Kepler-811 b
Astrophysical Synthesis & Habitability Characterization
Kepler-811 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-811, located approximately 3212.8 light-years (985.04 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0398% across the stellar disk), this world measures 2.7 Earth radii and has a measured mass of 7.75 Earth masses. Combining its mass and radius yields a mean bulk density of 2.17 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 19 km/s.
In its orbital architecture around Kepler-811, Kepler-811 b completes one full revolution every 23.584 Earth days at a semi-major axis of 0.15911 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 73.4 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 730 K (+457°C / +855°F) and receiving 78.59 S⊕ (~106,961 W/m²), Kepler-811 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-811 is classified as a stellar host with an effective photospheric temperature of 5,747 K, a radius of 1.24 R☉, a mass of 1.01 M☉, an estimated bolometric luminosity of 1.505 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.94 Gyr and a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-811 shines at apparent V-band magnitude 14.046 (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-811 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,747 K |
| Stellar Radius | 1.2400 R☉ |
| Stellar Mass | 1.0100 M☉ |
| Bolometric Luminosity | 1.505 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | 7.940 Gyr |
| Apparent Magnitude | V: 14.046 · G: 13.958 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.159110 AU |
| Orbital Period | 23.584 days |
| Mean Orbital Velocity | 73.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.2800° |
| Mean Bulk Density | 2.17 g/cm³ (19 km/s vesc) |
| Insolation Flux | 78.5900 S⊕ (~106,961 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3212.800 LY (985.041 pc) |