Kepler-928 b
Astrophysical Synthesis & Habitability Characterization
Kepler-928 b is a confirmed super-earth exoplanet orbiting the star Kepler-928, located approximately 1659.5 light-years (508.81 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0434% across the stellar disk), this world measures 1.59 Earth radii and has a measured mass of 3.15 Earth masses. Combining its mass and radius yields a mean bulk density of 4.32 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.25 g⊕ (12.26 m/s²), and an escape velocity of 15.7 km/s.
In its orbital architecture around Kepler-928, Kepler-928 b completes one full revolution every 3.932 Earth days at a semi-major axis of 0.0444 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 122.8 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 894 K (+621°C / +1150°F) and receiving 111.11 S⊕ (~151,221 W/m²), Kepler-928 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-928 is classified as a stellar host with an effective photospheric temperature of 4,700 K, a radius of 0.7 R☉, a mass of 0.73 M☉, an estimated bolometric luminosity of 0.215 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.37 Gyr and a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, Kepler-928 shines at apparent V-band magnitude 15.586 (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-928 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,700 K |
| Stellar Radius | 0.7000 R☉ |
| Stellar Mass | 0.7300 M☉ |
| Bolometric Luminosity | 0.215 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | 4.370 Gyr |
| Apparent Magnitude | V: 15.586 · G: 15.323 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.044400 AU |
| Orbital Period | 3.932 days |
| Mean Orbital Velocity | 122.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.1500° |
| Mean Bulk Density | 4.32 g/cm³ (15.7 km/s vesc) |
| Insolation Flux | 111.1100 S⊕ (~151,221 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1659.500 LY (508.809 pc) |