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 the early stages of planet formation, indicative of a picture in which planets form at characteristic mass scales with uniform separations. In this paper, we argue instead that intra-system uniformity in planet sizes and orbital spacings likely arose from the dynamical sculpting of initially overly packed planetary systems (in other words, the giant impact phase). With a suite of N-body simulations, we demonstrate that systems with random initial masses and compact planet spacings naturally develop intra-system uniformity, in quantitative agreement with observations, due to collisions between planets. Our results suggest that the pre-giant impact planet mass distribution is fairly wide and provide evidence for the prevalence of dynamical sculpting in shaping the observed population of exoplanets.

Automated summary

This study argues that the intra-system uniformity in planet sizes and orbital spacings is likely the result of the dynamical sculpting of initially overly packed planetary systems. The researchers demonstrate through simulations that collisions between planets naturally lead to intra-system uniformity, in quantitative agreement with observations.