My research focuses on the characterisation of exoplanet atmospheres using transits, eclipses and phase curve observations. To date, I've primarily used the Hubble and Spitzer space telescopes to observe gas-giant exoplanets orbiting close-in to their host stars, with atmospheric temperatures exceeding 700 Kelvin and reaching as high as 3,000 Kelvin. Of all the known exoplanets, these so-called 'hot Jupiters' are by far the easiest to study, with extended hydrogen-dominated atmospheres and strong thermal emission.
The ultimate questions motivating my research, however, are "Has life arisen on planets outside our solar system?" and, if so, "How common is life throughout the galaxy?" To address these big themes on the ubiquity of life, it'll be necessary to push down to smaller, cooler exoplanets and characterise their atmospheric make-ups. Excitingly, the field is poised to make significant strides in this direction over the coming decade, with survey missions such as TESS expected to discover hundreds of planets smaller than Neptune. This population is believed to divide into two broad categories: scaled-down versions of the gas and ice giants in our solar system with thick primordial atmospheres ('mini-Neptunes'), and more terrestrial-like planets composed primarily of rocks, metals, ices and liquids with thinner secondary atmospheres ('super-Earths'). Many of these new objects should be discovered around bright M dwarf stars and have atmospheric temperatures below 700 Kelvin. Relatively cool, sub-Neptune-sized planets such as these will be important stepping stones on the path towards eventually characterising the atmospheres of more Earth-like, potentially-habitable planets in the future.
Currently, I'm leading a number of Hubble and Spitzer programs to measure atmospheric spectra for transiting exoplanets. I'm also a co-investigator on the PanCET survey, which is the largest Hubble program ever awarded to study exoplanets. In the coming years, I'm looking forward to extending this work with the James Webb Space Telescope (launch date 2021). James Webb will provide unprecedented insights into exoplanet atmospheres by allowing us to measure spectra at higher signal-to-noise and spectral resolution across a much broader wavelength range than has previously been possible.
Image: Cloud tops from La Palma, Canary Islands