Stellar Activity, Exoplanet, Habitability, Planetary Atmospheres

This chapter will review the deep connection of planetary habitability and stellar irradiation. We present the long-term stellar evolution as one of the drivers of atmospheric escape and climate changes on exoplanets, as well as the chemistry driven by stellar UV and stellar energetic particles. Habitability is presented in the context of short and long-term stellar variability and evolution to layout what we understand and what we need to know about stellar irradiation to constrain our planetary atmospheric models and choose the best targets for future missions that may characterize those exoplanets.