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Astron. Astrophys. 318, L5-L8 (1997)

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Letter to the Editor

The problem of split comets revisited

Z. Sekanina

Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

Received 26 November 1996 / Accepted 19 December 1996


The results from studies of D/Shoemaker-Levy 9 and other recent split comets and comet pairs lead to the recognition of fundamental differences between breakup products of the tidally and the nontidally split comets and to the conclusive identification of the so-called dissipating comets as secondary nuclei of previously split comets, whose separately arriving principal nuclei had in most cases been missed. The primary 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 for the tidally split comets of more than two components. Dominant effects in the relative motions of fragments derived from the tidal disruptions are due to separation velocities, while differential decelerations (due, presumably, to outgassing-driven nongravitational perturbations) prevail for fragments derived from the nontidal breakups. This diversity is interpreted in terms of major differences between the breakup mechanisms for the two categories of objects and between the resulting mass distributions of fragments.

Key words: tidally and nontidally split comets – comet pairs – principal and secondary nuclei – configurations of fragments – separation velocity – differential deceleration

Send offprint requests to: Z. Sekanina


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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998