Capture of freely-floating planetesimal into protoplanetary disks

The standard core accretion theory of planet formation posits that asteroid-like bodies, called “planetesimals”, form within disks of gas and dust around young stars. These planetesimals may grow through collisions or, as recent studies suggest, through the process of pebble accretion. A major uncertainty is how the first planetesimals may have formed, especially in disks with little dust or those perturbed by companion stars.

We explore a scenario in which planetesimals arise in disks with favorable conditions, such as those with large amounts of solid material and no perturbing companion. Many planetesimals are scattered by giant planets, becoming free-floating planetesimals. These bodies could later be captured by other young stellar disks, accelerating planet formation.

Whereas previous studies assumed capture by aerodynamic drag, we instead investigate capture through the deepening gravitational potential well of a forming protostar. Using numerical simulations, we are modeling this process to determine capture rates. We have run simulations at varying initial velocities and impact parameters and used the final specific energy to derive velocity-dependent capture cross-sections for different collapse models.