Kepler-1399 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1399 b is a confirmed terrestrial exoplanet orbiting the star Kepler-1399, located approximately 4519.5 light-years (1385.7 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0143% across the stellar disk), this world measures 1.25 Earth radii and has a measured mass of 2.1 Earth masses. Combining its mass and radius yields a mean bulk density of 5.93 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.34 g⊕ (13.14 m/s²), and an escape velocity of 14.5 km/s.
In its orbital architecture around Kepler-1399, Kepler-1399 b completes one full revolution every 1.639 Earth days at a semi-major axis of 0.0276 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 183.2 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 1610 K (+1337°C / +2439°F) and receiving 1,707.25 S⊕ (~2,323,570 W/m²), Kepler-1399 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1399 is classified as a stellar host with an effective photospheric temperature of 5,735 K, a radius of 0.96 R☉, a mass of 0.97 M☉, an estimated bolometric luminosity of 0.894 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.37 Gyr and a metallicity of [Fe/H] = -0.03 dex (near-solar heavy-element abundance). From Earth, Kepler-1399 shines at apparent V-band magnitude 15.572 (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-1399 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,735 K |
| Stellar Radius | 0.9600 R☉ |
| Stellar Mass | 0.9700 M☉ |
| Bolometric Luminosity | 0.894 L☉ |
| Metallicity [Fe/H] | -0.030 dex |
| Stellar Age | 4.370 Gyr |
| Apparent Magnitude | V: 15.572 · G: 15.507 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.027600 AU |
| Orbital Period | 1.639 days |
| Mean Orbital Velocity | 183.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.5600° |
| Mean Bulk Density | 5.93 g/cm³ (14.5 km/s vesc) |
| Insolation Flux | 1707.2520 S⊕ (~2,323,570 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4519.500 LY (1385.700 pc) |