Institute for Advanced Study / Princeton University Joint Astrophysics Colloquium

With the advent of JWST, interpreting unprecedented observations of diverse exoplanet atmospheres requires a fundamental understanding of photochemistry, atmospheric dynamics, and aerosol microphysics. In this talk, I will demonstrate how modeling these processes is revolutionizing our understanding of worlds across the planetary mass spectrum.

I will first explore how cutting-edge models are decoding the complex chemistry and ubiquitous clouds of gas giants. I will discuss how photochemistry shapes atmospheric composition, highlighting recent insights from the hot Jupiter WASP-39b. I will then show how new 2D microphysical models reveal that dynamics drive inhomogeneous cloud coverage on hot Jupiters. These models are now testable via JWST limb-asymmetry observations, and I will show initial results from the JWST Mornings & Evenings Program that will catalog cloud asymmetries across the hot Jupiter regime.

Moving to smaller planets, I will show how heterogeneous nucleation—clouds forming on photochemical haze "seeds"—solves the mystery of the highly muted yet highly reflective spectra of sub-Neptunes like GJ 1214 b. For terrestrial exoplanets, I will outline new analytic methods for deriving physically-motivated day/night temperatures and demonstrate how nightside clouds on these tidally locked worlds can mimic atmosphere-free "bare rock" observations.

I will conclude by briefly linking this fundamental aerosol physics to volatile evolution in protoplanetary disks, bridging the gap between planet formation and evolved atmosphere characterization.