# AMD-stability and the classification of planetary systems

## TL;DR

This paper introduces the AMD-stability criterion, a practical tool for classifying the long-term stability of multiplanet systems based on their angular momentum deficit, aiding in understanding planetary system evolution.

## Contribution

It defines the AMD-stability criterion and applies it to classify 131 known multiplanet systems, enhancing stability assessment methods.

## Key findings

- Long-term stable systems are AMD-stable.
- Unstable systems require further dynamical analysis.
- The classification helps prioritize systems for detailed study.

## Abstract

We present here in full detail the evolution of the angular momentum deficit (AMD) during collisions as it was described in (Laskar, PRL,2000). Since then, the AMD has been revealed to be a key parameter for the understanding of the outcome of planetary formation models. We define here the AMD-stability criterion that can be easily verified on a newly discovered planetary system. We show how AMD-stability can be used to establish a classification of the multiplanet systems in order to exhibit the planetary systems that are long-term stable because they are AMD-stable, and those that are AMD-unstable which then require some additional dynamical studies to conclude on their stability. The AMD-stability classification is applied to the 131 multiplanet systems from The Extrasolar Planet Encyclopaedia database (exoplanet.eu) for which the orbital elements are sufficiently well known.