HD 189733 b
Reference profile for HD 189733 b: 2.22-day orbit, 2.4% transit depth in Vulpecula, atmospheric silicate clouds, and JWST H2S detection.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Distance | 64.5 ly | ± 0.05 ly | Gaia DR3 trigonometric parallax of host star | definitive | ESA Gaia Archive — Data Release 3 |
| Orbital Period | 2.218575 d | ± 0.000001 d | Multi-epoch transit or astrometric orbital fitting | definitive | NASA Exoplanet Archive |
| Semi-Major Axis | 0.03142 AU | ± 0.00052 AU | Keplerian third-law solution from stellar mass and orbital period | definitive | NASA Exoplanet Archive |
| Planetary Mass | 369.6 M⊕ | ± 8 M⊕ | Equivalent to 1.162 ± 0.025 Jupiter masses. | definitive | NASA Exoplanet Archive |
| Planetary Radius | 12.76 R⊕ | ± 0.14 R⊕ | Equivalent to 1.138 ± 0.013 Jupiter radii. | definitive | NASA Exoplanet Archive |
| Equilibrium Temperature | 1201 K | ± 13 K | Radiative equilibrium calculation from bolometric stellar insolation | definitive | NASA Exoplanet Archive |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots HD 189733 b — Cobalt-Blue Hot Jupiter Data at RA 20h 00m 43.71s, Dec +22° 42′ 39.1″ within Vulpecula, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Discovered in October 2005 by a French-led consortium monitoring radial velocities and photometric transits at Haute-Provence Observatory, HD 189733 b quickly became one of the two most intensively studied hot Jupiters in the sky. Because it orbits a relatively compact K2V orange dwarf just 64.5 light-years away, its 1.14-Jupiter-radius silhouette blocks an extraordinary 2.4 percent of the star's light during each 1.8-hour transit—producing the largest atmospheric transmission signal of any nearby gas giant.
In 2007, Spitzer Space Telescope infrared phase curves mapped the first thermal weather chart of an extrasolar world on HD 189733 b, revealing a hot spot displaced 16 to 30 degrees east of the substellar point by an equatorial super-rotating jet blowing at over 7,000 kilometers per hour. Hubble Space Telescope optical albedo measurements showed that the planet reflects blue light far more strongly than red, a signature of high-altitude silicate (glass) condensates scattering starlight. More recently, JWST NIRCam transmission spectra detected water, carbon dioxide, carbon monoxide, and the first definitive hydrogen sulfide (H₂S) signature outside the Solar System.
Positioned just 0.3 degrees east of the Dumbbell Nebula (M27) in Vulpecula, the host star shines at visual magnitude 7.67. Its 0.028-magnitude transit dip is deep enough that well-calibrated backyard CCD or CMOS setups on 4-inch to 8-inch telescopes routinely record high-precision transit light curves.
Practical Visual Observing Guide
- Located just 20 arcminutes east of M27 (Dumbbell Nebula) in Vulpecula; host star shines at V = 7.67.
- Produces a 2.4% (~0.028 mag) transit dip lasting 110 minutes every 2.2186 days—one of the easiest exoplanet transits for amateur astrophotographers.
- Exhibits a large radial velocity semi-amplitude of ~202 m/s.
Catalog Cross-Identifications & Aliases
Common Aliases: HD 189733 A b · HD 189733b · HIP 98505 b
| Catalog Authority | Identifier |
|---|---|
| NASAEXOPLANET | HD 189733 b |
| SIMBAD | HD 189733 b |
Related Objects, Comparisons & Guides
HD 209458 b (Osiris First Transiting Planet)
Coordinates, Gaia DR3 distance (48.3 pc), 3.5247-day transit period, 1.359 R♃ inflated radius, and atmospheric escape data for HD 209458 b.
51 Pegasi b (Dimidium First Hot Jupiter)
Coordinates, Gaia DR3 distance (15.46 pc), 4.2308-day orbital period, Nobel-winning radial-velocity discovery, and observing guide for 51 Pegasi b.
WASP-76 b — Molten-Iron-Rain Ultra-Hot Jupiter
Reference data for WASP-76 b: 1.85 Jupiter radii, 1.81-day orbit in Pisces, ESPRESSO iron-condensation asymmetry, and glory effect studies.
Exoplanet Transit & Radial Velocity Methods
How astronomers detect and characterize exoplanets using photometric transit depth ((Rp/R*)²), Doppler radial velocity (M sin i), and JWST transmission spectra.
Apparent vs Absolute Magnitude Explained
Understand the logarithmic Pogson astronomical magnitude scale, apparent visual magnitude (m), absolute magnitude (M at 10 parsecs), and bolometric corrections.
Scientific Sources & Dataset Provenance
- NASA Exoplanet Archive (2026-10-01 snapshot): Akeson, R. L., et al. 2013, PASP, 125, 989; NASA Exoplanet Archive (IPAC/Caltech) — NASA Exoplanet Science Institute (NExScI / Caltech / IPAC)
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC