K2-6 b
Astrophysical Synthesis & Habitability Characterization
K2-6 b is a confirmed sub-neptune exoplanet orbiting the star K2-6, located approximately 1033.3 light-years (316.82 parsecs) from the Solar System. First announced in 2015 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.057% across the stellar disk), this world measures 2.5 Earth radii and has a measured mass of 6.8 Earth masses. Combining its mass and radius yields a mean bulk density of 2.4 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.09 g⊕ (10.69 m/s²), and an escape velocity of 18.4 km/s.
In its orbital architecture around K2-6, K2-6 b completes one full revolution every 30.942 Earth days at a semi-major axis of 0.1898 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 66.7 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 615 K (+342°C / +648°F) and receiving 28.60 S⊕ (~38,925 W/m²), K2-6 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-6 is classified as a stellar host with an effective photospheric temperature of 5,850 K, a radius of 0.96 R☉, a mass of 0.97 M☉, an estimated bolometric luminosity of 0.968 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.14 dex (metal-poor relative to the Sun). From Earth, K2-6 shines at apparent V-band magnitude 12.66 (faint and requiring research-grade or CCD telescopic photometry) in the Southern 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 | K2-6 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,850 K |
| Stellar Radius | 0.9600 R☉ |
| Stellar Mass | 0.9700 M☉ |
| Bolometric Luminosity | 0.968 L☉ |
| Metallicity [Fe/H] | -0.140 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.660 · G: 12.502 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.189800 AU |
| Orbital Period | 30.942 days |
| Mean Orbital Velocity | 66.7 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.4199° |
| Mean Bulk Density | 2.4 g/cm³ (18.4 km/s vesc) |
| Insolation Flux | 28.6000 S⊕ (~38,925 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1033.300 LY (316.819 pc) |