Presentation #500.03 in the session Plenary 7.
The first discovered extrasolar worlds — giant, “hot Jupiter” planets orbiting perilously close to their parent stars — came as a surprise to solar-system-centric models of planet formation. This prompted the development of new theories to produce these unexpected planets. The dearth of observed close-in companions to hot Jupiters has previously supported the mechanism of high-eccentricity tidal migration, in which hot Jupiters form further out in their natal protoplanetary disks before being thrown inward via violent high-eccentricity tidal migration, stripping systems of any close-in planetary companions. By contrast, we demonstrate through a careful analysis of the full four-year Kepler dataset that a substantial fraction (20%) of hot Jupiters have additional close-in planetary companions. As a result, at least 20% of hot Jupiters must have a quiescent formation history such that they were able to retain nearby companions. We conclude with a new paradigm for hot Jupiter formation that is consistent with all current lines of evidence, in which 20% of hot Jupiters form in-situ and the other 80% undergo high-eccentricity migration.