irregular galaxy(redirected from Irr-I galaxy)
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A galaxy that does not have the clearly defined shape and structure of an elliptical, lenticular, or spiral galaxy. Irregular galaxies typically contain large amounts of gas and dust, and their stellar populations are relatively young.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.