Kepler-11 c
Astrophysical Synthesis & Habitability Characterization
Kepler-11 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-11, located approximately 2108.1 light-years (646.35 parsecs) from the Solar System. First announced in 2010 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.061% across the stellar disk), this world measures 2.87 Earth radii and has a measured mass of 2.9 Earth masses. Combining its mass and radius yields a mean bulk density of 0.68 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.35 g⊕ (3.43 m/s²), and an escape velocity of 11.2 km/s.
In its orbital architecture around Kepler-11, Kepler-11 c completes one full revolution every 13.024 Earth days at a semi-major axis of 0.107 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 89.4 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.026 (ranging from 0.1042 AU at periapsis to 0.1098 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 786 K (+513°C / +955°F) and receiving 107.22 S⊕ (~145,932 W/m²), Kepler-11 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-11 is classified as a stellar host with an effective photospheric temperature of 5,663 K, a radius of 1.065 R☉, a mass of 0.961 M☉, an estimated bolometric luminosity of 1.047 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.5 Gyr and a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-11 shines at apparent V-band magnitude 13.817 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-11 system is a multi-planet architecture hosting 6 confirmed worlds, with Kepler-11 c sharing its stellar neighborhood alongside Kepler-11 b, Kepler-11 d, Kepler-11 e, Kepler-11 f, Kepler-11 g.
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-11 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,663 K |
| Stellar Radius | 1.0650 R☉ |
| Stellar Mass | 0.9610 M☉ |
| Bolometric Luminosity | 1.047 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | 8.500 Gyr |
| Apparent Magnitude | V: 13.817 · G: 13.706 |
| System Architecture | 1 Star, 6 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.107000 AU |
| Orbital Period | 13.024 days |
| Mean Orbital Velocity | 89.4 km/s |
| Orbital Eccentricity (e) | 0.02600 |
| Orbital Inclination (i) | 89.5900° |
| Mean Bulk Density | 0.68 g/cm³ (11.2 km/s vesc) |
| Insolation Flux | 107.2240 S⊕ (~145,932 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2108.100 LY (646.346 pc) |