The relevance and future of the ultraviolet range

Abstract

To progress in our understanding of cool stars is instrumental to have access to UV (mid-high resolution) spectroscopy. In fact, the UV range supplies a richness of experimental data which is unmatched by any other spectral domain for the study of astrophysical plasmas since (1) almost all the resonance lines of all elements, covering plasmas from the coolest regimes (10-1000K) up to hot (some 10(5)K) temperatures are observed in the UV range, (2) the electronic transitions of the most abundant molecules, such as 112, are in the ultraviolet which is also sensitive to the presence of large molecules such as the PAHs and (3) some strong coronal lines (Fe XXII, Fe XVIII, Fe XXI) axe also observed in this range. As a consequence UV spectroscopy is instrumental to make advance on some of the key problems of modern astrophysics such as the formation of solar-like stars and planetary systems or the understanding of the solar-stellar connection and eventually of the Sun in a broad galactic context. Amazingly enough, the situation of (mid-high resolution) UV Spectroscopy is precarious; there is not any facility available in the whole planet Earth (unless FUSE that works in a very small Far-UV range) and no firm plans exist for the future. Only concerted efforts by the community will supply the information required to have the space agencies decide to release the funding needed for the support of these important Astrophysical study capabilities. This splinter session has been devoted to highlight the relevance of the UV range for the understanding of Cool Stars and to seek for world-wide coordination.