Dark nebula

Dark nebulae are astronomical objects. They do not emit or reflect light. They are seen when they hide stars and galaxies behind them. 

The astronomer Edward Emerson Barnard compiled a list of dark nebulae known as the Barnard Catalogue of Dark Markings in the Sky, or the Barnard Catalogue for short. The nebulae listed by Barnard have become known as Barnard objects..

These are the best-known dark nebulae:

 Coalsack nebula
 Cone nebula
 Dark Doodad nebula
 Dark Horse nebula
 Horsehead nebula (Barnard 33)
 Pipe nebula (also see Dark Horse nebula; includes Barnard 59, 77 and 78)
 Snake nebula (also see Dark Horse nebula

 References