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cosmic year(galactic year) The period of revolution of the Sun about the center of the Galaxy, equal to about 220 million years.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
cosmic year[′käz·mik ′yir]
The period of rotation of the Milky Way Galaxy, about 220 million years.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.