Unveiling the composition of exoplanets with atmosphere spectroscopy
IDPASC Portugal - PHD Programme 2017
2017 / 2018
Universidade do Porto
With already more than 3000 exoplanets detected, we know that exoplanets are ubiquitous in the galaxy. However, for most of them, their composition and atmospheric conditions (temperature, pressure, clouds, hazes, rain) are poorly known. Models exist which, given the density of the planet, assume the most likely composition and compute the most likely structure and temperature-pressure profile (Valencia et al 2007, 2010, Guillot et al. 1996). Unfortunately, all these models are degenerate with respect to the exact composition (Alibert 2016). The goal of this project is to raise some of those degeneracies by delivering insights in the composition of exoplanets. If detecting exoplanets is already a challenging task due to the high contrast and low angular separation between a planet and its host star, obtaining their spectra requires state-of-the art instrumentation. The past decades have seen the emergence of three techniques capable of obtaining spectral informations of exoplanet: high-angular resolution and high contrast imaging (Marois et al 2008 , Lagrange et al. 2010), high-precision photometry (Charbonneau et al. 2002, Stevenson et al. 2014), and high-spectral resolution cross correlation techniques (Snellen et al. 2010, Martins et al. 2015). For the ambitious objective of constraining exoplanet atmospheres, high-precision instruments are not enough. Extracting reliable spectral information on the observed exoplanet atmosphere requires advanced data reduction and analysis techniques coupled with state of the art modeling. This project proposes to the student, to benefit from the unique conditions offered by IA and our collaborators, to be at the junction between observation and theory. He will have to confront the data from several instruments enabling atmospheric characterization to the PHOENIX-BTSettl atmospheric models and extract robust information regarding the composition of exoplanets’ atmosphere. He will first start with archive and already published data from transit photometry (Sing et al. 2016 from WFC3@HST) and high-angular resolution and high-contrast data (Bonnefoy et al. 2016 SPHERE@VLT). Then he will analyze high-spectral resolution data using the cross correlation technique (Snellen et al. 2010 from CRIRES@VLT). An homogenous analysis of datasets coming from these different observational techniques has never been done before and will open new doors for atmospheric studies. The final step of this project will be to apply the developed analyses to different types of newly discovered planets and to explore trends in the atmospheric composition with respect to the characteristic of the observed planets, stars and observing techniques.