Intra-system uniformity: a natural outcome of dynamical sculpting

There is evidence that exoplanet systems display intra-system uniformity in mass, radius, and orbital spacing (like ”peas in a pod”) when compared with the system-to-system variations of planetary systems. This has been interpreted as the outcome of planet formation, indicative of a picture in which planets form at characteristic mass scales with uniform separations. Instead, we argue that intra-system uniformity in planet sizes and orbital spacings likely arose from the long-term dynamical sculpting of initially-overly-packed planetary systems. With a suite of N-body simulations, we demonstrate that systems with random initial masses and compact planet spacings naturally develop intra-system uniformity, with quantitative agreement to observations, due to collisions between planets. This challenges the assumptions underlying recent planet formation models and provides evidence for the importance of dynamical sculpting in shaping the observed population of exoplanets.