Flare-driven habitability: Expanding life's potential around low-mass stars

TL;DR

This paper expands the concept of habitability around low-mass stars by incorporating UV radiation from stellar flares, showing that flares can extend habitable zones and influence the potential for life on orbiting planets.

Contribution

It introduces a UV habitable zone concept that accounts for stellar flares and their UV flux, refining habitability criteria for planets around low-mass stars.

Findings

UV-HZ can extend to inner regions of traditional HZs.

Three planets around Kepler flaring stars are within both UV-HZ and LW-HZ.

Flares significantly increase habitability potential around low-mass stars.

Abstract

The traditional definition of the circumstellar habitable zone (HZ) focuses on liquid water, but neglects the crucial role of ultraviolet (UV) radiation in prebiotic chemistry. Low-mass stars typically emit insufficient UV radiation for photochemistry throughout the liquid water HZs during quiescent states. However, frequent flares can provide substantial UV fluxes, potentially fostering habitable conditions. We refine the concept of a UV habitable zone (UV-HZ) by incorporating a temperature-dependent model for RNA precursor synthesis. Furthermore, we explore a parameterized spectral energy distribution model and adopt an empirical flare frequency distribution for flares on different stars to quantify their UV contribution. Applying this framework to different flaring stars, we find the UV-HZ around low-mass stars can extend to inner regions, and overlap with the traditional HZ in wide ranges. Apply the analysis to 9 planets around Kepler flaring stars, three planets are located within both the refined UV-HZ and liquid water habitable zone (LW-HZ) without causing ozone depletion. Our findings highlight the significant role of flares in expanding the potential for life around low-mass stars, offering a revised perspective on exoplanet habitability criteria.