Metallicity Regulates Planet Formation across All Masses

Abstract The role of stellar metallicity in shaping planetary systems is central to our understanding of planet formation. While the core accretion paradigm is widely accepted as the dominant mechanism for forming low- and intermediate-mass planets, the origin of the most massive planets remains debated, with gravitational instability often invoked to explain their existence. In this study, we analyze the dependence of planet formation on metallicity using the total heavy-element mass fraction ( Z ), which is a proxy for the composition of the protoplanetary disk inferred from stellar photospheres. We show that even the most massive planets form preferentially in metal-rich environments. Z correlates not only with the presence of planets, but also with planetary system multiplicity and total planetary mass. The most massive planets are found in the most metal-rich environments, and in agreement with core-accretion theory, only the upper end of the planetary mass distribution shows a clear positive correlation with metallicity. These findings suggest that the chemical enrichment of protoplanetary disks plays a central role in shaping the full spectrum of planetary masses.