K2-226 b
Astrophysical Synthesis & Habitability Characterization
K2-226 b is a confirmed super-earth exoplanet orbiting the star K2-226, located approximately 689.1 light-years (211.27 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0252% across the stellar disk), this world measures 1.539 Earth radii and has a measured mass of 2.98 Earth masses. Combining its mass and radius yields a mean bulk density of 4.51 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.26 g⊕ (12.36 m/s²), and an escape velocity of 15.6 km/s.
In its orbital architecture around K2-226, K2-226 b completes one full revolution every 3.271 Earth days at a semi-major axis of 0.04095 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 136.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.22 carries the world between 0.0319 AU at periapsis and 0.05 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1187 K (+914°C / +1677°F) and receiving 332.76 S⊕ (~452,881 W/m²), K2-226 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-226 is classified as a stellar host with an effective photospheric temperature of 5,288 K, a radius of 0.889 R☉, a mass of 0.856 M☉, an estimated bolometric luminosity of 0.554 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.6 Gyr and a metallicity of [Fe/H] = -0.05 dex (near-solar heavy-element abundance). From Earth, K2-226 shines at apparent V-band magnitude 12.337 (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 | K2-226 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,288 K |
| Stellar Radius | 0.8890 R☉ |
| Stellar Mass | 0.8560 M☉ |
| Bolometric Luminosity | 0.554 L☉ |
| Metallicity [Fe/H] | -0.050 dex |
| Stellar Age | 9.600 Gyr |
| Apparent Magnitude | V: 12.337 · G: 12.092 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.040950 AU |
| Orbital Period | 3.271 days |
| Mean Orbital Velocity | 136.2 km/s |
| Orbital Eccentricity (e) | 0.22000 |
| Orbital Inclination (i) | 87.6000° |
| Mean Bulk Density | 4.51 g/cm³ (15.6 km/s vesc) |
| Insolation Flux | 332.7564 S⊕ (~452,881 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 689.100 LY (211.265 pc) |