Exoplanet Atmosphere Report · JWST NIRCam

HD 189733 b

Famous as the "blue planet" — its deep azure color, inferred from scattered starlight rather than a true photograph, is attributed to high-altitude scattering haze, though the exact particle composition (silicates are one candidate among several) isn't pinned down. One of the most intensively studied hot Jupiters, this page runs a simple two-window band-contrast statistic on its JWST NIRCam transmission spectrum and reports it next to the retrieval-based molecular significances Fu et al. (2024) actually publish.

Discovered 2005, radial velocity NASA Exoplanet Archive parameters JWST NIRCam spectrum, 139 points (Fu et al. 2024)
Artist's concept of the deep-blue hot Jupiter HD 189733 b

AI-generated artist's concept of HD 189733 b — not a real photograph. All data and figures in this report come from actual JWST NIRCam observations (see below).

The planet, in numbers

Queried live from the NASA Exoplanet Archive TAP service (pscomppars).

Radius12.67 Earth radii (~1.13 Jupiter radii)
Mass359.1 Earth masses (~1.13 Jupiter masses)
Orbital period2.22 days
Semi-major axis0.0313 AU
Equilibrium temperature1209 K
Host starHD 189733, K-type dwarf, Teff = 5052 K, 0.75 Rsun, 0.79 Msun
Distance19.8 parsecs (~64.5 light-years)
Discovery2005, radial velocity, transit confirmed shortly after

A hot Jupiter studied longer than almost any other

HD 189733 b's brightness and proximity (under 65 light-years away) have made it one of the single most observed exoplanets since its 2005 discovery: it hosts the first exoplanet weather map (Knutson et al., 2007), the first detection of scattered-light Rayleigh haze that gave rise to its "blue planet" reputation (Pont et al., 2013; the color itself was inferred, not directly imaged), and now, with JWST, some of the highest-precision transmission spectra obtained for any exoplanet.

The data behind this report comes from a JWST NIRCam study reporting a metal-enriched atmosphere with a detection of hydrogen sulfide (H2S) — a molecule rarely confirmed in an exoplanet atmosphere — alongside water and carbon dioxide.

Close-up 3D-rendered concept of HD 189733 b's blue, hazy atmosphere

AI-generated 3D-render-style concept of the planet's deep-blue haze layer — not an actual image of the planet.

Spectrum, full models, and ablation sensitivity

The figure compares the reduced NIRCam spectrum with both publication-supplied full-model medians after fitting one vertical offset, shows standardized residuals, and audits the shape mismatch of the supplied cloud-only and molecule-removed medians. The original two-window statistics remain a quick-look diagnostic, not molecule detections.

HD 189733 b JWST NIRCam transmission spectrum with H2O/H2S and CO2 windows highlighted
139 wavelength bins, 2.4-5.0 microns; free and grid retrieval-family products from the frozen Zenodo v1 archive. Generated by scripts/analyze_spectrum.py.
Wavelength bins139
Weighted mean depth24183 ppm
CO2-window contrast (this page)239 ppm (22.1σ)
H2O/H2S-window contrast (this page)255 ppm (24.7σ)
H2O / CO2 / CO / H2S (Fu et al. 2024)13.4σ / 11.2σ / 5σ / 4.5σ
Free full median χ² / dof147.22 / 138
Grid full median χ² / dof172.24 / 138

The supplied full medians describe the spectral shape well: reduced χ² = 1.067 (free) and 1.248 (grid). Removing opacity sources produces Δχ² of 1182–2908 and 1506–3178 relative to those family medians. These are deliberately not translated into significance: the ablation curves are fixed publication products, their parameters are not refitted here, and spectral covariance is unavailable. Fu et al. (2024)'s full retrieval provides the molecule-level results: H2O 13.4σ, CO2 11.2σ, CO 5σ, H2S 4.5σ.

Data and method notes

System parameters come from the NASA Exoplanet Archive. The spectrum and 12 model curves are pinned from Zenodo v1 (record 10.5281/zenodo.11459715; archive MD5 documented in SOURCE.md). See the analysis, model-comparison CSV, and structured summary. scripts/validate_data.py checks the committed subset identity.

AI-generated illustration of the James Webb Space Telescope

AI-generated illustration of the James Webb Space Telescope, whose NIRCam instrument took the real spectrum used in this report. Not an official mission photograph — see NASA/JWST for real imagery.

References

  1. Bouchy, F. et al., 2005. ELODIE metallicity-biased search for transiting Hot Jupiters. II. A very hot Jupiter transiting the bright K star HD 189733. Astronomy & Astrophysics, 444(1), pp.L15-L19.
  2. Knutson, H.A. et al., 2007. A map of the day-night contrast of the extrasolar planet HD 189733b. Nature, 447, pp.183-186.
  3. Pont, F. et al., 2013. The prevalence of dust on the exoplanet HD 189733b from Hubble Space Telescope camera spectroscopy. Monthly Notices of the Royal Astronomical Society, 432(4), pp.2917-2944.
  4. Fu, G. et al., 2024. Hydrogen sulfide and metal-enriched atmosphere for a Jupiter-mass exoplanet. Nature, 632, pp.752-757 (arXiv:2407.06163) — source of the spectrum and the retrieval significances quoted above.
  5. Zenodo record 10.5281/zenodo.11459715, "Products for 'Hydrogen sulfide and metal-enriched atmosphere for a Jupiter-mass exoplanet.'"
  6. NASA Exoplanet Archive, exoplanetarchive.ipac.caltech.edu.