Kepler-381 b
Astrophysical Synthesis & Habitability Characterization
Kepler-381 b is a confirmed terrestrial exoplanet orbiting the star Kepler-381, located approximately 871.9 light-years (267.32 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0034% across the stellar disk), this world measures 0.99 Earth radii and has a measured mass of 0.937 Earth masses. Combining its mass and radius yields a mean bulk density of 5.32 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.96 g⊕ (9.41 m/s²), and an escape velocity of 10.9 km/s.
In its orbital architecture around Kepler-381, Kepler-381 b completes one full revolution every 5.629 Earth days at a semi-major axis of 0.066 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 127.6 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 1576 K (+1303°C / +2377°F) and receiving 716.09 S⊕ (~974,592 W/m²), Kepler-381 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-381 is classified as a stellar host with an effective photospheric temperature of 6,152 K, a radius of 1.568 R☉, a mass of 1.144 M☉, an estimated bolometric luminosity of 3.16 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.57 Gyr and a metallicity of [Fe/H] = -0.202 dex (metal-poor relative to the Sun). From Earth, Kepler-381 shines at apparent V-band magnitude 10.47 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-381 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-381 b sharing its stellar neighborhood alongside Kepler-381 d, Kepler-381 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-381 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,152 K |
| Stellar Radius | 1.5680 R☉ |
| Stellar Mass | 1.1440 M☉ |
| Bolometric Luminosity | 3.16 L☉ |
| Metallicity [Fe/H] | -0.202 dex |
| Stellar Age | 2.570 Gyr |
| Apparent Magnitude | V: 10.470 · G: 10.546 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.066000 AU |
| Orbital Period | 5.629 days |
| Mean Orbital Velocity | 127.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.8000° |
| Mean Bulk Density | 5.32 g/cm³ (10.9 km/s vesc) |
| Insolation Flux | 716.0850 S⊕ (~974,592 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 871.900 LY (267.323 pc) |