An absorption nebula is a dense cloud of dust and gas. From the point of view of an observer on Earth, it absorbs the light from more distant stars, creating a dark, starless region.
Barnard 66 or LDN 1768 is one of a field of absorption nebulae spreading across the band of the Milky Way in southern Ophiuchus. This complex of dark nebulae lies more than five hundred light years from the Solar System, obscuring the light from the stars of the central Galaxy that lie beyond. Imagery provided by Aladin sky atlas