Kepler-109 c
Astrophysical Synthesis & Habitability Characterization
Kepler-109 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-109, located approximately 1548.8 light-years (474.86 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0307% across the stellar disk), this world measures 2.65 Earth radii and has a measured mass of 8.2 Earth masses. Combining its mass and radius yields a mean bulk density of 2.43 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.17 g⊕ (11.47 m/s²), and an escape velocity of 19.7 km/s.
In its orbital architecture around Kepler-109, Kepler-109 c completes one full revolution every 21.223 Earth days at a semi-major axis of 0.1546 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 79.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.098 carries the world between 0.1394 AU at periapsis and 0.1698 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 859 K (+586°C / +1087°F) and receiving 91.00 S⊕ (~123,851 W/m²), Kepler-109 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-109 is classified as a stellar host with an effective photospheric temperature of 5,950 K, a radius of 1.387 R☉, a mass of 1.094 M☉, an estimated bolometric luminosity of 2.163 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.2 Gyr and a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-109 shines at apparent V-band magnitude 12.398 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-109 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-109 c sharing its stellar neighborhood alongside Kepler-109 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-109 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,950 K |
| Stellar Radius | 1.3870 R☉ |
| Stellar Mass | 1.0940 M☉ |
| Bolometric Luminosity | 2.163 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | 6.200 Gyr |
| Apparent Magnitude | V: 12.398 · G: 12.296 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.154600 AU |
| Orbital Period | 21.223 days |
| Mean Orbital Velocity | 79.3 km/s |
| Orbital Eccentricity (e) | 0.09800 |
| Orbital Inclination (i) | 89.6300° |
| Mean Bulk Density | 2.43 g/cm³ (19.7 km/s vesc) |
| Insolation Flux | 91.0000 S⊕ (~123,851 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1548.800 LY (474.861 pc) |