DPS 35th Meeting, 1-6 September 2003
Session 49. KBO and Centaurs I
Oral, Chairs: M. Buie and S. A. Stern, Saturday, September 6, 2003, 3:30-5:40pm, DeAnza III

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[49.10] Asymmetric Capture in the 2:1 Resonance

R.A. Murray, E.I. Chiang (UC Berkeley)

Dynamical characteristics of Kuiper Belt Objects (KBOs) in resonance with Neptune preserve a record of events that shaped the outer solar system. In particular, the spatial distribution of 2:1 resonant KBOs reflects Neptune's migration history. Numerical simulations reveal that a faster Neptunian migration causes more 2:1 objects to be captured into libration about one libration center than about the other, with the result that up to three times more 2:1 KBOs might be discovered at longitudes trailing Neptune than leading it. This phenomenon is made possible by asymmetric libration, a hallmark of the 2:1 resonance not shared by the 3:2 resonance. We explore the dynamics of asymmetric libration analytically and provide physical, mechanistic explanations for these previous numerical findings. In the restricted 3-body problem, the perturber, Neptune, accelerates both the KBO and the Sun, contributing direct and indirect terms to the disturbing potential, respectively. The direct and indirect terms act in opposition to one another, and the balance between these perturbative effects leads to asymmetric libration. The averaged indirect potential is zero for the 3:2 resonance and thus asymmetric libration does not occur. We describe our mechanistic understanding of why, in numerical simulations that introduce a fast outward migration of Neptune, KBOs are preferentially captured around the libration center trailing Neptune. We provide a blow-by-blow account of the torques felt by a KBO near resonance to achieve a physical understanding of this asymmetry in capture outcomes.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.