Offsets in Laplace resonances: The case of Kepler-80

Planetary formation theories predict that planets can be captured in mean-motion resonances (MMRs) during the migration process in the protoplanetary disc. However, among the discovered extrasolar planets, there is an enormous variety of orbital architectures and generally the planet pairs are not precisely found at the nominal resonance, but instead present a resonant offset slightly exterior to it.

In this work we focus on Kepler-80 which falls into the category known as STIPs: Systems with Tightly packed Inner Planets. The planets of these systems are believed to form farther from the star and then migrate inward while the disc is present. Once the disc disperses, tidal interactions with the central star become important, usually slowly pushing the planets outwards.

Kepler-80 is a 6-planet STIP which exhibits a particular dynamical configuration. The planets are in 2 and 3-planet MMRs and the observed resonant offset grows with the distance to the star. We aim to understand whether the tides can generate this particular configuration of the offsets. To do so, we propose a realistic scenario for the formation of Kepler-80 and analyze how the tidal effects can transport from the inner planets to the outer ones through the resonances of the system.