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intracluster medium(in-tră-klus -ter) (ICM) The invisible medium that lies between the galaxies in a cluster. It is mostly comprised of hot (107–108 K) gas emitting strongly in X-rays. See clusters of galaxies; X-ray astronomy.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
intracluster medium[‚in·trə′kləs·tər ‚mēd·ē·əm]
A hot, tenuous gas that fills the space between the members of a cluster of galaxies and emits x-rays.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.