HD 149026 b
Astrophysical Synthesis & Habitability Characterization
HD 149026 b is a confirmed gas giant exoplanet orbiting the star HD 149026, located approximately 247.4 light-years (75.86 parsecs) from the Solar System. First announced in 2005 by Subaru Telescope using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 8.295 Earth radii (0.74 Jupiter radii) and has a measured mass of 120.775 Earth masses (0.38 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.17 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.76 g⊕ (17.26 m/s²), and an escape velocity of 42.7 km/s.
In its orbital architecture around HD 149026, HD 149026 b completes one full revolution every 2.876 Earth days at a semi-major axis of 0.04364 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 165.1 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 1626 K (+1353°C / +2467°F) and receiving 1,095.91 S⊕ (~1,491,534 W/m²), HD 149026 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 149026 is classified as a solar-type yellow star of spectral type G0 with an effective photospheric temperature of 6,179 K, a radius of 1.41 R☉, a mass of 1.42 M☉, an estimated bolometric luminosity of 2.6 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.6 Gyr and a metallicity of [Fe/H] = 0.32 dex (metal-rich relative to the Sun). From Earth, HD 149026 shines at apparent V-band magnitude 8.15 (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: Subaru Telescope · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 149026 |
| Spectral Type | G0 |
| Effective Temp (Teff) | 6,179 K |
| Stellar Radius | 1.4100 R☉ |
| Stellar Mass | 1.4200 M☉ |
| Bolometric Luminosity | 2.6 L☉ |
| Metallicity [Fe/H] | 0.320 dex |
| Stellar Age | 2.600 Gyr |
| Apparent Magnitude | V: 8.150 · G: 8.014 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.043640 AU |
| Orbital Period | 2.876 days |
| Mean Orbital Velocity | 165.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 84.5500° |
| Mean Bulk Density | 1.17 g/cm³ (42.7 km/s vesc) |
| Insolation Flux | 1095.9100 S⊕ (~1,491,534 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 247.400 LY (75.864 pc) |