We have now moved from a discovery mode of exoplanets to an analysis mode. In particular, it is important to derive the composition of the atmospheres of exoplanets. This can be done with transmission spectroscopy. As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet’s atmosphere, causing the planet to seem bigger; plotting the planet’s observed size as a function of the wavelength of the light produces a transmission spectrum. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet’s atmosphere.
While the FORS2 Instrument Scientist in Paranal, I led a project to exchange the LADC and thereby allow precision spectrophotometry with FORS2 to perform transmission spectroscopy and providing the best observational strategy. With my then student Elyar Sedaghati, we could then study the atmoshpere of WASP-17b, WASP-19b, and WASP-80b, as well as to show for the first time the presence of TiO in the atmosphere of an exoplanet. You can read the ESO Press Release and the paper. A follow-up was done with ESPRESSO.
Such kind of studies, using a different method, can indeed also be done with high-spectral resolution instrument, such as FEROS, HARPS or ESPRESSO. With colleagues, we have discovered the presence of sodium in one exoplanet and analysed 3 others, and we also showed that 2-m class telescopes may be useful for this kind of studies.
I was also the Porject Scientist for the Phase A of the FORS-Upgrade project and organised the "20th Anniversary of Science Exploration with FORS"Workshop, composing a book.
Speaking of planets, in my first career at ESO, I also participated actively in the very successful Venus Transit 2004 project.