Probing the atmospheres of outer worlds: transmission spectroscopy of exoplanets
Paulo Miles-Páez & Henri Boffin
Join us on a quest to find atoms and molecules in the atmospheres of hot Jupiters, and thereby help us understand how such massive planets ended up so close to their host star!
The last decades have seen a wealth of discoveries of new exoplanets, mostly thanks to the transit detection method, either from the ground or from space. The transit method not only allows us to detect candidate exoplanets; when combined with radial velocity measurements, it also provides us with unique opportunities to probe their physical properties, such as their bulk density and thus, indirectly, their composition. Moreover, transiting exoplanets offer the possibility to probe their atmospheric composition, in particular through the technique of transmission spectroscopy. This technique, which looks for the imprint a planetary atmosphere leaves on the stellar light, is based on the fact that the atoms and molecules of the planetary atmosphere may block part of the photons emitted by the host star. Thus, by measuring the apparent radius of a planet as a function of wavelength we can learn about which chemical species populate the planetary atmosphere.
The transit technique has been applied successfully in recent years using low- to mid-resolution time-resolved spectroscopy. Some remarkable results are the detection of hazes of sodium and potassium, as well as water and titanium oxide in the atmospheres of hot Jupiters. The application of this method requires, however, a very clear understanding of the data reduction process and the systematics affecting the data, as the effect we are looking for is very tiny, at the 100 parts-per-million scale. It is also necessary to use appropriate techniques to be able to retrieve the desired signal.
In this project, the student will embark on the analysis of time-resolved spectroscopic data of hot Jupiters while transiting their host star. The spectra were obtained with one of the best instruments on ESO’s Very Large Telescope, FORS2. The idea is to look how the transit depth of the planet changes as a function of wavelength and thereby discover the presence of atoms and molecules, or even clouds, in the planet’s atmosphere. By comparing the results obtained for several hot Jupiters, we will be able to look for possible correlations and put constraints on the place where the planet formed and how it moved.
#exoplanets #hotJupiter #atmosphere #spectroscopy #VLT #machinelearning