K2-111 b
Astrophysical Synthesis & Habitability Characterization
K2-111 b is a confirmed super-earth exoplanet orbiting the star K2-111, located approximately 653.6 light-years (200.39 parsecs) from the Solar System. First announced in 2017 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0182% across the stellar disk), this world measures 1.837 Earth radii and has a measured mass of 5.35 Earth masses. Combining its mass and radius yields a mean bulk density of 4.76 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.59 g⊕ (15.59 m/s²), and an escape velocity of 19.1 km/s.
In its orbital architecture around K2-111, K2-111 b completes one full revolution every 5.352 Earth days at a semi-major axis of 0.0565 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 114.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.134 carries the world between 0.0489 AU at periapsis and 0.0641 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1293 K (+1020°C / +1868°F) and receiving 490.00 S⊕ (~666,890 W/m²), K2-111 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-111 is classified as a solar-type yellow star of spectral type G2 with an effective photospheric temperature of 5,775 K, a radius of 1.25 R☉, a mass of 0.84 M☉, an estimated bolometric luminosity of 1.559 L☉. Stellar evolution modeling indicates an estimated stellar age of 12.3 Gyr and a metallicity of [Fe/H] = -0.46 dex (metal-poor relative to the Sun). From Earth, K2-111 shines at apparent V-band magnitude 11.13 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-111 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-111 b sharing its stellar neighborhood alongside K2-111 c.
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 | K2-111 |
| Spectral Type | G2 |
| Effective Temp (Teff) | 5,775 K |
| Stellar Radius | 1.2500 R☉ |
| Stellar Mass | 0.8400 M☉ |
| Bolometric Luminosity | 1.559 L☉ |
| Metallicity [Fe/H] | -0.460 dex |
| Stellar Age | 12.300 Gyr |
| Apparent Magnitude | V: 11.130 · G: 10.929 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.056500 AU |
| Orbital Period | 5.352 days |
| Mean Orbital Velocity | 114.9 km/s |
| Orbital Eccentricity (e) | 0.13400 |
| Orbital Inclination (i) | 86.3400° |
| Mean Bulk Density | 4.76 g/cm³ (19.1 km/s vesc) |
| Insolation Flux | 490.0000 S⊕ (~666,890 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 653.600 LY (200.394 pc) |