K2-203 b
Astrophysical Synthesis & Habitability Characterization
K2-203 b is a confirmed super-earth exoplanet orbiting the star K2-203, located approximately 541.9 light-years (166.15 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.023% across the stellar disk), this world measures 1.265 Earth radii and has a measured mass of 2.14 Earth masses. Combining its mass and radius yields a mean bulk density of 5.83 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.34 g⊕ (13.14 m/s²), and an escape velocity of 14.5 km/s.
In its orbital architecture around K2-203, K2-203 b completes one full revolution every 9.695 Earth days at a semi-major axis of 0.0824 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 92.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.23 carries the world between 0.0634 AU at periapsis and 0.1014 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 738 K (+465°C / +869°F) and receiving 49.63 S⊕ (~67,551 W/m²), K2-203 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-203 is classified as a stellar host with an effective photospheric temperature of 5,026 K, a radius of 0.765 R☉, a mass of 0.793 M☉, an estimated bolometric luminosity of 0.335 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.9 Gyr and a metallicity of [Fe/H] = -0.021 dex (near-solar heavy-element abundance). From Earth, K2-203 shines at apparent V-band magnitude 12.391 (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 | K2-203 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,026 K |
| Stellar Radius | 0.7650 R☉ |
| Stellar Mass | 0.7930 M☉ |
| Bolometric Luminosity | 0.335 L☉ |
| Metallicity [Fe/H] | -0.021 dex |
| Stellar Age | 6.900 Gyr |
| Apparent Magnitude | V: 12.391 · G: 12.122 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.082400 AU |
| Orbital Period | 9.695 days |
| Mean Orbital Velocity | 92.5 km/s |
| Orbital Eccentricity (e) | 0.23000 |
| Orbital Inclination (i) | 89.1200° |
| Mean Bulk Density | 5.83 g/cm³ (14.5 km/s vesc) |
| Insolation Flux | 49.6336 S⊕ (~67,551 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 541.900 LY (166.147 pc) |