|Right ascension||05h 35m 17.3s|
|Declination||-05o 23′ 28″|
|Type of object||Nebula|
|Dimensions||85 x 60 arc minutes|
|Magnitude||Apparent Mag: 4.0|
|Distance from Earth||1,344±20 ly|
|Parallax||2.57 ±0.15 mas|
The Orion Nebula (also known as Messier 42), is the brightest star forming, diffuse nebula in the sky, situated south of the belt of Orion. Having an apparent magnitude of +3, the nebula can be seen by the unaided eye in moderately dark skies. It is estimated to be some 24 light years across and is some 1,344±20 light years from Earth. The Orion Nebula itself is only part of a vastly larger star forming nebular region called the Orion Molecular Cloud Complex.
The Orion Nebula is one of the most studied and photographed objects in the night sky, and is among the most intensely studied celestial features by astronomers that have revealed a wealth of knowledge on how stars and planetary systems are formed from collapsing clouds of gas and dust.
The nebula was probably known to ancient people as it is visible to the naked eye, the Maya had a folk tale which dealt with the region of the sky with Orion. Ptolemy did include it in the Almagest (Great Book), Tycho Brahe also made note of the object in the late 16th century, and in 1603, Johann Bayer recorded it as Theta Orion in his Uranometria. Galileo also looked towards the region the nebular is located and detected several faint stars. None of these astronomers though, realized there was a nebula.
The credit for discovering the nebula is given to Nicholas-Claude Fabri de Peiresc who in 1610 first recorded of a cloudy nebulosity in the Orion constellation. Jesuit astronomer Johann Baptist Cysatus independently found the nebula in 1611 and published a note about it seven years later. It was independently rediscovered by Christiaan Huygens in 1656, who is often credited for its discovery. The designation M42 was given to the nebula by Charles Messier, who recorded it in the first edition of his catalog of deep sky objects in 1774 (completed in 1771). The nebula is also known as the first deep sky observation by William Herschel in 1774, using the new reflecting telescope he'd recently completed.
Using spectroscopy, the gaseous nature of the Orion Nebula was identified in 1865 by William Huggins. On September 30, 1880, the Orion Nebula became the first nebula to be successfully photographed, by Henry Draper, who later obtained a second, more detailed photograph of the Orion Nebula. In 1993, the Hubble Space Telescope first looked to the Orion Nebula, and in 2005 recorded the most detailed images of the nebula yet, photographing over 3,000 stars contained within.
Information and Structure
The Nebula itself is actually part of a larger nebula structure known as the Orion Molecular Cloud Complex that actually extends throughout the Orion constellation, and also holds the Horsehead Nebula, Barnard's Loop, M43, M78 and the Flame Nebula.
Various features in the Orion Nebula have been given their own names by observers over the years. The dark nebular lane that separates M34 from the main nebula And extending into the brightest part is nicknamed the "Fish's Mouth". The brighter regions located on both sides of this dark dust feature are known as the "wings". At the end of the "Fish's Mouth" is the open cluster of new stars called the "Trapezium cluster" (named after the original quartet of stars known there). "The Sword" is the name of the wing extension in the southeast of the nebula, while the brighter area of nebula below the Trapezium is referred to as "The Thrust". The large region in the west of the nebula is simply known as "The Sail".
The Trapezium Cluster itself, first observed by Galileo as a group of stars, is an open cluster of eight known newborn stars, several of which are binaries. The cluster was created right out of the nebula and each of the stars are within 1.5 light years of each other. It may be part of the larger Orion Nebula Cluster, which contain some 2,000 stars in total, spread over an area of 20 light years.
The Orion Nebula is the primary example of a stellar nursery where new stars are being born. Recent observations of the nebula have revealed approximately 700 stars in various stages of formation within the nebula. In addition, the Hubble has found over 150 proplys, (protoplanetary disks) in the nebula. Such systems are considered to be the earliest stages of solar system formation. The large number located just in this one nebula is viewed as evidence that the formation of star systems is a common occurrence in the universe.