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| Seen through small telescopes and binoculars as a fuzzy glow, M8 is a region of intense star formation with a characteristic pink hue from ionized hydrogen (Balmer H-α recombination line). While red is indeed the hydrogen emission in this image by the 8-m Gemini South telescope on Cerro Pachón in the Chilean Andes, the other colours are false. Ionized sulphur emission is coded in green and infrared starlight in blue.(Click on Image for larger viewing) |
Thanks to Cern Courier for link to
Picture of the Month
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The
Lagoon Nebula (catalogued as
Messier 8 or
M8, and as
NGC 6523) is a giant
interstellar cloud in the
constellation Sagittarius. It is classified as an
emission nebula and as an
H II region.
The Lagoon Nebula was discovered by
Guillaume Le Gentil in 1747 and is one of only two star-forming
nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with
binoculars, it appears as a distinct
oval cloudlike patch with a definite core. A fragile
star cluster appears superimposed on it.
Characteristics
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', 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.
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