K2-245 b
Astrophysical Synthesis & Habitability Characterization
K2-245 b is a confirmed sub-neptune exoplanet orbiting the star K2-245, located approximately 1487.5 light-years (456.06 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1013% across the stellar disk), this world measures 4.34 Earth radii (0.39 Jupiter radii) and has a measured mass of 17.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.17 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.92 g⊕ (9.02 m/s²), and an escape velocity of 22.4 km/s.
In its orbital architecture around K2-245, K2-245 b completes one full revolution every 11.893 Earth days at a semi-major axis of 0.0959 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 87.7 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 923 K (+650°C / +1202°F) and receiving 83.00 S⊕ (~112,963 W/m²), K2-245 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-245 is classified as a stellar host with an effective photospheric temperature of 5,793 K, a radius of 1.25 R☉, a mass of 0.83 M☉, an estimated bolometric luminosity of 1.579 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.45 dex (metal-poor relative to the Sun). From Earth, K2-245 shines at apparent V-band magnitude 12.755 (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 | K2-245 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,793 K |
| Stellar Radius | 1.2500 R☉ |
| Stellar Mass | 0.8300 M☉ |
| Bolometric Luminosity | 1.579 L☉ |
| Metallicity [Fe/H] | -0.450 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.755 · G: 12.564 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.095900 AU |
| Orbital Period | 11.893 days |
| Mean Orbital Velocity | 87.7 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.17 g/cm³ (22.4 km/s vesc) |
| Insolation Flux | 83.0000 S⊕ (~112,963 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1487.500 LY (456.064 pc) |