The Lagoon Nebula
The Lagoon Nebula is an attractive and intriguing object located about 4000 to 5000 light-years away towards the constellation of Sagittarius (the Archer). The 100 light-year wide nebula is a giant interstellar cloud where stars are forming. Scattered dark patches seen all over the nebula are huge clouds of gas and dust that are collapsing under their own weight and will soon give birth to clusters of young glowing stars. Some of the smallest clouds are known as “globules” and the most prominent ones have been catalogued by the astronomer E.E. Barnard.
A vast, shining star factory known as the Hourglass Nebula appears in the upper right of the bigger Lagoon Nebula. The vivid glow of the Hourglass comes courtesy of a powerful, hot, blue, 50 000 year old star named Herschel 36 that is imbedded in the heart of the region. Strong ultraviolet radiation from another star, Sagitarii 9, also heats up the nebula.
The Lagoon Nebula hosts the young open stellar cluster known as NGC 6530. This home for 50 to 100 stars twinkles in the lower left portion of the nebula. Observations suggest that the cluster is slightly in front of the nebula itself, though still enshrouded by dust, as revealed by the starlight’s reddening. This phenomenon occurs when small dust particles scatter light.
The name of the Lagoon Nebula derives from the wide lagoon-shaped dark lane located in the middle of the nebula that divides it into two glowing sections.
Giovanni Battista Hodierna discovered the Lagoon Nebula around 1654 and described it as a nebulous object. Philippe Loys de Chéseaux classified it as a cluster in 1746 when he managed to resolve individual stars. One year later, Guillaume Le Gentil added his own observations, and since then astronomers have considered the Lagoon Nebula as both a nebula and a stellar cluster. Charles Messier catalogued the Lagoon Nebula as the eighth entry in his catalogue (Messier 8) in 1764. As this partial history of cataloguing and re-cataloguing suggests, this outstanding object has remained a real icon for astronomy buffs over the years.