Effect of Core Cooling on the Radius of Sub-Neptune Planets

Understand

Sub-Neptune planets are very common in our galaxy and show a large diversity in their mass-radius relation.

• In sub-Neptunes most of the planet mass is in the rocky part (hereafter core) which is surrounded by a modest hydrogen-helium envelope.
• As a result, the total initial heat content of such a planet is dominated by that of the core.
• Nonetheless, most studies contend that the core cooling will only have a minor effect on the radius evolution of the gaseous envelope, because the core's cooling is in sync with the envelope, i.e., most of the initial heat is released early on timescales of about 10-100 Myr.