Context. The chemical composition of stars that have orbiting planets
provides important clues about the frequency, architecture, and
composition of exoplanet systems. Aims: We explore the
possibility that stars from different galactic populations that have
different intrinsic abundance ratios may produce planets with a
different overall composition. Methods: 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.
Results: 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. Conclusions: 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.