An Etymological Dictionary of Astronomy and Astrophysics

An aggregation of → dust grains in the space between stars.
Interstellar dust absorbs, scatters, and polarizes the light from distant stars, causing the → interstellar extinction. Large dark regions in the plane of the Milky Way and other galaxies are caused by → intervening clouds of dust.
The conclusive proof for the presence of a general and selective interstellar absorption is due to R. J. Trumpler (1930). See also → reddening; → very small grain; → big grain; → PAH.

See also: → interstellar; → dust.