# Plausible Compositions of the Seven TRAPPIST-1 Planets Using Long-term Dynamical Simulations

## TL;DR

This study uses long-term dynamical simulations to explore plausible compositions of the TRAPPIST-1 planets, revealing most are Earth-like with some likely having volatile-rich envelopes.

## Contribution

It provides a comprehensive set of stable orbital solutions for the TRAPPIST-1 system considering mass uncertainties, aiding future compositional analyses.

## Key findings

- Most planets are consistent with Earth-like composition.
- TRAPPIST-1f likely has a volatile-rich envelope.
- Identified stable orbital configurations over millions of years.

## Abstract

TRAPPIST-1 is a nearby ultra-cool dwarf that is host to a remarkable planetary system consisting of seven transiting planets. The orbital properties and radii of the planets have been well-constrained, and recently the masses of the inner six planets have been measured with additional ground and space-based photometric observations. Large uncertainties in these mass measurements have prevented a robust analysis of the planetary compositions. Here we perform many thousands of N-body dynamical simulations with planet properties perturbed from the observed values and identify those that are stable for millions of years. This allows us to identify self-consistent orbital solutions that can be used in future studies. From our range of dynamical masses, we find that most of the planets are consistent with an Earth-like composition, where TRAPPIST-1f is likely to have a volatile-rich envelope.