Kepler-1239 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1239 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1239, located approximately 6981.7 light-years (2140.6 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0287% across the stellar disk), this world measures 2.9 Earth radii and has a measured mass of 8.75 Earth masses. Combining its mass and radius yields a mean bulk density of 1.98 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.4 km/s.
In its orbital architecture around Kepler-1239, Kepler-1239 b completes one full revolution every 5.191 Earth days at a semi-major axis of 0.0625 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 131 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 1183 K (+910°C / +1670°F) and receiving 462.91 S⊕ (~630,021 W/m²), Kepler-1239 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1239 is classified as a stellar host with an effective photospheric temperature of 6,564 K, a radius of 1.57 R☉, a mass of 1.4 M☉, an estimated bolometric luminosity of 4.105 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.62 Gyr and a metallicity of [Fe/H] = 0.22 dex (metal-rich relative to the Sun). From Earth, Kepler-1239 shines at apparent V-band magnitude 15.391 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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-1239 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,564 K |
| Stellar Radius | 1.5700 R☉ |
| Stellar Mass | 1.4000 M☉ |
| Bolometric Luminosity | 4.105 L☉ |
| Metallicity [Fe/H] | 0.220 dex |
| Stellar Age | 1.620 Gyr |
| Apparent Magnitude | V: 15.391 · G: 15.395 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.062500 AU |
| Orbital Period | 5.191 days |
| Mean Orbital Velocity | 131 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3000° |
| Mean Bulk Density | 1.98 g/cm³ (19.4 km/s vesc) |
| Insolation Flux | 462.9100 S⊕ (~630,021 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 6981.700 LY (2140.600 pc) |