http://arxiv.org/abs/1801.02458

The discovery of Pluto’s small moons in the last decade brought attention to the dynamics of the dwarf planet’s satellites. Recent work has considered resonant interactions in the orbits of Pluto’s small moons, with the Pluto-Charon system apparently inducing rotational chaos in non-spherical moons without the need of resonance. However, New Horizons observations suggest that despinning due to tidal dissipation has not taken place. Still, a tidally evolving Styx does appear to exhibit intermittent obliquity variations and episodes of tumbling, suggesting some form of chaos in the rotational dynamics. With these systems in mind, we study a planar $N$-body system in which all the bodies are point masses, except for a single rigid body. We then present a reduced model consisting of a planar $N$-body problem with the rigid body treated as a 1D continuum (i.e. the body is treated as a rod with an arbitrary mass distribution). Such a model provides a good approximation to highly asymmetric geometries, such as the recently observed interstellar asteroid ‘Oumuamua, but is also amenable to analysis. We analytically demonstrate the existence of homoclinic chaos in the case where one of the orbits is nearly circular by way of the Melnikov method, and give numerical evidence for chaos when the orbits are more complicated. We show that the extent of chaos in parameter space is strongly tied to the deviations from a purely circular orbit. These results suggest that chaos is ubiquitous in many-body problems when one or more of the rigid bodies exhibits non-spherical and highly asymmetric geometries. The excitation of chaotic rotations does not appear to require tidal dissipation, obliquity variation, or orbital resonance. Such dynamics give a possible explanation for routes to chaotic dynamics observed in $N$-body systems such as the Pluto system where some of the bodies are highly non-spherical.

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J. Kwiecinski, A. Kovacs, A. Krause, et. al.

Tue, 9 Jan 18

94/94

Comments: 27 pages, 7 figures. arXiv admin note: text overlap with arXiv:1701.05594 by other authors

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