DR 21 is a large molecular cloud[1] located in the constellation Cygnus, discovered in 1966 as a radio continuum source by Downes and Rinehart.

[4] A number of different molecules have been detected in the region by their radio emission, including formaldehyde, ammonia, water and carbon monoxide.

DR 21 contains complex patterns of dust and gas, which glow in the infrared due to the presence of organic compounds known as polycyclic aromatic hydrocarbons.

Jagged patterns within DR 21 result from interactions with interstellar wind, radiation pressure, magnetic fields, and gravity.

[7] Feedback from the massive stars may ultimately disrupt the cloud, however this has not yet happened due to the region's extreme youth.