My doctoral thesis "From Hot Jupiters to Super-Earths: An Exploration of Exoplanet Atmospheres with Space-Based Telescopes" was awarded the 2023/2024 prize for Outstanding Excellence in a Doctoral Dissertation in the Faculty of Science, and is available through the University of Bristol library
Abstract
The known population of planets in our universe is highly diverse, spanning system configurations, masses and radii, and compositions beyond anything seen in our Solar System. In order to understand this complex picture, explorations of their atmospheres have begun to characterise exoplanets in more detail, with space-based telescopes proving an invaluable tool in this effort. By combining transmission spectroscopy observations, which search for wavelength-dependent changes in a planet’s transit depth caused by its atmosphere, with comprehensive modelling efforts, we are able to probe the key processes at play within these atmospheres.
I present transmission spectra and the inferences gained for three planetary systems from the largest, fluffiest gas giants down to a sub-Neptune and super-Earth pair. Combining new Hubble observations with Spitzer photometry, I produced the transmission spectrum of the hot Jupiter WASP-17b, and used a comprehensive suite of atmospheric retrieval models to explore the potential range of compositions allowed by the data, unearthing a degeneracy in the metallicity of the atmosphere. At the dawn of the JWST era, I developed an end-to-end open-source reduction pipeline, ExoTiC-JEDI, designed for analysing transmission observations obtained by the NIRSpec instrument. Using JWST as part of the ERS Transiting Exoplanet Early Release Science Program, I led the analysis of the hot Saturn WASP-39b, as observed with the NIRSpec/G395H mode, identifying the presence of sulphur dioxide, a molecule produced by photochemical reactions in the upper atmosphere. Revisiting WASP-17b, I took a second look at its atmosphere, now with JWST, to reassess the results provided by Hubble and refine the true nature of its composition. Since exploring smaller mass planets often requires brighter host stars, I pushed JWST to its limits by analysing the atmospheres of the sub-Neptune and super-Earth orbiting the bright star TOI-836. I assessed the implications of each planet’s transmission spectrum on their possible metallicities, cloud properties and interiors given the architecture of the system.
Spanning across the mass-temperature space, these observations have enabled the development of tools and the exploration of instrument behaviours needed to push our understanding to more extreme exoplanets and to more complex chemistries, continuing the legacy of Hubble and beginning the era of JWST.
I present transmission spectra and the inferences gained for three planetary systems from the largest, fluffiest gas giants down to a sub-Neptune and super-Earth pair. Combining new Hubble observations with Spitzer photometry, I produced the transmission spectrum of the hot Jupiter WASP-17b, and used a comprehensive suite of atmospheric retrieval models to explore the potential range of compositions allowed by the data, unearthing a degeneracy in the metallicity of the atmosphere. At the dawn of the JWST era, I developed an end-to-end open-source reduction pipeline, ExoTiC-JEDI, designed for analysing transmission observations obtained by the NIRSpec instrument. Using JWST as part of the ERS Transiting Exoplanet Early Release Science Program, I led the analysis of the hot Saturn WASP-39b, as observed with the NIRSpec/G395H mode, identifying the presence of sulphur dioxide, a molecule produced by photochemical reactions in the upper atmosphere. Revisiting WASP-17b, I took a second look at its atmosphere, now with JWST, to reassess the results provided by Hubble and refine the true nature of its composition. Since exploring smaller mass planets often requires brighter host stars, I pushed JWST to its limits by analysing the atmospheres of the sub-Neptune and super-Earth orbiting the bright star TOI-836. I assessed the implications of each planet’s transmission spectrum on their possible metallicities, cloud properties and interiors given the architecture of the system.
Spanning across the mass-temperature space, these observations have enabled the development of tools and the exploration of instrument behaviours needed to push our understanding to more extreme exoplanets and to more complex chemistries, continuing the legacy of Hubble and beginning the era of JWST.
Thesis Poster
A summary poster of my thesis work was presented at Exoclimes VI, and is available below
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Thesis Summary poster as presented at Exoclimes VI in June 2023
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HEADER IMAGE CREDIT: NASA, ESA, G. BACON
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