Core-powered mass-loss and the radius distribution of small exoplanets

Sivan Ginzburg*, Hilke E. Schlichting, Re'em Sari

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

305 Scopus citations


Recent observations identify a valley in the radius distribution of small exoplanets, with planets in the range 1.5-2.0 R® significantly less common than somewhat smaller or larger planets. This valley may suggest a bimodal population of rocky planets that are either engulfed by massive gas envelopes that significantly enlarge their radius, or do not have detectable atmospheres at all. One explanation of such a bimodal distribution is atmospheric erosion by high-energy stellar photons. We investigate an alternative mechanism: the luminosity of the cooling rocky core, which can completely erode light envelopes while preserving heavy ones, produces a deficit of intermediate sized planets. We evolve planetary populations that are derived from observations using a simple analytical prescription, accounting selfconsistently for envelope accretion, cooling and mass-loss, and demonstrate that core-powered mass-loss naturally reproduces the observed radius distribution, regardless of the high-energy incident flux. Observations of planets around different stellar types may distinguish between photoevaporation, which is powered by the high-energy tail of the stellar radiation, and corepowered mass-loss, which depends on the bolometric flux through the planet's equilibrium temperature that sets both its cooling and mass-loss rates.

Original languageAmerican English
Pages (from-to)759-765
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 1 May 2018

Bibliographical note

Publisher Copyright:
© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.


  • Planets and satellites: Atmospheres
  • Planets and satellites: Physical evolution


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