When
3:30 p.m., March 23, 2010
Where
Kuiper Space Sciences Building 308
Dr. Andrew Youdin of the Canadian Institute for Theoretical Astrophysics, is the scheduled speaker.
Abstract: Recent years have seen significant advances in our understanding of how planetesimals, solids bigger than a kilometer, first formed. I will describe dynamical processes that compliment the collisional sticking of small grains. Self-gravity can collect a sea of small solids into a gravitationally bound planetesimal, but stirring by turbulent gas is a formidable obstacle. However several processes can concentrate particles in gas disks --- both despite and because of turbulence. The most powerful is the streaming instability, mediated by two-way drag forces between solids and gas. Overdense particle clumps can then collapse gravitationally into planetesimals. Numerical simulations demonstrate the viability of these mechanisms. I will discuss outstanding questions, and connections to the planetesimal belts in our Solar System. Finally I will briefly comment on a different type of gravitational collapse, that of gas disks into giant planets and brown dwarfs. I will discuss whether recently imaged exoplanets could form by this mechanism.
Abstract: Recent years have seen significant advances in our understanding of how planetesimals, solids bigger than a kilometer, first formed. I will describe dynamical processes that compliment the collisional sticking of small grains. Self-gravity can collect a sea of small solids into a gravitationally bound planetesimal, but stirring by turbulent gas is a formidable obstacle. However several processes can concentrate particles in gas disks --- both despite and because of turbulence. The most powerful is the streaming instability, mediated by two-way drag forces between solids and gas. Overdense particle clumps can then collapse gravitationally into planetesimals. Numerical simulations demonstrate the viability of these mechanisms. I will discuss outstanding questions, and connections to the planetesimal belts in our Solar System. Finally I will briefly comment on a different type of gravitational collapse, that of gas disks into giant planets and brown dwarfs. I will discuss whether recently imaged exoplanets could form by this mechanism.
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LPL Colloquium
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