Scientific objectives and preliminary plans for EUV and X-ray observations of late-type stars

Abstract

<p indent="0mm">Searching for extraterrestrial life is one of the most important targets for exploration of the universe. To achieve this goal, it is of critical importance to understand the connection between host stars (mainly cool dwarf stars) and habitable exoplanets. In recent years, more and more researchers have realized that the space weather phenomenon (i.e., solar activity and its impact on the Earth space environment) should also exist in star-planet systems beyond the solar system. As the main sources of space weather, various types of magnetic activity in host stars’ coronae can produce strong electromagnetic and particle radiation that could damage biological tissues, change the chemical composition and lead to the erosion of the planetary atmospheres, thus affecting the origin and survival of life. However, our understanding of the stellar coronae is very limited, which greatly hampers our understanding of the impact of space weather on habitability. Thus, we suggest effectively probing the physical parameters of the coronae and monitoring various types of coronal activity of host stars as soon as possible. To achieve this, we need to build next-generation dedicated EUV and X-ray<sc>(1–350 Å,</sc> most importantly <sc>170–285 Å</sc> and <sc>90–140 Å)</sc> telescopes to perform long-term and continuous spectroscopic and photometric observations of nearby host stars (including but not limited to the host stars of some potentially habitable exoplanets). We describe detailed scientific objectives for such observations, propose the required technical specifications to achieve these scientific goals, and provide preliminary designs of the optical systems. With these telescopes, we could unambiguously detect stellar coronal mass ejections, probe large-scale coronal structures such as coronal holes and active region loop systems, routinely measure the coronal magnetic field, and largely enrich our understanding of stellar flares and coronal plasma properties. By monitoring changes in the stellar emission during exoplanet transits, we may also infer critical information about exoplanetary atmospheres, ionospheres and magnetospheres. Based on these observations, we can substantially improve our understanding of exoplanetary space weather and accurately evaluate its role in forming a habitable world.