How Neptune Pushed the Boundaries of Our Solar System

Model studies are providing increasing evidence that the orbit of the planet Neptune was originally much smaller than it is today. In his Perspective, Morbidelli explains the latest insights into how Neptune9s migration may have pushed small objects at the primordial edge of the Solar System outward, creating the various components of the Kuiper belt (a population of small bodies at the outer edge of today9s Solar System). The models also provide an explanation for Neptune9s current orbit. It remains unclear, however, exactly when the migration took place.