Habitability in Different Milky Way Stellar Environments: a Stellar Interaction Dynamical Approach

TL;DR

This study uses dynamical simulations to assess how different Milky Way environments impact planetary system stability and habitability, focusing on stellar flybys and their effects on debris disks and Oort clouds.

Contribution

It introduces a comprehensive dynamical approach to evaluate the influence of various Galactic environments on planetary habitability and debris disk stability.

Findings

Low likelihood of Solar planetary disk disruption within 8 Myr

Habitable zones in open clusters are generally stable if clusters dissolve quickly

Probability assessments of Oort cloud existence in different Galactic regions

Abstract

Every Galactic environment is characterized by a stellar density and a velocity dispersion. With this information from literature, we simulated flyby encounters for several Galactic regions, numerically calculating stellar trajectories as well as orbits for particles in disks; our aim was to understand the effect of typical stellar flybys on planetary (debris) disks in the Milky Way Galaxy. For the Solar neighborhood, we examined nearby stars with known distance, proper motions, and radial velocities. We found occurrence of a disturbing impact to the Solar planetary disk within the next 8 Myr to be highly unlikely; perturbations to the Oort cloud seem unlikely as well. Current knowledge of the full phase space of stars in the Solar neighborhood, however, is rather poor, and thus we cannot rule out the existence of a star that is more likely to approach than those for which we have complete kinematic information. We studied the effect of stellar encounters on planetary orbits within the habitable zones of stars in more crowded stellar environments, such as stellar clusters. We found that in open clusters habitable zones are not readily disrupted; this is true if they evaporate in less than 108 years. For older clusters the results may not be the same. We specifically studied the case of Messier 67, one of the oldest open clusters known, and show the effect of this environment on debris disks. We also considered the conditions in globular clusters, the Galactic nucleus, and the Galactic bulge-bar. We calculated the probability of whether Oort clouds exist in these Galactic environments.