IC 5146 (also Caldwell 19, Sh 2-125, and the Cocoon Nebula) is a reflection[1]/emission[2] nebula and Caldwell object 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 also known as Collinder 470.[3] It shines at magnitude +10.0[4]/+9.3[2]/+7.2.[5] Its celestial coordinates are RA 21h 53.5m, dec+47° 16′. It is located near the naked-eye star Pi Cygni, the open cluster NGC 7209 in Lacerta, and the bright open cluster M39.[1][4] The cluster is about 4,000 ly away, and the central star that lights it formed about 100,000 years ago;[6] the nebula is about 12 arcmins across, which is equivalent to a span of 15 light years.[5] 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.
