Monday 23 Jan 2017: Cloudy nights on exoplanets
Dr. Vivien Parmentier - University of Arizona
Physics, 4th Floor 11:00-12:00
Over a large range of equilibrium temperatures clouds seem to dominate the transmission spectrum of exoplanets atmospheres but no trends allowing the classification of these objects have yet emerged. Recently, Kepler observations of the light reflected by hot Jupiters show that an inhomogeneous, asymetric and time-dependent cloud coverage is present in these planets. Interestingly, this asymmetry depends on the equilibrium temperature of the planet.
Using state-of-the-art three dimensional models of hot Jupiters atmospheres I will show that longitudinal and latitudinal asymmetry in the cloud coverage is expected for these hot planets. The presence of such an inhomogeneous cloud coverage can bias the retrieved abundances from transmission and secondary eclipse spectra and even lead to erroneous molecular detections. Cloudy nightsides further solves the apparent contradiction between models and observations, as cloudless models systematically underestimate the phase curve amplitude of hot Jupiters while overestimating the maximum offset. The longitudinal cloud asymetry being a strong function of the condensation temperature of the cloud species, it is a telltale of the cloud composition. Observations and models converge towards a similar conclusion: an L/T-like transition is expected for hot Jupiters, with silicate clouds disappearing from the cooler planets and being replaced by manganese sulfide clouds.