]</ref> Its outer envelope has a filamentary structure as well as rather faint bipolar extensions. These knots are separated from the main nebula and have been observed in other planetary nebulae such as the [[Hourglass nebula]]. These are located upto 80 arcseconds from the main body of the nebula.<ref name=arxiv/> A [[white dwarf]] [[star]] can be found at the centre of the nebula.
The nebula is composed of a variety of different [[element]]s, the most abundant being [[helium]], [[nitrogen]], [[oxygen]], [[neon]], [[sulphur]] and [[argon]].<ref>Girard, P., Köppen, J. and Acker, A. (2006). Chemical compositions and plasma parameters of planetary nebulae with Wolf-Rayet and wels type central stars. ''Astronomy & Astrophysics'', 463(1), pp.265-274. [https://arxiv.org/abs/astro-ph/0611149 arXiv:astro-ph/0611149]</ref> Evidence for H<sub>2</sub> molecules as well as polycyclic [[Aliphatic and aromatic compounds|aromatic]] [[hydrocarbons]] has been observed.<ref name=arxiv/> The nebula is expanding, as is seen in most other planetary nebulae, at 41 km/s.<ref name=illinois/> The central white dwarf is cool compared to most planetary nebulae and has a [[luminosity]] 1,000 greater than that of the [[Sun]]. However it is still very hot by everyday standards at 58,000 k.<ref name=illinois/> As a result it emits vast quantities of [[ultraviolet]] radiation. This [[ionization|ionizes]] the enveloping gas causing it to glow. However the in the outer region, this radiation is not as intense so does not fully ionize (strip the [[atom]]s of all their [[electron]]s) as it does in the inner regions. Consequently the nebula can be seen to be green/blue (due to hydrogen and oxygen) in the centre but red (due to nitrogen) in its outer region.<ref name=esa/>
==References==
{{reflist}}
{{Nebulae}}
[[Category:Astronomy]]
[[Category:Nebulae]]