A Universal Cloud Composition on the Nightsides of Hot Jupiters

Abstract

The day and nightside temperatures of hot Jupiters are diagnostic of heat transport processes in their atmospheres. Recent observations have shown that the nightsides of hot Jupiters are a nearly constant 1100 K for a wide range of equilibrium temperatures (T${}_{eq}$), lower than those predicted by 3D global circulation models. Here we investigate the impact of nightside clouds on the observed nightside temperatures of hot Jupiters using an aerosol microphysics model. We find that silicates dominate the cloud composition, forming an optically thick cloud deck on the nightsides of all hot Jupiters with T${}_{eq}$ $\le$ 2100 K. The observed nightside temperature is thus controlled by the optical depth profile of the silicate cloud with respect to the temperature-pressure profile. As nightside temperatures increase with T${}_{eq}$, the silicate cloud is pushed upwards, forcing observations to probe cooler altitudes. The cloud vertical extent remains fairly constant due to competing impacts of increasing vertical mixing strength with T${}_{eq}$ and higher rates of sedimentation at higher altitudes. These effects, combined with the intrinsically subtle increase of the nightside temperature with T${}_{eq}$ due to decreasing radiative timescale at higher instellation levels lead to low, constant nightside photospheric temperatures consistent with observations. Our results suggest a drastic reduction in the day-night temperature contrast when nightside clouds dissipate, with the nightside emission spectra transitioning from featureless to feature-rich. We also predict that cloud absorption features in the nightside emission spectra of hot Jupiters should reach $\ge$100 ppm, potentially observable with the James Webb Space Telescope.

10 pages and 5 figures. Accepted for publication in ApJL

References in corpus (10)

• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• An ultrahot gas-giant exoplanet with a stratosphere
• Transmission spectral properties of clouds for hot Jupiter exoplanets
• A consistent retrieval analysis of 10 Hot Jupiters observed in transmission
• Spitzer Phase Curve Constraints for WASP-43b at 3.6 and 4.5 microns
• The Atmospheric Circulation of the Hot Jupiter WASP-43b: Comparing Three-Dimensional Models to Spectrophotometric Data
• The Atmospheric Circulation of Ultra-hot Jupiters
• Magnetic Effects in Hot Jupiter Atmospheres
• Transit Signatures of Inhomogeneous Clouds on Hot Jupiters: Insights From Microphysical Cloud Modeling
• Overcast on Osiris: 3D radiative-hydrodynamical simulations of a cloudy hot Jupiter using the parameterised, phase-equilibrium cloud formation code EddySed

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