Messier Index/M8
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.
| Lagoon Nebula | |
|---|---|
 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 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
- ↑ a b c "SIMBAD Astronomical Database". Results for M8. Retrieved 2006-11-15.
- ↑ 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.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ "SIMBAD Astronomical Database". Results for Hourglass Nebula. Retrieved 2006-12-22.