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During the first million years of evolution, nascent planetary systems are embedded in dense disk-shaped clouds of gas. These circumstellar disks are home to a myriad of hydrodynamical processes, which bring about turbulence and the emergence of viscous-like behavior, enabling accretion of gas onto the protostar. Meanwhile, micron-sized dust grains embedded in the disk are growing through coagulation onto pebbles and rocks. Losing angular momentum to gas drag, the pebbles drift toward the star in a process that turns out to be hydrodynamically unstable. This "streaming instability" has a positive feedback effect on the small solids, concentrating them strongly enough to achieve gravitational collapse into km-sized bodies, forming the first planetesimals, that subsequently grow through accretion of the remaining pebbles. Giant storm systems in the disk, similar to Jupiter’s Great Red Spot, may exist in quiescent zones of the disk. These are even more prone to collecting solid material, producing the first terrestrial planets and cores of giant planets. In this talk, I will discuss the state of the art and recent advances in the field of planet formation, as well as pressing problems such as how to find evidence for streaming instability in the Kuiper belt objects, the structures observed in high resolution ALMA and VLA images of circumstellar disks, and how to interpret them. |
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