Since the discovery of the first exoplanet around a sun-like star 25 years ago, enormous progress has been made in the exoplanet field. The number of known exoplanets has increased to over 4000 today. Even more excitingly, we have begun to probe the atmospheres of some these planets using both space-based and ground-based telescopes.
In most cases, these studies focus on transiting planets where we can either study the planetary atmosphere in transmission as the planet passes in front of its host star (which allows a direct determination of the composition and extent of the atmosphere), or by looking for the light emitted directly by the planet. To measure the light coming from a planet we can either observe the secondary eclipse, when the planet passes behind its host star, or measure the phase-curve variations as the planet orbits its star. In the latter case, we are looking at differences in the emission between the day- and night-side as they rotate in and out of view as the planet orbits its star.
By observing the systems at a high spectral resolution, however, we can directly separate the atomic and molecular lines from the planet from lines arising in its host-star or the Earth’s atmosphere by taking advantage of the Doppler shifting of the planet’s lines due to the planets’ high orbital speed. This allows us to determine both the composition and orbital velocity of the planet, and can be used to determine the atmospheric composition and structure even if the planet does not transit its host star. This makes high spectral resolution observations of planetary atmospheres incredibly powerful.
The aim of this project is to take advantage of new instruments, such as CRIRES+ and ESPRESSO, and use these high-resolution spectrographs to study the atmospheres of exoplanets. This will both increase the sample of characterised atmospheres, as well as probe the atmospheres over a wider wavelength range, thereby targeting more species (e.g., Fe, CO, CO2, H2O, TiO, VO) and allowing a better determination of the planet’s chemical composition. As part of this project, we will improve current techniques and develop new ones. For example, QUB has recently pioneered the use of Doppler tomography for such studies – and such techniques will act as pathfinders for the efficient exoplanet characterisation with the next generation of large telescopes, such as the E-ELT. Ultimately, this may be able to provide the first detection of life outside the Solar System.
Supervisor: Dr. Ernst de Mooij email@example.com