Planetary systems in a star cluster I: the Solar system scenario

TL;DR

This study uses numerical simulations to explore how planetary systems similar to our Solar system evolve within star clusters, revealing the effects of stellar encounters on planetary survival and system diversity over 50 million years.

Contribution

It provides new insights into the dynamical evolution and survival rates of Solar-like planetary systems in star clusters, highlighting the role of stellar encounters and cluster density.

Findings

Most planetary systems remain intact within star clusters.

A small percentage of planets escape over 50 Myr, with escape rates up to 5.3%.

Jupiter acts as a protective barrier for terrestrial planets in low-density environments.

Abstract

Young stars are mostly found in dense stellar environments, and even our own Solar system may have formed in a star cluster. Here, we numerically explore the evolution of planetary systems similar to our own Solar system in star clusters. We investigate the evolution of planetary systems in star clusters. Most stellar encounters are tidal, hyperbolic, and adiabatic. A small fraction of the planetary systems escape from the star cluster within 50 Myr; those with low escape speeds often remain intact during and after the escape process. While most planetary systems inside the star cluster remain intact, a subset is strongly perturbed during the first 50 Myr. Over the course of time, 0.3 % - 5.3 % of the planets escape, sometimes up to tens of millions of years after a stellar encounter occurred. Survival rates are highest for Jupiter, while Uranus and Neptune have the highest escape rates. Unless directly affected by a stellar encounter itself, Jupiter frequently serves as a barrier that protects the terrestrial planets from perturbations in the outer planetary system. In low-density environments, Jupiter provides protection from perturbations in the outer planetary system, while in high-density environments, direct perturbations of Jupiter by neighbouring stars is disruptive to habitable-zone planets. The diversity amongst planetary systems that is present in the star clusters at 50 Myr, and amongst the escaping planetary systems, is high, which contributes to explaining the high diversity of observed exoplanet systems in star clusters and in the Galactic field