Astrophysical studies of extrasolar planetary systems using infrared interferometric techniques

The study of extrasolar planetary systems has thrived during the last two decades, stimulated by the discovery of circumstellar dust and extrasolar planets around main sequence stars. However, direct imaging of planetary systems has been possible in only very special cases so far due to the huge contrast and to the small angular separation between stars and their environments. Even for these favourable cases, the inner regions where terrestrial planets are expected to be forming and where life could develop have not been investigated yet due to the lack of appropriate tools. Infrared interferometry is a very promising technique in this context, as it provides the required angular resolution to separate the emissions from the star and its immediate neighbourhood.
The present work aims at developing the high dynamic range capabilities of interferometric techniques for the characterisation of planetary systems. As a first step, we demonstrate that current interferometric facilities have the potential of detecting dust in the first few astronomical units of massive debris disks around nearby stars. Our observations of Vega with the FLUOR near-infrared beam combiner at the CHARA Array reveal the presence of warm dust responsible for a K-band flux 78 times fainter than the stellar photospheric emission. In order to extend the imaging of planetary systems to fainter disks and to giant extrasolar planets, we investigate in a second step the performance of future ground-based nulling interferometers, taking into account atmospheric eff ects in a realistic way. Our simulations show that a nulling instrument installed at the ESO Very Large Telescope Interferometer would detect circumstellar features as faint as a few 10^-4 of the stellar flux. Finally, the third part of this work focuses on the implementation of nulling interferometry on future space-borne missions, the goal being to characterise extrasolar planets with sizes down to that of the Earth.