Kepler-139 d
Astrophysical Synthesis & Habitability Characterization
Kepler-139 d is a confirmed super-earth exoplanet orbiting the star Kepler-139, located approximately 1275.4 light-years (391.04 parsecs) from the Solar System. First announced in 2023 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0221% across the stellar disk), this world measures 1.695 Earth radii and has a measured mass of 2 Earth masses. Combining its mass and radius yields a mean bulk density of 2.26 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 0.7 g⊕ (6.86 m/s²), and an escape velocity of 12.2 km/s.
In its orbital architecture around Kepler-139, Kepler-139 d completes one full revolution every 7.306 Earth days at a semi-major axis of 0.075553 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 112.5 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 972 K (+699°C / +1290°F) and receiving 172.30 S⊕ (~234,500 W/m²), Kepler-139 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-139 is classified as a stellar host with an effective photospheric temperature of 5,622 K, a radius of 1.045 R☉, a mass of 1.078 M☉, an estimated bolometric luminosity of 0.979 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 d sharing its stellar neighborhood alongside Kepler-139 b, Kepler-139 c, 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) | 5,622 K |
| Stellar Radius | 1.0450 R☉ |
| Stellar Mass | 1.0780 M☉ |
| Bolometric Luminosity | 0.979 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) | 0.075553 AU |
| Orbital Period | 7.306 days |
| Mean Orbital Velocity | 112.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.9700° |
| Mean Bulk Density | 2.26 g/cm³ (12.2 km/s vesc) |
| Insolation Flux | 172.3000 S⊕ (~234,500 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1275.400 LY (391.038 pc) |