IC 5146, the Cocoon Nebula is a reflection/emission nebula in the constellation Cygnus. It is located 2500 light years from Earth and has a width of about 15 light years. The nebula is surrounded by the dark dust clouds of Bernard 169 which continues to the west, forming a "tail" behind the Cocoon.
The shape of the nebula resulted from the formation of BD +46°3474, the star that illuminates the nebula, near the surface and carving a cavity out of the material of the nebula.
IC 1546 is an active star forming region and young stars are seen in both the emission nebula, where gas has been ionized by massive young stars, and in the dark molecular cloud that forms the "tail". "A 2018 study exploring the internal kinematics of young clusters with ages from 1 to 5 million years identified 115 members of IC 5146, located at a distance of 758 to 809 parsecs (2,472 to 2,639 light years).
In 2008, infrared observations with the Spitzer Space Telescope identified more than 200 young stellar objects in the region of the Cocoon Nebula. These are found both in the emission nebula, where they ionize the surrounding gas, and in the dark patch of nebulosity in the western part of the Cocoon." [2]
[1]
https://en.wikipedia.org/wiki/IC_5146[2]
https://www.constellation-guide.com/cocoon-nebula/
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