Jupiter-like uniform metal enrichment in a system of multiple giant exoplanets

TL;DR

This study uses JWST to analyze the atmospheric composition of three exoplanets, revealing they are uniformly enriched in heavy elements, indicating efficient solid accretion during their formation, similar to Jupiter and Saturn.

Contribution

First detailed chemical analysis of multiple exoplanet atmospheres showing uniform heavy element enrichment, suggesting common formation processes across different planetary systems.

Findings

Exoplanets show high heavy element enrichment similar to Jupiter and Saturn.

Enrichment is consistent across volatile and refractory elements.

Supports efficient solid accretion during giant planet formation.

Abstract

The accretion of icy and rocky solids during the formation of a gas giant planet is poorly constrained and challenging to model. Refractory species, like sulfur, are only present in solids in the protoplanetary disk where planets form. Measuring their abundance in planetary atmospheres is one of the most direct ways of constraining the extent and mechanism of solid accretion. Using the unprecedented sensitivity of NASA's James Webb Space Telescope (JWST), we measure a detailed chemical make-up of three massive gas giants orbiting the star HR~8799 including direct detections of H$_2$O, CO, CH$_4$, CO$_2$, H$_2$S, $^{13}$CO, and C$^{18}$O. We find these planets are uniformly and highly enriched in heavy elements compared to the star irrespective of their volatile (carbon and oxygen) or refractory (sulfur) nature, which strongly suggests efficient accretion of solids during their formation. This composition closely resembles that of Jupiter and Saturn and demonstrates that this enrichment also occurs in systems of multiple gas giant planets orbiting stars beyond the Solar System. This discovery hints at a shared origin for the heavy element enrichment of giant planets across a wider range of planet masses and orbital separations than previously anticipated.