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Dynamics of Comets: Recent Developments and New Challenges

Published online by Cambridge University Press:  19 July 2016

Julio A. Fernández
Julio A. Fernández*
Affiliation:
Departamento de Astronomía, Facultad de Ciencias, Tristán Narvaja 1674, 11200 Montevideo, URUGUAY E-mail julio@fisica.edu.uy

Abstract

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There is a broad consensus that long-period comets come from a huge reservoir surrounding the solar system, as proposed originally by Oort. Yet, the classical picture of the Oort cloud has substantially changed during the last decade. In addition to passing stars, the tidal force of the galactic disk and giant molecular clouds have also been identified as major perturbers of the Oort cloud. In particular, the latter may be responsible for limiting the size of the stable Oort cloud to no more than ≈ 104AU, i.e. about one tenth of the classical Oort's radius.

Most comets are injected into the planetary region by the quasi-steady action of the tidal force of the galactic disk. The concentration of aphelion points of dynamically young comets toward mid-galactic latitudes is a consequence of its dominant influence. The frequency of comet passages into the inner planetary region could experience significant fluctuations with time as the Oort cloud meets random strong perturbers. The observed ordered pattern of most comet aphelia, associated with the galactic structure, argues against a recent strong perturbation of the Oort cloud.

The origin of the Jupiter family has become another point of intense debate. Jupiter family comets may come from a transneptunian comet belt -the Kuiper belt- from where they can reach the planetary region through chaotic motion. The Kuiper belt has become accessible to large telescopes, as shown by the recent discoveries of 1992QB1 and 1993FW, possibly belt members. The major challenge will be to explore the region usually inaccessible to external perturbers that goes from ~30 AU to a few thousand AU. A significant mass may have been locked there from the beginnings of the solar system, giving rise to an inner core that feeds the outer or classical Oort cloud. Our aim will be to briefly discuss some of the topics summarized here.

Type
Dynamics
Information
Symposium - International Astronomical Union , Volume 160: Asteroids, Comets, Meteors 1993 , 1994 , pp. 223 - 240
Copyright
Copyright © Kluwer 1994 

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