K2-157 b
Astrophysical Synthesis & Habitability Characterization
K2-157 b is a confirmed terrestrial exoplanet orbiting the star K2-157, located approximately 973.2 light-years (298.37 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0099% across the stellar disk), this world measures 0.935 Earth radii and has a measured mass of 1.14 Earth masses. Combining its mass and radius yields a mean bulk density of 7.69 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 1.3 g⊕ (12.75 m/s²), and an escape velocity of 12.4 km/s.
In its orbital architecture around K2-157, K2-157 b completes one full revolution every 0.365 Earth days at a semi-major axis of 0.00962 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 286.5 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2432 K (+2159°C / +3918°F) and receiving 6,660.00 S⊕ (~9,064,260 W/m²), K2-157 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-157 is classified as a solar-type yellow star of spectral type G9 V with an effective photospheric temperature of 5,334 K, a radius of 0.86 R☉, a mass of 0.89 M☉, an estimated bolometric luminosity of 0.537 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.8 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, K2-157 shines at apparent V-band magnitude 12.942 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-157 system is a multi-planet architecture hosting 3 confirmed worlds, with K2-157 b sharing its stellar neighborhood alongside K2-157 c, K2-157 d.
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 | K2-157 |
| Spectral Type | G9 V |
| Effective Temp (Teff) | 5,334 K |
| Stellar Radius | 0.8600 R☉ |
| Stellar Mass | 0.8900 M☉ |
| Bolometric Luminosity | 0.537 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 8.800 Gyr |
| Apparent Magnitude | V: 12.942 · G: 12.642 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.009620 AU |
| Orbital Period | 0.365 days |
| Mean Orbital Velocity | 286.5 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.2000° |
| Mean Bulk Density | 7.69 g/cm³ (12.4 km/s vesc) |
| Insolation Flux | 6660.0000 S⊕ (~9,064,260 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 973.200 LY (298.373 pc) |