Resilient habitability of nearby exoplanet systems

TL;DR

This study assesses the potential for Earth-like planets in the habitable zones of 34 nearby star systems with known giant planets, considering past planetary system instabilities and identifying promising candidates for future observation.

Contribution

It introduces the concept of resilient habitability, quantifies how past instabilities affect planet stability in habitable zones, and provides a list of promising systems for future study.

Findings

Most systems have reduced stable habitable zones after considering past instabilities.

Identified specific systems with high resilient habitability potential.

Uncertainties in planetary eccentricities affect habitability assessments.

Abstract

We investigate the possibility of finding Earth-like planets in the habitable zone of 34 nearby FGK-dwarfs, each known to host one giant planet exterior to their habitable zone detected by RV. First we simulate the dynamics of the planetary systems in their present day configurations and determine the fraction of stable planetary orbits within their habitable zones. Then, we postulate that the eccentricity of the giant planet is a result of an instability in their past during which one or more other planets were ejected from the system. We simulate these scenarios and investigate whether planets orbiting in the habitable zone survive the instability. Explicitly we determine the fraction of test particles, originally found in the habitable zone, which remain in the habitable zone today. We label this fraction the resilient habitability of a system. We find that for most systems the probability of planets existing [or surviving] on stable orbits in the habitable zone becomes significantly smaller when we include a phase of instability in their history. We present a list of candidate systems with high resilient habitability for future observations. These are: HD 95872, HD 154345, HD 102843, HD 25015, GJ 328, HD 6718 and HD 150706. The known planets in the last two systems have large observational uncertainties on their eccentricities, which propagate into large uncertainties on their resilient habitability. Further observational constraints of these two eccentriciti