A story of titanium in the atmosphere of the ultra-hot Jupiter WASP-121 b

by Dr Jens Hoeijmakers (Lund University)

Friday 25 Apr 2025, 10:30 → 12:30 Europe/Stockholm

FC61Jens HoeijmakersJens HoeijmakersJens HoeijmakersJens Hoeijmakers (AlbaNova Main Building)

The hottest gas giant exoplanets (termed ultra-hot Jupiters) have atmospheres that are distinct from their cooler siblings. Similar to the photospheres of stars, the gas is mostly in atomic form, partially ionised and free of clouds. These properties make these planets highly interesting objects of study via high-resolution spectroscopy, by which we can resolve lines of many different metals to probe the atmospheres. As atomic chemistry is much simpler than molecular and cloud chemistry, in theory these objects are especially amenable to spectroscopic study and model inference. This talk focusses on the curious case of WASP-121 b. With a temperature close to 2400 K, this planet hosts many metals in atomic form, but also simple oxides, including TiO and VO -- that dominate the spectra of M-dwarf stars of similar temperatures. Although vanadium and VO have been detected, titanium-bearing species have been markedly absent from this planet. Using several high-resolution spectroscopic datasets, we have repeatedly investigated this planet's atmosphere in search for titanium, and are now able to paint a crude picture of how the global, three-dimensional climate of this planet makes the story of titanium a complex one. Our results underscore that three-dimensional modelling of the atmosphere is indispensable if we are to infer global planetary properties from our observed spectra.