Neptune’s resonances in the scattered disk
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The scattered disk objects (SDOs) are thought to be a small fraction of the ancient population of leftover planetesimals in the outer Solar system that were gravitationally scattered by the giant planets and have managed to survive primarily by capture and sticking in Neptune’s exterior mean motion resonances (MMRs). In order to advance understanding of the role of MMRs in the dynamics of the SDOs, we investigate the phase space structure of a large number of Neptune’s MMRs in the semi-major axis range 33–140 au by use of Poincaré sections of the circular planar restricted three-body model for the full range of particle eccentricity pertinent to SDOs. We find that, for eccentricities corresponding to perihelion distances near Neptune’s orbit, distant MMRs have stable regions with widths that are surprisingly large and of similar size to those of the closer-in MMRs. We identify a phase-shifted second resonance zone that exists in the phase space at planet-crossing eccentricities but not at lower eccentricities; this second resonance zone plays an important role in the dynamics of SDOs in lengthening their dynamical lifetimes. Our non-perturbative measurements of the sizes of the stable resonance zones confirm previous results and provide an additional explanation for the prominence of the N : 1 sequence of MMRs over the N : 2, N : 3 sequences and other MMRs in the population statistics of SDOs; our results also provide a tool to more easily identify resonant objects.
KeywordsRestricted three-body problem Kuiper belt Orbital resonance Chaos Resonance sticking Minor planets
We thank Kathryn Volk for discussions. We also thank Tabare Gallardo and an anonymous reviewer for providing helpful reviews. LL acknowledges funding from National Natural Science Foundation of China (11572166) and China Scholarship Council. RM acknowledges funding from NASA (Grants NNX14AG93G and 80NSSC19K0785) and NSF (Grant AST-1824869).
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