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Related to Hirayama family: asteroid belt
Hirayama family[‚hi·rä′yä·mä ‚fam·lē]
A clustering of asteroids whose orbits have similar values of semimajor axis, eccentricity, and inclination; over 100 such families have been tabulated.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.