K2-26 b
Astrophysical Synthesis & Habitability Characterization
K2-26 b is a confirmed sub-neptune exoplanet orbiting the star K2-26, located approximately 323.1 light-years (99.05 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.2216% across the stellar disk), this world measures 2.67 Earth radii and has a measured mass of 7.61 Earth masses. Combining its mass and radius yields a mean bulk density of 2.2 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 18.9 km/s.
In its orbital architecture around K2-26, K2-26 b completes one full revolution every 14.567 Earth days at a semi-major axis of 0.0962 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 71.8 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 430 K (+157°C / +315°F) and receiving 5.80 S⊕ (~7,894 W/m²), K2-26 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-26 is classified as a low-mass red dwarf of spectral type M1.0 V with an effective photospheric temperature of 3,785 K, a radius of 0.52 R☉, a mass of 0.56 M☉, an estimated bolometric luminosity of 0.05 L☉. Stellar evolution modeling indicates an estimated stellar age of 1 Gyr and a metallicity of [Fe/H] = -0.13 dex (metal-poor relative to the Sun). From Earth, K2-26 shines at apparent V-band magnitude 14.528 (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 | K2-26 |
| Spectral Type | M1.0 V |
| Effective Temp (Teff) | 3,785 K |
| Stellar Radius | 0.5200 R☉ |
| Stellar Mass | 0.5600 M☉ |
| Bolometric Luminosity | 0.05 L☉ |
| Metallicity [Fe/H] | -0.130 dex |
| Stellar Age | 1.000 Gyr |
| Apparent Magnitude | V: 14.528 · G: 13.752 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.096200 AU |
| Orbital Period | 14.567 days |
| Mean Orbital Velocity | 71.8 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 88.4000° |
| Mean Bulk Density | 2.2 g/cm³ (18.9 km/s vesc) |
| Insolation Flux | 5.8000 S⊕ (~7,894 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 323.100 LY (99.050 pc) |