ExoAtmospheres
IAC community database for exoplanet atmospheric observations
HD 209458 b
| Planet status | Confirmed |
|---|---|
| Planet type | Hot Jupiter |
| Period | 3.52472 d |
| Mass | 0.69 MJ 219.282 M⊕ |
| Radius | 1.38 RJ 15.456 R⊕ |
| Semi major axis | 0.04747 AU |
| Star name | HD 209458 |
| Star distance | 47 pc |
| Star teff | 6092 K |
| Star radius | 1.203 R☉ |
| Temperature (calculated) | 1478 K |
| V | 7.65 mag |
| J | 6.591 mag |
| K | 6.308 mag |
| Alternate names | |
| Exoplanet Encyclopaedia |  |
Molecules
Cloudy: Detection
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JWST-MIRI | Magnesium Silicate Clouds in the Atmosphere of HD 209458b from a Rule-Based Tree-Structured Data Reduction2026, Katy L. Chubb, David Grant et al. |
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Featureless spectra: Upper limit
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G-B: High resolution IR | Searching for Molecular Signatures in 14 Transiting Exoplanets with SPIRou2026, A. Masson, S. Vinatier et al. |
SPIRou cross-correlation observations does not show molecular signals |
Na: No detection
|
G-B: High resolution visible | An Initial Assessment of the Hanle Echelle Spectrograph for Exoplanet Atmosphere Studies2025, Manjunath Bestha, Athira Unni et al. |
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He: Detection
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G-B: High resolution IR | HET/HPF observations of Helium in warm, hot, and ultra-hot Jupiters2025, Jaume Orell-Miquel, Kyra Sampson et al. |
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H2O: Detection Molecular ratios: C/O, etc...: Detection CO: Upper limit CH4: Upper limit NH3: Upper limit HCN: Upper limit
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G-B: High resolution IR | The watery atmosphere of HD~209458~b revealed by joint $K$- and $L$-band high-resolution spectroscopy2025, Luke Finnerty, Julie Inglis et al. |
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H2O: Detection CO2: Detection Cloudy: Detection Molecular ratios: C/O, etc...: Detection
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JWST-NIRCam | Osiris revisited: Confirming a solar metallicity and low C/O in HD 209458b2025, N. Bachmann, L. Kreidberg et al. |
Combination of HST/WFC3 + JWST/NIRCam data. Cloudy models preferred |
Molecular ratios: C/O, etc...: Detection
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HST WFC3 | Re-analysis of 10 Hot-Jupiter Atmospheres with disequilibrium chemistry retrieval2025, Deborah Bardet, Quentin Changeat et al. |
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CO2: Detection H2O: Detection Molecular ratios: C/O, etc...: Detection
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JWST-NIRCam | A Detailed Investigation of HD 209458 b HST & JWST Transmission Spectra with SANSAR2025, Avinash Verma, Jayesh Goyal et al. |
NIRCam observations alone can lead to overestimation of abundances, and should be used with optical and near-IR obs |
Na: Upper limit
|
G-B: High resolution visible | The GAPS programme at TNG LXVI. A homogeneous search for Na i and its possible variability in ten gas giant exoplanets2024, D. Sicilia, L. Malavolta et al. |
Unclear result from the analysis of several transits. |
Na: No detection
|
G-B: High resolution visible | Probing Na in giant exoplanets with ESPRESSO and 3D NLTE stellar spectra2024, G. Canocchi, G. Morello et al. |
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H2O: Detection CH4: No detection CO: No detection HCN: No detection NH3: No detection
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G-B: High resolution IR | Four HD 209458 b transits through CRIRES+: Detection of H$_2$O and non-detections of C$_2$H$_2$, CH$_4$, and HCN2024, D. Blain, R. Landman et al. |
Four transits with CRIRES+ |
Albedo: 0.52 Phase curve: Yes Dayside Temperature (occultation): 1420 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. |
He: Upper limit
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G-B: High resolution IR | Probing atmospheric escape through metastable He I triplet lines in 15 exoplanets observed with SPIRou2024, A. Masson, S. Vinatier et al. |
Tentative detection |
CO2: Detection H2O: Detection Molecular ratios: C/O, etc...: Detection CH4: Upper limit HCN: Upper limit
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JWST-NIRCam | JWST transmission spectroscopy of HD 209458b: a super-solar metallicity, a very low C/O, and no evidence of CH4, HCN, or C2H22023, Qiao Xue, Jacob L. Bean et al. |
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H2O: Detection CH4: Detection CO: 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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Mn: Detection
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G-B: High resolution visible | Characterization of exoplanetary atmospheres through a model-unbiased spectral survey methodology2022, Lira-Barria, A., Rojo, P. M. et al. |
Three atomic lines found with detection, but method lacked corrections for deformation of lines, it might need reviewing |
CO: Detection H2O: Detection CH4: Detection HCN: Detection NH3: Detection
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G-B: High resolution IR | Five carbon- and nitrogen-bearing species in a hot giant planet's atmosphere2021, Paolo Giacobbe, Matteo Brogi et al. |
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Na: No detection
