The effects of stellar winds on the magnetospheres and potential habitability of exoplanets

TL;DR

This study investigates how stellar winds from solar-mass stars affect the magnetospheres of Earth-like exoplanets in habitable zones, showing most can sustain protective magnetic fields, especially around less active stars.

Contribution

The paper introduces a computationally efficient method to estimate magnetospheric sizes of Earth-like exoplanets around solar-type stars using two wind models, highlighting their potential for habitability.

Findings

Most simulated planets can maintain magnetospheres of ~5 Earth radii or larger.

Earth analogues around solar-type stars older than 1.5 Gyr can sustain Earth-sized magnetospheres.

Stars with 0.6 - 0.8 solar masses and low activity are optimal targets for habitable exoplanets.

Abstract

Context: The principle definition of habitability for exoplanets is whether they can sustain liquid water on their surfaces, i.e. that they orbit within the habitable zone. However, the planet's magnetosphere should also be considered, since without it, an exoplanet's atmosphere may be eroded away by stellar winds. Aims: The aim of this paper is to investigate magnetospheric protection of a planet from the effects of stellar winds from solar-mass stars. Methods: We study hypothetical Earth-like exoplanets orbiting in the host star's habitable zone for a sample of 124 solar-mass stars. These are targets that have been observed by the Bcool collaboration. Using two wind models, we calculate the magnetospheric extent of each exoplanet. These wind models are computationally inexpensive and allow the community to quickly estimate the magnetospheric size of magnetised Earth-analogues orbiting cool stars. Results: Most of the simulated planets in our sample can maintain a magnetosphere of ~5 Earth radii or larger. This suggests that magnetised Earth analogues in the habitable zones of solar analogues are able to protect their atmospheres and is in contrast to planets around young active M dwarfs. In general, we find that Earth-analogues around solar-type stars, of age 1.5 Gyr or older, can maintain at least a Paleoarchean Earth sized magnetosphere. Our results indicate that planets around 0.6 - 0.8 solar-mass stars on the low activity side of the Vaughan-Preston gap are the optimum observing targets for habitable Earth analogues.