Forming planetesimals from gravitational collapse

Abstract: The formation of 1-100 km planetesimals from dust and pebbles is a critical and possibly determinative step in establishing the architecture of extrasolar planetary systems. One physically viable pathway involves the spontaneous clustering of small solid particles through the streaming instability, followed by gravitational collapse. I will discuss the results of new simulations of planetesimal formation, that confirm some prior results and provide evidence that the mass function of planetesimals formed in laminar disks is independent of the aerodynamic properties of the particles that participate in the instability. I will highlight open questions and connections to a global scenario of planet formation in which mobility plays the central role.