Department of Astronomy
Center for Radiophysics & Space Research
The primordial sculpting of exoplanetary system architectures
Chris Spalding (Caltech)
622 Space Sciences
For centuries, ideas regarding planet formation were finely tuned to match our own Solar System, with its 8 coplanar planets orbiting a well-aligned star. Now, short-period exoplanetary systems are emerging that exhibit large stellar obliquities, together with mutually inclined planetary orbits, quite literally turning traditional planet formation theory on its head. In this talk I will describe how stellar obliquity is in fact a natural consequence of planet formation within a dense star cluster. Specifically, gravitational torques from companion stars are capable of tugging the disk out of alignment with the host star. Subsequently, owing to these systems' close-in configuration, stellar oblateness plays a critical role in their dynamical evolution - even modest stellar obliquity will often disrupt the coplanarity of the resulting planetary system. This effect provides a compelling explanation for the so-called Kepler Dichotomy, whereby only half of Kepler transiting systems appear to possess a coplanar architecture. Cumulatively I place stellar obliquity and the Kepler Dichotomy within a common theoretical framework, and discuss avenues toward falsification using upcoming observational efforts.