Abstract

Exoplanets with radii between 1-4 Earth radii are the most abundant planets known to date and regularly appear in tightly-packed multiple-planet systems. A significant fraction of them are enshrouded in gaseous envelopes that are massive enough to significantly contribute to the planet’s radius. I will review current planet formation theories and present a simple analytical prescription, accounting self-consistently for gas accretion, cooling and mass-loss of super-earths. I will demonstrate that the luminosity of the cooling rocky core, can erode light envelopes while preserving heavy ones resulting in a valley in the radius distribution of small exoplanets even in the absence of any photo-evaporation. I will conclude with a comparison of observations and theoretical predictions, highlighting that even super-Earths that appear as barren rocky cores today likely formed with primordial hydrogen and helium envelopes and discuss the signature of giant impacts in close-in exoplanet systems.