A Primordial Origin for Extrasolar Stellar Obliquity and its Role in Sculpting the Kepler Dichotomy

ABSTRACT: The Solar System planets possess orbital planes differing by only a few degrees, inspiring the centuries-old hypothesis that planets form in disks, with the Sun's spin axes misaligned by a further 6 degrees. Only very recently has it been possible to observationally determine whether extrasolar planetary architectures typically share this coplanarity. Through analysis of planetary transit data, it has emerged that many, mostly hotter, stars hosting hot Jupiters possess significant stellar obliquities, ranging all the way from well-aligned to retrograde, anti-aligned. Furthermore, roughly half of multi-transiting systems of Super-Earths possess significant mutual inclinations between orbits (the "Kepler Dichotomy"). In this talk, I will show that spin-orbit misalignments naturally emerge during the disk-hosting stage of planet formation by way of secular torques between disks and outer companion stars. I then demonstrate that primordially-generated stellar obliquities are capable of driving the observed mutual inclinations between the orbital planes of super-Earth planets, in response to the stellar quadrupole moment. Accordingly, an early pathway for the excitation of spin-orbit misalignments places hot Jupiter and super Earth configurations within a united framework.