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IC 5146 Cocoon Nebula
Tina Geelhoed

Previous image Up to Astr110 Index Next image Cocoon Nebula (IC 5146)

IC 5146, The Cocoon Nebula, is a fantastic display of color, especially an intense fuchsia. It is huge; based on the image above, the diameter is about 8 light years wide. Sadly, although it is so large, people cannot look up into the night sky and see this breathtaking nebula. It’s much too far away to see with the naked eye. In fact, the Cocoon Nebula is approximately 4,000 light years away. In other words, we see what the nebula looked like 4,000 years ago. Looking with a high-powered telescope, one can look toward the northern constellation, Cygnus, which looks like a cross.

A nebula is essentially a cloud of the ingredients that make up stars—basically, gas and dust. The reason for the reddish pink color of the nebula is because of a certain kind of emission called H II emission. This starts off with Hydrogen atoms that become energized by surrounding hot stars, especially the bright star in the very middle. Mainly that one star, in addition to the other bright ones, is producing enough heat to ionize the hydrogen. Many stars are forming in the nebula, classifying it also as a stellar nursery.  This hot, ionized hydrogen gas emits the certain light wave of that pinkish red as it moves from a high energy state to a lower one. That color is unique to hydrogen. Not only are astronomical photos beautiful; we can actually learn about the composition of the nebula by its colors. The Cocoon Nebula may not be visible with the naked eye, but that makes it all the more magnificent when we can see it in photos. It’s larger than we can comprehend, yet so far away that we can barely see it.



Crawford, Ken. "IC 5146: The Cocoon Nebula ." Astronomy Picture of the Day. Ed. Robert Nemiroff and Jerry Bonnell. NASA, Aug. Web. 6 Dec. 2010. <>.

O'Dell, C. R. "Nebula." World Book Online Reference Center. 2005. World Book, Inc.

Right Ascension (J2000) 21:53:24
Declination (J2000) +47:16:00
Filters used B (blue), C (clear),R (red), V (visual)
Exposure time per filter B, R, and V (300 sec.) and C (60 sec.)
Date observed




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