Measuring stellar activity with AXIS, a high resolution X-ray imager

How does stellar activity affect the evolution and habitability of exoplanets? The probe class Advanced X-ray Imaging Satellite (AXIS) will have a 1-arcsecond PSF over a 30-arcminute field of view and, in comparison to Chandra, will be 20 times more sensitive to X-ray emission from stars. X-rays are correlated with magnetic activity, rotation, stellar age, and EUV emission — knowledge of which is important for modeling atmospheric chemistry and assessing habitability of exoplanets. AXIS is the only probe class mission with the sensitivity and imaging resolution to measure the X-ray luminosity and variability of stars in clusters, which will serve to reconstruct the activity history across different stellar types. AXIS would also provide the unique opportunity to pioneer the field of exoplanet transits in the X-ray, to directly measure the extent of exospheres and evaporating atmospheres.