Kepler-122 c
Astrophysical Synthesis & Habitability Characterization
Kepler-122 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-122, located approximately 3351.1 light-years (1027.45 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1959% across the stellar disk), this world measures 5.87 Earth radii (0.52 Jupiter radii) and has a measured mass of 29 Earth masses. Combining its mass and radius yields a mean bulk density of 0.79 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.84 g⊕ (8.24 m/s²), and an escape velocity of 24.9 km/s.
In its orbital architecture around Kepler-122, Kepler-122 c completes one full revolution every 12.466 Earth days at a semi-major axis of 0.108 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 94.3 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 897 K (+624°C / +1155°F) and receiving 160.50 S⊕ (~218,439 W/m²), Kepler-122 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-122 is classified as a stellar host with an effective photospheric temperature of 6,050 K, a radius of 1.216 R☉, a mass of 0.982 M☉, an estimated bolometric luminosity of 1.777 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.94 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, Kepler-122 shines at apparent V-band magnitude 14.403 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-122 system is a multi-planet architecture hosting 5 confirmed worlds, with Kepler-122 c sharing its stellar neighborhood alongside Kepler-122 b, Kepler-122 d, Kepler-122 e, Kepler-122 f.
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-122 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,050 K |
| Stellar Radius | 1.2160 R☉ |
| Stellar Mass | 0.9820 M☉ |
| Bolometric Luminosity | 1.777 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | 7.940 Gyr |
| Apparent Magnitude | V: 14.403 · G: 14.222 |
| System Architecture | 1 Star, 5 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.108000 AU |
| Orbital Period | 12.466 days |
| Mean Orbital Velocity | 94.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3900° |
| Mean Bulk Density | 0.79 g/cm³ (24.9 km/s vesc) |
| Insolation Flux | 160.4990 S⊕ (~218,439 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3351.100 LY (1027.450 pc) |