Kepler-328 b
Astrophysical Synthesis & Habitability Characterization
Kepler-328 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-328, located approximately 7218.5 light-years (2213.19 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0396% across the stellar disk), this world measures 2.3 Earth radii and has a measured mass of 28.5 Earth masses. Combining its mass and radius yields a mean bulk density of 12.92 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 5.39 g⊕ (52.86 m/s²), and an escape velocity of 39.4 km/s.
In its orbital architecture around Kepler-328, Kepler-328 b completes one full revolution every 34.921 Earth days at a semi-major axis of 0.2199 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 68.5 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 602 K (+329°C / +624°F) and receiving 57.08 S⊕ (~77,685 W/m²), Kepler-328 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-328 is classified as a stellar host with an effective photospheric temperature of 6,064 K, a radius of 1.06 R☉, a mass of 1.15 M☉, an estimated bolometric luminosity of 1.363 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.57 Gyr and a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, Kepler-328 shines at apparent V-band magnitude 15.794 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-328 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-328 b sharing its stellar neighborhood alongside Kepler-328 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-328 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,064 K |
| Stellar Radius | 1.0600 R☉ |
| Stellar Mass | 1.1500 M☉ |
| Bolometric Luminosity | 1.363 L☉ |
| Metallicity [Fe/H] | 0.080 dex |
| Stellar Age | 2.570 Gyr |
| Apparent Magnitude | V: 15.794 · G: 15.604 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.219900 AU |
| Orbital Period | 34.921 days |
| Mean Orbital Velocity | 68.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.9600° |
| Mean Bulk Density | 12.92 g/cm³ (39.4 km/s vesc) |
| Insolation Flux | 57.0790 S⊕ (~77,685 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 7218.500 LY (2213.190 pc) |