Galactic archaeology meets exoplanets: linking stellar birth radii to exoplanet demographics

Stars observed in the solar vicinity were not necessarily born there. Radial mixing can redistribute stellar populations across the Galactic disc, decoupling their present-day locations from the environments in which they formed. We summarise a framework that combines Galactic chemical evolution models with a generalised additive model to infer stellar birth radii. We apply it to 1327 predominantly thin-disc planet hosts with homogeneous ages, Gaia DR3 astrometry, and SWEET-Cat atmospheric parameters. We find that giant-planet systems preferentially trace metal-rich inner-disc birth environments, whereas rocky-only systems are less centrally concentrated; and no clear relation between radial displacement and detected planet multiplicity. Planet-host stars that migrate towards the inner parts of the Galaxy have systems with larger orbital separations; however, this may partly reflect the known dependence of planetary orbital properties on host-star metallicity rather than a causal effect of Galactic stellar migration. These results illustrate how Galactic archaeology can complement exoplanet demographics by linking planetary systems to their probable birth environments.