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Formation and Retention of Planets in Disks

The ill fate of the building blocks of planets in gaseous disks around young stars stands as one of the major unsolved problems in the theory of planet formation. Our current level of understanding indicates that solids in circumstellar disks migrate into the star or are destroyed in collisions on timescales that are much too short to allow the assembly of kilometer sized bodies that can grow further without such problems. In this seminar I will discuss how the most recent models rely on turbulent motions in the disk in order to breach these barriers. Special focus will be given to the possibility of persistent storm systems (aka vortices) in accretion disks, that have long been considered as a route for fast planet formation, and show that they lead to the assemblage of planetary embryos of Moon to Mars mass. Once the planets are formed in the hydrodynamical and magnetohydrodynamical simulations, we solve for the photoevaporation of the gas disk. While the gas dissipates, we follow the multi-million disk migration and N-body evolution of the ensemble of planets, showing that they eventually coalesce into bodies of the order of tens of Earth masses. I will also discuss a recently proposed photoelectric instability in the debris disk that is left after the gas evaporates. Due to this instability, the system evolves into sharp eccentric narrow rings, similar to those observed in debris disks and usually attributed to the presence of hypothetical undetected planets. Finally, I will discuss pressing problems such as the asymmetries observed in ALMA images of circumstellar disks, and how high end computing with the current generation of clusters of >100,000 processors can be used to solve them.

MP 203

Wladimir Lyra (NASA/JPL-Caltech)

April 05, 2013
11:00 - 12:00