absorption nebula

1. A mass of interstellar gas and dust that absorbs most or all of the light from the stars behind it. Absorption nebulae appear as irregular dark patches and collectively cover about two percent of the sky. Some absorption nebulae, especially the Coalsack near the constellations Centaurus and Southern Cross, are visible to the naked eye.
2. Also called dark cloud dark nebula
3. See more at nebula