Kepler-1398 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1398 b is a confirmed terrestrial exoplanet orbiting the star Kepler-1398, located approximately 2779.5 light-years (852.2 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0049% across the stellar disk), this world measures 0.9 Earth radii and has a measured mass of 0.666 Earth masses. Combining its mass and radius yields a mean bulk density of 5.04 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.82 g⊕ (8.04 m/s²), and an escape velocity of 9.6 km/s.
In its orbital architecture around Kepler-1398, Kepler-1398 b completes one full revolution every 2.788 Earth days at a semi-major axis of 0.03909 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 152.5 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 1510 K (+1237°C / +2259°F) and receiving 1,249.49 S⊕ (~1,700,553 W/m²), Kepler-1398 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1398 is classified as a stellar host with an effective photospheric temperature of 6,126 K, a radius of 1.18 R☉, a mass of 1.13 M☉, an estimated bolometric luminosity of 1.759 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.09 Gyr and a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, Kepler-1398 shines at apparent V-band magnitude 13.752 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-1398 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-1398 b sharing its stellar neighborhood alongside Kepler-1398 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-1398 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,126 K |
| Stellar Radius | 1.1800 R☉ |
| Stellar Mass | 1.1300 M☉ |
| Bolometric Luminosity | 1.759 L☉ |
| Metallicity [Fe/H] | 0.010 dex |
| Stellar Age | 3.090 Gyr |
| Apparent Magnitude | V: 13.752 · G: 13.661 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.039090 AU |
| Orbital Period | 2.788 days |
| Mean Orbital Velocity | 152.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.4700° |
| Mean Bulk Density | 5.04 g/cm³ (9.6 km/s vesc) |
| Insolation Flux | 1249.4880 S⊕ (~1,700,553 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2779.500 LY (852.204 pc) |