Contributed Talk - Splinter Exoplanets

Thursday, 16 September 2021, 17:00   (virtual Exo)

The potential of polarimetry to characterize clouds in exoplanetary atmospheres

M. Lietzow, S. Wolf
Kiel University

Clouds are an essential part of (exo)planetary atmospheres. Cloud particles do not only have an impact on the transmission spectra during transits. They also scatter the incoming stellar radiation and affect the reflected and thus polarize the planetary flux. Therefore, observing the reflected polarized flux at different planetary phase angles potentially allows characterizing clouds in the exoplanetary atmosphere. For this purpose, we investigate the polarization state of the scattered flux of exoplanetary atmospheres with various cloud compositions. We calculate the optical properties of different cloud condensates, which are predicted by cloud formation models, and apply the 3D Monte Carlo code POLARIS to solve the radiative transfer in the exoplanetary atmosphere (Reissl et al. 2016; Lietzow et al. 2021). We find that the scattered polarized radiation is a very characteristic function of size and complex refractive index of the cloud condensates and planetary phase angle. Given the accuracy of existing high-precision polarimeters, scattered light polarimetry has the potential to become a powerful tool to characterize exoplanetary atmospheres.