Kepler-189 c
Astrophysical Synthesis & Habitability Characterization
Kepler-189 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-189, located approximately 1929.3 light-years (591.53 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0846% across the stellar disk), this world measures 2.38 Earth radii and has a measured mass of 22.7 Earth masses. Combining its mass and radius yields a mean bulk density of 9.28 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 4.01 g⊕ (39.32 m/s²), and an escape velocity of 34.5 km/s.
In its orbital architecture around Kepler-189, Kepler-189 c completes one full revolution every 20.135 Earth days at a semi-major axis of 0.137 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 74 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 544 K (+271°C / +520°F) and receiving 18.81 S⊕ (~25,602 W/m²), Kepler-189 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-189 is classified as a stellar host with an effective photospheric temperature of 5,235 K, a radius of 0.75 R☉, a mass of 0.803 M☉, an estimated bolometric luminosity of 0.379 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.98 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-189 shines at apparent V-band magnitude 14.971 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-189 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-189 c sharing its stellar neighborhood alongside Kepler-189 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-189 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,235 K |
| Stellar Radius | 0.7500 R☉ |
| Stellar Mass | 0.8030 M☉ |
| Bolometric Luminosity | 0.379 L☉ |
| Metallicity [Fe/H] | -0.040 dex |
| Stellar Age | 3.980 Gyr |
| Apparent Magnitude | V: 14.971 · G: 14.821 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.137000 AU |
| Orbital Period | 20.135 days |
| Mean Orbital Velocity | 74 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.2800° |
| Mean Bulk Density | 9.28 g/cm³ (34.5 km/s vesc) |
| Insolation Flux | 18.8110 S⊕ (~25,602 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1929.300 LY (591.534 pc) |