# Binary Survival in the Outer Solar System

## TL;DR

This paper investigates the formation and survival of equal-size binary objects in the Kuiper belt, analyzing how dynamical processes affect their presence in different populations and what this reveals about the early solar system.

## Contribution

It provides a detailed analysis of binary survival probabilities in the Kuiper belt, considering formation scenarios and dynamical disruptions during planetary migration.

## Key findings

- Tighter binaries have higher survival chances in the Kuiper belt.
- Widest binaries in the hot population have less than 1% survival probability.
- Satellites of large KBOs are likely to survive during dynamical implantation.

## Abstract

As indicated by their special characteristics, the cold classical Kuiper belt objects (KBOs) formed and survived at 42-47 au. Notably, they show a large fraction of equal-size binaries whose formation is probably related to the accretion of KBOs themselves. These binaries are uncommon in other --hot, resonant, scattered-- populations, which are thought to have been implanted from the massive disk below 30 au to >30 au during Neptune's migration. Here we highlight the possibility that equal-size binaries formed in the disk but were subsequently removed by impacts and/or dynamical effects (e.g., scattering encounters with Neptune). We determine the dependence of these processes on the size and separation of binary components. Our results indicate that tighter binaries, if they formed in the massive disk, have relatively good chances of survival (unless the disk was long-lived). In contrast, the widest binaries in the hot population, such as 2002 VF130, have a very low survival probability (<1%) even if the massive disk was short-lived. They may represent a trace of lucky survivors of a much larger population of the original disk binaries, or they formed at ~30-40~au and dodged the impact- and encounter-related perturbations that we studied here. We find that all known satellites of the largest KBOs would survive during the dynamical implantation of these bodies in the Kuiper belt. The low orbital eccentricities of Pluto's small moons may have been excited by impacts and/or encounters of the Pluto system to Neptune.