Editing Sagittarius (constellation) (section)

==== Nebulae ====
Sagittarius contains several well-known nebulae, including the [[Lagoon Nebula]] (Messier 8), near λ Sagittarii; the [[Omega Nebula]] (Messier 17), near the border with [[Scutum (constellation)|Scutum]]; and the [[Trifid Nebula]] (Messier 20), a large nebula containing some very young, hot stars.
* The [[Lagoon Nebula]] (M8) is an emission nebula that is located 5,000 light-years from Earth and measures 140 light-years by 60 light-years ([[celestial sphere|1.5°]]). Though it appears grey in telescopes to the unaided eye, long-exposure photographs reveal its pink hue, common to emission nebulae.<ref name="Wilkins Dunn 2006" /> It is fairly bright, with an integrated magnitude of 3.0.{{sfn|Levy|2005|p=108}} The Lagoon Nebula was discovered independently by [[John Flamsteed]] in 1680,{{sfn|Levy|2005|p=109}} [[Guillaume Le Gentil]] in 1747,<ref name="Wilkins Dunn 2006" /> and [[Charles Messier]] in 1764.{{sfn|Levy|2005|p=109}} The central area of the Lagoon Nebula is also known as the Hourglass Nebula, so named for its distinctive shape. The Hourglass Nebula has its shape because of matter propelled by [[Herschel 36]]. The Lagoon Nebula also features three [[dark nebula]]e listed in the [[Barnard Catalogue]].<ref name="Wilkins Dunn 2006" /> The Lagoon Nebula was instrumental in the discovery of [[Bok globules]], as [[Bart Bok]] studied prints of the nebula intensively in 1947. Approximately 17,000 Bok globules were discovered in the nebula nine years later as a part of the [[Palomar Sky Survey]]; studies later showed that Bok's hypothesis that the globules held [[protostar]]s was correct.{{sfn|Levy|2005|pp=111–112}}
* The [[Omega Nebula]] is a fairly bright nebula, sometimes called the Horseshoe Nebula or Swan Nebula.  It has an integrated magnitude of 6.0 and is 4890 light-years from Earth. It was discovered in 1746 by [[Jean-Philippe de Cheseaux|Philippe Loys de Chésaux]]; observers since him have differed greatly in how they view the nebula, hence its myriad of names. Most often viewed as a checkmark, it was seen as a swan by [[George Frederick Chambers|George F. Chambers]] in 1889, a loon by [[Roy Bishop]], and as a curl of smoke by [[Camille Flammarion]].{{sfn|Levy|2005|p=103}}
* The [[Trifid Nebula]] (M20, NGC 6514) is an emission nebula in Sagittarius that lies less than two degrees from the Lagoon Nebula. Discovered by French comet-hunter [[Charles Messier]], it is located between 2,000 and 9,000 light-years from Earth and has a diameter of approximately 50 light-years. The outside of the Trifid Nebula is a bluish [[reflection nebula]]; the interior is pink with two dark bands that divide it into three areas, sometimes called "lobes". Hydrogen in the nebula is ionized, creating its characteristic color, by a central triple star, which formed in the intersection of the two dark bands.<ref name="Wilkins Dunn 2006" /> M20 is associated with a cluster that has a magnitude of 6.3.{{sfn|Levy|2005|p=114}}
* The [[Red Spider Nebula]] (NGC 6537) is a planetary nebula located at a distance of about 4000 light-years from Earth.
* [[NGC 6559]] is a star-forming region located at a distance of about 5000 light-years from Earth, in the constellation of Sagittarius, showing both emission (red) and reflection (blue) regions.

In addition, several other nebulae have been located within Sagittarius and are of interest to astronomy.
* [[NGC 6445]] is a [[planetary nebula]] with an approximate magnitude of 11. A large nebula at over one [[arcminute]] in diameter, it appears very close to the [[globular cluster]] [[NGC 6440]].{{sfn|Levy|2005|p=133}}
* [[NGC 6638]] is a dimmer globular at magnitude 9.2, though it is more distant than M71 at a distance of 26,000 light-years. It is a Shapley class VI cluster; the classification means that it has an intermediate concentration at its core. It is approximately a degree away from the brighter globulars [[Messier 22|M22]] and [[Messier 28|M28]]; NGC 6638 is southeast and southwest of the clusters respectively.{{sfn|Levy|2005|pp=167–168}}