IC 5146

IC 5146, also known as Cocoon Nebula known, is an astronomical nebula with an embedded star cluster in the constellation Cygnus. The cluster is called Collinder 470

The nebula has an apparent extension of about 10 arc minutes and is about 3,000 light-years from Earth; its physical dimension is approximately 10 light years.

The nebula is a star forming region with ionized atomic hydrogen and has both emitting, reflective and absorbing components. IC 5146 is seen from the Earth at the eastern end of the elongated dark cloud Barnard 168, and together with this, part of a large molecular cloud. Just to the west is the reflection nebula of vdB 147, which probably also belongs to the complex.

The inside of the cloud, running, brisk star formation leads to the formation of a young open star cluster called Collinder 470, an apparent brightness of 7.2 mag and an estimated age of a few hundred thousand years. This cluster and in particular the brightest star in its center, BD 46 ° 3474 (type B0 V, 10 mag), are responsible for the ionization of the nebula and thus for its lights. They create a " cave " in the dust and gas of the molecular cloud and thus open up the view into its interior.

The fog was photographically discovered by Edward Barnard on a recording from October 11, 1893, and later independently also by Max Wolf (28 July 1894).