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

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.

Accepted for publication in Astronomy & Astrophysics

References in corpus (18)

• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• Mass-Radius Relationships for Solid Exoplanets
• alpha-, r-, and s-process element trends in the Galactic thin and thick disks
• Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• A New Planet Around an M Dwarf: Revealing a Correlation Between Exoplanets and Stellar Mass
• The Gaia-ESO Survey: the Galactic Thick to Thin Disc transition
• Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances
• Habitable Evaporated Cores: Transforming Mini-Neptunes into Super-Earths in the Habitable Zones of M Dwarfs
• Exploring the alpha-enhancement of metal-poor planet-hosting stars. The Kepler and HARPS samples
• On the Age of the TRAPPIST-1 System
• Oxygen abundances in G- and F-type stars from HARPS
• On the "Galactic Habitable Zone"
• Bayesian analysis of interiors of HD 219134b, Kepler-10b, Kepler-93b, CoRoT-7b, 55 Cnc e, and HD 97658b using stellar abundance proxies
• A peculiarity of metal-poor stars with planets ?
• CNO behaviour in planet-harbouring stars. II. Carbon abundances in stars with and without planets using the CH band
• The Galactic habitable zone around M and FGK stars with chemical evolution models with dust
• The Metallicity Dependence of Giant Planet Incidence

Cited by in corpus (3)

• A giant exoplanet orbiting a very low-mass star challenges planet formation models
• Influence of sub- and super-solar metallicities on the compositions of solid planetary building blocks
• Small Planets in the Galactic Context: Host Star Kinematics, Iron, and $\alpha$ Element Enhancement