Spectroscopy of Exoplanets

Atmospheric spectra play a key role in characterising exoplanets, providing constraints for their composition, physical and chemical processes, and shedding light on the mechanisms of planet formation and evolution. We are on the cusp of a new wave of exoplanet discovery focussed on spectroscopy, with several facilities coming to fruition in coming decade that will transform our knowledge of exoplanets. At Cardiff, we have played a major role in the development of the Ariel space mission, to be launched in 2028, which will perform the first large-scale transit spectroscopic survey of over 1000 exoplanets, as well as the EXCITE balloon-borne experiment (due to fly in 2024), the first mission devoted to exoplanet phase curve spectroscopy.

The student will be a member of the international teams working on the Ariel and EXCITE projects. The PhD project will involve detailed study and optimisation of the transit and phase curve spectroscopic techniques used in Ariel and EXCITE to maximise each mission's scientific potential. We will do this through generating high fidelity synthetic data, developing and optimising data reduction techniques and pipelines, and analysing spectra using forward modelling and Bayesian spectral retrieval methods. This framework will be used to investigate instrument and data reduction performance, assess and correct astrophysical and instrumental systematics, and optimise scientific performance and return. The student will investigate how spectroscopic survey data can be used to constrain theories of exoplanet origins and evolution, while through the EXCITE project they will investigate how phase curve spectra can be used to constrain the physics and chemistry of hot Jupiter atmospheres.

The performance and scientific potential of Ariel and EXCITE will also be compared against other observatories such as JWST (launch 2022) and the Hubble WFC3, applying processing algorithms and spectral analysis tools to both synthetic and real data. This will involve analysis of Hubble archival data or early JWST data including retrieval of atmospheric physical and chemical characteristics. In addition the potential for these and future facilities to study the atmospheres of low-mass planets such as Earths, super-Earths and mini-Neptunes will be explored, touching on the requirements for biomarker detection and exoplanet habitability.