Kepler-436 b
Astrophysical Synthesis & Habitability Characterization
Kepler-436 b 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 2015 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1289% across the stellar disk), this world measures 2.73 Earth radii and has a measured mass of 7.9 Earth masses. Combining its mass and radius yields a mean bulk density of 2.14 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 19 km/s.
In its orbital architecture around Kepler-436, Kepler-436 b completes one full revolution every 64.002 Earth days at a semi-major axis of 0.339 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 57.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.19 carries the world between 0.2746 AU at periapsis and 0.4034 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.730 R⊕, Kepler-436 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star Kepler-436 is classified as a stellar host with an effective photospheric temperature of 4,651 K, a radius of 0.697 R☉, a mass of 0.729 M☉, an estimated bolometric luminosity of 0.204 L☉. Stellar evolution modeling indicates an estimated stellar age of 3 Gyr and a metallicity of [Fe/H] = 0.01 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 b sharing its stellar neighborhood alongside Kepler-436 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-436 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,651 K |
| Stellar Radius | 0.6970 R☉ |
| Stellar Mass | 0.7290 M☉ |
| Bolometric Luminosity | 0.204 L☉ |
| Metallicity [Fe/H] | 0.010 dex |
| Stellar Age | 3.000 Gyr |
| Apparent Magnitude | V: 15.971 · G: 15.862 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.339000 AU |
| Orbital Period | 64.002 days |
| Mean Orbital Velocity | 57.6 km/s |
| Orbital Eccentricity (e) | 0.19000 |
| Orbital Inclination (i) | 89.9300° |
| Mean Bulk Density | 2.14 g/cm³ (19 km/s vesc) |
| Insolation Flux | 1.6900 S⊕ (~2,300 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1920.600 LY (588.867 pc) |