The 10 pc Neighborhood of Habitable Zone Exoplanetary Systems: Threat Assessment from Stellar Encounters & Supernovae

TL;DR

This study assesses the local stellar environment of nearby habitable zone exoplanet systems using Gaia data, identifying potential threats from stellar encounters and supernovae, and comparing their similarity to the solar neighborhood.

Contribution

It introduces a method to evaluate stellar neighborhood risks to habitability and compares the environments of known habitable systems to the solar system.

Findings

HD 165155 likely experiences stellar flybys within 5 Gyr.

Two high-mass stars could produce supernovae threatening habitable systems.

HD 40307 most resembles the solar neighborhood.

Abstract

The habitability of a planet is influenced by both its parent star and the properties of its local stellar neighborhood. Potential threats to habitability from the local stellar environment mainly arise from two factors: cataclysmic events such as powerful stellar explosions and orbital perturbations induced by close stellar encounters. Among the 4,500+ exoplanet-hosting stars, about 140+ are known to host planets in their habitable zones. In this study, we use \textit{Gaia DR3} data to investigate the 10~pc stellar neighborhood of the 84 habitable zone systems (HZS) closest to the Sun. We assess the possible risks that local stellar environment of these HZS pose to their habitability. In particular, we find that HD~165155 has a high stellar density around it, making it likely to experience at least one flyby encounter within a span of 5~Gyr. We also identified two high-mass stars ($M \geq 8 M_\odot$) as potential progenitors of supernovae, which could threaten the long-term survivability of habitable zone systems HD~48265 and TOI-1227. Further, to quantify the similarity between habitable zone stars and the Sun, as well as their respective 10~pc stellar environments, we employ various astrophysical parameters to define a Solar Similarity Index (SSI) and a Neighborhood Similarity Index (NSI). Our analysis suggests that HD~40307 exhibits the closest resemblance to the solar system, while HD~165155 shows the least resemblance.