The theory of planet formation: present and future
Planets form in disks. But the processes through which dust grains in disks evolve into planets are still controversial. I will start this contribution with reviewing the classical model of planet formation, which envisions a transition to a disk dominated by planetesimals (km-size bodies) and a sharp distinction between rocky planets and gas giants. I will demonstrate that this picture conflicts with key observational findings, chiefly the inferred presence of mm/cm-size particles and the discovery of the new super-Earths class of planets. Some implications of these discoveries for planet formation theory will be addressed and I will outline directions for future research in this field.