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Exoplanet Science Seminar

Evolution of Circumstellar Disks and Planet Formation
Presented by Wladimir Lyra (Host: Wes Traub)
California Institute of Technology

Thursday, October 31, 2013
4:00 P.M. in 169-336

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-size dust grains embedded in the disk are growing through coagulation onto pebbles and rocks. Turbulence has a positive effect on these small solids, concentrating them into transient high pressure regions for long enough to achieve gravitational collapse into km-sized bodies, forming the first planetesimals. 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. Once the planets are formed, gravitational interactions, migration through the disk, and jitter from the turbulent gas define the system's final architecture. Concurrently, high energy photons from the central star slowly evaporate the gas, eventually leaving behind a disk of dust and debris. These debris disks tend to show a variety of non-trivial structures attributed to planetary perturbations and utilized to constrain the properties of the unseen exoplanets. In this talk I will discuss the state of the art and recent advances in the field of planet formation, and provide an alternative explanation for some of the structure seen in debris disks around young stars.

About the Speaker
Dr Wladimir Lyra, Sagan Fellow California Institute of Technology Division of Geological & Planetary Sciences 1200 E California Blvd MC 150-21 Pasadena, CA 91125 Tel:+1 626-395-8862 (Caltech), +1 818.393.2487 (JPL) web:

Center for Exoplanet Science

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