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[8.06] The Scattered Disk as a Source of Halley-Type Comets

H.F. Levison (SWRI), M.J. Duncan (Queen's U.), L. Dones (SWRI), B. Gladman (UBC)

We will discuss a new dynamical mechanism for producing Halley-type comets from the scattered disk of comets. Levison & Duncan (1997, Icarus 108, 18) and Duncan & Levison (1997, Science 276, 1670) showed that a significant number of objects leave the scattered disk by evolving to semi-major axes greater than 1000\,AU. We find that once these objects reach semi-major axes on the order of 10,000\,AU, a significant fraction immediately have their perihelia driven inward by the Galactic tides. Approximately 0.01% of the objects that reach 10,000\,AU then evolve onto orbits similar to the observed Halley-like comets due to gravitational interactions with the giant planets. The orbital element distribution resulting from this process is statistically consistent with observations. Our model predicts a temporal variation in the influx of HTCs with a period of roughly 120 Myrs. At the peak there should be roughly 10 times as many HTCs as currently observed (i.e. there should be weak HTC showers).

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.