CAOSP abstracts, Volume: 40, No.: 2, year: 2010

Abstract: Considering the model of the initial disc of planetesimals consisting of 14799 test particles, we simulated the formation of the populations of small bodies in the outer region of the solar system for an initial 2-Gyr period. We aimed to provide a common reference model of the formation of all inner and outer parts of the Oort cloud. In this paper, we deal with a picture of the trans-Neptunian-belt populations which can be outlined within our simple model. The dynamical evolution of massless test particles is followed via numerical integration of their orbits. We consider perturbations by four giant planets in their current orbits and with their current masses, as well as perturbations by the Galactic tide and passing stars. Our simulation qualitatively reproduces almost all structural features observed in the trans-Neptunian region. Unfortunately, there are a lot of quantitative discrepancies between our model and observed reality implying the main conclusion that the assumption of a dynamically very cold initial proto-planetary disc (with eccentricity ∼0.01 and inclination ∼0.01 rad), which extends beyond the heliocentric distance of about 34 AU, is inconsistent with the observed structure of trans-Neptunian population of small bodies. A big discrepancy is the survival of an almost untouched initial model population beyond ∼ 34 AU which is not observed. Two following positive observed details of the TN-population structure can, perhaps, be explained with the help of our simple model. Concerning the first, we showed that the outer border of the range of Neptune's perturbation on the dynamically cold orbits is identical with the outer border of 2:1 mean-motion resonance with this planet, where a sharp decrease of the number density of bodies belonging to the classical Edgeworth-Kuiper belt is observed. Most probably, this decrease is related to Neptune's ability to significantly influence the motion of small bodies, if we assume that these bodies formed closer to the Sun and were transported into the belt by Neptune. Second, the outer border of the objects of the so-called detached subpopulation is approximately at the same heliocentric distance of 100 AU in both model and observational samples.

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Last update: October 29, 2010