The disruption of multiplanet systems through resonance with a binary orbit

Abstract

Most exoplanetary systems in binary stars are of S-type, and consist of one or more planets orbiting a primary star with a wide binary stellar companion1, 2. Planetary eccentricities and mutual inclinations can be large3, 4, perhaps forced gravitationally by the binary companion4, 5, 6. Earlier work on single planet systems5, 7, 8, 9, 10 appealed to the Kozai–Lidov instability11, 12 wherein a sufficiently inclined binary orbit excites large-amplitude oscillations in the planet’s eccentricity and inclination. The instability, however, can be quenched by many agents that induce fast orbital precession, including mutual gravitational forces in a multiplanet system5, 13. Here we report that orbital precession, which inhibits Kozai–Lidov cycling in a multiplanet system, can become fast enough to resonate with the orbital motion of a distant binary companion. Resonant binary forcing results in dramatic outcomes ranging from the excitation of large planetary eccentricities and mutual inclinations to total disruption. Processes such as planetary migration14, 15 can bring an initially non-resonant system into resonance. As it does not require special physical or initial conditions, binary resonant driving is generic and may have altered the architecture of many multiplanet systems. It can also weaken the multiplanet occurrence rate in wide binaries, and affect planet formation in close binaries.