Show simple item record

Files in this item


Item metadata

dc.contributor.authorHelling, Ch
dc.contributor.authorGourbin, P.
dc.contributor.authorWoitke, P.
dc.contributor.authorParmentier, V.
dc.identifier.citationHelling , C , Gourbin , P , Woitke , P & Parmentier , V 2019 , ' Sparkling nights and very hot days on WASP-18b : the formation of clouds and the emergence of an ionosphere ' , Astronomy & Astrophysics , vol. 626 , A133 .
dc.identifier.otherPURE: 258237595
dc.identifier.otherPURE UUID: 1069dc53-e9c7-491a-9dec-315d325c6ef8
dc.identifier.otherWOS: 000472594300005
dc.identifier.otherScopus: 85068425656
dc.description.abstractContext. WASP-18b is an ultra-hot Jupiter with a temperature difference of up to 2500 K between day and night. Such giant planets begin to emerge as a planetary laboratory for understanding cloud formation and gas chemistry in well-tested parameter regimes in order to better understand planetary mass loss and for linking observed element ratios to planet formation and evolution. Aims. We aim to understand where clouds form, their interaction with the gas-phase chemistry through depletion and enrichment, the ionisation of the atmospheric gas, and the possible emergence of an ionosphere on ultra-hot Jupiters. Methods. We used 1D profiles from a 3D atmosphere simulation for WASP-18b as input for kinetic cloud formation and gas-phase chemical equilibrium calculations. We solved our kinetic cloud formation model for these 1D profiles, which sample the atmosphere of WASP-18b at 16 different locations along the equator and in the mid-latitudes. We derived the gas-phase composition consistently. Results. The dayside of WASP-18b emerges as completely cloud-free as a result of the very high atmospheric temperatures. In contrast, the nightside is covered in geometrically extended and chemically heterogeneous clouds with dispersed particle size distributions. The atmospheric C/O ratio increases to >0.7 and the enrichment of the atmospheric gas with cloud particles is ρd/ρgas > 10−3. The clouds that form at the limbs appear located farther inside the atmosphere, and they are the least extended. Not all day- to nightside terminator regions form clouds. The gas phase is dominated by H2, CO, SiO, H2O, H2S, CH4, and SiS. In addition, the dayside has a substantial degree of ionisation that is due to ions such as Na+, K+, Ca+, and Fe+. Al+ and Ti+ are the most abundant of their element classes. We find that WASP-18b, as one example for ultra-hot Jupiters, develops an ionosphere on the dayside.
dc.relation.ispartofAstronomy & Astrophysicsen
dc.rights© 2019, ESO. This work has been made available online in accordance with the publisher's policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at
dc.subjectPlanets and satellites: atmospheresen
dc.subjectSolid state: refractoryen
dc.subjectPlanets and satellites: gaseous planetsen
dc.subjectInfrared: planetary systemsen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleSparkling nights and very hot days on WASP-18b : the formation of clouds and the emergence of an ionosphereen
dc.typeJournal articleen
dc.contributor.institutionUniversity of St Andrews. St Andrews Centre for Exoplanet Scienceen
dc.contributor.institutionUniversity of St Andrews. School of Physics and Astronomyen
dc.description.statusPeer revieweden

This item appears in the following Collection(s)

Show simple item record