Kepler-1138 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1138 b is a confirmed super-earth exoplanet orbiting the star Kepler-1138, located approximately 2845.2 light-years (872.33 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 1.7 Earth radii and has a measured mass of 3.53 Earth masses. Combining its mass and radius yields a mean bulk density of 3.96 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.22 g⊕ (11.96 m/s²), and an escape velocity of 16.1 km/s.
In its orbital architecture around Kepler-1138, Kepler-1138 b completes one full revolution every 3.171 Earth days at a semi-major axis of 0.0415 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 142.4 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 1080 K (+807°C / +1485°F) and receiving 245.90 S⊕ (~334,675 W/m²), Kepler-1138 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1138 is classified as a stellar host with an effective photospheric temperature of 5,582 K, a radius of 0.92 R☉, a mass of 0.95 M☉, an estimated bolometric luminosity of 0.737 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.37 Gyr and a metallicity of [Fe/H] = 0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-1138 shines at apparent V-band magnitude 15.885 (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-1138 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,582 K |
| Stellar Radius | 0.9200 R☉ |
| Stellar Mass | 0.9500 M☉ |
| Bolometric Luminosity | 0.737 L☉ |
| Metallicity [Fe/H] | 0.040 dex |
| Stellar Age | 4.370 Gyr |
| Apparent Magnitude | V: 15.885 · G: 15.336 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041500 AU |
| Orbital Period | 3.171 days |
| Mean Orbital Velocity | 142.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 85.1100° |
| Mean Bulk Density | 3.96 g/cm³ (16.1 km/s vesc) |
| Insolation Flux | 245.9040 S⊕ (~334,675 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2845.200 LY (872.328 pc) |