Horsehead nebula in the background of starry sky. Some image elements furnished by NASA.

Horsehead nebula is a dark cloud of dust and gas is a region in the Orion Molecular Cloud Complex where star formation is taking place. It is located in the constellation of Orion, which is prominent in the winter evening sky in the Northern Hemisphere and the summer evening sky in the Southern Hemisphere. The darkness of the Horsehead is caused mostly by thick dust blocking the light of stars behind it. This nebula is distant 1500 year light.