The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as an H II region.
|H II region|
M8, the Lagoon Nebula
|Observation data: J2000 epoch|
|Right ascension||18h 03m 37s|
|Declination||−24° 23′ 12″|
|Distance||4,100 ly (1,250 pc)|
|Apparent magnitude (V)||6.0|
|Apparent dimensions (V)||90 × 40 arcmins|
|Radius||55 × 20 ly|
|Designations||Sharpless 25, RCW 146, Gum 72
NGC 6523, NGC 6530,
The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. In the foreground is the open cluster NGC 6530.
The Lagoon Nebula is estimated to be between 4,000-6,000 light-years from the Earth. In the sky of Earth, it spans 90' by 40', which translates to an actual dimension of 110 by 50 light years. Like many nebulas, it appears pink in time-exposure color photos but is gray to the eye peering through binoculars or a telescope, human vision having poor color sensitivity at low light levels. The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296. It also includes a funnel-like or tornado-like structure caused by a hot O-type star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula. The Lagoon Nebula also contains at its centre a structure known as the Hourglass Nebula (so named by John Herschel), which should not be confused with the better known Hourglass Nebula in the constellation of Musca. In 2006 the first four Herbig–Haro objects were detected within the Hourglass, also including HH 870. This provides the first direct evidence of active star formation by accretion within it.
- "SIMBAD Astronomical Database". Results for M8. Retrieved 2006-11-15.
- Arias, J. I.; Barbá, R. H.; Maíz Apellániz, J.; Morrell, N. I.; Rubio, M. (2006). "The infrared Hourglass cluster in M8". Monthly Notices of the Royal Astronomical Society. 366 (3): 739–757. arXiv: . Bibcode:2006MNRAS.366..739A. doi:10.1111/j.1365-2966.2005.09829.x.
- "SIMBAD Astronomical Database". Results for Hourglass Nebula. Retrieved 2006-12-22.
- "Stormy seas in Sagittarius". Retrieved 31 July 2015.
- The images show the sky at different levels: from the view seen by the unaided eye to one seen through an amateur telescope, with a final zoom in onto the Lagoon Nebula as seen through a professional telescope.
|Wikimedia Commons has media related to Lagoon Nebula.|
- Breaking Waves in the Stellar Lagoon — ESA/Hubble Photo Release
- Messier 8, SEDS Messier pages
- NightSkyInfo.com - M8, the Lagoon Nebula
- Messier 8, Pete's Astrophotography Gallery
- Messier 8, Lagoon Nebula, Map
- Astronomy Picture of the Day (APOD): Lagoon Nebula 
- The Scale of the Universe (Astronomy Picture of the Day 2012 March 12)
- The Lagoon Nebula on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- Lagoon Nebula (M8) on Constellation Guide
- 7/30/2015 Photo release Hubble Space Telescope