Messier Index/M8< Messier Index
M8, the Lagoon Nebula Courtesy Hunter Wilson
|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|
|Absolute magnitude (V)||???|
|Other designations||Sharpless 25, RCW 146, Gum 72
NGC 6523, NGC 6530,
The Lagoon Nebula (catalogued as Messier 8 or M8, and as NGC 6523) is a giant w:interstellar cloud in the w:constellation Sagittarius. It is classified as an w:emission nebula and as an w:H II region.
The Lagoon Nebula was discovered by w:Guillaume Le Gentil in 1747 and is one of only two star-forming w:nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with w:binoculars, it appears as a distinct w:oval cloudlike patch with a definite core. A fragile w:star cluster appears superimposed on it.
The Lagoon Nebula is estimated to be 4,100 w:light-years from the Earth. In the sky of Earth, it spans 90' by 40', translates to an actual dimension of 110 by 50 light years. Like many nebulas, it appears w:pink in time-exposure color photos but is gray to the eye peering through w:binoculars or a w:telescope, w:human vision having poor color sensitivity at low light levels.
The nebula contains a number of w: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 w:tornado-like structure caused by a hot O-type star that pours out w: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 w:John Herschel), which should not be confused with the better known w:Hourglass Nebula in the constellation of w:Musca. In 2006 the first four w:Herbig-Haro objects were detected within the Hourglass, also including w:HH 870. This provides the first direct evidence of active star formation by accretion within it.
- "SIMBAD Astronomical Database". Results for M8. http://simbad.u-strasbg.fr/Simbad. 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. doi:10.1111/j.1365-2966.2005.09829.x. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006MNRAS.366..739A.
- "SIMBAD Astronomical Database". Results for Hourglass Nebula. http://simbad.u-strasbg.fr/Simbad. Retrieved 2006-12-22.