A dark nebula is a type of interstellar cloud that is dense enough to block light from objects behind it, such as stars and galaxies. These clouds are composed mainly of gas and dust, making them appear as dark patches in the night sky. Dark nebulae are often found in regions of star formation, where they can serve as the birthplace for new stars. One well-known example of a dark nebula is the Horsehead Nebula, located in the constellation of Orion. Dark nebulae play a crucial role in the life cycle of stars, as they provide the material needed for star formation and can influence the surrounding environment in space.