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Created page with "{{Night Sky | image = | designation =Messier 8 NGC 6523 | rightascension =18<sup>h</sup> 03<sup>m</sup> 37<sup>s</sup> | declination..."
{{Night Sky
| image =
| designation =[[Messier catalogue|Messier 8]]
NGC 6523
| rightascension =18<sup>h</sup> 03<sup>m</sup> 37<sup>s</sup>
| declination =-24° 23′ 12″
| distance =4,100 ly
| constellation =[[Sagittarius]]
| type =[[Emission nebula]]
| dimensions = 90' x 40'
| magnitude =6
| redshift =
| radvelocity =
| propmotion =
| parallax =
}}
The '''Lagoon nebula''' ([[Messier catalogue|M8]], NGC 6523) is an [[emission nebula]] in the [[constellation]] of [[Sagittarius]].<ref name=seds>[http://www.messier.seds.org/m/m008.html M8] from messier.seds.org</ref> It contains an [[open cluster]] of [[star]]s that has a magnitude of 4.6.<ref name=messier-objects>[http://www.messier-objects.com/messier-8-lagoon-nebula/ M8] from constellation-guide.com</ref> It is only just visible to the naked eye under good observation conditions and one of the larger nebulae in Sagittarius.<ref name=earthsky>[http://earthsky.org/clusters-nebulae-galaxies/the-lagoon-nebula-messier-8 The Lagoon nebula] from earthsky.org</ref>
==History==
The Lagoon nebula was discovered by Giovanni Battista Hodierna at some point before 1654 and independently by John Flamsteed in or around 1680.<ref name=seds/> Stars were first resolved by Philippe Loys de Chéseaux in 1746 and so Chéseaux classified it as a cluster. Then in 1747, Guillaume Le Gentil observed the nebula and the cluster simultaneously and catalogued the two together. [[Charles Messier]] added both the nebula and the cluster to his [[Messier catalogue|catalogue]], but mainly described the cluster.<ref name=messier-objects/> [[William Herschel]] catalogued the nebula as two components, and his son John Herschel then added the star cluster and a separate entry in Herschel's catalogue.
==Properties and Structure==
With apparent dimensions of 90'x40', three times that of a full [[moon]], the Lagoon nebula is a particularly large nebula. These dimensions correspond to it being 110x50 [[light year]]s.<ref name=messier-objects/> Its name comes from the dark [[gas]] cloud in the centre, similar to a sandbar separating two lagoons.<ref name=earthsky/> M8 is a H II region, meaning it is mostly composed of [[Ionization|ionized]] [[hydrogen]].
===Open Cluster===
The [[open cluster]] housed inside M8 has been designated NGC 6530 and classified as Trumpler type "II m n".<ref name=seds/> The 50-100 stars in the cluster are loosely concentrated in the centre, and have some range in their magnitude. It is thought the cluster is located in front of the nebula as there is little in the way of reddening that would be expected if it were behind. The hot stars cause the nebula to glow.<ref name=messier-objects/>
===Hourglass Nebula===
The Hourglass nebula if found inside the brightest region of M8. First observed by John Herschel, its name is derived from its shape. It is however a separate object from the Engraved Hourglass nebula in [[Musca]]. The extremely large, hot stars illuminate this region, specifically Herschel 36. In 2006, scientists discovered four [[Herbig-Haro object]]s.<ref name=messier-objects/> These are occur where jets of gas collide with other gas and [[dust]] at high speeds and are often found near young stars.
==References==
{{reflist}}
{{Nebulae}}
[[Category:Astronomy]]
[[Category:Nebulae]]
[[Category:Messier Objects]]
| image =
| designation =[[Messier catalogue|Messier 8]]
NGC 6523
| rightascension =18<sup>h</sup> 03<sup>m</sup> 37<sup>s</sup>
| declination =-24° 23′ 12″
| distance =4,100 ly
| constellation =[[Sagittarius]]
| type =[[Emission nebula]]
| dimensions = 90' x 40'
| magnitude =6
| redshift =
| radvelocity =
| propmotion =
| parallax =
}}
The '''Lagoon nebula''' ([[Messier catalogue|M8]], NGC 6523) is an [[emission nebula]] in the [[constellation]] of [[Sagittarius]].<ref name=seds>[http://www.messier.seds.org/m/m008.html M8] from messier.seds.org</ref> It contains an [[open cluster]] of [[star]]s that has a magnitude of 4.6.<ref name=messier-objects>[http://www.messier-objects.com/messier-8-lagoon-nebula/ M8] from constellation-guide.com</ref> It is only just visible to the naked eye under good observation conditions and one of the larger nebulae in Sagittarius.<ref name=earthsky>[http://earthsky.org/clusters-nebulae-galaxies/the-lagoon-nebula-messier-8 The Lagoon nebula] from earthsky.org</ref>
==History==
The Lagoon nebula was discovered by Giovanni Battista Hodierna at some point before 1654 and independently by John Flamsteed in or around 1680.<ref name=seds/> Stars were first resolved by Philippe Loys de Chéseaux in 1746 and so Chéseaux classified it as a cluster. Then in 1747, Guillaume Le Gentil observed the nebula and the cluster simultaneously and catalogued the two together. [[Charles Messier]] added both the nebula and the cluster to his [[Messier catalogue|catalogue]], but mainly described the cluster.<ref name=messier-objects/> [[William Herschel]] catalogued the nebula as two components, and his son John Herschel then added the star cluster and a separate entry in Herschel's catalogue.
==Properties and Structure==
With apparent dimensions of 90'x40', three times that of a full [[moon]], the Lagoon nebula is a particularly large nebula. These dimensions correspond to it being 110x50 [[light year]]s.<ref name=messier-objects/> Its name comes from the dark [[gas]] cloud in the centre, similar to a sandbar separating two lagoons.<ref name=earthsky/> M8 is a H II region, meaning it is mostly composed of [[Ionization|ionized]] [[hydrogen]].
===Open Cluster===
The [[open cluster]] housed inside M8 has been designated NGC 6530 and classified as Trumpler type "II m n".<ref name=seds/> The 50-100 stars in the cluster are loosely concentrated in the centre, and have some range in their magnitude. It is thought the cluster is located in front of the nebula as there is little in the way of reddening that would be expected if it were behind. The hot stars cause the nebula to glow.<ref name=messier-objects/>
===Hourglass Nebula===
The Hourglass nebula if found inside the brightest region of M8. First observed by John Herschel, its name is derived from its shape. It is however a separate object from the Engraved Hourglass nebula in [[Musca]]. The extremely large, hot stars illuminate this region, specifically Herschel 36. In 2006, scientists discovered four [[Herbig-Haro object]]s.<ref name=messier-objects/> These are occur where jets of gas collide with other gas and [[dust]] at high speeds and are often found near young stars.
==References==
{{reflist}}
{{Nebulae}}
[[Category:Astronomy]]
[[Category:Nebulae]]
[[Category:Messier Objects]]