The starting place for star formation. Gas, dust and other matter begins to clump together here and eventually stars are born. Leftover bits are thought to form planets, comets and other solar system objects.
Found within galaxies, bright diffuse nebulae are regions of hydrogen gas where new stars are being formed. Protostars begin to emerge as areas of the nebulae begin to shrink as a result of the pull of it’s own gravity.
There are two types of nebulae associated with the late stages of star formation. Planetary nebulae are composed of gas thrown off by red giant stars. Supernova remnants are the leftovers of exploded massive stars.
Those nebulae that appear dark have no stars illuminating them and can only be seen when silhouetted against a bright background.