Planetary Science Seminar

Disks around young stars consist mainly of gas which is believed to disperse shortly after planet formation, with inferred disk lifetimes of a few million years. Measuring gas disk masses has proven to be difficult; therefore, the amount of gas present at various stages of planet formation is very uncertain. Gas affects the formation, composition and early dynamical evolution of planetary systems, and the evolution of the gas disk thus remains a key outstanding problem. I will discuss disk evolution as predicted by theoretical models that include the effects of viscosity and mass loss driven by thermal winds. We consider the contemporaneous evolution of dust grains and find that most of the dust mass is retained, and possibly converted into planetesimals, after the disk is dispersed. The gas is partly accreted on to the star and partly removed by the wind. I will also discuss the current state of observational diagnostics of disk physical conditions and disk evolution in relation to model results.