Constraints on Evolutionary Timescales for M Dwarf Planets from Dynamical Stability Arguments

TL;DR

This study explores how dynamical stability timescales of exoplanets around M dwarf stars influence potential biological evolution, using simulations to connect orbital dynamics with planetary habitability over stellar ages.

Contribution

It introduces a Monte Carlo framework to assess how dynamical sculpting timescales impact biological evolution, focusing on M dwarf planetary systems and observational data from Kepler and TESS.

Findings

Shorter dynamical intervals in multi-planet systems.

Older stars' planets may experience longer dynamical stability.

Dynamical effects vary with stellar age and detection method.

Abstract

The diversity of dynamical conditions among exoplanets is now well established. Yet, the relevance of orbital dynamical timescales to biological evolutionary timescales is poorly understood. Given that even minor orbital changes may place significant pressure on any organisms living on a planet, dynamical sculpting has important implications for the putative evolution of life. In this manuscript, we employ a Monte Carlo framework to investigate how a range of exoplanetary dynamical sculpting timescales affects timescales for biological evolution. We proceed with minimal assumptions for how dynamical sculpting proceeds and the emergence and persistence of life. We focus our investigation on M dwarf stars, the most common exoplanetary hosts in the Milky Way. We assign dynamical statuses, dependent on stellar age, to a suite of planetary systems, varying the rate of dynamical disruption within limits that are consistent with present-day planet demographics. We then simulate the observed yield of planets according to the completeness of NASA's Kepler and TESS missions, and investigate the properties of these samples. With this simplified approach, we find that systems hosting multiple transiting planets ought to have, on average, shorter dynamically-uninterrupted intervals than single-transiting systems. However, depending upon the rate of dynamical sculpting, planets orbiting older stars will exhibit the opposite trend. Even modest constraints on stellar age would help identify "older" stars for which this holds. The degree of these effects varies, dependent upon both the intrinsic dynamical demographics of exoplanets and whether we consider planets detected by NASA's Kepler or TESS missions.