Physics & Astronomy Colloquium – Spring 2020 – Yang
February 26 @ 3:30 pm - 5:00 pm
Speaker: Chao-Chin Yang (University of Nevada, Las Vegas)
Title: Planetesimal Formation through the Streaming Instability
The formation of kilometer-scale planetesimals is one of the most difficult stages in the course of planet formation around young stars. It is faced with several major barriers. Direct dust growth by coagulation is limited, up to mm to cm in size, due to inefficient sticking, bouncing, and fragmentation at collision. Even if the dust grains manage to grow past cm in size, they continually lose angular momentum to their surrounding gas due to constant head wind, leading to rapid orbital decay to the star. One promising mechanism for circumventing these barriers is the streaming instability, in which the solids actively participate in the dust-gas dynamics to concentrate themselves to high density, leading to direct gravitational collapse and the formation of planetesimals.
I will review our current understanding of the streaming instability and planetesimal formation. Specifically, how the instability operates, under what conditions it drives strong concentration of solid materials, the initial mass function of the resulting planetesimals, and its interaction with turbulent gas will be examined.
Dr. Chao-Chin Yang is a postdoctoral scholar in the Department of Physics and Astronomy at the University of Nevada, Las Vegas in the United States. His research is in in theoretical astrophysics, including planet formation and migration, galactic dynamics, the interstellar medium, and computational astrophysics. His studies primarily involves computer simulations, using state-of-the-art high-end computing facilities. He is one of the core developers for the Pencil Code, a high-order finite-difference code for compressible magnetohydrodynamics (MHD) coupled with solid particles.
Currently, his work is focused on understanding processes that may affect the formation of kilometer-scale planetesimals in protoplanetary disks, one of the most difficult stages in the course of planet formation. These processes include, but are not limited to, dust-gas dynamics, dust coagulation, and MHD turbulence.