ExoAtmospheres
IAC community database for exoplanet atmospheric observations
WASP-121 b
| Planet status | Confirmed |
|---|---|
| Planet type | UltraHot Jupiter |
| Period | 1.2749255 d |
| Mass | 1.184 MJ 376.2752 M⊕ |
| Radius | 1.865 RJ 20.888 R⊕ |
| Semi major axis | 0.02544 AU |
| Star name | WASP-121 |
| Star distance | 270 pc |
| Star teff | 6460 K |
| Star radius | 1.458 R☉ |
| Temperature (calculated) | 2358 K |
| V | 10.4 mag |
| J | 9.625 mag |
| K | 9.374 mag |
| Alternate names | |
| Exoplanet Encyclopaedia |  |
Molecules
H2O: Detection CO2: Detection CH4: Detection Molecular ratios: C/O, etc...: Detection Atmospheric dynamics: Detection Phase curve: Yes Dayside Temperature (occultation): 99999 K |
JWST-NIRSpec | A Physically Driven Parameterisation of Multidimensional Atmospheres: Application to the JWST Phase Curve of WASP-121b2026, Yuanheng Yang, Guo Chen et al. |
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SiO: Detection Molecular ratios: C/O, etc...: Detection Albedo: 0.22 Dayside Temperature (occultation): 2889 K |
JWST-MIRI | The panchromatic JWST dayside spectrum of WASP-121 b reveals a refractory-rich formation2026, K. Angelique Kahle, Paul Mollière et al. |
The atmosphere is enriched in volatile and refractory species. |
CO: Detection H2O: Detection
|
JWST-NIRSpec | Atmospheric asymmetries in WASP-121 b revealed by rotational transits detected with JWST2026, Cyril Gapp, Aurélien Falco et al. |
Observed changes of the transmission spectrum with orbital phase |
He: Detection H: Detection
|
JWST-NIRISS | A complex structure of escaping helium spanning more than half the orbit of the ultra-hot Jupiter WASP-121\,b2025, Romain Allart, Louis-Philippe Coulombe et al. |
Extended pre and post-tails of escaping He. Halpha detection in the Supl. Material |
Albedo: 0.28 Phase curve: Yes Dayside Temperature (occultation): 2717 K |
JWST-NIRISS | Precise Constraints on the Energy Budget of WASP-121 b from its JWST NIRISS/SOSS Phase Curve2025, Jared Splinter, Louis-Philippe Coulombe et al. |
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CO: Detection Fe: Detection Y: Detection H2O: Upper limit
|
G-B: High resolution IR | Atmospheric composition and circulation of the ultra-hot Jupiter WASP-121b with joint NIRPS, HARPS and CRIRES+ transit spectroscopy2025, Valentina Vaulato, Melissa J. Hobson et al. |
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H2O: Detection CO: Detection VO: Detection H-: Detection Molecular ratios: C/O, etc...: Detection
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JWST-NIRISS | Enriched volatiles and refractories but deficient titanium on the dayside atmosphere of WASP-121b revealed by JWST/NIRISS2025, Stefan Pelletier, Louis-Philippe Coulombe et al. |
Day side emission spectrum. Data can be explained with TiO or reflected light (Albedo = 0.16) |
H2O: Detection OH: Detection Fe: Detection Mg: Detection
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G-B: High resolution IR | Quantifying thermal water dissociation in the dayside photosphere of WASP-121 b using NIRPS2025, Luc Bazinet, Romain Allart et al. |
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H2: Detection H2O: Detection SiO: Detection
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JWST-NIRSpec | WASP-121b's transmission spectrum observed with JWST/NIRSpec G395H reveals thermal dissociation and SiO in the atmosphere2025, Cyril Gapp, Thomas M. Evans-Soma et al. |
The spectrum observed with JWST/NIRSpec G395H reveals thermal dissociation in the atmosphere |
CO2: Detection H2O: Detection SiO: Detection CH4: Detection Molecular ratios: C/O, etc...: Detection
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JWST-NIRSpec | SiO and a super-stellar C/O ratio in the atmosphere of the giant exoplanet WASP-121b2025, Thomas M. Evans-Soma, David K. Sing et al. |
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Phase curve: Yes Dayside Temperature (occultation): 2779 K |
Spitzer | An Analysis of Spitzer Phase Curves for WASP-121b and WASP-77Ab2025, Brian Davenport, Thomas Kennedy et al. |
Phase curves at 3.6um and 4.5um. |
H: Detection Li: Detection Na: Detection K: Detection Ca+: Detection Mg: Detection Sr: Detection Sr+: Detection Mn: Detection Ti: Detection V: Detection Cr: Detection Fe: Detection Fe+: Detection Co: Detection Ni: Detection Ba+: Detection Atmospheric dynamics: Detection
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G-B: High resolution visible | Titanium chemistry of WASP-121 b with ESPRESSO in 4-UT mode2025, B. Prinoth, J. V. Seidel et al. |
