Kepler-331 d
Astrophysical Synthesis & Habitability Characterization
Kepler-331 d is a confirmed super-earth exoplanet orbiting the star Kepler-331, located approximately 1892.1 light-years (580.12 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0934% across the stellar disk), this world measures 1.64 Earth radii and has a measured mass of 3.33 Earth masses. Combining its mass and radius yields a mean bulk density of 4.16 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.24 g⊕ (12.16 m/s²), and an escape velocity of 15.9 km/s.
In its orbital architecture around Kepler-331, Kepler-331 d completes one full revolution every 32.134 Earth days at a semi-major axis of 0.159 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 53.8 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.
ℹ️ Thermal & Atmospheric Regime: Current photometric and spectroscopic constraints for Kepler-331 d place it outside the conservative habitable zone definition pending further atmospheric characterization.
The host star Kepler-331 is classified as a stellar host with an effective photospheric temperature of 4,347 K, a radius of 0.492 R☉, a mass of 0.653 M☉, an estimated bolometric luminosity of 0.078 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.2 Gyr and a metallicity of [Fe/H] = 0.118 dex (metal-rich relative to the Sun). From Earth, Kepler-331 shines at apparent V-band magnitude 16.199 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-331 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-331 d sharing its stellar neighborhood alongside Kepler-331 b, Kepler-331 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-331 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,347 K |
| Stellar Radius | 0.4920 R☉ |
| Stellar Mass | 0.6530 M☉ |
| Bolometric Luminosity | 0.078 L☉ |
| Metallicity [Fe/H] | 0.118 dex |
| Stellar Age | 1.200 Gyr |
| Apparent Magnitude | V: 16.199 · G: 15.836 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.159000 AU |
| Orbital Period | 32.134 days |
| Mean Orbital Velocity | 53.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.8400° |
| Mean Bulk Density | 4.16 g/cm³ (15.9 km/s vesc) |
| Insolation Flux | 6.0650 S⊕ (~8,254 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1892.100 LY (580.119 pc) |