Resonant Repulsion of Kepler Planet Pairs

TL;DR

This paper explains the observed distribution of Kepler planet pairs near resonances as a result of resonant repulsion caused by weak dissipation, especially tides, which pushes planets just beyond resonance.

Contribution

It introduces the concept of resonant repulsion due to dissipation as a natural explanation for the distribution of planet pairs near resonances, linking it to tidal effects.

Findings

Resonant repulsion explains the excess of planet pairs just wide of resonance.

Tidal dissipation with a quality factor ~10 can account for observed orbital separations.

Initial orbits show little preference for resonances after accounting for resonant repulsion.

Abstract

Planetary systems discovered by the Kepler space telescope exhibit an intriguing feature. While the period ratios of adjacent low-mass planets appear largely random, there is a significant excess of pairs that lie just wide of resonances and a deficit on the near side. We demonstrate that this feature naturally arises when two near-resonant planets interact in the presence of weak dissipation that damps eccentricities. The two planets repel each other as orbital energy is lost to heat. This moves near-resonant pairs just beyond resonance, by a distance that reflects the integrated dissipation they experienced over their lifetimes. We find that the observed distances may be explained by tides if tidal dissipation is unexpectedly efficient (tidal quality factor ~10). Once the effect of resonant repulsion is accounted for, the initial orbits of these low mass planets show little preference for resonances. This could constrain their origin.