Answer:

nebula

Answer	Crossword Clue
NEBULA	Diffuse mass of interstellar dust
NEBULA	Mass of interstellar dust
NEBULA	Interstellar formation

NEBULA	Group of distant galaxies
NEBULA	Space cloud
NEBULA	Crab ..
NEBULA	Horsehead ..
NEBULA	Cloud in Orion
NEBULA	Cosmic cloud
NEBULA	Interstellar cloud
NEBULA	Interstellar dust cloud

NEBULA	Space spiral
NEBULA	Very, very, very distant cloud
NEBULA	Crab, for one
NEBULA	Astronomer's sighting
NEBULA	Possible outcome of a supernova explosion
NEBULA	Cloud of dust and gas in space
NEBULA	Cloud viewed by astronomers
NEBULA	Hubble sighting

NEBULA	Intergalactic cloud
NEBULA	Astronomical gas cloud
NEBULA	Cluster of stars
NEBULA	Astronomical cloud
NEBULA	Literally, "cloud"
NEBULA	Cloud of interstellar dust
NEBULA	Dumbbell, e.g.
NEBULA	Award for sci-fi writers

NEBULA	Gaseous body of stellar substance.
NEBULA	Seen in the sword hilt of Orion.
NEBULA	Cloudlike mass in the heavens.
NEBULA	Cloudy celestial body.
NEBULA	Part of the Milky Way.
NEBULA	Bright spot in night sky.
NEBULA	Celestial structure.
NEBULA	Milky way.

NEBULA	Celestial phenomenon.
NEBULA	Astronomer's concern.
NEBULA	Sky sight
NEBULA	Cloudlike mass
NEBULA	Astronomer's subject