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J.M. Hahn, R. Malhotra (LPI)
Prior investigations have shown that the orbits of the giant planets can migrate while they are still embedded in a remnant disk of planetesimal debris (Fernandez and Ip 1984). This hypothesis is further motivated by the highly eccentric and inclined orbits of Pluto and its cohort of Kuiper Belt objects that lie at Neptune's mean-motion resonances. One natural explanation for the origin of these peculiar orbits is that these bodies were trapped at Neptune's mean-motion resonances that swept the disk as that planet's orbit expanded radially outwards (Malhotra 1993, 1995).
We have investigated the planet-migration phenomenon via direct numerical integration of a system of giant planets embedded in a massive planetesimal debris disk. If resonant trapping by Neptune is fairly inefficient, then the planet's migration rate and its net radial displacement \Delta a varies with the mass of the planetesimal disk. But if resonance trapping is sufficiently efficient, an opposing torque develops as planetesimals accumulate at the resonances. This opposing torque tends to stall planet-migration once the trapped planetesimal mass exceeds Neptune's. Note that the planet-migration/resonance trapping mechanism tends to concentrate debris at resonances. Since the frequency of collisions and hence the dust generation rate varies as density2, we speculate that this mechanism might be responsible for the formation of dust rings around \epsilon Eridani and Fomalhaut.
The author(s) of this abstract have provided an email address for comments about the abstract: hahn@lpi.jsc.nasa.gov