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Atmospheric dynamics: Detection Fe: Detection Na: Detection H: Detection
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G-B: High resolution visible | Vertical structure of an exoplanet's atmospheric jet stream2025, Julia V. Seidel, Bibiana Prinoth et al. |
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Atmospheric dynamics: Detection
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JWST-NIRSpec | An absolute mass, precise age, and hints of planetary winds for WASP-121 A and b from a JWST NIRSpec phase curve2025, David K. Sing, Thomas M. Evans-Soma et al. |
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He: Detection
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G-B: High resolution IR | The overflowing atmosphere of WASP-121 b: High-resolution He I λ10833 transmission spectroscopy with VLT/CRIRES<SUP>+</SUP>2024, Czesla, S., Nail, F. et al. |
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Molecular ratios: C/O, etc...: Detection H2O: Detection CO: Detection OH: Detection
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G-B: High resolution IR | The Roasting Marshmallows Program with IGRINS on Gemini South II -- WASP-121 b has super-stellar C/O and refractory-to-volatile ratios2024, Peter C. B. Smith, Jorge A. Sanchez et al. |
Emission observations with IGRINS |
CO: Detection H2O: Detection Fe: Detection Ni: Detection Molecular ratios: C/O, etc...: Detection
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G-B: High resolution IR | CRIRES+ and ESPRESSO reveal an atmosphere enriched in volatiles relative to refractories on the ultra-hot Jupiter WASP-121b2024, Stefan Pelletier, Björn Benneke et al. |
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Albedo: 0.31 Phase curve: Yes Dayside Temperature (occultation): 2680 K |
Spitzer | A Comprehensive Analysis Spitzer 4.5 $μ$m Phase Curve of Hot Jupiters2024, Lisa Dang, Taylor J. Bell et al. |
Dayside and nightside temperatures from phase curve at 4.5 um. |
CO: Detection H2O: Detection
|
G-B: High resolution IR | Phase-resolving the absorption signatures of water and carbon monoxide in the atmosphere of the ultra-hot Jupiter WASP-121b with GEMINI-S/IGRINS2024, Joost P. Wardenier, Vivien Parmentier et al. |
Phase resolved detections of molecular absorptions |
Fe: Detection
|
G-B: High resolution visible | Searching for NLTE effects in the high-resolution transmission spectrum of WASP-121 b with Cloudy for Exoplanets2024, M. E. Young, E. F. Spring et al. |
Unable to conclusively remark on the presence of NLTE effects in the atmosphere of WASP-121 b |
Molecular ratios: C/O, etc...: Detection Cloudy: Detection
|
HST WFC3 | Is the atmosphere of the ultra-hot Jupiter WASP-121b variable?2024, Quentin Changeat, Jack W. Skinner et al. |
identified signals consistent with quasi-periodic weather patterns |
Albedo: 0.34 Phase curve: Yes |
Spitzer | Spitzer thermal phase curve of WASP-121 b2023, Morello, G., Changeat, Q. et al. |
Td = 2680_{45}^{+60} K |
Fe: Detection Mg: Detection Ni: Upper limit Cr: Detection Mn: Upper limit V: Detection Ca: Detection Ti: Upper limit
|
G-B: High resolution visible | Retrieval Survey of Metals in Six Ultrahot Jupiters: Trends in Chemistry, Rain-out, Ionization, and Atmospheric Dynamics2023, Gandhi, Siddharth, Kesseli, Aurora et al. |
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TiO: Detection VO: Detection H2O: Detection
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G-B: Low resolution visible | Detection of TiO and VO in the atmosphere of WASP-121b and Evidence for its temporal variation2023, Qinglin Ouyang, Wei Wang et al. |
Chemical compositions of the terminator region may change over long timescales |
Na: Detection
|
G-B: High resolution visible | Detection of a high-velocity sodium feature on the ultra-hot Jupiter WASP-121 b2023, J. V. Seidel, F. Borsa et al. |
Detection of a high-velocity sodium features |
Phase curve: Yes Dayside Temperature (occultation): 926 K |
JWST-NIRSpec | A JWST NIRSpec phase curve for WASP-121b: dayside emission strongest eastward of the substellar point and nightside conditions conducive to cloud formation2023, Thomas Mikal-Evans, David K. Sing et al. |
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H: Detection Fe+: Detection Ca+: Detection
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G-B: High resolution visible | High-resolution atmospheric retrievals of WASP-121b transmission spectroscopy with ESPRESSO: Consistent relative abundance constraints across multiple epochs and instruments2022, Cathal Maguire, Neale P. Gibson et al. |
