Galactic Environments of the Sun and Cool Stars

TL;DR

Understanding the galactic environments of cool stars, including the Sun, is crucial for assessing interstellar matter penetration and its implications for planetary habitability and climate stability.

Contribution

This paper analyzes the interaction between stars and interstellar clouds to estimate astrosphere sizes and their impact on planetary environments.

Findings

The Sun's heliosphere has likely excluded most interstellar matter for the past few million years.

Astrosphere sizes vary among nearby stars based on interstellar cloud encounters.

Inner planets are more likely to have stable climates due to reduced interstellar influence.

Abstract

The importance of understanding the current and historical galactic environments of cool stars is discussed. The penetration of interstellar gas into a stellar astrosphere is a function of the interaction of the star with the interstellar cloud surrounding the star, and this factor needs to be understood if an efficient search for life-bearing planets is to be made. For the Sun, both current and historical galactic conditions are such that if a solar wind were present, it would have excluded most inflowing interstellar matter from the inner regions of the heliosphere for the past few million years. Variations in heliosphere size over the recent historical path of the Sun are estimated, along with estimates of astrosphere sizes for selected nearby stars. Considering only possible effects due to encounters with interstellar clouds, stable planetary climates are more likely for inner than outer planets.