DPS 34th Meeting, October 2002
Session 9. Centaurs and Kuiper Belt Objects II
Oral, Chair(s): D. Jewitt and R. Millis, Monday, October 7, 2002, 4:30-6:00pm, Ballroom

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[9.02] Centaurs: The Transition Between the Kuiper Belt and Jupiter-Family Comets

M. S. Tiscareno, R. Malhotra (U of Arizona)

We have explored the dynamical behavior of known Centaurs (defined here as objects with perihelia between the orbits of Jupiter and Neptune), using a mixed-variable symplectic integrator with the capability to process close planetary encounters (Duncan~\textit{et~al.}~1998, Wisdom and Holman~1991). This class of objects almost certainly constitutes the transitional population between the Kuiper Belt and the Jupiter-Family comets~(JFC's). Previous investigations have used a hypothetical population of objects escaping from the Kuiper Belt, with the Kuiper Belt assumed to be dynamically ``cold" (i.~e.,~of small orbital eccentricities and inclinations). The observed transient population has higher eccentricities and inclinations than previous models account for. The dynamical evolution of this sample of Centaurs is less orderly than the planet-to-planet hand-off described in previous investigations. In our simulations, we find that this transient population diffuses into the JFC's and other sinks, but (not~surprisingly) does not diffuse back into the parameter space representing the presumed Kuiper Belt source. The median dynamical lifetime is 9~Myr, although a number of bodies survived to the end of our simulation time of 100~Myr. The most common fate for these objects is ejection from the Solar system. Using the number of observed JFC's to calibrate, we estimate the present total number of bodies in this transitional population, which may be called either ``ecliptic comets" or ``Centaurs," to be on the order of 106. Our simulations predict that their surface number density peaks near r=30~AU heliocentric distance; it falls off steeply at smaller distances and more gradually, as ~r-1.5, at larger distances, while the perihelia remain near or below 30~AU.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.