K2-189 b
Astrophysical Synthesis & Habitability Characterization
K2-189 b is a confirmed super-earth exoplanet orbiting the star K2-189, located approximately 789.7 light-years (242.11 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0214% across the stellar disk), this world measures 1.403 Earth radii and has a measured mass of 2.55 Earth masses. Combining its mass and radius yields a mean bulk density of 5.09 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 15.1 km/s.
In its orbital architecture around K2-189, K2-189 b completes one full revolution every 2.588 Earth days at a semi-major axis of 0.0361 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 151.7 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1203 K (+930°C / +1706°F) and receiving 497.00 S⊕ (~676,417 W/m²), K2-189 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-189 is classified as a stellar host with an effective photospheric temperature of 5,442 K, a radius of 0.879 R☉, a mass of 0.85 M☉, an estimated bolometric luminosity of 0.608 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.1 dex (near-solar heavy-element abundance). From Earth, K2-189 shines at apparent V-band magnitude 12.398 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-189 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-189 b sharing its stellar neighborhood alongside K2-189 c.
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 | K2-189 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,442 K |
| Stellar Radius | 0.8790 R☉ |
| Stellar Mass | 0.8500 M☉ |
| Bolometric Luminosity | 0.608 L☉ |
| Metallicity [Fe/H] | -0.100 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.398 · G: 12.254 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.036100 AU |
| Orbital Period | 2.588 days |
| Mean Orbital Velocity | 151.7 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 88.1134° |
| Mean Bulk Density | 5.09 g/cm³ (15.1 km/s vesc) |
| Insolation Flux | 497.0000 S⊕ (~676,417 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 789.700 LY (242.113 pc) |