Dr. Janna Levin
Simulating Planetesimal Formation in the Kuiper Belt and Beyond
Rixin Li, University of Arizona
A critical step in planet formation is to build super-km-sized planetesimals in protoplanetary disks. The origin and demographics of planetesimals are crucial to understanding the Solar System, circumstellar disks, and exoplanets. I will overview the current status of planetesimal formation theory. Specifically, I will present our recent simulations of planetesimal formation by the streaming instability, a mechanism to aerodynamically concentrate pebbles in protoplanetary disks. I will then discuss the connections between our numerical models and recent astronomical observations and Solar System explorations. I will explain why all planetesimals likely formed as binaries.
Protoplanetary disk rotation curves and the kinematic detection of protoplanets
Simon Casassus, Universidad de Chile
Direct detections of protoplanets still embedded in a gaseous protoplanetary disk have been remarkably elusive in their thermal-IR radiation. Yet most models for the structures observed in disks involve planet/disk interactions. The gas and dust density fields are thus appealing proxies to trace embedded bodies, but they are not sufficient to ascertain a planetary origin. New hopes for protoplanet detection come from the disk kinematics, which should also bear their dynamical imprint. The last couple of years have seen the first indirect detection of protoplanets, with the observation of small deviations from Keplerian rotation in molecular line channel maps, and their reproduction in hydrodynamical simulations. Can we use the gas kinematics directly to pin-point the location and measure the dynamical mass of giant planets? The theoretical velocity reversal along the wakes of a protoplanet should be observable as a Doppler-flip, provided that the background flow is adequately subtracted. This axially symmetric flow is a generalized rotation curve, including also the radial and vertical velocity components, which bear the imprint of accretion, winds, and of the theoretical meridional flows in the case of planet/disk interactions. I will present a technique to calculate disk rotation curves, with applications to ALMA long baseline data in HD100546 and in HD163296.