A Pathway for Collisional Planetesimal Growth in the Ice Dominant Region of Protoplanetary Disks
Physical and Biological Sciences
Physics (Astrophysics)
The "meter-size barrier'' of planet formation has been one of the most persistent problems in formation models and our overall understanding of early stages of planet formation and evolution. Models demonstrate that once the dust and gas in a planet-forming disk coagulate into roughly meter-size boulders, growth completely halts and gravity is not sufficient to maintain the structural integrity of the boulders; instead, almost all grains begin to break apart from collisions or rapidly inspiral into their host-star. Previous studies of centimeter- to meter-size grain evolution fail to model the full parameter space necessary to capture the growth, inward drift, and fragmentation processes of these grains. We created an analytic model of these processes and consider all the relevant drag forces, material compositions, and most up-to-date observed protoplanetary disk properties and iceline calculations. The model’s flexibility allows tests of grain stability and motion across an extremely broad parameter space, including where dust and ice grains will break apart due to collisions as a function of particle size, strength, composition, and distance from the host-star. We find that for certain grain compositions, fragmentation may not be a dominating factor and can potentially allow particles to grow to very large sizes, overcoming the meter-size barrier.
