The first full broadband transmission spectrum of an exoplanet. The chemistry of WASP-39b revealed from 0.5 to 12 μm with JWST

The JWST Transiting Exoplanet Early Release Science program was designed to improve our understanding of exoplanetary atmospheres by providing us with transmission spectra at wavelengths never probed before and with unprecedented precisions. After a multi-year effort involving hundreds of exoplanetary scientists across the world, we present the first complete broadband spectrum of WASP-39b from 0.5 to 12 microns as observed by JWST/NIRSpec-PRISM, JWST/NIRSpec-G395H, JWST/NIRCam, JWST/NIRISS, and JWST/MIRI from a cohesive synthesis data effort from Carter & May 2024 and Powell et al. 2024. In this talk we will share our findings on the chemical composition of the planet – as described by the multiple molecular features observed and their inferred chemical abundances – and the planet’s properties such as atmospheric metallicity and carbon-to-oxygen (C/O) ratio that best explain the spectra. We link these to the formation and evolution history of the planet, harnessing additional lever arms for planetary formation such as the sulfur-to-oxygen, sodium-to-oxygen, and potassium-to-oxygen ratios. Finally, we describe the important lessons learned from interpreting this first-of-its-kind broadband JWST spectrum, combining the expertise of different teams and tools, with key recommendations for upcoming observations with this space telescope.