A sub-Saturn Mass-Radius Desert for Planets with Equilibrium Temperature Less than 600 K

TL;DR

This study identifies a distinct sub-Saturn mass-radius desert among exoplanets with equilibrium temperatures below 600 K, supporting core-accretion theory and highlighting differences in planetary migration histories.

Contribution

It reveals a previously unobserved mass-radius desert for low-temperature exoplanets, linking it to planetary formation and migration processes.

Findings

A desert in the mass-radius distribution for planets >20 Earth masses and 4.0-7.5 Earth radii at T<600 K.

Presence of many planets in the same mass-radius range at T>630 K.

Differences in planet populations suggest migration history impacts planetary characteristics.

Abstract

The sample of exoplanets from the NASA Exoplanet Archive with equilibrium temperature less than 600 K and with low uncertainty for both mass and radius measurements is found to have a desert in the mass-radius distribution consistent with predictions from the core-accretion scenario. This sub-Saturn mass-radius desert is almost completely barren of any planets with both a mass greater than 20 Earth masses and a radius in the range 4.0 to 7.5 Earth radii for the sample of planets with equilibrium temperature less than 600 K. In contrast, the sample of planets with equilibrium temperature greater than 630 K includes a large fraction of planets with mass-radius values that fall into the less than 600 K sub-Saturn mass-radius desert. The difference between the two populations may result from differences in migration history in the core-accretion scenario.