HD 189733 b
Astrophysical Synthesis & Habitability Characterization
HD 189733 b is a confirmed gas giant exoplanet orbiting the star HD 189733, located approximately 64.5 light-years (19.76 parsecs) from the Solar System. First announced in 2005 by Haute-Provence Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.666 Earth radii (1.13 Jupiter radii) and has a measured mass of 359.148 Earth masses (1.13 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.97 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.24 g⊕ (21.97 m/s²), and an escape velocity of 59.6 km/s.
In its orbital architecture around HD 189733, HD 189733 b completes one full revolution every 2.219 Earth days at a semi-major axis of 0.03126 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 153.3 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1209 K (+936°C / +1717°F) and receiving 356.00 S⊕ (~484,516 W/m²), HD 189733 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 189733 is classified as an orange K-type star of spectral type K2 V with an effective photospheric temperature of 5,052 K, a radius of 0.75 R☉, a mass of 0.79 M☉, an estimated bolometric luminosity of 0.329 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.4 Gyr and a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, HD 189733 shines at apparent V-band magnitude 7.67 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: Haute-Provence Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 189733 |
| Spectral Type | K2 V |
| Effective Temp (Teff) | 5,052 K |
| Stellar Radius | 0.7500 R☉ |
| Stellar Mass | 0.7900 M☉ |
| Bolometric Luminosity | 0.329 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | 1.400 Gyr |
| Apparent Magnitude | V: 7.670 · G: 7.414 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.031260 AU |
| Orbital Period | 2.219 days |
| Mean Orbital Velocity | 153.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 85.7100° |
| Mean Bulk Density | 0.97 g/cm³ (59.6 km/s vesc) |
| Insolation Flux | 356.0000 S⊕ (~484,516 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 64.500 LY (19.764 pc) |