Astr112 Photography Projects, Fall 2007

Orion Nebula (M42), Julia Vander Molen

The Orion Nebula is the brightest diffuse nebula in the sky. It is illuminated by a young open star cluster called the Trapezium Cluster, the brightest area of the photograph. The dust and gas from the Orion Nebula formed the stars in the Trapezium Cluster. The Orion Nebula is both a reflection and an emission nebula. In an emission nebula, hydrogen gas is ionized by the Trapezium stars behind the nebula which causes it to glow redder, as seen in the pinkish parts of the photograph. The reflection nebula is caused by the light from the Trapezium which gets scattered by the dust in the nebula and causes the dust to glow bluer (the more purple parts of the photograph). In the lower left part of the picture, the thickness of the dust is obscuring much of the light coming from the stars behind the nebula, causing the stars to look both fainter and more yellow. In the upper right corner, the dust is so thick that it lets almost no starlight through.

The Orion Nebula was found by Johann Baptist Cysatus in 1611. It is located about 1,500 light years from Earth and has a linear diameter of about 30 light-years. The Orion Nebula extends 1 degree in diameter over the night sky—almost four times the area of the full moon. This photograph only shows about 9 light years, or 21 arc minutes, of the entire nebula. One can faintly see the Orion Nebula surrounding the star in the middle of Orion’s sword. It can be seen with the naked eye under good viewing conditions.

William Herschel once appropriately described it as "an unformed fiery mist, the chaotic material of future suns."

References:

Freedman and Kaufmann, Universe: Stars and Galaxies. 3rd Ed. 472. 2007.

Frommert, Hartmut and Kronberg, Christine. “Messier 42.” 4 October 2007.
http://www.seds.org/messier/m/m042.html