Physics of planets: Observing extrasolar giant planets with Darwin/TPF

The development of such instruments as DARWIN or TPF represents a great opportunity to study in detail a new population of astrophysical objects: extrasolar giant planets. With radii about ten times larger than that of terrestrial planets, giant planets orbiting other stars than our Sun will be easily detectable by DARWIN/TPF. It is expected that the orbital parameters of hundreds of these objects will have been determined by 2010, most of them with indirect techniques such as radial velocimetry and astrometry. Of those, a few tens of the systems will be oriented in such a way that the planet or planets will transit in front of their star, thus permitting to measure their radii. Observing these systems with DARWIN/TPF will be of considerable importance: their infrared luminosity will then become measurable, as well as important molecular absorption features. This will yield much tighter constraints on their age and composition, thus allowing to better understand of planet formation in general.