There might be giants: unseen Jupiter-mass planets as sculptors of tightly-packed planetary systems

TL;DR

This study explores how unseen Jupiter-mass planets can influence the orbital arrangements of inner super-Earth systems, potentially explaining the compact configurations observed in some exoplanetary systems.

Contribution

It introduces N-body simulations including unseen giant planets to demonstrate their role in shaping the architecture of compact planetary systems.

Findings

Giant planets tend to break wide mean-motion resonances.

Inner planets migrate into tighter resonances due to giant companions.

Presence of giants increases Laplace resonance occurrence.

Abstract

The limited completeness of the Kepler sample for planets with orbital periods $\gtrsim$ 1 yr leaves open the possibility that exoplanetary systems may host undetected giant planets. Should such planets exist, their dynamical interactions with the inner planets may prove vital in sculpting the final orbital configurations of these systems. Using an $N$-body code with additional forces to emulate the effects of a protoplanetary disc, we perform simulations of the assembly of compact systems of super-Earth-mass planets with unseen giant companions. The simulated systems are analogous to Kepler-11 or Kepler-32 in that they contain 4 or 5 inner super-Earths, but our systems also contain longer-period giant companions which are unlikely to have been detected by Kepler. We find that giant companions tend to break widely-spaced, first-order mean-motion resonances, allowing the inner planets to migrate into tighter resonances. This leads to more compact architectures and increases the occurrence rate of Laplace resonant chains.