Mass-radius relations and core-envelope decompositions of super-earths and sub-neptunes

Alex R. Howe, Adam S. Burrows, Wesley Verne

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


Many exoplanets have been discovered with radii of 1-4 R , between that of Earth and Neptune. A number of these are known to have densities consistent with solid compositions, while others are "sub-Neptunes" likely to have significant H2-He envelopes. Future surveys will no doubt significantly expand these populations. In order to understand how the measured masses and radii of such planets can inform their structures and compositions, we construct models both for solid layered planets and for planets with solid cores and gaseous envelopes, exploring a range of core masses, H2-He envelope masses, and associated envelope entropies. For planets in the super-Earth/sub-Neptune regime for which both radius and mass are measured, we estimate how each is partitioned into a solid core and gaseous envelope, associating a specific core mass and envelope mass with a given exoplanet. We perform this decomposition for both "Earth-like" rock-iron cores and pure ice cores, and find that the necessary gaseous envelope masses for this important sub-class of exoplanets must range very widely from zero to many Earth masses, even for a given core mass. This result bears importantly on exoplanet formation and envelope evaporation processes.

Original languageEnglish (US)
Article number173
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 1 2014

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planetary systems
  • planets and satellites: atmospheres
  • planets and satellites: composition
  • planets and satellites: general
  • planets and satellites: interiors


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