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Shucked Peas in a Pod: the Breakdown of Intra-system Uniformity

Presentation #607.11 in the session Population Statistics and Mass-Radius Relations.

Published onApr 03, 2024
Shucked Peas in a Pod: the Breakdown of Intra-system Uniformity

Planets in compact multi-transiting systems have a well-documented tendency to have similar radii to one another, commonly called the “peas-in-a-pod” phenomenon. In a scenario where photoevaporation or core-powered mass loss dominates the distribution of planetary radii, theory predicts a modest, smoothly changing size ordering trend of smallest-to-largest with insolation. We find that the planets in the radius gap (roughly 1.8 Earth radii, dependent upon stellar mass) deviate from the “peas-in-a-pod” self-similarly phenomenon: rather than appearing similar to their neighbors, planets in the radius gap exhibit a clear deficit of similarly-sized adjacent planets. We test a variety of planetary samples, to assess the statistical robustness of our finding. This break in the usual size-ordering phenomenon indicates that systems with a planet in the radius gap may be shaped by a process other than photoevaporation or core-powered mass loss. The details of the radius ratio distribution provide evidence for what process is at work and may have implications for the formation and composition of exoplanets in multi-planet systems.

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