Kepler-318 b
Astrophysical Synthesis & Habitability Characterization
Kepler-318 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-318, located approximately 1595.4 light-years (489.14 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1319% across the stellar disk), this world measures 4.71 Earth radii (0.42 Jupiter radii) and has a measured mass of 19.9 Earth masses. Combining its mass and radius yields a mean bulk density of 1.05 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.9 g⊕ (8.83 m/s²), and an escape velocity of 23 km/s.
In its orbital architecture around Kepler-318, Kepler-318 b completes one full revolution every 4.663 Earth days at a semi-major axis of 0.056 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 130.7 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 1039 K (+766°C / +1411°F) and receiving 333.15 S⊕ (~453,416 W/m²), Kepler-318 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-318 is classified as a stellar host with an effective photospheric temperature of 5,746 K, a radius of 1.189 R☉, a mass of 1.073 M☉, an estimated bolometric luminosity of 1.383 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.95 Gyr and a metallicity of [Fe/H] = 0.332 dex (metal-rich relative to the Sun). From Earth, Kepler-318 shines at apparent V-band magnitude 13.442 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-318 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-318 b sharing its stellar neighborhood alongside Kepler-318 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-318 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,746 K |
| Stellar Radius | 1.1890 R☉ |
| Stellar Mass | 1.0730 M☉ |
| Bolometric Luminosity | 1.383 L☉ |
| Metallicity [Fe/H] | 0.332 dex |
| Stellar Age | 0.950 Gyr |
| Apparent Magnitude | V: 13.442 · G: 13.281 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.056000 AU |
| Orbital Period | 4.663 days |
| Mean Orbital Velocity | 130.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.6600° |
| Mean Bulk Density | 1.05 g/cm³ (23 km/s vesc) |
| Insolation Flux | 333.1490 S⊕ (~453,416 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1595.400 LY (489.141 pc) |