The HST-JWST Transmission Spectrum of Ultra-hot Jupiter WASP-178b

To understand the formation and evolution of substellar objects light-years away, we must look for clues in their atmospheres. In particular, the population of ultra-hot Jupiters are irradiated enough to vaporize refractory material, opening a new window into giant planet formation through the first measurements of rock-to-ice ratios. WASP-178b is one such ultra-hot Jupiter. Here we present a first-look at WASP-178b's UV-to-IR transmission spectrum spanning 0.2-5.1 microns through 4 separate transits with HST/WFC3/G280+G102+G141 and JWST/NIRSpec/G395H. UV absorption spanning nearly 20 scale heights indicates the presence of metals in the planet's atmosphere, while H₂O and CO absorption is evident in the IR. The abundance of refractory and volatile elements is retrieved within the PETRA framework, enabling preliminary constraints on the planet's formation.