K2-338 b
Astrophysical Synthesis & Habitability Characterization
K2-338 b is a confirmed terrestrial exoplanet orbiting the star K2-338, located approximately 511.9 light-years (156.95 parsecs) from the Solar System. First announced in 2021 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0225% across the stellar disk), this world measures 1.03 Earth radii and has a measured mass of 1.08 Earth masses. Combining its mass and radius yields a mean bulk density of 5.45 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.02 g⊕ (10 m/s²), and an escape velocity of 11.5 km/s.
In its orbital architecture around K2-338, K2-338 b completes one full revolution every 3.851 Earth days.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 783 K (+510°C / +950°F), K2-338 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-338 is classified as a stellar host with an effective photospheric temperature of 4,558 K, a radius of 0.63 R☉, a mass of 0.66 M☉, an estimated bolometric luminosity of 0.154 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.23 dex (metal-poor relative to the Sun). From Earth, K2-338 shines at apparent V-band magnitude 13.322 (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 | K2-338 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,558 K |
| Stellar Radius | 0.6300 R☉ |
| Stellar Mass | 0.6600 M☉ |
| Bolometric Luminosity | 0.154 L☉ |
| Metallicity [Fe/H] | -0.230 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.322 · G: 13.046 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 3.851 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.45 g/cm³ (11.5 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 511.900 LY (156.951 pc) |