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Astron. Astrophys. 323, 986-998 (1997)

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Dynamics of comets in the outer planetary region

II. Enhanced planetary masses and orbital evolutionary paths *

G.B. Valsecchi 1, 2 and A. Manara 3

1 Observatoire de la Côte d'Azur, B.P. 229, F-06304 Nice, France
2 I.A.S. - Planetologia, viale dell'Università 11, I-00185 Roma, Italy
3 Osservatorio Astronomico di Brera, via Brera 28, I-20121 Milano, Italy

Received 24 May 1996 / Accepted 5 July 1996


We study the effect of increasing the masses of the outer planets to speed up the numerical integration of orbital evolutions of fictitious comets subject to planetary close encounters. We use Öpik's theory to model encounters on crossing orbits, and find that the distribution of energy perturbations, and especially of its tails, is changed significantly depending on the range of initial conditions considered and on the enhancement factor used for the planetary masses. We then analyze nearly tangent, low-velocity encounters making use of a simple argument based on the opening of Hill's surfaces of zero velocity, again finding that the energy perturbation distribution depends on the mass enhancement factor. To check these results we compare the outcomes of integrations done with masses enhanced by the factors 10 and 40 to those of integrations done with the real masses, coming once more to the same conclusion; we put these findings in perspective, discussing the more general issue of the dynamical paths followed by potential short-period comets in the region of the outer planets. Results concerning the orbital evolution of comets obtained by integrations performed with enhanced masses should be considered with caution.

Key words: comets: general – celestial mechanics

* Appendix A and B are only available in electronic form at http://cdsweb.u-strasbg.fr/abstract/htlm

Send offprint requests to: G.B. Valsecchi

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998