Habitability of exoplanets orbiting flaring stars
Rebecca Szabó, Valentin D. Ivanov, M. Švanda
TL;DR
This work assesses the habitability prospects of exoplanets around flaring stars, highlighting that while many habitable-zone planets (notably around M-dwarfs) exist, stellar activity—particularly UV/X-ray flares—poses risks to atmospheres and potential biospheres. It surveys how flares impact planetary atmospheres, ozone, and prebiotic chemistry, and emphasizes the need for large-scale, high-cadence, multi-wavelength spectroscopic monitoring across thousands of stars to quantify flare statistics and risks. The authors advocate a Wide Field Survey Telescope (WST)-like facility with extreme multiplexing and fast, flexible data handling to enable ensemble studies and real-time follow-up of flares, complemented by Gaia, SDSS, 4MOST, ZTF, Rubin, and Euclid data. The resulting insights would clarify the viability of life on planets around active stars and guide future observational strategies, instrument designs, and interdisciplinary collaborations in radiative biology. The work outlines concrete technical and strategic milestones to realize such a project by the 2040s.
Abstract
As of late 2025 there are about 70 exoplanets that meet the formal criterion of having equilibrium temperatures allowing the presence of liquid water and about 50 of them orbit M-stars, known for their strong chromospheric activity. Most of these stars are close to the Sun and the planet-to-star mass and luminosity ratios are advantageous, allowing for a more detailed follow-up than of planets orbiting hotter and more massive stars. Many more planets orbiting late-type stars are expected to be discovered by Gaia and PLATO in the following years. However, the lingering question remains whether the UV and X-ray emission, associated with the stellar activity, allows for complex life. A comprehensive study focused on properties of flaring exoplanet hosts and their activity, on a much larger scale than these few tens (soon to become hundreds) of stars with habitable planets is called for, to answer the question if such stars can harbor habitable planets. The proposed Wide Field Survey telescope is well suited for this study.