What type of nebula is a vast cloud of matter that has not yet formed into stars?

A dark nebula is a type of nebula characterized by its dense cloud of gas and dust that obscures the light from objects behind it, such as stars and other celestial bodies. Unlike bright nebulae, which are regions where star formation is actively occurring and emit light, a dark nebula is primarily composed of material that has not yet undergone the process of star formation. This vast cloud of matter serves as an important component in the lifecycle of stars, as it provides the necessary raw materials that can eventually collapse under gravity to form new stars.

Although bright nebulae, planetary nebulae, and supernova remnants are also types of nebulae, they involve processes that indicate the presence of stars either forming or having already formed. Bright nebulae emit their own light due to ionization, planetary nebulae are remnants of dying stars shedding their outer layers, and supernova remnants are the aftermath of explosive stellar deaths. These conditions do not apply to dark nebulae, which remain opaque and are primarily composed of unformed matter.