Super-Earths in multi-planet systems tend to form in resonant chains — orbital periods locked in simple ratios like 3:2 or 2:1. Migration through the protoplanetary disk pushes planets into these configurations naturally. But when we observe mature systems, most aren't in resonance. The chains broke. The question is what broke them.
Hadden and Wu propose: planetesimals. Not planet-sized objects. Debris. A population containing a few percent of the system's total mass — leftover building material from the formation epoch. These small bodies scatter through the resonant chain, and the chain shatters.
The mechanism has two stages. First, the “rattle.” Planetesimals passing through the system exchange angular momentum with the planets, nudging them slightly away from their precise resonant positions. The chain doesn't break yet — the resonant lock is robust to small perturbations. But the planets are now oscillating around their equilibrium positions with larger amplitude.
Then, the “break.” When the accumulated perturbations push a planet pair past the resonance's stability boundary, the system goes dynamically unstable. Orbits cross. Planets scatter off each other. Some get ejected, some collide, and the survivors settle into a non-resonant configuration.
The disproportionality is what's interesting. A few percent of the system mass destroys the architecture that the remaining 97% built. The resonant chain is a high-order configuration — it requires precise relationships between all the orbital periods. Disrupting any one link can cascade through the entire structure. The planetesimals don't need to overpower the planets. They just need to accumulate enough small pushes to cross a threshold.
When the debris is Pluto-mass, the instabilities can take tens to hundreds of millions of years to develop. The system looks stable for a geological epoch, then collapses. The slow fuse is part of the mechanism — the delay between formation and destruction explains why we see some young systems still in resonance while older systems have broken free.
The pattern generalizes. High-order configurations — where many components must maintain precise relationships — are vulnerable to persistent low-level noise from components that seem too small to matter. The noise accumulates in the phases, not the amplitudes. The planets barely move, but their timing drifts. And in a resonant chain, timing is everything.