K2-221 b
Astrophysical Synthesis & Habitability Characterization
K2-221 b is a confirmed super-earth exoplanet orbiting the star K2-221, located approximately 1039.8 light-years (318.81 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0264% across the stellar disk), this world measures 1.679 Earth radii and has a measured mass of 3.46 Earth masses. Combining its mass and radius yields a mean bulk density of 4.03 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.23 g⊕ (12.06 m/s²), and an escape velocity of 16.1 km/s.
In its orbital architecture around K2-221, K2-221 b completes one full revolution every 2.399 Earth days.
ℹ️ Thermal & Atmospheric Regime: Current photometric and spectroscopic constraints for K2-221 b place it outside the conservative habitable zone definition pending further atmospheric characterization.
The host star K2-221 is classified as a stellar host with an effective photospheric temperature of 5,716 K, a radius of 0.9476 R☉, a mass of 1.0108 M☉, an estimated bolometric luminosity of 0.86 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.13 dex (metal-rich relative to the Sun). From Earth, K2-221 shines at apparent V-band magnitude 12.571 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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 | K2-221 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,716 K |
| Stellar Radius | 0.9476 R☉ |
| Stellar Mass | 1.0108 M☉ |
| Bolometric Luminosity | 0.86 L☉ |
| Metallicity [Fe/H] | 0.130 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.571 · G: 12.415 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 2.399 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 85.4471° |
| Mean Bulk Density | 4.03 g/cm³ (16.1 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1039.800 LY (318.810 pc) |