Kepler-117 b
Astrophysical Synthesis & Habitability Characterization
Kepler-117 b is a confirmed gas giant exoplanet orbiting the star Kepler-117, located approximately 4747.4 light-years (1455.57 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2116% across the stellar disk), this world measures 8.059 Earth radii (0.72 Jupiter radii) and has a measured mass of 29.875 Earth masses. Combining its mass and radius yields a mean bulk density of 0.31 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.46 g⊕ (4.51 m/s²), and an escape velocity of 21.5 km/s.
In its orbital architecture around Kepler-117, Kepler-117 b completes one full revolution every 18.796 Earth days at a semi-major axis of 0.1445 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 83.6 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.0493 (ranging from 0.1374 AU at periapsis to 0.1516 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 984 K (+711°C / +1312°F) and receiving 157.54 S⊕ (~214,413 W/m²), Kepler-117 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-117 is classified as a warm F-type star of spectral type F8 V with an effective photospheric temperature of 6,150 K, a radius of 1.606 R☉, a mass of 1.129 M☉, an estimated bolometric luminosity of 3.31 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.3 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-117 shines at apparent V-band magnitude 14.282 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-117 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-117 b sharing its stellar neighborhood alongside Kepler-117 c.
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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-117 |
| Spectral Type | F8 V |
| Effective Temp (Teff) | 6,150 K |
| Stellar Radius | 1.6060 R☉ |
| Stellar Mass | 1.1290 M☉ |
| Bolometric Luminosity | 3.31 L☉ |
| Metallicity [Fe/H] | -0.040 dex |
| Stellar Age | 5.300 Gyr |
| Apparent Magnitude | V: 14.282 · G: 14.247 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.144500 AU |
| Orbital Period | 18.796 days |
| Mean Orbital Velocity | 83.6 km/s |
| Orbital Eccentricity (e) | 0.04930 |
| Orbital Inclination (i) | 88.7400° |
| Mean Bulk Density | 0.31 g/cm³ (21.5 km/s vesc) |
| Insolation Flux | 157.5410 S⊕ (~214,413 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4747.400 LY (1455.570 pc) |