HD 109749 b
Astrophysical Synthesis & Habitability Characterization
HD 109749 b is a confirmed gas giant exoplanet orbiting the star HD 109749, located approximately 205.7 light-years (63.08 parsecs) from the Solar System. First announced in 2005 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 11.1 Earth radii (0.99 Jupiter radii) and has a measured mass of 85.814 Earth masses (0.27 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.35 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.7 g⊕ (6.86 m/s²), and an escape velocity of 31.1 km/s.
In its orbital architecture around HD 109749, HD 109749 b completes one full revolution every 5.24 Earth days at a semi-major axis of 0.0615 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 127.7 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 1251 K (+978°C / +1792°F) and receiving 409.50 S⊕ (~557,324 W/m²), HD 109749 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 109749 is classified as a solar-type yellow star of spectral type G3 V with an effective photospheric temperature of 5,824 K, a radius of 1.22 R☉, a mass of 1.13 M☉, an estimated bolometric luminosity of 1.536 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.3 Gyr and a metallicity of [Fe/H] = 0.24 dex (metal-rich relative to the Sun). From Earth, HD 109749 shines at apparent V-band magnitude 8.08 (accessible to binoculars and small amateur telescopes) in the Southern 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 109749 |
| Spectral Type | G3 V |
| Effective Temp (Teff) | 5,824 K |
| Stellar Radius | 1.2200 R☉ |
| Stellar Mass | 1.1300 M☉ |
| Bolometric Luminosity | 1.536 L☉ |
| Metallicity [Fe/H] | 0.240 dex |
| Stellar Age | 3.300 Gyr |
| Apparent Magnitude | V: 8.080 · G: 8.025 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.061500 AU |
| Orbital Period | 5.24 days |
| Mean Orbital Velocity | 127.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.35 g/cm³ (31.1 km/s vesc) |
| Insolation Flux | 409.4961 S⊕ (~557,324 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 205.700 LY (63.082 pc) |