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Astrophysics Luncheon Seminar

Core Accretion: Contrasting Planetesimal-driven and Fragment-driven Scenarios
Presented by Chris Ormel
University of California, Berkeley

Monday, January 30, 2012
12:00 noon in 169-336

Abstract
In the core accretion scenario for giant planet formation, the first critical step is the formation of a solid core -- massive enough to gravitationally bind the nebular gas. But how do cores acquire their mass in the first place? It is believed that planet formation proceeds 'oligarchicly', where a few large bodies (embryos) consume liberally from a reservoir of smaller bodies (planetesimals). Modeling this phase requires us to understand and synthesise many physical processes simultaneously. I will show that the outcome of these models is very sensitive to the choices for key model parameters regarding the gas (e.g., the turbulent strength) and material properties (e.g., the planetesimal size). In particular, I will emphasize the role of collisions and argue that fragments of planetesimals, or small particles in general, can dominate the solid mass reservoir. Accretion scenarios in which fragments play the dominant role will be investigated. This requires a rethinking of the use of the proper gravitational cross section, since gas drag forces will rival the gravitational (2-body) force.


SVCP Astrophysics


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