Kepler-307 c
Astrophysical Synthesis & Habitability Characterization
Kepler-307 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-307, located approximately 1877.3 light-years (575.58 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0614% across the stellar disk), this world measures 2.2 Earth radii and has a measured mass of 3.64 Earth masses. Combining its mass and radius yields a mean bulk density of 1.88 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 14.4 km/s.
In its orbital architecture around Kepler-307, Kepler-307 c completes one full revolution every 13.073 Earth days at a semi-major axis of 0.10896 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 90.7 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 739 K (+466°C / +871°F) and receiving 44.00 S⊕ (~59,884 W/m²), Kepler-307 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-307 is classified as a stellar host with an effective photospheric temperature of 5,367 K, a radius of 0.814 R☉, a mass of 0.907 M☉, an estimated bolometric luminosity of 0.493 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.95 Gyr and a metallicity of [Fe/H] = 0.19 dex (metal-rich relative to the Sun). From Earth, Kepler-307 shines at apparent V-band magnitude 14.149 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-307 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-307 c sharing its stellar neighborhood alongside Kepler-307 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-307 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,367 K |
| Stellar Radius | 0.8140 R☉ |
| Stellar Mass | 0.9070 M☉ |
| Bolometric Luminosity | 0.493 L☉ |
| Metallicity [Fe/H] | 0.190 dex |
| Stellar Age | 0.950 Gyr |
| Apparent Magnitude | V: 14.149 · G: 14.056 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.108960 AU |
| Orbital Period | 13.073 days |
| Mean Orbital Velocity | 90.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.3700° |
| Mean Bulk Density | 1.88 g/cm³ (14.4 km/s vesc) |
| Insolation Flux | 44.0000 S⊕ (~59,884 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1877.300 LY (575.581 pc) |