Kepler-305 c
Astrophysical Synthesis & Habitability Characterization
Kepler-305 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-305, located approximately 2832.6 light-years (868.48 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.143% across the stellar disk), this world measures 3.3 Earth radii (0.29 Jupiter radii) and has a measured mass of 6 Earth masses. Combining its mass and radius yields a mean bulk density of 0.92 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.55 g⊕ (5.39 m/s²), and an escape velocity of 15.1 km/s.
In its orbital architecture around Kepler-305, Kepler-305 c completes one full revolution every 8.291 Earth days at a semi-major axis of 0.07568 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 99.3 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 728 K (+455°C / +851°F) and receiving 65.10 S⊕ (~88,601 W/m²), Kepler-305 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-305 is classified as a stellar host with an effective photospheric temperature of 5,080 K, a radius of 0.8 R☉, a mass of 0.76 M☉, an estimated bolometric luminosity of 0.382 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.37 Gyr and a metallicity of [Fe/H] = 0.09 dex (metal-rich relative to the Sun). From Earth, Kepler-305 shines at apparent V-band magnitude 15.851 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-305 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-305 c sharing its stellar neighborhood alongside Kepler-305 e, Kepler-305 b, Kepler-305 d.
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-305 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,080 K |
| Stellar Radius | 0.8000 R☉ |
| Stellar Mass | 0.7600 M☉ |
| Bolometric Luminosity | 0.382 L☉ |
| Metallicity [Fe/H] | 0.090 dex |
| Stellar Age | 4.370 Gyr |
| Apparent Magnitude | V: 15.851 · G: 15.766 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.075680 AU |
| Orbital Period | 8.291 days |
| Mean Orbital Velocity | 99.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 83.4500° |
| Mean Bulk Density | 0.92 g/cm³ (15.1 km/s vesc) |
| Insolation Flux | 65.1000 S⊕ (~88,601 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2832.600 LY (868.477 pc) |