Towards Exoplanetary Science in the Era of JWST

Abstract

Our understanding of exoplanets has advanced dramatically over the past two decades as we have moved from simply detecting these objects, to performing precise characterisations of their atmospheres. Despite these advancements, many fundamental questions remain, such as: how did these objects form, what is their composition, and what is the overall structure and dynamics of their atmospheres? With the launch of the James Webb Space Telescope (\textit{JWST}) and the advanced observational capabilities it provides, it will be possible to step closer and closer towards the answers to these questions. However, given the lifetime of \textit{JWST} will be limited, as a community we must ensure that the opportunity that it provides is not squandered. Efficient and effective use of \textit{JWST} cannot be achieved without first understanding the atmospheres of currently known targets to the best of our ability, the overall considerations when performing exoplanet observations, and finally the predicted limitations and feasibility of \textit{JWST} observations in particular. In this work I present a range of studies to further these goals. Firstly, I perform an in-depth and holistic investigation into the atmosphere of the transiting hot Jupiter exoplanet WASP-6b, revealing a host of molecular and atmospheric features and identifying it as a favourable \textit{JWST} target. The impact of stellar heterogeneity of WASP-6 on the overall transmission spectrum is also quantified, revealing measurable biases in the determination of its atmospheric properties without correcting for such effects. Secondly, I perform a range of detailed \textit{JWST} observation simulations of transiting exoplanets, based on state-of-the-art forward model spectra. Specifically, these simulations explore the significance of theorised atmospheric features due to disequilibrium chemistry, the presence of clouds, and the fundamental assumptions of forward models. Finally, I produce the most sophisticated simulations of \textit{JWST} direct imaging to date, incorporating up-to-date estimates of \textit{JWST} performance and the latest planetary evolution models. From these simulations I generate detection probability maps for a range of coronagraphic imaging modes, describing exactly to what degree these modes will be able to explore the known exoplanet population. In particular, I reveal that \textit{JWST} will be best suited towards directly imaging exoplanets as low as 0.1 $M_\textrm{J}$ separated further than 100 au from their host star.