K2-11 b
Astrophysical Synthesis & Habitability Characterization
K2-11 b is a confirmed gas giant exoplanet orbiting the star K2-11, located approximately 1074.1 light-years (329.31 parsecs) from the Solar System. First announced in 2015 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0181% across the stellar disk), this world measures 7.55 Earth radii (0.67 Jupiter radii) and has a measured mass of 44.4 Earth masses (0.14 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.57 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.78 g⊕ (7.65 m/s²), and an escape velocity of 27.1 km/s.
In its orbital architecture around K2-11, K2-11 b completes one full revolution every 39.938 Earth days at a semi-major axis of 0.2257 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 61.5 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 734 K (+461°C / +862°F) and receiving 9.84 S⊕ (~13,392 W/m²), K2-11 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-11 is classified as a solar-type yellow star of spectral type G8 with an effective photospheric temperature of 5,433 K, a radius of 5.15 R☉, a mass of 1.35 M☉, an estimated bolometric luminosity of 20.733 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.12 dex (metal-poor relative to the Sun). From Earth, K2-11 shines at apparent V-band magnitude 13.409 (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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-11 |
| Spectral Type | G8 |
| Effective Temp (Teff) | 5,433 K |
| Stellar Radius | 5.1500 R☉ |
| Stellar Mass | 1.3500 M☉ |
| Bolometric Luminosity | 20.733 L☉ |
| Metallicity [Fe/H] | -0.120 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.409 · G: 13.150 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.225700 AU |
| Orbital Period | 39.938 days |
| Mean Orbital Velocity | 61.5 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.57 g/cm³ (27.1 km/s vesc) |
| Insolation Flux | 9.8400 S⊕ (~13,392 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1074.100 LY (329.309 pc) |