Direct Observation of Extra-Solar Planets with an Infrared Interferometer

J.-M. Mariotti, V. Coudé du Foresto, G. Perrin
Observatoire de Paris, Meudon, France

The unexpected discovery of Jupiter-size planets very close to their parent stars (two examples of which are 51 Peg and Tau Boo) creates a challenge for theories of planetary formation and structure. Only a direct measurement of their mass and luminosity (not accessible via the current radial velocity techniques) can help discriminate between the different planetary models that have been proposed for this new class of objects.

Direct observation of such extra-solar planets with an infrared interferometer is a difficult task because of the very high dynamic range required (typically 3¥104 to 3¥105), but not impossible if a very careful spatial filtering and calibration is imposed upon the recombined beams. High accuracy visibility measurements have already been demonstrated with the FLUOR unit at the IOTA interferometer.

We propose an observing strategy to monitor hot extra-solar planets of the 51 Peg class. Our calculations show that these programs can be carried out with infrared interferometers such as the VLTI, provided that they are equipped with a single-mode instrument and a fringe tracker.