Rattle-and-Break: the Impact of Planetesimal Scattering on Super-Earth Resonant Chains

TL;DR

This paper investigates how scattering of planetesimals can disrupt or modify super-Earth resonant chains, explaining observed orbital distributions and the timing of chain breaking.

Contribution

It extends the 'breaking-the-chains' model by incorporating planetesimal scattering effects, revealing how small-mass debris can reshape planetary resonant configurations.

Findings

Planetesimal scattering can widen planet pairs from resonances.

Some chains remain stable despite scattering, matching observations.

Scattering-induced instabilities can occur tens to hundreds of Myr after formation.

Abstract

The spacings of super-Earths in multi-transiting systems exhibit a distribution that is broad and mostly featureless, with the exception of notable excesses of planet pairs situated a few percent wide of first-order mean motion resonances (MMRs). In this work, we extend the so-called "breaking-the-chains" model to account for both of these characteristics. Assuming that super-Earths are settled into stable chains of resonances after disk-driven migration, we show that scattering a planetesimal population that contains only a few percent of a system's mass can reorganize primordial chains in remarkable ways. The planetesimal scattering "rattles" the chains by repelling adjacent planet pairs wide of their initial MMRs. Some chains remain rattled but otherwise intact and make up the observed excesses wide of MMRs. In other systems, however, this initial rattling sows the seeds of later orbital instabilities that break the chains entirely. If individual planetesimals' masses are of order a Pluto mass or so, the onset of these instabilities can occur tens or hundreds of Myr after birth, naturally explaining the apparent disappearance of near-resonant pairs on this timescale. The origin of such Pluto-mass debris is currently unknown.