HD 102117 b
Astrophysical Synthesis & Habitability Characterization
HD 102117 b is a confirmed gas giant exoplanet orbiting the star HD 102117, located approximately 129.1 light-years (39.58 parsecs) from the Solar System. First announced in 2005 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 8.47 Earth radii (0.76 Jupiter radii) and has a measured mass of 54.031 Earth masses (0.17 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.49 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.75 g⊕ (7.35 m/s²), and an escape velocity of 28.3 km/s.
In its orbital architecture around HD 102117, HD 102117 b completes one full revolution every 20.813 Earth days at a semi-major axis of 0.15 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 78.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 0.132 AU at periapsis and 0.168 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 781 K (+508°C / +946°F) and receiving 63.85 S⊕ (~86,905 W/m²), HD 102117 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 102117 is classified as a solar-type yellow star of spectral type G6 V with an effective photospheric temperature of 5,655 K, a radius of 1.23 R☉, a mass of 1.06 M☉, an estimated bolometric luminosity of 1.388 L☉. Stellar evolution modeling indicates an estimated stellar age of 10 Gyr and a metallicity of [Fe/H] = 0.28 dex (metal-rich relative to the Sun). From Earth, HD 102117 shines at apparent V-band magnitude 7.47 (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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 102117 |
| Spectral Type | G6 V |
| Effective Temp (Teff) | 5,655 K |
| Stellar Radius | 1.2300 R☉ |
| Stellar Mass | 1.0600 M☉ |
| Bolometric Luminosity | 1.388 L☉ |
| Metallicity [Fe/H] | 0.280 dex |
| Stellar Age | 10.000 Gyr |
| Apparent Magnitude | V: 7.470 · G: 7.282 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.150000 AU |
| Orbital Period | 20.813 days |
| Mean Orbital Velocity | 78.4 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.49 g/cm³ (28.3 km/s vesc) |
| Insolation Flux | 63.8539 S⊕ (~86,905 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 129.100 LY (39.579 pc) |