Cloud Formation on Hot Jupiters and Brown Dwarfs

Thursday 5 July, 12:50

Clouds on extrasolar worlds are seemingly abundant and interfere with observations; however, little is known about their properties. In this talk I will present the first application of a bin-scheme microphysical and vertical transport model to determine the size distribution of cloud particles in the atmospheres of hot Jupiters and very low gravity brown dwarfs. We predict particle size distributions from first principles and investigate how observed cloud properties depend on the atmospheric thermal structure and vertical mixing. For hot Jupiters, I will show that the predicted realistic size distributions are frequently bimodal and irregular in shape, the cloud properties on the east and west limbs show distinct differences that increase with increasing equilibrium temperature, and the cloud opacities are roughly constant across a broad wavelength range with the exception of features in the mid-infrared.  We predict that it is unlikely that silicate or titanium clouds are responsible for the optical Rayleigh scattering slope seen in many hot Jupiters. We suggest that cloud opacities in emission may serve as sensitive tracers of the thermal state of a planet’s deep interior through the existence or lack of a cold trap in the deep atmosphere. We find that using the fully resolved size distribution of cloud particles as opposed to a mean particle typically changes cloud opacities by a factor of ~3-5.

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