Kepler-208 c
Astrophysical Synthesis & Habitability Characterization
Kepler-208 c is a confirmed super-earth exoplanet orbiting the star Kepler-208, located approximately 2528.8 light-years (775.33 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0094% across the stellar disk), this world measures 1.39 Earth radii and has a measured mass of 2.51 Earth masses. Combining its mass and radius yields a mean bulk density of 5.15 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 km/s.
In its orbital architecture around Kepler-208, Kepler-208 c completes one full revolution every 7.467 Earth days at a semi-major axis of 0.079 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 115.1 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 1141 K (+868°C / +1594°F) and receiving 300.17 S⊕ (~408,525 W/m²), Kepler-208 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-208 is classified as a stellar host with an effective photospheric temperature of 6,092 K, a radius of 1.314 R☉, a mass of 1.082 M☉, an estimated bolometric luminosity of 2.134 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.68 Gyr and a metallicity of [Fe/H] = -0.042 dex (near-solar heavy-element abundance). From Earth, Kepler-208 shines at apparent V-band magnitude 13.561 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-208 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-208 c sharing its stellar neighborhood alongside Kepler-208 b, Kepler-208 d, Kepler-208 e.
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-208 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,092 K |
| Stellar Radius | 1.3140 R☉ |
| Stellar Mass | 1.0820 M☉ |
| Bolometric Luminosity | 2.134 L☉ |
| Metallicity [Fe/H] | -0.042 dex |
| Stellar Age | 4.680 Gyr |
| Apparent Magnitude | V: 13.561 · G: 13.538 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.079000 AU |
| Orbital Period | 7.467 days |
| Mean Orbital Velocity | 115.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.9800° |
| Mean Bulk Density | 5.15 g/cm³ (15 km/s vesc) |
| Insolation Flux | 300.1650 S⊕ (~408,525 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2528.800 LY (775.328 pc) |