Statistical Properties of Exoplanets

Since the detection a decade ago of the planetary companion of 51 Peg, more than 200 extrasolar planets have been unveiled, mostly by radial-velocity measurements but also in a few cases by photometric transit observations or in microlensing experiments. They present a wide variety of characteristics such as large masses with small orbital separations, high eccentricities, period resonances in multiplanet systems, etc. Meaningful features of the statistical distributions of orbital parameters for giant planets or of parent stellar properties have emerged. We discuss them in the context of the constraints they provide for planet-formation models, and in comparison to Neptune-mass planets in short-period orbits recently detected by radial-velocity surveys. Finally, the role of radial-velocity follow-up measurements of transit candidates is emphasized. Planetary physical parameters are determined, bringing important constraints for inner planet structure models.