Kepler-117 c
Astrophysical Synthesis & Habitability Characterization
Kepler-117 c 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 0.4963% across the stellar disk), this world measures 12.341 Earth radii (1.1 Jupiter radii) and has a measured mass of 584.78 Earth masses (1.84 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.72 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.84 g⊕ (37.66 m/s²), and an escape velocity of 77 km/s.
In its orbital architecture around Kepler-117, Kepler-117 c completes one full revolution every 50.79 Earth days at a semi-major axis of 0.2804 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 60.1 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.0323 (ranging from 0.2713 AU at periapsis to 0.2895 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 704 K (+431°C / +808°F) and receiving 41.86 S⊕ (~56,976 W/m²), Kepler-117 c 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 c sharing its stellar neighborhood alongside Kepler-117 b.
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) | 0.280400 AU |
| Orbital Period | 50.79 days |
| Mean Orbital Velocity | 60.1 km/s |
| Orbital Eccentricity (e) | 0.03230 |
| Orbital Inclination (i) | 89.6400° |
| Mean Bulk Density | 1.72 g/cm³ (77 km/s vesc) |
| Insolation Flux | 41.8630 S⊕ (~56,976 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4747.400 LY (1455.570 pc) |