Measuring the evaporation of close-in extra-solar planets

The discovery with HST of evaporation of the transiting exoplanet HD209458b hasraised the possibility that the evolution of closein planets is dominated bymass loss. To date, however, this remains the only detection of evaporationbecause STIS was lost shortly after making this discovery. Here we show thatXMMNewton transit spectroscopy is also sensitive to absorption by materialevaporating from closein extrasolar planets. Indeed, Xray continuumabsorption has the potential to measure mass loss rates, whereas HST could onlyplace a lower limit. We propose an XMMNewton transit observation of the nearestand brightest transiting planet, HD189733b. Simultaneous measurement of Xrayirradiation and evaporation rates will provide the first direct test of planetary evaporation models. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]