Kepler-405 c
Astrophysical Synthesis & Habitability Characterization
Kepler-405 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-405, located approximately 3473.8 light-years (1065.08 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2289% across the stellar disk), this world measures 4.66 Earth radii (0.42 Jupiter radii) and has a measured mass of 19.6 Earth masses. Combining its mass and radius yields a mean bulk density of 1.07 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 22.9 km/s.
In its orbital architecture around Kepler-405, Kepler-405 c completes one full revolution every 29.727 Earth days at a semi-major axis of 0.188 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 68.8 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 557 K (+284°C / +543°F) and receiving 14.09 S⊕ (~19,171 W/m²), Kepler-405 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-405 is classified as a stellar host with an effective photospheric temperature of 5,818 K, a radius of 0.893 R☉, a mass of 0.873 M☉, an estimated bolometric luminosity of 0.82 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.09 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, Kepler-405 shines at apparent V-band magnitude 16.181 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-405 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-405 c sharing its stellar neighborhood alongside Kepler-405 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-405 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,818 K |
| Stellar Radius | 0.8930 R☉ |
| Stellar Mass | 0.8730 M☉ |
| Bolometric Luminosity | 0.82 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 2.090 Gyr |
| Apparent Magnitude | V: 16.181 · G: 15.802 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.188000 AU |
| Orbital Period | 29.727 days |
| Mean Orbital Velocity | 68.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.0900° |
| Mean Bulk Density | 1.07 g/cm³ (22.9 km/s vesc) |
| Insolation Flux | 14.0860 S⊕ (~19,171 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3473.800 LY (1065.080 pc) |