Secular Perturbations from Exterior Giants Strongly Influence Gap Complexity in Peas-in-a-Pod Exoplanetary Systems

TL;DR

This study shows that secular gravitational effects from outer giant planets can increase the apparent complexity of inner planetary system gaps, explaining observed irregularities without requiring additional formation processes.

Contribution

It demonstrates that secular dynamics from exterior giants can account for increased gap complexity in tightly packed inner systems, using second-order secular theory.

Findings

Secular interactions can significantly increase observed gap complexity.

Outer giants influence the orbital architecture of inner planets.

Secular effects can create artificial non-transiting geometries.

Abstract

It has been demonstrated that systems of tightly packed inner planets with giant exterior companions tend to have less regular orbital spacings than those without such companions. We investigate whether this observed increase in the gap complexity of the inner systems can be explained solely as the result of secular dynamics caused by the disturbing potential of the exterior companions. Amplification of mutual orbital inclinations in the inner system due to such secular dynamics may lead to the inner system attaining non-mutually transiting geometries, thereby creating artificial observed gaps that result in a higher calculated gap complexity. Using second-order secular theory, we compute time-averaged observed gap complexities along a favorable line of sight for a set of hypothetical systems, both with and without an outer giant. We find that these secular interactions can significantly contribute to the observed gap complexity dichotomy in tightly packed multiple-planet systems.