K2-66 b
Astrophysical Synthesis & Habitability Characterization
K2-66 b is a confirmed sub-neptune exoplanet orbiting the star K2-66, located approximately 1676 light-years (513.88 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0187% across the stellar disk), this world measures 2.49 Earth radii and has a measured mass of 21.3 Earth masses. Combining its mass and radius yields a mean bulk density of 7.61 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 3.44 g⊕ (33.73 m/s²), and an escape velocity of 32.7 km/s.
In its orbital architecture around K2-66, K2-66 b completes one full revolution every 5.07 Earth days at a semi-major axis of 0.05983 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 128.4 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1372 K (+1099°C / +2010°F) and receiving 840.00 S⊕ (~1,143,240 W/m²), K2-66 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-66 is classified as a stellar host with an effective photospheric temperature of 5,887 K, a radius of 1.67 R☉, a mass of 1.11 M☉, an estimated bolometric luminosity of 3.005 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.047 dex (near-solar heavy-element abundance). From Earth, K2-66 shines at apparent V-band magnitude 11.71 (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 | K2-66 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,887 K |
| Stellar Radius | 1.6700 R☉ |
| Stellar Mass | 1.1100 M☉ |
| Bolometric Luminosity | 3.005 L☉ |
| Metallicity [Fe/H] | -0.047 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 11.710 · G: 11.996 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.059830 AU |
| Orbital Period | 5.07 days |
| Mean Orbital Velocity | 128.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.6000° |
| Mean Bulk Density | 7.61 g/cm³ (32.7 km/s vesc) |
| Insolation Flux | 840.0000 S⊕ (~1,143,240 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1676.000 LY (513.877 pc) |