HD 117207 b
Astrophysical Synthesis & Habitability Characterization
HD 117207 b is a confirmed gas giant exoplanet orbiting the star HD 117207, located approximately 105.5 light-years (32.36 parsecs) from the Solar System. First announced in 2004 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 13.4 Earth radii (1.2 Jupiter radii) and has a measured mass of 669.347 Earth masses (2.11 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.53 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.73 g⊕ (36.58 m/s²), and an escape velocity of 79.1 km/s.
In its orbital architecture around HD 117207, HD 117207 b completes one full revolution every 2621.75 Earth days (7.18Julian years) at a semi-major axis of 3.787 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 15.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.157 carries the world between 3.1924 AU at periapsis and 4.3816 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 147 K (-126°C / -195°F) and an incident flux of 0.08 S⊕ (~110 W/m²), surface water and volatile species on HD 117207 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 117207 is classified as a solar-type yellow star of spectral type G7 IV-V with an effective photospheric temperature of 5,732 K, a radius of 1.074 R☉, a mass of 1.053 M☉, an estimated bolometric luminosity of 1.117 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.192 Gyr and a metallicity of [Fe/H] = 0.19 dex (metal-rich relative to the Sun). From Earth, HD 117207 shines at apparent V-band magnitude 7.26 (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 117207 |
| Spectral Type | G7 IV-V |
| Effective Temp (Teff) | 5,732 K |
| Stellar Radius | 1.0740 R☉ |
| Stellar Mass | 1.0530 M☉ |
| Bolometric Luminosity | 1.117 L☉ |
| Metallicity [Fe/H] | 0.190 dex |
| Stellar Age | 4.192 Gyr |
| Apparent Magnitude | V: 7.260 · G: 7.077 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.787000 AU |
| Orbital Period | 2621.75 days |
| Mean Orbital Velocity | 15.7 km/s |
| Orbital Eccentricity (e) | 0.15700 |
| Orbital Inclination (i) | 76.6000° |
| Mean Bulk Density | 1.53 g/cm³ (79.1 km/s vesc) |
| Insolation Flux | 0.0811 S⊕ (~110 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 105.500 LY (32.355 pc) |