Kepler-425 b
Astrophysical Synthesis & Habitability Characterization
Kepler-425 b is a confirmed gas giant exoplanet orbiting the star Kepler-425, located approximately 2109.1 light-years (646.65 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 1.3656% across the stellar disk), this world measures 10.962 Earth radii (0.98 Jupiter radii) and has a measured mass of 79.45 Earth masses (0.25 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 0.66 g⊕ (6.47 m/s²), and an escape velocity of 30.1 km/s.
In its orbital architecture around Kepler-425, Kepler-425 b completes one full revolution every 3.797 Earth days at a semi-major axis of 0.0464 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 132.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.33, swinging from 0.0311 AU at periapsis out to 0.0617 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1070 K (+797°C / +1467°F) and receiving 229.04 S⊕ (~311,718 W/m²), Kepler-425 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-425 is classified as an orange K-type star of spectral type K1 V with an effective photospheric temperature of 5,170 K, a radius of 0.86 R☉, a mass of 0.93 M☉, an estimated bolometric luminosity of 0.474 L☉. Stellar evolution modeling indicates an estimated stellar age of 5 Gyr and a metallicity of [Fe/H] = 0.24 dex (metal-rich relative to the Sun). From Earth, Kepler-425 shines at apparent V-band magnitude 14.845 (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-425 |
| Spectral Type | K1 V |
| Effective Temp (Teff) | 5,170 K |
| Stellar Radius | 0.8600 R☉ |
| Stellar Mass | 0.9300 M☉ |
| Bolometric Luminosity | 0.474 L☉ |
| Metallicity [Fe/H] | 0.240 dex |
| Stellar Age | 5.000 Gyr |
| Apparent Magnitude | V: 14.845 · G: 14.730 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.046400 AU |
| Orbital Period | 3.797 days |
| Mean Orbital Velocity | 132.9 km/s |
| Orbital Eccentricity (e) | 0.33000 |
| Orbital Inclination (i) | 87.0200° |
| Mean Bulk Density | 0.33 g/cm³ (30.1 km/s vesc) |
| Insolation Flux | 229.0360 S⊕ (~311,718 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2109.100 LY (646.647 pc) |