IC 5146 (also Caldwell 19, Sh 2-125, and the Cocoon Nebula)
is a reflection/emission 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. 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] The cluster is about 4,000 ly
away, and the central star that lights it formed about 100,000 years ago;
the nebula is about 12 arcmins across, which is equivalent to a span of
15 light years. 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.