The Interplay of Planetary Uniformity and Near-Resonant Dynamics

Planets orbiting the same star tend to display a striking degree of uniformity in their size, mass, and orbital spacing, exhibiting a “peas-in-a-pod” phenomenon that serves to place invaluable constraints on the formation of multiple-planet systems. It has been recently demonstrated that such uniformity occurs across both near-resonant and non-resonant planetary configurations, but a direct comparison has yet to be made between these two sub-populations themselves. The question thus remains if there exists a discernible relationship between mean motion resonance (MMR) and the emergence of peas-in-a-pod architectures, and if the degree of planetary uniformity itself differs between near-resonant and non-resonant configurations such that the two modes may be astrophysically distinct in their evolution. Accordingly, we shall present in this talk a comparative size uniformity analysis for 48 near-resonant and 251 non-resonant multi-planet systems from the California Kepler Survey (CKS) catalog. We find that near-resonant configurations display enhanced size uniformity as compared to their non-resonant counterparts, both across entire systems and between planetary pairs within the same system. These results are broadly consistent with a variety of formation paradigms for multiple-planet systems, such as convergent migration within a turbulent protoplanetary disk or planet-planet interactions incited by postnebular dynamical instabilities, though further investigation is necessary to assess whether non-resonant and near-resonant configurations are themselves achieved via a singular process or distinct evolutionary channels.