Rapid Dynamical Chaos In An Exoplanetary System
Author(s)Holman, Matthew J.; Agol, Eric; Carter, Joshua Adam; Lissauer, Jack J.; Ragozzine, Darin
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We report on the long-term dynamical evolution of the two-planet Kepler-36 system, which consists of a super-Earth and a sub-Neptune in a tightly packed orbital configuration. The orbits of the planets, which we studied through numerical integrations of initial conditions that are consistent with observations of the system, are chaotic with a Lyapunov time of only ~10 years. The chaos is a consequence of a particular set of orbital resonances, with the inner planet orbiting 34 times for every 29 orbits of the outer planet. The rapidity of the chaos is due to the interaction of the 29:34 resonance with the nearby first-order 6:7 resonance, in contrast to the usual case in which secular terms in the Hamiltonian play a dominant role. Only one contiguous region of phase space, accounting for ~4.5% of the sample of initial conditions studied, corresponds to planetary orbits that do not show large-scale orbital instabilities on the timescale of our integrations (~200 million years). Restricting the orbits to this long-lived region allows a refinement of estimates of the masses and radii of the planets. We find that the long-lived region consists of the initial conditions that satisfy the Hill stability criterion by the largest margin. Any successful theory for the formation of this system will need to account for why its current state is so close to unstable regions of phase space.
DepartmentKavli Institute for Astrophysics and Space Research; Massachusetts Institute of Technology. Department of Physics
The Astrophysical Journal
Deck, Katherine M., Matthew J. Holman, Eric Agol, Joshua A. Carter, Jack J. Lissauer, Darin Ragozzine, and Joshua N. Winn. Rapid Dynamical Chaos in an Exoplanetary System. The Astrophysical Journal 755, no. 1 (August 10, 2012): L21.