The Lagoon Nebula, catalogued as Messier 8 and as NGC 6523, is a giant interstellar cloud in the constellation Sagittarius (the Archer). It is classified as an emission nebula and as an H II region and was discovered by Giovanni Hodierna before 1654. M8 is estimated to be between 4,000-6,000 light years from the Earth, spanning 140 by 60 light years. The name refers to the curving dark furrow that cuts nearly through the middle of the nebula, dividing it in half.
Although the name definitely suits the beauty of this object, “lagoon” does suggest tranquillity and there is nothing placid about the high-energy radiation causing these intricate clouds to glow. This new NASA/ESA Hubble Space Telescope image shows the region is filled with intense winds from hot stars, churning funnels of gas, and energetic star formation, all embedded within an intricate haze of gas
and pitch-dark dust. 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.
Lagoon Nebula’s surrounding region contains many fine objects. It Is complemented on its eastern side by NGC 6530 – a loose open star cluster composed of more than a hundred known bright members and hundreds of fainter members probably accompanying them. Just half a degree north lies another prominent diffuse nebula, M20, the “Trifid”, in the same low-power field with the open star cluster M21. Sweeping an area 1° southeast of M8 is the globular cluster NGC 6544, and NGC 6553; another globular located one more degree to the southeast.
Credits: NASA, Night Sky Info, Wikipedia.