Astr110 Photography Projects, Fall 2006

Cocoon Nebula, Erin Holwerda

The Cocoon Nebula is located 4,000 light years away within a newly developing open star cluster.  Open star clusters are numerous stars which are roughly the same distance, age,and chemical composition. They are clustered together because they formed out of some common cloud.  The nebula is very faint and often difficult to see with a telescope even though it is so large.  The calculation of the nebula’s diameter was completed using the small angle formula and the angular diameter found from the picture taken.  Its angular diameter is about 420 arcseconds and thus the diameter of the nebula is about 8.14 light years.

The Cocoon Nebula, like many nebulas, is an emission nebula, reflection nebula, and an absorption nebula.  Each one of these nebula has defining characteristics which is able to be seen within this picture.  The bluish color of the Cocoon Nebula is typical of the reflection nebulas which can be seen faintly on the edges of this picture.  The largest star in the center is most likely reflecting its light causing the blue color at the edge of this nebula.  This color is coming from carbon dust grains reflecting light from near by stars.  The red color is typical of emission nebulas and is ionized hydrogen gas.  Finally, the absorption nebula is one which are interstellar clouds blocking dust from being seen.  This accounts for dark areas within the nebula.  Note that in the dark areas all you are able to see faint red stars which remain red because all of their blue light has been reflected out already.  The blue light is reflected away from us if the interstellar clouds are blocking the dust and if the clouds are in the background the dust reflects toward us allowing us to see some blue color.

References:
Cannistra, Steve. Starry Wonders Astrophotography. 2006. 9 Nov. 2006 <http://www.starrywonders.com/>.

Nemiroff , Robert. Astronomy Picture of the Day. Ed. Jerry Bonnell. 1 Mar. 1999. NASA. 9 Nov. 2006 <http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html>.

Nemiroff , Robert. Astronomy Picture of the Day. Ed. Jerry Bonnell. 15 Jan. 2004. NASA. 9 Nov. 2006 <http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html>.

Nemiroff , Robert. Astronomy Picture of the Day. Ed. Jerry Bonnell. 21 May 2005. NASA. 9 Nov. 2006 <http://antwrp.gsfc.nasa.gov/apod/dark_nebulae.html>.

Nemiroff , Robert. Astronomy Picture of the Day. Ed. Jerry Bonnell. 14 Oct. 2002. NASA. 9 Nov. 2006 <http://apod.gsfc.nasa.gov/apod/ap021014.html>.

Nemiroff , Robert. Astronomy Picture of the Day. Ed. Jerry Bonnell. 10 Apr. 2003. NASA. 9 Nov. 2006 <http://antwrp.gsfc.nasa.gov/apod/ap030410.html>.