My research principally revolves around the development and application of atmospheric retrieval techniques for transiting exoplanets. Areas of interest include: exoplanet characterisation ranging from gaseous giants to rocky worlds, radiative transfer, atmospheric physics and chemistry, and techniques to identify and study biosignatures with future telescopes.


Previous Research


A metal-rich atmosphere for a neptune-mass exoplanet


Atmospheric studies of Neptune-mass exoplanets are now possible. We applied the retrieval code POSEIDON to reveal the atmospheric composition of the Exo-Neptune HAT-P-26b. We find an atmosphere high in water content (>1%), indicating it encountered ice-rich planetesimals during its formation. We also find evidence of metal hydrides, suggesting a recent asteroid impact as the cause.


Observability of H2O in cool Gas giant exoplanets


Jupiter’s water is hidden from view trapped in clouds deep in its atmosphere. Future telescopes, such as NASA’s WFIRST mission, will observe light reflected off exoplanets slightly warmer than Jupiter. We investigated the conditions necessity on exoplanets for water signatures to become visible and what factors influence their prominence.


Detection of Titanium Oxide in a hot jupiter atmosphere

Observations of the hot Jupiter WASP-19b with the Very Large Telescope revealed a feature-rich transmission spectrum. An extensive atmospheric retrieval analysis using POSEIDON revealed a high significance detection of titanium oxide (TiO). This was the first detection of a heavy metallic molecule in an exoplanet atmosphere.


Evidence of nitrogen chemistry in hot jupiters


The presence of nitrogen-bearing molecules at detectable levels in hot Jupiter atmospheres has traditionally been neglected. We showed that if disequilibrium processes, such as strong vertical winds or photochemistry, are present then ammonia (NH3) and hydrogen cyanide (HCN) could be detectable. We then demonstrated evidence of NH3 in WASP-31b and HCN in WASP-63b’s atmospheres.

Precise chemistry from cloudy exoplanets


Precisely measuring the chemistry of cloudy exoplanet atmospheres has been a notable problem. By creating a new retrieval code, POSEIDON, we demonstrated that the inclusion of patchy clouds within models allows one to ‘peer beneath the clouds’ and obtain precise measurements of the chemsitry and clouds in an atmosphere at the same time.