The discovery of extrasolar planets and the determination of their orbital properties have provided golden opportunities for new advancements in the quest to understand the origin and evolution of planets and planetary systems. While their bizarre variety presents a challenge for the existing theories, their ubiquity suggests that planetary formation is a robust process. Combining data obtained from solar system exploration, star formation studies and the searches for extra solar planets, we address some outstanding issues concerning critical processes of grain condensation, planetesimal coagulation, and gas accretion. Some implications of these investigations are: 1) the amount of heavy elements available for planetary formation in protostellar disks is retained at a similar level as that empirically inferred for the primordial solar nebula, through self regulated processes and 2) the critical stages of planet formation, from grain condensation, planetesimal coagulation, to gas accretion, proceed on the timescale of a few million years.

Observations

Ongoing searches of extra solar planets (ESPs) have led to their discovery around ten per cent of the solar-type stars on various target lists (Marcy & Butler 1998). The dynamical properties of many ESPs are very different from those of planets in the solar system. The first ESP discovered, while having a mass (Mp) similar to that of Jupiter (MJ), is located 100 times closer to its host star 51 Peg than Jupiter is to the Sun (Mayor & Queloz 1995). The period (P) distribution of ESPs has a noticeable concentration between 3–7 days.