The Densities of Planets and the Masses of Host Stars

TL;DR

This study analyzes data from the CoRoT space telescope to explore how the density of transiting exoplanets relates to their mass and host star mass, revealing trends in planetary composition and density variations.

Contribution

It provides new insights into the relationship between planet density, mass, and host star mass using CoRoT data, highlighting trends across different planetary mass ranges.

Findings

Planets over 1000 Earth masses have densities >6 g/cm³ and are around more massive stars.

All planets between 15 and 600 Earth masses have densities less than 3 g/cm³.

Density increases steadily for lower-mass planets without a sharp transition.

Abstract

Studies of transiting extra-solar planets are of key importance for understanding the nature of planets outside our Solar System, because their densities can be determined, constraining of what the planets are made of. Using the data obtained by the CoRoT space telescope we study the relation between the density of planets, their mass, and the mass of their host stars. Although planets of the same mass can have different densities, we still find some trends. Planets with more than 1000 MEarth (about 3 MJup have densities larger than 6 gcm-3, and are preferentially found in stars that are more massive than the Sun. All known planets in the mass-range between 15 and 600 MEarth (about 0.05 to 2 MJup) have densities of less than 3 gcm-3. When going further down in the mass of the planets, the density increases steadily, and there is no sudden transition from gaseous to rocky planets. Based on the current sample, we do not find any difference for planets at different galactocentric distances.