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Classical T Tauri stars are bright in the soft X-ray and far UV bands, because of large amounts of plasma at T~10⁵-10⁶ K, associated with the accretion-shock regions. Inspecting the emission from the shock region is important since it can potentially reveal fundamental properties of the accretion-stream material (i.e. geometry/density/velocity/abundances). However, the precise location of these hot plasmas (pre-shock? post-shock? different shock regions with different temperatures?) is still unclear. To constrain location and properties of these accretion-related hot plasmas, X-rays and UV observations are needed. The next XMM call (deadline 6 October 2017) offers the possibility to investigate this issue. I would like to discuss with you the opportunity to propose a joint XMM+HST program, focused on TW Hya, to perform time-resolved high-resolution spectroscopy on time scales down to 15 ks, simultaneously in the X-ray and UV bands. Correlated or uncorrelated variability of plasmas at 10⁵ and 10⁶ K will indicate whether or not they are located in the same accretion-shock regions. That will provide important constraints on the physical properties of the accretion streams in CTTS.

Abstract: For decades the Solar System has been our sole example of a planetary system, resulting in the classical view of planetary formation as a local, orderly process producing stable planetary systems. The ever growing sample of known exoplanets, however, has shown us the major role played by orbital migration and chaos in determining the evolution of planetary systems in our galaxy. This brought to questioning our very understanding of the history of the Solar System and to suggesting that it also could have undergone a more violent evolution than previously thought. In this talk I will describe how the compositional information on the planetary bodies of the Solar System can be used to shed new light on its past, illustrating the past and current investigations performed in the framework of the NASA missions Dawn and Juno, and I’ll discuss how the same principles, if not the same techniques, can be used to investigate of histories of extrasolar planets.