Constraining planet structure and composition from stellar chemistry: trends in different stellar populations

TL;DR

This study investigates how stellar chemical compositions across different galactic populations influence the predicted structure and composition of exoplanets, revealing significant variations in planetary building blocks that impact habitability.

Contribution

It introduces a model linking stellar abundances to planetary composition differences across galactic populations, enhancing understanding of planet formation diversity.

Findings

Discovered significant differences in iron-to-silicate ratios among planets from different stellar populations.

Showed water mass fractions vary notably between galactic populations.

Provided constraints for planet formation models based on stellar chemistry.

Abstract

The chemical composition of stars that have orbiting planets provides important clues about the frequency, architecture, and composition of exoplanet systems. We explore the possibility that stars from different galactic populations that have different intrinsic abundance ratios may produce planets with a different overall composition. We compiled abundances for Fe, O, C, Mg, and Si in a large sample of solar neighbourhood stars that belong to different galactic populations. We then used a simple stoichiometric model to predict the expected iron-to-silicate mass fraction and water mass fraction of the planet building blocks, as well as the summed mass percentage of all heavy elements in the disc. Assuming that overall the chemical composition of the planet building blocks will be reflected in the composition of the formed planets, we show that according to our model, discs around stars from different galactic populations, as well as around stars from different regions in the Galaxy, are expected to form rocky planets with significantly different iron-to-silicate mass fractions. The available water mass fraction also changes significantly from one galactic population to another. The results may be used to set constraints for models of planet formation and chemical composition. Furthermore, the results may have impact on our understanding of the frequency of planets in the Galaxy, as well as on the existence of conditions for habitability.