Tracking the Grist and Flakes of Planetesimals with Dust Polarization

How planetesimals form and evolve in circumstellar disks is one of the most important questions in astrophysics. In this talk, I will demonstrate that polarization is a unique tool for studying the microscopic properties of dust grains throughout the planet formation process. In protoplanetary disks, ALMA has revolutionized the field of disk-scale polarization by detecting and resolving percent-level polarization. I will first present observational evidence of large, scattering, aligned grains. I will then introduce a new grain alignment mechanism that can trace the relative motion between dust and gas offering a connection to how planetesimals form. In debris disks, where planetesimals have fully formed, I will demonstrate how dust polarization, aided by neural networks, can constrain dust composition.