Atmospheric accretion, evolution and loss: creating the observed valley in the super-Earth radius distribution without photo-evaporation

Tuesday 3 July, 12:40

Recent observations identify a valley in the radius distribution of small exoplanets. We evolve planetary populations that are derived from observations using a simple analytical prescription, accounting self-consistently for envelope accretion, cooling and mass-loss, and demonstrate that the luminosity of the cooling rocky core, can erode light envelopes while preserving heavy ones. This results in a deficit of intermediate sized planets and hence naturally reproduces the valley in the observed radius distribution, even in the absence of high-energy radiation from the host star. Observations of planets around different stellar types may distinguish between photoevaporation, which is powered by the high-energy tail of the stellar radiation, and core-powered mass-loss, which depends on the bolometric flux through the planet's equilibrium temperature as this sets both the planet’s cooling and mass-loss rates.

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