Kepler-128 c
Astrophysical Synthesis & Habitability Characterization
Kepler-128 c is a confirmed super-earth exoplanet orbiting the star Kepler-128, located approximately 1292.8 light-years (396.38 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0071% across the stellar disk), this world measures 1.521 Earth radii and has a measured mass of 3.38 Earth masses. Combining its mass and radius yields a mean bulk density of 5.3 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.46 g⊕ (14.32 m/s²), and an escape velocity of 16.7 km/s.
In its orbital architecture around Kepler-128, Kepler-128 c completes one full revolution every 22.8 Earth days at a semi-major axis of 0.16517 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 78.8 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.037 (ranging from 0.1591 AU at periapsis to 0.1713 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 843 K (+570°C / +1058°F) and receiving 130.98 S⊕ (~178,262 W/m²), Kepler-128 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-128 is classified as a stellar host with an effective photospheric temperature of 6,072 K, a radius of 1.659 R☉, a mass of 1.184 M☉, an estimated bolometric luminosity of 3.357 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.07 Gyr and a metallicity of [Fe/H] = -0.03 dex (near-solar heavy-element abundance). From Earth, Kepler-128 shines at apparent V-band magnitude 11.693 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-128 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-128 c sharing its stellar neighborhood alongside Kepler-128 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-128 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,072 K |
| Stellar Radius | 1.6590 R☉ |
| Stellar Mass | 1.1840 M☉ |
| Bolometric Luminosity | 3.357 L☉ |
| Metallicity [Fe/H] | -0.030 dex |
| Stellar Age | 4.070 Gyr |
| Apparent Magnitude | V: 11.693 · G: 11.289 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.165170 AU |
| Orbital Period | 22.8 days |
| Mean Orbital Velocity | 78.8 km/s |
| Orbital Eccentricity (e) | 0.03700 |
| Orbital Inclination (i) | 89.5300° |
| Mean Bulk Density | 5.3 g/cm³ (16.7 km/s vesc) |
| Insolation Flux | 130.9790 S⊕ (~178,262 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1292.800 LY (396.379 pc) |