THE PROBLEM OF SPLIT COMETS REVISITED

The results from studies of D/Shoemaker-Levy 9 and other recent split comets and comet pairs lead to the recognition of fundamental differen ces between breakup products of the tidally and the nontidally split c omets and to the conclusive identification of the so-called dissipatin g comets as secondary nuclei of previously split comets, whose separat ely arriving principal nuclei had in most cases been missed. The prima ry attribute of the nontidally split comets is the leading position of the principal nucleus, with all the companion nuclei trailing behind, eventually along the orbit. No such configuration has been observed f or the tidally split comets of more than two components. Dominant effe cts in the relative motions of fragments derived from the tidal disrup tions are due to separation velocities, while differential deceleratio ns (due, presumably, to outgassing-driven nongravitational perturbatio ns) prevail for fragments derived from the nontidal breakups. This div ersity is interpreted in terms of major differences between the breaku p mechanisms for the two categories of objects and between the resulti ng mass distributions of fragments.