K2-116 b
Astrophysical Synthesis & Habitability Characterization
K2-116 b is a confirmed sub-earth exoplanet orbiting the star K2-116, located approximately 161.1 light-years (49.39 parsecs) from the Solar System. First announced in 2017 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0089% across the stellar disk), this world measures 0.69 Earth radii and has a measured mass of 0.257 Earth masses. Combining its mass and radius yields a mean bulk density of 4.31 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.54 g⊕ (5.3 m/s²), and an escape velocity of 6.8 km/s.
In its orbital architecture around K2-116, K2-116 b completes one full revolution every 4.655 Earth days at a semi-major axis of 0.048 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 112.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.06 carries the world between 0.0451 AU at periapsis and 0.0509 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 783 K (+510°C / +950°F) and receiving 78.60 S⊕ (~106,975 W/m²), K2-116 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-116 is classified as a stellar host with an effective photospheric temperature of 4,348 K, a radius of 0.6694 R☉, a mass of 0.6945 M☉, an estimated bolometric luminosity of 0.144 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, K2-116 shines at apparent V-band magnitude 10.8 (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 | K2-116 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,348 K |
| Stellar Radius | 0.6694 R☉ |
| Stellar Mass | 0.6945 M☉ |
| Bolometric Luminosity | 0.144 L☉ |
| Metallicity [Fe/H] | 0.010 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 10.800 · G: 10.328 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.048000 AU |
| Orbital Period | 4.655 days |
| Mean Orbital Velocity | 112.2 km/s |
| Orbital Eccentricity (e) | 0.06000 |
| Orbital Inclination (i) | 89.0900° |
| Mean Bulk Density | 4.31 g/cm³ (6.8 km/s vesc) |
| Insolation Flux | 78.6000 S⊕ (~106,975 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 161.100 LY (49.386 pc) |