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Open AccessArticle

The Effect of Clouds as an Additional Opacity Source on the Inferred Metallicity of Giant Exoplanets

1
Institut für Physik, Universität Rostock, D-18051 Rostock, Germany
2
Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt (DLR) Berlin, D-12489 Berlin, Germany
*
Author to whom correspondence should be addressed.
Atmosphere 2019, 10(11), 664; https://doi.org/10.3390/atmos10110664
Received: 16 October 2019 / Revised: 25 October 2019 / Accepted: 26 October 2019 / Published: 30 October 2019
(This article belongs to the Special Issue Modeling and Simulation of Planetary Atmospheres)
Atmospheres regulate the planetary heat loss and therefore influence planetary thermal evolution. Uncertainty in a giant planet’s thermal state contributes to the uncertainty in the inferred abundance of heavy elements it contains. Within an analytic atmosphere model, we here investigate the influence that different cloud opacities and cloud depths can have on the metallicity of irradiated extrasolar gas giants, which is inferred from interior models. In this work, the link between inferred metallicity and assumed cloud properties is the thermal profile of atmosphere and interior. Therefore, we perform coupled atmosphere, interior, and evolution calculations. The atmosphere model includes clouds in a much simplified manner; it includes long-wave absorption but neglects shortwave scattering. Within that model, we show that optically thick, high clouds have negligible influence, whereas deep-seated, optically very thick clouds can lead to warmer deep tropospheres and therefore higher bulk heavy element mass estimates. For the young hot Jupiter WASP-10b, we find a possible enhancement in inferred metallicity of up to 10% due to possible silicate clouds at ∼0.3 bar. For WASP-39b, whose observationally derived metallicity is higher than predicted by cloudless models, we find an enhancement by at most 50%. However, further work on cloud properties and their self-consistent coupling to the atmospheric structure is needed in order to reduce uncertainties in the choice of model parameter values, in particular of cloud opacities. View Full-Text
Keywords: extrasolar planets: hot Jupiters; atmospheres; clouds; individuals: WASP-10b, WASP-39b extrasolar planets: hot Jupiters; atmospheres; clouds; individuals: WASP-10b, WASP-39b
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Poser, A.J.; Nettelmann, N.; Redmer, R. The Effect of Clouds as an Additional Opacity Source on the Inferred Metallicity of Giant Exoplanets. Atmosphere 2019, 10, 664.

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