Modelling the local and global cloud formation on HD 189733b

Lee, Elspeth K. H.; Helling, Christiane; Dobbs-Dixon, Ian; Juncher, D.

doi:10.1051/0004-6361/201525982

Cited by 86 publications

(128 citation statements)

References 61 publications

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“…However, Fe[s] rich grains are expected to reside below the photosphere of HD 189733b (Lee et al 2015;Helling et al 2016a), where they would have negligible effects on the observable scattered and emitted light.…”

Section: Discussionmentioning

confidence: 99%

“…(28)). The cloud particle mean grain size, a [cm], and mean grain area, A [cm 2 ], of the cloud particles in each RHD cell can be found from the dust moment values, L j (Woitke & Helling 2003Lee et al 2015). Assuming an arithmetic log-normal distribution of cloud particle sizes (e.g.…”

Section: Scattering Of L-packets By Dust and Gasmentioning

confidence: 99%

“…(12)) are also calculated at the effective cloud particle size. Effective (n, k) coefficients of the cloud particles required as input for Mie theory are calculated for mixed material cloud particles using effective medium theory in the same way as Lee et al (2015).…”

Section: Cloud and Gas Opacitymentioning

confidence: 99%

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Dynamic mineral clouds on HD 189733b

Lee

Wood

Dobbs-Dixon

et al. 2017

A&A

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Context. As the 3D spatial properties of exoplanet atmospheres are being observed in increasing detail by current and new generations of telescopes, the modelling of the 3D scattering effects of cloud forming atmospheres with inhomogeneous opacity structures becomes increasingly important to interpret observational data. Aims. We model the scattering and emission properties of a simulated cloud forming, inhomogeneous opacity, hot Jupiter atmosphere of HD 189733b. We compare our results to available Hubble Space Telescope (HST) and Spitzer data and quantify the effects of 3D multiple scattering on observable properties of the atmosphere. We discuss potential observational properties of HD 189733b for the upcoming Transiting Exoplanet Survey Satellite (TESS) and CHaracterising ExOPlanet Satellite (CHEOPS) missions. Methods. We developed a Monte Carlo radiative transfer code and applied it to post-process output of our 3D radiative-hydrodynamic, cloud formation simulation of HD 189733b. We employed three variance reduction techniques, i.e. next event estimation, survival biasing, and composite emission biasing, to improve signal to noise of the output. For cloud particle scattering events, we constructed a log-normal area distribution from the 3D cloud formation radiative-hydrodynamic results, which is stochastically sampled in order to model the Rayleigh and Mie scattering behaviour of a mixture of grain sizes. Results. Stellar photon packets incident on the eastern dayside hemisphere show predominantly Rayleigh, single-scattering behaviour, while multiple scattering occurs on the western hemisphere. Combined scattered and thermal emitted light predictions are consistent with published HST and Spitzer secondary transit observations. Our model predictions are also consistent with geometric albedo constraints from optical wavelength ground-based polarimetry and HST B band measurements. We predict an apparent geometric albedo for HD 189733b of 0.205 and 0.229, in the TESS and CHEOPS photometric bands respectively. Conclusions. Modelling the 3D geometric scattering effects of clouds on observables of exoplanet atmospheres provides an important contribution to the attempt to determine the cloud properties of these objects. Comparisons between TESS and CHEOPS photometry may provide qualitative information on the cloud properties of nearby hot Jupiter exoplanets.

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Section: Discussionmentioning

confidence: 99%

Section: Scattering Of L-packets By Dust and Gasmentioning

confidence: 99%

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Dynamic mineral clouds on HD 189733b

Lee

Wood

Dobbs-Dixon

et al. 2017

A&A

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“…Despite their importance, the composition of these clouds remains unknown, partly because their optical properties are more sensitive to physical properties such as the particle size than chemical composition (Heng & Demory 2013) and partly because their vertical distribution is very sensitive to unconstrained processes such as vertical mixing (Morley et al 2013;Lee et al 2015). To date no correlation has been observed between the presence of clouds and fundamental planetary parameters such as irradiation or gravity, although it is theoretically expected (Sudarsky et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Transitions in the Cloud Composition of Hot Jupiters

Parmentier

Fortney

Showman

et al. 2016

ApJ

320

436

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Over a large range of equilibrium temperatures, clouds shape the transmission spectrum of hot Jupiter atmospheres, yet their composition remains unknown. Recent observations show that the Kepler lightcurves of some hot Jupiters are asymmetric: for the hottest planets, the lightcurve peaks before secondary eclipse, whereas for planets cooler than ∼1900 K, it peaks after secondary eclipse. We use the thermal structure from 3D global circulation models to determine the expected cloud distribution and Kepler lightcurves of hot Jupiters. We demonstrate that the change from an optical lightcurve dominated by thermal emission to one dominated by scattering (reflection) naturally explains the observed trend from negative to positive offset. For the cool planets the presence of an asymmetry in the Kepler light curve is a telltale sign of the cloud composition, because each cloud species can produce an offset only over a narrow range of effective temperatures. By comparing our models and the observations, we show that the cloud composition of hot Jupiters likely varies with equilibrium temperature. We suggest that a transition occurs between silicate and manganese sulfide clouds at a temperature near 1600 K, analogous to the L/T transition on brown dwarfs. The cold trapping of cloud species below the photosphere naturally produces such a transition and predicts similar transitions for other condensates, including TiO. We predict that most hot Jupiters should have cloudy nightsides, that partial cloudiness should be common at the limb, and that the dayside hot spot should often be cloud-free.

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“…The equation of state provides the abundances of opacity species (ions, atoms, molecules, cloud particles) that influence the local temperature through radiative transfer effects. Theoretical calculations now suggest that clouds should be very prevalent throughout these atmospheres (Lee et al 2015).…”

Section: Ionisation Processes In Ultracool Atmospheresmentioning

confidence: 96%

Atmospheric Electrification in Dusty, Reactive Gases in the Solar System and Beyond

et al. 2016

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Detailed observations of the solar system planets reveal a wide variety of local atmospheric conditions. Astronomical observations have revealed a variety of extrasolar planets none of which resembles any of the solar system planets in full. Instead, the most massive amongst the extrasolar planets, the gas giants, appear very similar to the class of (young) brown dwarfs which are amongst the oldest objects in the Universe. Despite this diversity, solar system planets, extrasolar planets and brown dwarfs have broadly similar global temperatures between 300 and 2500 K. In consequence, clouds of different chemical species form in their atmospheres. While the details of these clouds differ, the fundamental physical processes are the same. Further to this, all these objects were observed to produce radio and X-ray emissions. While both kinds of radiation are well studied on Earth and to a lesser extent on the solar system planets, the occurrence of emissions that potentially originate from accelerated electrons on brown dwarfs, extrasolar planets and protoplanetary disks is not well understood yet. This paper offers an interdisciplinary view on electrification processes and their feedback on their hosting environment in meteorology, volcanology, planetology and research on extrasolar planets and planet formation.

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Modelling the local and global cloud formation on HD 189733b

Cited by 86 publications

References 61 publications

Dynamic mineral clouds on HD 189733b

Dynamic mineral clouds on HD 189733b

Transitions in the Cloud Composition of Hot Jupiters

Atmospheric Electrification in Dusty, Reactive Gases in the Solar System and Beyond

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