date: 2010 June 16 (Wed) 16:00-
room: Kobe University, Science and Technology Research Building #4-809
speaker: Koji Wada (Chitech)
title: To be, or not to be: that is the question of dust aggregates
abstract: Impact processes in our Solar system play a crucial role in formation and evolution of the planets. In particular, formation process of planetesimals through collisions of dust aggregates still remains unclear. We perform numerical simulations of aggregate collisions to examine the evolution of dust aggregates in protoplanetary disks. As a result, we have found that aggregates are not compressed well by their mutual collisions and the fractal dimension of the compressed aggregates is at most ~ 2.5. The aggregates composed of ice particles are feasible to grow even if the impact velocities are as high as a few tens of m/s. These numerical results suggest that very fluffy planetesimals can be formed in protoplanetary disks by direct collisional growth of dust. There are still many problems remaining, such as the feasibility of collisional growth of silicate aggregates. We believe that these problems are resolved through our collision simulations and the growth of dust aggregates are fully understood in the future.