Kepler-256 e
Astrophysical Synthesis & Habitability Characterization
Kepler-256 e is a confirmed sub-neptune exoplanet orbiting the star Kepler-256, located approximately 3347.8 light-years (1026.43 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0274% across the stellar disk), this world measures 2.35 Earth radii and has a measured mass of 6.12 Earth masses. Combining its mass and radius yields a mean bulk density of 2.6 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 18.1 km/s.
In its orbital architecture around Kepler-256, Kepler-256 e completes one full revolution every 10.682 Earth days at a semi-major axis of 0.096 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 97.8 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 897 K (+624°C / +1155°F) and receiving 98.90 S⊕ (~134,603 W/m²), Kepler-256 e orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-256 is classified as a stellar host with an effective photospheric temperature of 5,551 K, a radius of 1.301 R☉, a mass of 1.037 M☉, an estimated bolometric luminosity of 1.442 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.82 Gyr and a metallicity of [Fe/H] = 0.26 dex (metal-rich relative to the Sun). From Earth, Kepler-256 shines at apparent V-band magnitude 15.178 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-256 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-256 e sharing its stellar neighborhood alongside Kepler-256 b, Kepler-256 c, Kepler-256 d.
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-256 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,551 K |
| Stellar Radius | 1.3010 R☉ |
| Stellar Mass | 1.0370 M☉ |
| Bolometric Luminosity | 1.442 L☉ |
| Metallicity [Fe/H] | 0.260 dex |
| Stellar Age | 1.820 Gyr |
| Apparent Magnitude | V: 15.178 · G: 15.015 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.096000 AU |
| Orbital Period | 10.682 days |
| Mean Orbital Velocity | 97.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.9200° |
| Mean Bulk Density | 2.6 g/cm³ (18.1 km/s vesc) |
| Insolation Flux | 98.9000 S⊕ (~134,603 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3347.800 LY (1026.430 pc) |