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Ca+: Detection V+: Detection Fe+: Detection Ni+: Detection Ti: No detection
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G-B: High resolution visible | The Mantis Network III: A titanium cold-trap on the ultra-hot Jupiter WASP-121 b2022, H. J. Hoeijmakers, D. Kitzmann et al. |
A titanium cold-trap on the ultra-hot Jupiter WASP-121 b |
Ba+: Detection
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G-B: High resolution visible | Detection of barium in the atmospheres of the ultra-hot gas giants WASP-76b and WASP-121b2022, T. Azevedo Silva, O. D. S. Demangeon et al. |
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Na: Detection
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G-B: High resolution visible | A survey of sodium absorption in ten giant exoplanets with high-resolution transmission spectroscopy2022, Adam B. Langeveld, Nikku Madhusudhan et al. |
Confirmed the previously reported detections of Na using HARPS |
H2O: Detection H-: Detection VO: Detection TiO: Detection
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HST WFC3 | Five key exoplanet questions answered via the analysis of 25 hot Jupiter atmospheres in eclipse2022, Quentin Changeat, Billy Edwards et al. |
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Phase curve: Yes |
TESS | Comprehensive Analysis of the Full TESS Orbital Phase Curve of WASP121b2022, Eftekhar, M. |
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Phase curve: Yes |
HST WFC3 | Diurnal variations in the stratosphere of the ultrahot giant exoplanet WASP-121b2022, Thomas Mikal-Evans, David K. Sing et al. |
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Fe: Detection Cr: Detection Mg: Detection V: Detection
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G-B: High resolution visible | Relative abundance constraints from high-resolution optical transmission spectroscopy of WASP-121b, and a fast model-filtering technique for accelerating retrievals2022, Neale P. Gibson, Stevanus K. Nugroho et al. |
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Sc+: Detection
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G-B: High resolution visible | An inventory of atomic species in the atmosphere of WASP-121b using UVES high-resolution spectroscopy2021, Stephanie R. Merritt, Neale P. Gibson et al. |
UVES spectrograph |
Na: Detection H: Detection K: Detection Li: Detection Ca+: Detection Mg: Detection Fe: Detection Fe+: Detection Cr: Detection V: Detection
|
G-B: High resolution visible | Atmospheric Rossiter-McLaughlin effect and transmission spectroscopy of WASP-121b with ESPRESSO2021, Borsa, F., Allart, R. et al. |
ESPRESSO and VLT data. Also detected V. |
Phase curve: Yes |
TESS | Systematic Phase Curve Study of Known Transiting Systems from Year One of the TESS Mission2020, Wong, Ian, Shporer, Avi et al. |
Strong detections of secondary eclipse (486+/-59 ppm) and planetary brightness modulation. |
Mg: Detection Na: Detection Ca: Detection Cr: Detection Fe: Detection Ni: Detection V: Detection
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G-B: High resolution visible | Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS). IV. A spectral inventory of atoms and molecules in the high-resolution transmission spectrum of WASP-121 b2020, Hoeijmakers, H. J., Seidel, J. V. et al. |
V detection. |
Cr: Detection Fe: Detection Fe+: Detection V: Detection
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G-B: High resolution visible | Neutral Cr and V in the Atmosphere of Ultra-hot Jupiter WASP-121 b2020, Ben-Yami, Maya, Madhusudhan, Nikku et al. |
Detection of Cr and V, and confirmation of Fe and Fe+ using HARPS observations |
H: Detection Na: Detection Fe: Detection
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G-B: High resolution visible | Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b2020, Cabot, Samuel H. C., Madhusudhan, Nikku et al. |
H-alpha, Na I and Fe I detected with HARPS |
Mg+: Detection Fe+: Detection
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HST STIS | The Hubble Space Telescope PanCET Program: Exospheric Mg II and Fe II in the Near-ultraviolet Transmission Spectrum of WASP-121b Using Jitter Decorrelation2019, Sing, David K., Lavvas, Panayotis et al. |
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H2O: Detection
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HST WFC3 | A Population Study of Gaseous Exoplanets2018, Tsiaras, A., Waldmann, I. P. et al. |