Asteroid families

The assignment of asteroids to families on the basis of observational data is discussed, reviewing the history of asteroid studies and summarizing the results of recent investigations. The theory of family creation by explosive breakup of a large parent asteroid is outlined; planetary perturbations of the orbits are taken into account, the proper-element methods and identification criteria employed by different investigators are listed in a table; and data from physical studies of the families are compiled in graphs. Consideration is given to collisional-origin models and the effects of self-gravitation on the postimpact dynamical evolution of asteroids.