Kepler-436 c
Astrophysical Synthesis & Habitability Characterization
Kepler-436 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-436, located approximately 1920.6 light-years (588.87 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0905% across the stellar disk), this world measures 2.33 Earth radii and has a measured mass of 6.04 Earth masses. Combining its mass and radius yields a mean bulk density of 2.63 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.11 g⊕ (10.89 m/s²), and an escape velocity of 18 km/s.
In its orbital architecture around Kepler-436, Kepler-436 c completes one full revolution every 16.797 Earth days at a semi-major axis of 0.11452 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 74.2 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 503 K (+230°C / +446°F) and receiving 14.52 S⊕ (~19,762 W/m²), Kepler-436 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-436 is classified as a stellar host with an effective photospheric temperature of 4,685 K, a radius of 0.71 R☉, a mass of 0.75 M☉, an estimated bolometric luminosity of 0.218 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.07 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-436 shines at apparent V-band magnitude 15.971 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-436 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-436 c sharing its stellar neighborhood alongside Kepler-436 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-436 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,685 K |
| Stellar Radius | 0.7100 R☉ |
| Stellar Mass | 0.7500 M☉ |
| Bolometric Luminosity | 0.218 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 4.070 Gyr |
| Apparent Magnitude | V: 15.971 · G: 15.862 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.114520 AU |
| Orbital Period | 16.797 days |
| Mean Orbital Velocity | 74.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.0200° |
| Mean Bulk Density | 2.63 g/cm³ (18 km/s vesc) |
| Insolation Flux | 14.5200 S⊕ (~19,762 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1920.600 LY (588.867 pc) |