K2-156 b
Astrophysical Synthesis & Habitability Characterization
K2-156 b is a confirmed terrestrial exoplanet orbiting the star K2-156, located approximately 489.9 light-years (150.21 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0265% across the stellar disk), this world measures 1.1 Earth radii and has a measured mass of 1.37 Earth masses. Combining its mass and radius yields a mean bulk density of 5.68 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.13 g⊕ (11.08 m/s²), and an escape velocity of 12.5 km/s.
In its orbital architecture around K2-156, K2-156 b completes one full revolution every 0.813 Earth days at a semi-major axis of 0.0149 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 199.3 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1347 K (+1074°C / +1965°F) and receiving 654.04 S⊕ (~890,143 W/m²), K2-156 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-156 is classified as a stellar host with an effective photospheric temperature of 4,460 K, a radius of 0.62 R☉, a mass of 0.66 M☉, an estimated bolometric luminosity of 0.136 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.33 dex (metal-poor relative to the Sun). From Earth, K2-156 shines at apparent V-band magnitude 13.4 (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 | K2-156 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,460 K |
| Stellar Radius | 0.6200 R☉ |
| Stellar Mass | 0.6600 M☉ |
| Bolometric Luminosity | 0.136 L☉ |
| Metallicity [Fe/H] | -0.330 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.400 · G: 12.948 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.014900 AU |
| Orbital Period | 0.813 days |
| Mean Orbital Velocity | 199.3 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.8000° |
| Mean Bulk Density | 5.68 g/cm³ (12.5 km/s vesc) |
| Insolation Flux | 654.0363 S⊕ (~890,143 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 489.900 LY (150.210 pc) |