K2-126 b
Astrophysical Synthesis & Habitability Characterization
K2-126 b is a confirmed super-earth exoplanet orbiting the star K2-126, located approximately 335.8 light-years (102.95 parsecs) from the Solar System. First announced in 2017 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0772% across the stellar disk), this world measures 1.97 Earth radii and has a measured mass of 4.54 Earth masses. Combining its mass and radius yields a mean bulk density of 3.27 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.17 g⊕ (11.47 m/s²), and an escape velocity of 17 km/s.
In its orbital architecture around K2-126, K2-126 b completes one full revolution every 7.386 Earth days at a semi-major axis of 0.0656 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 96.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.06 carries the world between 0.0617 AU at periapsis and 0.0695 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 601 K (+328°C / +622°F) and receiving 35.30 S⊕ (~48,043 W/m²), K2-126 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-126 is classified as a stellar host with an effective photospheric temperature of 4,339 K, a radius of 0.65 R☉, a mass of 0.69 M☉, an estimated bolometric luminosity of 0.134 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, K2-126 shines at apparent V-band magnitude 12.759 (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 | K2-126 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,339 K |
| Stellar Radius | 0.6500 R☉ |
| Stellar Mass | 0.6900 M☉ |
| Bolometric Luminosity | 0.134 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.759 · G: 12.401 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.065600 AU |
| Orbital Period | 7.386 days |
| Mean Orbital Velocity | 96.6 km/s |
| Orbital Eccentricity (e) | 0.06000 |
| Orbital Inclination (i) | 89.4000° |
| Mean Bulk Density | 3.27 g/cm³ (17 km/s vesc) |
| Insolation Flux | 35.3000 S⊕ (~48,043 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 335.800 LY (102.953 pc) |