KCTF Evolution of Trans-Neptunian Binaries: Connecting Formation to Observation

TL;DR

This paper uses KCTF simulations to show how tidal forces and solar torques can significantly alter trans-Neptunian binary orbits, explaining observed populations of tight, circular systems and predicting stability based on gravitational properties.

Contribution

It introduces a new stability parameter and demonstrates how tidal evolution shapes TNB orbital distributions, linking formation theories to observations.

Findings

Tidal dissipation can drastically shrink and circularize TNB orbits.

A large population of tight, circular TNBs can result from KCTF evolution.

Some TNBs require a strong gravitational quadrupole for orbital stability.

Abstract

Recent observational surveys of trans-neptunian binary (TNB) systems have dramatically increased the number of known mutual orbits. Our Kozai Cycle Tidal Friction (KCTF) simulations of synthetic trans-neptunian binaries show that tidal dissipation in these systems can completely reshape their original orbits. Specifically, solar torques should have dramatically accelerated the semimajor axis decay and circularization timescales of primordial (or recently excited) TNBs. As a result, our initially random distribution of TNBs in our simulations evolved to have a large population of tight circular orbits. This tight circular population appears for a range of TNO physical properties, though a strong gravitational quadrupole can prevent some from fully circularizing. We introduce a stability parameter to predict the effectiveness of KCTF on a TNB orbit, and show that a number of known TNBs must have a large gravitational quadrupole to be stable.