Planetary System Disruption by Galactic Perturbations to Wide Binary Stars

TL;DR

This study uses numerical simulations to show that galactic perturbations can significantly disrupt planetary systems in wide binary stars, leading to planetary ejections and increased orbital eccentricities, which aligns with observed exoplanet data.

Contribution

It reveals that galactic influences on wide binary stars can reshape planetary systems over billions of years, a factor previously underappreciated in planetary evolution models.

Findings

Wide binary companions can strongly perturb planetary systems.

Observed exoplanet eccentricities support galactic perturbation effects.

Most isolated giant exoplanet systems likely have additional distant planets.

Abstract

Nearly half of the exoplanets found within binary star systems reside in very wide binaries with average stellar separations beyond 1,000 AU (1 AU being the Earth-Sun distance), yet the influence of such distant binary companions on planetary evolution remains largely unstudied. Unlike their tighter counterparts, the stellar orbits of wide binaries continually change under the influence of the Galactic tide and impulses from other passing stars. Here we report numerical simulations demonstrating that the variable nature of wide binary star orbits dramatically reshapes the planetary systems they host, typically Gyrs after formation. Contrary to previous understanding, wide binary companions may often strongly perturb planetary systems, triggering planetary ejections and exciting orbital eccentricities of surviving planets. Indeed, observed exoplanet eccentricities offer evidence of this; giant exoplanet orbits within wide binaries are statistically more eccentric than those around isolated stars. Both eccentricity distributions are well-reproduced when we assume isolated stars and wide binaries host similar planetary systems whose outermost giant planets are scattered beyond ~10 AU from their parent stars via early internal instabilities. Consequently, our results suggest that although wide binaries eventually truncate their planetary systems, most isolated giant exoplanet systems harbor additional distant, still undetected planets.