K2-187 b
Astrophysical Synthesis & Habitability Characterization
K2-187 b is a confirmed terrestrial exoplanet orbiting the star K2-187, located approximately 1079.3 light-years (330.92 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0176% across the stellar disk), this world measures 1.2 Earth radii and has a measured mass of 1.87 Earth masses. Combining its mass and radius yields a mean bulk density of 5.97 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.3 g⊕ (12.75 m/s²), and an escape velocity of 14 km/s.
In its orbital architecture around K2-187, K2-187 b completes one full revolution every 0.774 Earth days at a semi-major axis of 0.0164 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 230.5 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1815 K (+1542°C / +2808°F) and receiving 2,367.25 S⊕ (~3,221,830 W/m²), K2-187 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-187 is classified as a stellar host with an effective photospheric temperature of 5,438 K, a radius of 0.83 R☉, a mass of 0.967 M☉, an estimated bolometric luminosity of 0.541 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, K2-187 shines at apparent V-band magnitude 13.102 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-187 system is a multi-planet architecture hosting 4 confirmed worlds, with K2-187 b sharing its stellar neighborhood alongside K2-187 c, K2-187 d, K2-187 e.
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 | K2-187 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,438 K |
| Stellar Radius | 0.8300 R☉ |
| Stellar Mass | 0.9670 M☉ |
| Bolometric Luminosity | 0.541 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.102 · G: 12.867 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.016400 AU |
| Orbital Period | 0.774 days |
| Mean Orbital Velocity | 230.5 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.7000° |
| Mean Bulk Density | 5.97 g/cm³ (14 km/s vesc) |
| Insolation Flux | 2367.2520 S⊕ (~3,221,830 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1079.300 LY (330.916 pc) |