K2-263 b
Astrophysical Synthesis & Habitability Characterization
K2-263 b is a confirmed sub-neptune exoplanet orbiting the star K2-263, located approximately 529.9 light-years (162.48 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0735% across the stellar disk), this world measures 2.513 Earth radii and has a measured mass of 15.4 Earth masses. Combining its mass and radius yields a mean bulk density of 5.35 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 2.44 g⊕ (23.93 m/s²), and an escape velocity of 27.7 km/s.
In its orbital architecture around K2-263, K2-263 b completes one full revolution every 50.819 Earth days at a semi-major axis of 0.2573 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 55.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.08 carries the world between 0.2367 AU at periapsis and 0.2779 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 482 K (+209°C / +408°F) and receiving 8.17 S⊕ (~11,119 W/m²), K2-263 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-263 is classified as a solar-type yellow star of spectral type G9 V with an effective photospheric temperature of 5,368 K, a radius of 0.85 R☉, a mass of 0.88 M☉, an estimated bolometric luminosity of 0.538 L☉. Stellar evolution modeling indicates an estimated stellar age of 7 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, K2-263 shines at apparent V-band magnitude 11.568 (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 | K2-263 |
| Spectral Type | G9 V |
| Effective Temp (Teff) | 5,368 K |
| Stellar Radius | 0.8500 R☉ |
| Stellar Mass | 0.8800 M☉ |
| Bolometric Luminosity | 0.538 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | 7.000 Gyr |
| Apparent Magnitude | V: 11.568 · G: 11.406 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.257300 AU |
| Orbital Period | 50.819 days |
| Mean Orbital Velocity | 55.1 km/s |
| Orbital Eccentricity (e) | 0.08000 |
| Orbital Inclination (i) | 89.2710° |
| Mean Bulk Density | 5.35 g/cm³ (27.7 km/s vesc) |
| Insolation Flux | 8.1700 S⊕ (~11,119 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 529.900 LY (162.481 pc) |