noun
dark nebula
Astronomical term for a dense interstellar cloud that obscures light from background stars.
暗黒星雲は、背後の星の光を遮って黒く見える。
A dark nebula appears dark because it blocks the light from stars behind it.
星雲 is a general term for nebula, while 暗黒星雲 specifically refers to a dark nebula that absorbs light.
Compound of 暗黒 (darkness) and 星雲 (nebula). The exact historical derivation is uncertain; the spelling is conventionally associated with the astronomical meaning.