Geosciences Dept. Seminar: Mass-Radius Diversity of Sub-Neptune Planets: the Role of the Rocky Core

Abstract: 

Sub-Neptune planets are very common in our galaxy and show a great diversity in their mass-radius relation. Most studies attempt to relate this diversity to planet composition. However, the thermal evolution of the planet, and in particular the thermal evolution of the rocky part (core) can play a key role in this diversity. In sub-Neptunes, in contrast to smaller (terrestrial) and larger (giants) planets, the core is the dominant energy reservoir, while the gaseous envelope determines the planet’s radius. We calculate the thermal evolution of sub-Neptunes, accounting for different core formation conditions and different heat transport rates and examine the effects on the planetary mass-radius relation in time. We show that the observed radius can substantially vary for similar planets with different core thermal properties. We conclude that the planet formation scenario and core thermal evolution can have long term effects on planet radius and cannot be neglected in evolutionary calculations of sub-Neptune planets. Future observations are expected to exclude some of the models and constrain the core properties.

Seminar Organizer: Prof. Eyal Haifetz