Kepler-139 c
Astrophysical Synthesis & Habitability Characterization
Kepler-139 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-139, located approximately 1275.4 light-years (391.04 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0568% across the stellar disk), this world measures 3.38 Earth radii (0.3 Jupiter radii) and has a measured mass of 13 Earth masses. Combining its mass and radius yields a mean bulk density of 1.86 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.14 g⊕ (11.18 m/s²), and an escape velocity of 21.9 km/s.
In its orbital architecture around Kepler-139, Kepler-139 c completes one full revolution every 157.073 Earth days at a semi-major axis of 0.586 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 40.6 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.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 3.380 R⊕, Kepler-139 c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star Kepler-139 is classified as a stellar host with an effective photospheric temperature of 5,594 K, a radius of 1.3 R☉, a mass of 1.078 M☉, an estimated bolometric luminosity of 1.485 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.1 Gyr and a metallicity of [Fe/H] = 0.35 dex (metal-rich relative to the Sun). From Earth, Kepler-139 shines at apparent V-band magnitude 12.775 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-139 system is a multi-planet architecture hosting 5 confirmed worlds, with Kepler-139 c sharing its stellar neighborhood alongside Kepler-139 d, Kepler-139 b, Kepler-139 f, Kepler-139 e.
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-139 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,594 K |
| Stellar Radius | 1.3000 R☉ |
| Stellar Mass | 1.0780 M☉ |
| Bolometric Luminosity | 1.485 L☉ |
| Metallicity [Fe/H] | 0.350 dex |
| Stellar Age | 5.100 Gyr |
| Apparent Magnitude | V: 12.775 · G: 12.677 |
| System Architecture | 1 Star, 5 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.586000 AU |
| Orbital Period | 157.073 days |
| Mean Orbital Velocity | 40.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 90.0000° |
| Mean Bulk Density | 1.86 g/cm³ (21.9 km/s vesc) |
| Insolation Flux | 3.0230 S⊕ (~4,114 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1275.400 LY (391.038 pc) |