Kepler-378 b
Astrophysical Synthesis & Habitability Characterization
Kepler-378 b is a confirmed sub-earth exoplanet orbiting the star Kepler-378, located approximately 496.1 light-years (152.09 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0105% across the stellar disk), this world measures 0.75 Earth radii and has a measured mass of 0.347 Earth masses. Combining its mass and radius yields a mean bulk density of 4.54 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.62 g⊕ (6.08 m/s²), and an escape velocity of 7.6 km/s.
In its orbital architecture around Kepler-378, Kepler-378 b completes one full revolution every 16.092 Earth days at a semi-major axis of 0.112 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 75.7 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 503 K (+230°C / +446°F) and receiving 17.82 S⊕ (~24,252 W/m²), Kepler-378 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-378 is classified as a stellar host with an effective photospheric temperature of 4,661 K, a radius of 0.671 R☉, a mass of 0.78 M☉, an estimated bolometric luminosity of 0.191 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.24 Gyr and a metallicity of [Fe/H] = 0.137 dex (metal-rich relative to the Sun). From Earth, Kepler-378 shines at apparent V-band magnitude 12.619 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-378 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-378 b sharing its stellar neighborhood alongside Kepler-378 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-378 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,661 K |
| Stellar Radius | 0.6710 R☉ |
| Stellar Mass | 0.7800 M☉ |
| Bolometric Luminosity | 0.191 L☉ |
| Metallicity [Fe/H] | 0.137 dex |
| Stellar Age | 3.240 Gyr |
| Apparent Magnitude | V: 12.619 · G: 12.455 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.112000 AU |
| Orbital Period | 16.092 days |
| Mean Orbital Velocity | 75.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.6900° |
| Mean Bulk Density | 4.54 g/cm³ (7.6 km/s vesc) |
| Insolation Flux | 17.8190 S⊕ (~24,252 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 496.100 LY (152.094 pc) |