Retention of a Primordial Cold Classical Kuiper Belt in an Instability-Driven Model of Solar System Formation

TL;DR

This paper demonstrates that the cold classical Kuiper belt can survive an instability-driven formation process, with specific Neptune precession dynamics preserving its unexcited orbital state, supported by analytical and N-body simulations.

Contribution

It introduces an analytical model and simulation evidence showing the cold Kuiper belt's survival during planetary instability, explaining its preserved dynamical coherence.

Findings

Cold belt survives planetary instability.

Fast Neptune precession preserves cold belt's unexcited state.

Contamination explains Kuiper belt's diversity.

Abstract

The cold classical population of the Kuiper belt exhibits a wide variety of unique physical characteristics, which collectively suggest that its dynamical coherence has been maintained through out the solar system's lifetime. Simultaneously, the retention of the cold population's relatively unexcited orbital state has remained a mystery, especially in the context of a solar system formation model, that is driven by a transient period of instability, where Neptune is temporarily eccentric. Here, we show that the cold belt can survive the instability, and its dynamical structure can be reproduced. We develop a simple analytical model for secular excitation of cold KBOs and show that comparatively fast apsidal precession and nodal recession of Neptune, during the eccentric phase, are essential for preservation of an unexcited state in the cold classical region. Subsequently, we confirm our results with self-consistent N-body simulations. We further show that contamination of the hot classical and scattered populations by objects of similar nature to that of cold classicals has been instrumental in shaping the vast physical diversity inherent to the Kuiper belt.