Kepler-917 b
Astrophysical Synthesis & Habitability Characterization
Kepler-917 b is a confirmed super-earth exoplanet orbiting the star Kepler-917, located approximately 11286.7 light-years (3460.51 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0531% across the stellar disk), this world measures 1.91 Earth radii and has a measured mass of 4.31 Earth masses. Combining its mass and radius yields a mean bulk density of 3.41 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.18 g⊕ (11.57 m/s²), and an escape velocity of 16.8 km/s.
In its orbital architecture around Kepler-917, Kepler-917 b completes one full revolution every 2.97 Earth days at a semi-major axis of 0.0378 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 138.4 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 991 K (+718°C / +1324°F) and receiving 228.11 S⊕ (~310,458 W/m²), Kepler-917 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-917 is classified as a stellar host with an effective photospheric temperature of 5,418 K, a radius of 0.76 R☉, a mass of 0.8 M☉, an estimated bolometric luminosity of 0.447 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.17 Gyr and a metallicity of [Fe/H] = -0.38 dex (metal-poor relative to the Sun). From Earth, Kepler-917 shines at apparent V-band magnitude 15.896 (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-917 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,418 K |
| Stellar Radius | 0.7600 R☉ |
| Stellar Mass | 0.8000 M☉ |
| Bolometric Luminosity | 0.447 L☉ |
| Metallicity [Fe/H] | -0.380 dex |
| Stellar Age | 4.170 Gyr |
| Apparent Magnitude | V: 15.896 · G: 15.853 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.037800 AU |
| Orbital Period | 2.97 days |
| Mean Orbital Velocity | 138.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.7500° |
| Mean Bulk Density | 3.41 g/cm³ (16.8 km/s vesc) |
| Insolation Flux | 228.1100 S⊕ (~310,458 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 11286.700 LY (3460.510 pc) |