Kepler-528 b
Astrophysical Synthesis & Habitability Characterization
Kepler-528 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-528, located approximately 2557.8 light-years (784.23 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0324% across the stellar disk), this world measures 2.08 Earth radii and has a measured mass of 4.98 Earth masses. Combining its mass and radius yields a mean bulk density of 3.05 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.15 g⊕ (11.28 m/s²), and an escape velocity of 17.3 km/s.
In its orbital architecture around Kepler-528, Kepler-528 b completes one full revolution every 19.783 Earth days at a semi-major axis of 0.14219 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 78.2 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 708 K (+435°C / +815°F) and receiving 68.97 S⊕ (~93,870 W/m²), Kepler-528 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-528 is classified as a stellar host with an effective photospheric temperature of 5,807 K, a radius of 1.06 R☉, a mass of 1.01 M☉, an estimated bolometric luminosity of 1.146 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.5 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-528 shines at apparent V-band magnitude 14.064 (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-528 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,807 K |
| Stellar Radius | 1.0600 R☉ |
| Stellar Mass | 1.0100 M☉ |
| Bolometric Luminosity | 1.146 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 5.500 Gyr |
| Apparent Magnitude | V: 14.064 · G: 13.903 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.142190 AU |
| Orbital Period | 19.783 days |
| Mean Orbital Velocity | 78.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.9700° |
| Mean Bulk Density | 3.05 g/cm³ (17.3 km/s vesc) |
| Insolation Flux | 68.9710 S⊕ (~93,870 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2557.800 LY (784.230 pc) |