The Department of Astronomy 2025-2026 Colloquium Series Presents:

"JWST Reveals the Atmospheres of Sub-Neptune Exoplanets"

Sub-Neptunes are planets smaller than Neptune with thick, gaseous atmospheres. They are the most common type of planet in our galaxy, despite not having a solar system analog. Prior to the JWST mission, the study of sub-Neptune atmospheres was typically thwarted by low signal-to-noise measurements due to the small size of these planets, and pervasive cloud layers that prevented detailed measurement of atmospheric properties. JWST, with its large aperture and broad IR wavelength coverage, promised to finally open the door to the characterization of planets smaller than Neptune, and it has delivered. I will present some of the first JWST observations of sub-Neptune exoplanets along with the interpretation of those intriguing measurements. We have begun to address key questions about the nature of sub-Neptune aerosols (clouds or haze) and the chemical composition of their atmospheres, yet many outstanding questions remain. I will outline future prospects for the study of sub-Neptunes with JWST and what we still hope to learn about their formation and evolution, and the physical and chemical processes that govern their atmospheres. I will conclude with some thoughts on how we can leverage population-level studies of sub-Neptune atmospheres with JWST to address these important topics.