Princeton University Extrasolar Planet Discussion Group

The streaming instability of particles and gas in protoplanetary disks is probably now the favored theoretical model for building planetesimals. It finds support from Kuiper Belt observations, and there are reasonable prospects for using it as part of predictive models for where and when planetesimals form in different disks. There remain, however, quite basic uncertainties. I'll discuss some recent results on the predicted mass function, on the effect of turbulence, and on the role of particle size distributions, together with ideas for future directions.