K2-31 b
Astrophysical Synthesis & Habitability Characterization
K2-31 b is a confirmed gas giant exoplanet orbiting the star K2-31, located approximately 360.5 light-years (110.53 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 1.9504% across the stellar disk), this world measures 11.882 Earth radii (1.06 Jupiter radii) and has a measured mass of 563.83 Earth masses (1.77 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.85 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.99 g⊕ (39.13 m/s²), and an escape velocity of 77.1 km/s.
In its orbital architecture around K2-31, K2-31 b completes one full revolution every 1.258 Earth days at a semi-major axis of 0.022 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 190.3 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 1688 K (+1415°C / +2579°F) and receiving 1,272.00 S⊕ (~1,731,192 W/m²), K2-31 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-31 is classified as a solar-type yellow star of spectral type G7 V with an effective photospheric temperature of 5,280 K, a radius of 0.78 R☉, a mass of 0.91 M☉, an estimated bolometric luminosity of 0.424 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, K2-31 shines at apparent V-band magnitude 10.802 (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 | K2-31 |
| Spectral Type | G7 V |
| Effective Temp (Teff) | 5,280 K |
| Stellar Radius | 0.7800 R☉ |
| Stellar Mass | 0.9100 M☉ |
| Bolometric Luminosity | 0.424 L☉ |
| Metallicity [Fe/H] | 0.080 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 10.802 · G: 10.537 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.022000 AU |
| Orbital Period | 1.258 days |
| Mean Orbital Velocity | 190.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 79.9000° |
| Mean Bulk Density | 1.85 g/cm³ (77.1 km/s vesc) |
| Insolation Flux | 1272.0000 S⊕ (~1,731,192 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 360.500 LY (110.527 pc) |