Kepler-103 c
Astrophysical Synthesis & Habitability Characterization
Kepler-103 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-103, located approximately 1613.9 light-years (494.83 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1123% across the stellar disk), this world measures 5.454 Earth radii (0.49 Jupiter radii) and has a measured mass of 58.47 Earth masses (0.18 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.99 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.97 g⊕ (19.32 m/s²), and an escape velocity of 36.6 km/s.
In its orbital architecture around Kepler-103, Kepler-103 c completes one full revolution every 179.61 Earth days at a semi-major axis of 0.6679 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 40.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.103 carries the world between 0.5991 AU at periapsis and 0.7367 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 434 K (+161°C / +322°F) and receiving 5.97 S⊕ (~8,125 W/m²), Kepler-103 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-103 is classified as a solar-type yellow star of spectral type G2 with an effective photospheric temperature of 6,047 K, a radius of 1.492 R☉, a mass of 1.212 M☉, an estimated bolometric luminosity of 2.67 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.03 Gyr and a metallicity of [Fe/H] = 0.15 dex (metal-rich relative to the Sun). From Earth, Kepler-103 shines at apparent V-band magnitude 11.883 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-103 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-103 c sharing its stellar neighborhood alongside Kepler-103 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-103 |
| Spectral Type | G2 |
| Effective Temp (Teff) | 6,047 K |
| Stellar Radius | 1.4920 R☉ |
| Stellar Mass | 1.2120 M☉ |
| Bolometric Luminosity | 2.67 L☉ |
| Metallicity [Fe/H] | 0.150 dex |
| Stellar Age | 6.030 Gyr |
| Apparent Magnitude | V: 11.883 · G: 12.247 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.667900 AU |
| Orbital Period | 179.61 days |
| Mean Orbital Velocity | 40.5 km/s |
| Orbital Eccentricity (e) | 0.10300 |
| Orbital Inclination (i) | 89.7040° |
| Mean Bulk Density | 1.99 g/cm³ (36.6 km/s vesc) |
| Insolation Flux | 5.9700 S⊕ (~8,125 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1613.900 LY (494.832 pc) |