# The role of dissipative evolution for three-planet, near-resonant extrasolar systems

## TL;DR

This paper extends the understanding of how dissipative forces influence the orbital evolution of three-planet systems near mean-motion resonances, revealing that additional physical processes are likely involved in shaping observed architectures.

## Contribution

It generalizes the dissipative divergence framework from three-body to multi-resonant chains and applies it to observed three-planet systems, highlighting limitations of current models.

## Key findings

- Some systems' architectures are consistent with resonant locking followed by dissipation.
- Most systems' configurations cannot be explained by simple migration and dissipation alone.
- Additional physical mechanisms are likely important in early planetary system evolution.

## Abstract

Early dynamical evolution of close-in planetary systems is shaped by an intricate combination of planetary gravitational interactions, orbital migration, and dissipative effects. While the process of convergent orbital migration is expected to routinely yield resonant planetary systems, previous analyses have shown that the semi-major axes of initially resonant pairs of planets will gradually diverge under the influence of long-term energy damping, producing an overabundance of planetary period ratios in slight excess of exact commensurability. While this feature is clearly evident in the orbital distribution of close-in extrasolar planets, the existing theoretical picture is limited to the specific case of the planetary three-body problem. In this study, we generalise the framework of dissipative divergence of resonant orbits to multi-resonant chains, and apply our results to the current observational census of well-characterised three-planet systems. Focusing on the 2:1 and 3:2 commensurabilities, we identify three 3-planet systems, whose current orbital architecture is consistent with an evolutionary history wherein convergent migration first locks the planets into a multi-resonant configuration and subsequent dissipation repels the orbits away from exact commensurability. Nevertheless, we find that the architecture of the overall sample of multi planetary systems is incompatible with this simple scenario, suggesting that additional physical mechanisms must play a dominant role during the early stages of planetary systems' dynamical evolution.