Messier Index/M8

Lagoon Nebula
M8HunterWilson.jpg
M8, the Lagoon Nebula Courtesy Hunter Wilson
Observation data: J2000 epoch
Type Emission
Right ascension 18h 03m 37s[1]
Declination −24° 23′ 12″[1]
Distance 4,100 ly (1,250 pc)[2]
Apparent magnitude (V) 6.0
Apparent dimensions (V) 90 × 40 arcmins
Constellation Sagittarius
Physical characteristics
Radius 55 × 20 ly
Absolute magnitude (V) ???
Notable features
Other designations Sharpless 25, RCW 146, Gum 72
M8 contains:
    NGC 6523, NGC 6530[1],
    Hourglass nebula[3]

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.

Characteristics

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.

left|thumb|Central region of the Lagoon Nebula, showing the Hourglass Nebula to the right

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.[2]

References

  1. a b c "SIMBAD Astronomical Database". Results for M8. http://simbad.u-strasbg.fr/Simbad. Retrieved 2006-11-15. 
  2. a b 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. 
  3. "SIMBAD Astronomical Database". Results for Hourglass Nebula. http://simbad.u-strasbg.fr/Simbad. Retrieved 2006-12-22. 

External links

Last modified on 24 August 2009, at 22:06