Kepler-426 b
Astrophysical Synthesis & Habitability Characterization
Kepler-426 b is a confirmed gas giant exoplanet orbiting the star Kepler-426, located approximately 2751.8 light-years (843.7 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 1.4829% across the stellar disk), this world measures 12.22 Earth radii (1.09 Jupiter radii) and has a measured mass of 108.06 Earth masses (0.34 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.33 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.72 g⊕ (7.06 m/s²), and an escape velocity of 33.3 km/s.
In its orbital architecture around Kepler-426, Kepler-426 b completes one full revolution every 3.218 Earth days at a semi-major axis of 0.0414 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 140 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.18 carries the world between 0.0339 AU at periapsis and 0.0489 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1300 K (+1027°C / +1881°F) and receiving 410.72 S⊕ (~558,994 W/m²), Kepler-426 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-426 is classified as a solar-type yellow star of spectral type G1 V with an effective photospheric temperature of 5,725 K, a radius of 0.92 R☉, a mass of 0.91 M☉, an estimated bolometric luminosity of 0.816 L☉. Stellar evolution modeling indicates an estimated stellar age of 6 Gyr and a metallicity of [Fe/H] = -0.21 dex (metal-poor relative to the Sun). From Earth, Kepler-426 shines at apparent V-band magnitude 15.032 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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-426 |
| Spectral Type | G1 V |
| Effective Temp (Teff) | 5,725 K |
| Stellar Radius | 0.9200 R☉ |
| Stellar Mass | 0.9100 M☉ |
| Bolometric Luminosity | 0.816 L☉ |
| Metallicity [Fe/H] | -0.210 dex |
| Stellar Age | 6.000 Gyr |
| Apparent Magnitude | V: 15.032 · G: 14.807 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041400 AU |
| Orbital Period | 3.218 days |
| Mean Orbital Velocity | 140 km/s |
| Orbital Eccentricity (e) | 0.18000 |
| Orbital Inclination (i) | 85.7400° |
| Mean Bulk Density | 0.33 g/cm³ (33.3 km/s vesc) |
| Insolation Flux | 410.7230 S⊕ (~558,994 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2751.800 LY (843.695 pc) |