Long-term stability of planets in and around binary stars

TL;DR

This study uses N-body simulations to analyze how binary star systems influence the long-term stability of planets, revealing that the binary fraction significantly impacts the prevalence of stable planetary systems in the galaxy.

Contribution

It provides new insights into the stability of planets in binary systems and how star-forming region dynamics affect planetary habitability over time.

Findings

Binary systems can host stable planets depending on orbital parameters.

Dynamical encounters can induce long-term planetary system instabilities.

The overall fraction of stable systems is mainly determined by the binary fraction.

Abstract

Planets are observed to orbit the component star(s) of stellar binary systems on so-called circumprimary or circumsecondary orbits, as well as around the entire binary system on so-called circumbinary orbits. Depending on the orbital parameters of the binary system a planet will be dynamically stable if it orbits within some critical separation of the semimajor axis in the circumprimary case, or beyond some critical separation for the circumbinary case. We present N-body simulations of star-forming regions that contain populations of primordial binaries to determine the fraction of binary systems that can host stable planets at various semimajor axes, and how this fraction of stable systems evolves over time. Dynamical encounters in star-forming regions can alter the orbits of some binary systems, which can induce long-term dynamical instabilities in the planetary system and can even change the size of the habitable zone(s) of the component stars. However, the overall fraction of binaries that can host stable planetary systems is not greatly affected by either the assumed binary population, or the density of the star-forming region. Instead, the critical factor in determining how many stable planetary systems exist in the Galaxy is the stellar binary fraction - the more stars that are born as singles in stellar nurseries, the higher the fraction of stable planetary systems.