Telescopes and Techniques for the High-Resolution Characterisation of Exoplanets

Abstract

In this thesis I present two strands of research relating to the characterisation of exoplanets in high resolution. The first investigates high-resolution Doppler spectroscopy (HRDS) – a technique for detecting chemical species in exoplanet atmospheres. I present results from analysing high-resolution spectra of three hot Jupiters – HD 209458b, HD 189733b and 51 Pegasi b. Evidence for H2O, CO and of HCN was found in all three datasets – the latter molecule had not previously been found in an exoplanet atmosphere. These studies used HRDS analysis techniques common to the literature but put their associated hyperparameters on an explicit, quantitative footing. This meant different techniques could have their robustness probed and be compared. Doing so revealed that the removal of telluric contamination from infrared spectra should be treated carefully as it has the potential to introduce biases in detections of chemical species. If robust though, such HRDS detections could aid the tracing of exoplanets’ formation and migration histories which are thought to leave significant imprints on their present day atmospheric compositions.

The second strand of my research is in developing SUPER-SHARP, an optical alignment technology for use in future large aperture unfolding space telescopes. Such facilities and technologies are needed for conducting the high spatial resolution observations required for characterising Earth-like exoplanets. In this work I have developed an automated alignment routine for telescopes with segmented primary mirrors. Starting from methods documented in the literature, I derived the necessary theory and validated the routine using numerical and ray tracing simulations. I then tested it experimentally by implementing the alignment routine – producing a proof-of-concept self-aligning telescope capable of capturing diffraction-limited thermal infrared imagery. This technology demonstrator has an autonomously aligned segmented primary mirror. It achieves sub-micron alignment through the use of optical metrology and nano-positioning actuators driven by my software in a closed loop control system. Finally, I also prototyped and tested potentially novel primary mirror optics that were invented to improve the compactness/practicality of this alignment technology.