K2-188 c
Astrophysical Synthesis & Habitability Characterization
K2-188 c is a confirmed sub-neptune exoplanet orbiting the star K2-188, located approximately 1457.3 light-years (446.82 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0475% across the stellar disk), this world measures 2.83 Earth radii and has a measured mass of 8.4 Earth masses. Combining its mass and radius yields a mean bulk density of 2.04 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.05 g⊕ (10.3 m/s²), and an escape velocity of 19.3 km/s.
In its orbital architecture around K2-188, K2-188 c completes one full revolution every 7.81 Earth days at a semi-major axis of 0.0785 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 109.3 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1026 K (+753°C / +1387°F) and receiving 230.63 S⊕ (~313,885 W/m²), K2-188 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-188 is classified as a stellar host with an effective photospheric temperature of 5,977 K, a radius of 1.19 R☉, a mass of 1.06 M☉, an estimated bolometric luminosity of 1.621 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, K2-188 shines at apparent V-band magnitude 12.657 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-188 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-188 c sharing its stellar neighborhood alongside K2-188 b.
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 | K2-188 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,977 K |
| Stellar Radius | 1.1900 R☉ |
| Stellar Mass | 1.0600 M☉ |
| Bolometric Luminosity | 1.621 L☉ |
| Metallicity [Fe/H] | -0.010 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.657 · G: 12.490 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.078500 AU |
| Orbital Period | 7.81 days |
| Mean Orbital Velocity | 109.3 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 88.0976° |
| Mean Bulk Density | 2.04 g/cm³ (19.3 km/s vesc) |
| Insolation Flux | 230.6280 S⊕ (~313,885 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1457.300 LY (446.821 pc) |