The peculiar climates of ultra-hot Jupiters

Ultra-hot Jupiters are an emerging class of exoplanets, consisting of the hottest known gas giants found on close orbits around their parent stars. Atmospheric follow up of these atmospheres can reveal great detail about their nature, composition, and climate. In this thesis is presented the first example of an ultra-hot Jupiter being defined, with an explanation of the unique chemistry that identifies this sub-population of planets. In particular we discuss the importance of the hydrogen anion (H-) and molecular dissociation on the observed spectra of ultra-hot Jupiters. The target of this first study is WASP-18b, a particularly massive and bright ultra-hot Jupiter, is also studied in this thesis from the perspective of its climate. We use a full-orbit phase curve of WASP-18b to recover a wavelength-dependent temperature map of the surface of the planet, which allows us to place constraints on the planet’s climate through a comparison to 3D climate models.
The final chapters of this thesis present a new technique for analyzing phase curves of exoplanets, that in particular enables the study of exoplanet climates with partial phase curves that do not cover the full orbit of the planet. This technique is applied to an archival partial phase curve of WASP-12b, another well studied ultra-hot Jupiter, and provides new constraints on its climate. This technique is also applied to the previously presented full phase curve of WASP-18b, which reveals spectral variations that could not be recovered with classical methods.