Kepler-311 d
Astrophysical Synthesis & Habitability Characterization
Kepler-311 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-311, located approximately 2539.6 light-years (778.65 parsecs) from the Solar System. First announced in 2023 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0264% across the stellar disk), this world measures 2.05 Earth radii and has a measured mass of 4.86 Earth masses. Combining its mass and radius yields a mean bulk density of 3.11 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.16 g⊕ (11.38 m/s²), and an escape velocity of 17.2 km/s.
In its orbital architecture around Kepler-311, Kepler-311 d completes one full revolution every 232.04 Earth days at a semi-major axis of 0.7326 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 34.3 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-311 d place it outside the conservative habitable zone definition pending further atmospheric characterization.
The host star Kepler-311 is classified as a stellar host with an effective photospheric temperature of 5,903 K, a radius of 1.156 R☉, a mass of 0.974 M☉, an estimated bolometric luminosity of 1.456 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.95 Gyr and a metallicity of [Fe/H] = -0.1 dex (near-solar heavy-element abundance). From Earth, Kepler-311 shines at apparent V-band magnitude 13.902 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-311 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-311 d sharing its stellar neighborhood alongside Kepler-311 b, Kepler-311 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-311 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,903 K |
| Stellar Radius | 1.1560 R☉ |
| Stellar Mass | 0.9740 M☉ |
| Bolometric Luminosity | 1.456 L☉ |
| Metallicity [Fe/H] | -0.100 dex |
| Stellar Age | 1.950 Gyr |
| Apparent Magnitude | V: 13.902 · G: 13.754 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.732600 AU |
| Orbital Period | 232.04 days |
| Mean Orbital Velocity | 34.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.7000° |
| Mean Bulk Density | 3.11 g/cm³ (17.2 km/s vesc) |
| Insolation Flux | 2.7100 S⊕ (~3,688 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2539.600 LY (778.654 pc) |