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G-B: High resolution visible | The atmosphere of HD 209458b seen with ESPRESSO. No detectable planetary absorptions at high resolution2021, Casasayas-Barris, N., Palle, E. et al. |
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TiO: Detection Na: Detection
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G-B: Low resolution visible | Broadband transmission spectroscopy of HD 209458b with ESPRESSO: evidence for Na, TiO, or both2020, Santos, N. C., Cristo, E. et al. |
Models suggest there is ambiguity in the species detected and other absorbers may be needed to explain data. |
FeH: Upper limit
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G-B: High resolution IR | A Search for FeH in Hot-Jupiter Atmospheres with High-dispersion Spectroscopy2020, Kesseli, Aurora Y., Snellen, I. A. G. et al. |
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Fe+: Detection Mg: No detection Mg+: No detection
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HST STIS | Near-ultraviolet Transmission Spectroscopy of HD 209458b: Evidence of Ionized Iron Beyond the Planetary Roche Lobe2020, Cubillos, Patricio E., Fossati, Luca et al. |
Detection of iron in HD209458b and non-detection of Mg and Mg+. |
He: Detection
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G-B: High resolution IR | He I λ 10 830 Å in the transmission spectrum of HD209458 b2019, Alonso-Floriano, F. J., Snellen, I. A. G. et al. |
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H2O: Detection
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G-B: High resolution IR | Water vapor detection in the transmission spectra of HD 209458 b with the CARMENES NIR channel2019, A. Sánchez-López, F. J. Alonso-Floriano et al. |
Water vapor detection in the transmission spectra of HD 209458 b with the CARMENES NIR channel |
CO: Detection H2O: Upper limit
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G-B: High resolution IR | Retrieving Temperatures and Abundances of Exoplanet Atmospheres with High-resolution Cross-correlation Spectroscopy2019, Brogi, MatteoLine, Michael R. |
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He: Upper limit
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G-B: High resolution IR | Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b2018, Nortmann, Lisa, Pallé, Enric et al. |
He analysis in the appendix |
H2O: Detection
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HST WFC3 | A Population Study of Gaseous Exoplanets2018, Tsiaras, A., Waldmann, I. P. et al. |
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H2O: Detection
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HST WFC3 | A New Approach to Analyzing HST Spatial Scans: The Transmission Spectrum of HD 209458 b2016, Tsiaras, A., Waldmann, I. P. et al. |
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Na: Detection H2O: Detection
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HST STIS | A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion2015, David K. Sing, Jonathan J. Fortney et al. |
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Phase curve: Yes |
Spitzer | The Ground-based H-, K-, and L-band Absolute Emission Spectra of HD 209458b2014, Zellem, Robert T., Griffith, Caitlin A. et al. |
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C+: Detection Si+: Detection
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HST-COS | Observations of Mass Loss from the Transiting Exoplanet HD 209458b2010, Linsky, Jeffrey L., Yang, Hao et al. |
Detection of Si++ |
CO: Detection
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G-B: High resolution IR | The orbital motion, absolute mass and high-altitude winds of exoplanet HD209458b2010, Snellen, Ignas A. G., de Kok, Remco J. et al. |
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Na: Detection
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G-B: High resolution visible | Ground-based detection of sodium in the transmission spectrum of exoplanet HD209458b2008, I. A. G. Snellen, S. Albrecht et al. |
Reanalysis of Subaru/HDS dataset |
Phase curve: Yes |
Spitzer | Hot nights on extrasolar planets: mid-infrared phase variations of hot Jupiters2007, Cowan, N. B., Agol, E. et al. |
Multi-epoch 8 micron phase measurements yielded an upper limit on the thermal phase variations. |
Na: Upper limit Li: Upper limit H: Upper limit
|
G-B: High resolution visible | Subaru HDS Transmission Spectroscopy of the Transiting Extrasolar Planet HD 209458b2005, Narita, Norio, Suto, Yasushi et al. |
Upper limits with Subaru/HDS |
C+: Detection O: Detection
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HST STIS | Detection of Oxygen and Carbon in the Hydrodynamically Escaping Atmosphere of the Extrasolar Planet HD 209458b2004, Vidal-Madjar, A., Désert, J. -M. et al. |
Transmission analysis of atomic/ionic lines in the UV. No signals detected for other species. |
H: Detection
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HST STIS | An extended upper atmosphere around the extrasolar planet HD209458b2003, Vidal-Madjar, A., Lecavelier des Etangs, A. et al. |
Ly-alpha line detection |
Na: Detection
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HST STIS | Detection of an Extrasolar Planet Atmosphere2002, Charbonneau, David, Brown, Timothy M. et al. |
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He: Upper limit
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G-B:Low resolution IR | Search for spectroscopical signatures of transiting HD 209458b's exosphere2001, Moutou, C., Coustenis, A. et al. |
Observations affected by fringing but upper limit for He is derived |