Kepler-418 c
Astrophysical Synthesis & Habitability Characterization
Kepler-418 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-418, located approximately 3269.8 light-years (1002.53 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1961% across the stellar disk), this world measures 5.221 Earth radii (0.47 Jupiter radii) and has a measured mass of 23.7 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 0.87 g⊕ (8.53 m/s²), and an escape velocity of 23.8 km/s.
In its orbital architecture around Kepler-418, Kepler-418 c completes one full revolution every 12.218 Earth days at a semi-major axis of 0.10632 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 94.7 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 835 K (+562°C / +1044°F) and receiving 107.60 S⊕ (~146,444 W/m²), Kepler-418 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-418 is classified as a stellar host with an effective photospheric temperature of 5,822 K, a radius of 1.081 R☉, a mass of 0.957 M☉, an estimated bolometric luminosity of 1.205 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.1 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, Kepler-418 shines at apparent V-band magnitude 14.824 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-418 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-418 c sharing its stellar neighborhood alongside Kepler-418 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-418 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,822 K |
| Stellar Radius | 1.0810 R☉ |
| Stellar Mass | 0.9570 M☉ |
| Bolometric Luminosity | 1.205 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 2.100 Gyr |
| Apparent Magnitude | V: 14.824 · G: 14.649 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.106320 AU |
| Orbital Period | 12.218 days |
| Mean Orbital Velocity | 94.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.1500° |
| Mean Bulk Density | 0.92 g/cm³ (23.8 km/s vesc) |
| Insolation Flux | 107.6000 S⊕ (~146,444 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3269.800 LY (1002.530 pc) |