TY - JOUR
T1 - SiO and a super-stellar C/O ratio in the atmosphere of the giant exoplanet WASP-121 b
AU - Evans-Soma, Thomas M.
AU - Sing, David K.
AU - Barstow, Joanna K.
AU - Piette, Anjali A.A.
AU - Taylor, Jake
AU - Lothringer, Joshua D.
AU - Reggiani, Henrique
AU - Goyal, Jayesh M.
AU - Ahrer, Eva Maria
AU - Mayne, Nathan J.
AU - Rustamkulov, Zafar
AU - Kataria, Tiffany
AU - Christie, Duncan A.
AU - Gapp, Cyril
AU - Dong, Jiayin
AU - Foreman-Mackey, Daniel
AU - Hattori, Soichiro
AU - Marley, Mark S.
N1 - Publisher Copyright:
© The Author(s) 2025.
PY - 2025/6
Y1 - 2025/6
N2 - Refractory elements such as iron, magnesium and silicon can be detected in the atmospheres of ultrahot giant planets. This provides an opportunity to quantify the amount of refractory material accreted during formation, along with volatile gases and ices. However, simultaneous detections of refractories and volatiles have proved challenging, as the most prominent spectral features of associated atoms and molecules span a broad wavelength range. Here, using a single JWST observation of the ultrahot giant planet WASP-121 b, we report detections of H2O (5.5–13.5σ), CO (10.8–12.8σ) and SiO (5.7–6.2σ) in the planet’s dayside atmosphere and CH4 (3.1–5.1σ) in the nightside atmosphere. We measure super-stellar values for the atmospheric C/H, O/H, Si/H and C/O ratios, which point to the joint importance of pebbles and planetesimals in giant planet formation. The CH4-rich nightside composition is also indicative of dynamical processes, such as strong vertical mixing, having a profound influence on the chemistry of ultrahot giant planets.
AB - Refractory elements such as iron, magnesium and silicon can be detected in the atmospheres of ultrahot giant planets. This provides an opportunity to quantify the amount of refractory material accreted during formation, along with volatile gases and ices. However, simultaneous detections of refractories and volatiles have proved challenging, as the most prominent spectral features of associated atoms and molecules span a broad wavelength range. Here, using a single JWST observation of the ultrahot giant planet WASP-121 b, we report detections of H2O (5.5–13.5σ), CO (10.8–12.8σ) and SiO (5.7–6.2σ) in the planet’s dayside atmosphere and CH4 (3.1–5.1σ) in the nightside atmosphere. We measure super-stellar values for the atmospheric C/H, O/H, Si/H and C/O ratios, which point to the joint importance of pebbles and planetesimals in giant planet formation. The CH4-rich nightside composition is also indicative of dynamical processes, such as strong vertical mixing, having a profound influence on the chemistry of ultrahot giant planets.
UR - https://www.scopus.com/pages/publications/105007150872
UR - https://www.scopus.com/pages/publications/105007150872#tab=citedBy
U2 - 10.1038/s41550-025-02513-x
DO - 10.1038/s41550-025-02513-x
M3 - Article
AN - SCOPUS:105007150872
SN - 2397-3366
VL - 9
SP - 845
EP - 861
JO - Nature Astronomy
JF - Nature Astronomy
IS - 6
ER -