K2-331 c
Astrophysical Synthesis & Habitability Characterization
K2-331 c is a confirmed sub-neptune exoplanet orbiting the star K2-331, located approximately 689.6 light-years (211.43 parsecs) from the Solar System. First announced in 2021 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0553% across the stellar disk), this world measures 2.72 Earth radii and has a measured mass of 7.85 Earth masses. Combining its mass and radius yields a mean bulk density of 2.15 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 19 km/s.
In its orbital architecture around K2-331, K2-331 c completes one full revolution every 22.997 Earth days.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 673 K (+400°C / +752°F), K2-331 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-331 is classified as a stellar host with an effective photospheric temperature of 5,994 K, a radius of 1.06 R☉, a mass of 1.1 M☉, an estimated bolometric luminosity of 1.301 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, K2-331 shines at apparent V-band magnitude 11.305 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-331 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-331 c sharing its stellar neighborhood alongside K2-331 b.
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 | K2-331 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,994 K |
| Stellar Radius | 1.0600 R☉ |
| Stellar Mass | 1.1000 M☉ |
| Bolometric Luminosity | 1.301 L☉ |
| Metallicity [Fe/H] | 0.080 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 11.305 · G: 11.195 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 22.997 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.15 g/cm³ (19 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 689.600 LY (211.430 pc) |