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F. Roig, D. Nesvorny, S. Ferraz-Mello (IAG/USP)
It is shown that in addition to four outer planets (Jupiter
to Neptune) also Pluto should be taken into account in
studies of the orbital dynamics in the trans--Neptunian
region. Pluto effect is particularly large on the orbits in
the 2:3 Neptune mean motion resonance. The trajectories
found stable over the age of the solar system when only the
gravitational effect of four outer planets is considered are
often destabilized there in the effect of close Pluto
approaches. We estimate that many dynamically primordial
bodies moving initially with low to moderate amplitudes in
the 2:3 Neptune resonance (semimajor axis 39.45 AU) have
been removed from their respective, otherwise stable
locations, when their resonant amplitudes increased in the
course of close encounters with Pluto. At large libration
amplitude the orbits became exposed to chaotic changes and
objects were ejected from the 2:3 resonance to
Neptune--crossing trajectories. The process of the resonant
amplitude excitation was especially efficient for the orbits
with moderate and large inclinations (i>8 deg), where more
than 50% of the population has been removed on
4\times109 years. We estimate that the remaining part of
the primordial resonant population at these inclinations
should have had its resonant amplitude excited to about 80
degrees. The effect of Pluto on low--inclination orbits is
smaller. We have examined the distribution of 33 objects
observed on the 2:3 resonant orbits (Plutinos) and found,
that there could actually exist indications of the above
mechanism. The resonant amplitudes of Plutinos are unusually
high for 0.15 The author(s) of this abstract have provided an email address
for comments about the abstract:
froig@iagusp.usp.br