This image includes three of the four types of nebulosity, namely reflection, emission and absorption. Maybe there's a planetary nebula hiding somewhere in there too!
IC 5146 (aka Caldwell 19, Sh 2-125, and the Cocoon Nebula) is a reflection/emission nebula in the constellation Cygnus. The NGC description refers to IC 5146 as a cluster of 9.5 mag stars involved in a bright and dark nebula. The cluster is about 4,000 ly away. The nebula is about 12 arcmins across, equivalent to a span of 15 light years.
General opinion is that the massive star in the center of the red emission nebula opened a hole in an existing molecular cloud through which much of the glowing material flows. The same star, which formed about 100,000 years ago, now provides the energy source for much of the emitted and reflected light from this nebula.
Being enveloped in a cloud of dust and gas the emission nebula lacks the definition of other well-known emission nebula.
When viewing IC 5146, dark nebula Barnard 168 (B168) is an inseparable part of the experience, forming a dark lane that surrounds the cluster and projects westward forming the appearance of a trail behind the Cocoon.
Observations of IC 5146 by the Spitzer Space Telescope and the Chandra X-ray Observatory have collectively identified hundreds of young stellar objects. Young stars are seen in both the emission nebula, where gas has been ionized by massive young stars, and in the infrared-dark molecular cloud that forms the "tail".
Sources:
https://en.wikipedia.org/wiki/IC_5146http://www.starrywonders.com/cocoon.htmlhttps://apod.nasa.gov/apod/ap140918.html
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