Research Article

Chaotic dynamics of stellar spin in binaries and the production of misaligned hot Jupiters

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Science  12 Sep 2014:
Vol. 345, Issue 6202, pp. 1317-1321
DOI: 10.1126/science.1254358

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Orbits don't forget their chaotic pasts

Many exoplanets orbit in planes that don't correspond to their star's spin axis. This phenomenon may be the fossil record of a dynamical history. Storch et al. demonstrate in simulations that the evolution of a star's spin is key in determining how its planets' orbits are eventually oriented. A binary companion body can drive a hot Jupiter to migrate inward, which induces chaotic behavior in the stellar spin axis and feedback down the line. If we can accurately replicate the statistics observed in planetary surveys, we may understand better how planets form.

Science, this issue p. 1317

Abstract

Many exoplanetary systems containing hot Jupiters are observed to have highly misaligned orbital axes relative to the stellar spin axes. Kozai-Lidov oscillations of orbital eccentricity and inclination induced by a binary companion, in conjunction with tidal dissipation, constitute a major channel for the production of hot Jupiters. We demonstrate that gravitational interaction between the planet and its oblate host star can lead to chaotic evolution of the stellar spin axis during Kozai cycles. As parameters such as the planet mass and stellar rotation period are varied, periodic islands can appear in an ocean of chaos, in a manner reminiscent of other dynamical systems. In the presence of tidal dissipation, the complex spin evolution can leave an imprint on the final spin-orbit misalignment angles.

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