M-42 and M-43, An Emission Nebula in Orion
aka The Great Orion Nebula, (NGC 1976)

Nicolas-Claude Fabri de Peiresc: (Nov. 26, 1610) 'In the middle of Orion .... Composed of two stars, there is a nebula....'

Giovanni Battista Hodierna: (1654) '.... [shines] in the sword of Orion and includes 22 stars as one can see with the telescope. But this Luminosa is more admirable because of some un-resolvable luminosity in whose middle can be seen three stars....'

Christiaan Huygens: (1656) '....in the sword of Orion are three stars quite close together. In 1656.... twelve showed themselves.... Three of these almost touched each other and, with four others, shone through a nebula so that the space around them seemed brighter than the rest of the heavens....'

C. Messier: (March 4th, 1769) '...the fine nebula in Orion's sword, around the star Theta which is included with three other stars, smaller than can be seen in some good instruments. Messier has prepared a drawing in which he has included the details of this Great Nebula with the greatest care, which can be seen in the Memoirs of the Academy for 1771. Huyghens discovered it in 1656. It had been observed since by many astronomers. Reported on the English Atlas.'

The Orion Nebula (M-42 and M-43; aka NGC 1976) is one of the brightest emission nebulae (gas cloud shining by its own light) to be found in the sky. It can be seen with the un-aided eye as a fuzzy star in the sword region of Orion, and even small binoculars reveals its nebulous nature. M-42 is in fact a blister on the surface of a much larger nebula, the Orion Molecular Cloud Complex (OMC). The OMC extends throughout the constellation of Orion and includes Barnard's Loop, the Horsehead Nebula, M43, M78 and the Flame Nebula. M-42/43 is a region of ionized gas and a major star forming region. The gas glows because it is being excited by ultraviolet light from the newly formed stars in the Trapezium Star Cluster. While many older sources say that the Orion Nebula is 1,600 light years away, several studies carried out in 2006 and 2007 agree on a closer distance of 1,350 light years.

• M-42, NGC 1976
• Magnitude: 4.0
• Constellation: Orion
• RA: 05h 35m 24.0s
• Dec: : -05° 27' 00" Epoch 2000
• Size (mins) 66 x 60
• Classification: Emission Nebula.
  

George Normandin, KAS

December 29th, 2007