Extra-solar planets: Clues to planetary formation

Radial velocity surveys have revealed up to now about 115 extra-solar planets, among which a few multi-planetary systems. The discovered planets present a wide variety of orbital elements and masses, which are raising many problems and questions regarding the processes involved in their formation. The statistical analysis of the distributions of orbital elements, planetary masses, and relations between these, is however already giving some strong constraints on the formation of the planetary systems. Furthermore, the study of the planet host stars has revealed the crucial role of the stellar metallicity on the giant planet formation. In this paper we will review the current status of the research on this subject.