The orbital distribution of trans-Neptunian objects beyond 50 au

TL;DR

This study models the dynamical evolution of trans-Neptunian objects beyond 50 au, predicting their orbital clustering near Neptune resonances and estimating their population sizes, which aligns with recent observations.

Contribution

It introduces a numerical model of Neptune's slow migration that explains the orbital clustering and population estimates of distant Kuiper Belt Objects beyond 50 au.

Findings

Objects near resonances are consistent with model predictions.

Estimated populations at key resonances match observational data.

Orbits tend to cluster near, but not exactly in, Neptune resonances.

Abstract

The dynamical structure of the Kuiper belt beyond 50 au is not well understood. Here we report results of a numerical model with long-range, slow and grainy migration of Neptune. The model implies that bodies scattered outward by Neptune to semimajor axes a>50 au often evolve into resonances which subsequently act to raise the perihelion distances of orbits to q>40 au. The implication of the model is that the orbits with 50<a<100 au and q>40 au should cluster near (but not in) the resonances with Neptune (3:1 at a=62.6 au, 4:1 at a=75.9 au, 5:1 at a=88.0 au, etc.). The recent detection of several distant Kuiper Belt Objects (KBOs) near resonances is consistent with this prediction, but it is not yet clear whether the orbits are really non-resonant as our model predicts. We estimate from the model that there should presently be ~1600-2400 bodies at the 3:1 resonance and ~1000-1400 bodies at the 4:1 resonance (for q>40 au and diameters D>100 km). These results favorably compare with the population census of distant KBOs inferred from existing observations.