Name/Affiliation: Eric Jensen (Swarthmore College)
Are planetary orbits aligned with binary orbits?
Many extrasolar planets follow orbits that differ markedly from the nearly circular and coplanar orbits found in our solar system. These orbits, along with the population of hot Jupiters orbiting close to their host stars, suggest substantial orbital evolution after planet formation. A possible driver of this evolution is the influence of a stellar or substellar binary companion on an orbit that is inclined relative to the planetary orbital plane. It is currently unknown how common it is for planetary and binary orbits to be misaligned, though a handful of young binary systems are known to host misaligned disks. Here we report the first results of a campaign to map the misalignment of planet-forming disks in binaries using ALMA. We detect the Keplerian rotation of both two disks in the young binary HK Tau, measuring their full three-dimensional angular momentum orientation and showing that they are misaligned by 60°-70°. Thus, at least one disk is substantially misaligned with the binary orbit. This misalignment is present at the time of planet formation and presumably is an outcome of the binary formation process. If confirmed in a larger sample of systems, this indicates that misalignment-driven mechanisms may be an important driver of the diversity of planetary orbits.