Kepler-47 c
Astrophysical Synthesis & Habitability Characterization
Kepler-47 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-47, located approximately 3343.2 light-years (1025.02 parsecs) from the Solar System. First announced in 2012 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2074% across the stellar disk), this world measures 4.65 Earth radii (0.41 Jupiter radii) and has a measured mass of 3.17 Earth masses. Combining its mass and radius yields a mean bulk density of 0.17 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.15 g⊕ (1.47 m/s²), and an escape velocity of 9.2 km/s.
In its orbital architecture around Kepler-47, Kepler-47 c completes one full revolution every 303.227 Earth days at a semi-major axis of 0.9638 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 34.6 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.044 (ranging from 0.9214 AU at periapsis to 1.0062 AU at apoapsis), the planet experiences minimal orbital distance variation.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 4.650 R⊕, Kepler-47 c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star Kepler-47 is classified as a stellar host with an effective photospheric temperature of 5,636 K, a radius of 0.936 R☉, a mass of 0.957 M☉, an estimated bolometric luminosity of 0.793 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.25 dex (metal-poor relative to the Sun). From Earth, Kepler-47 shines at apparent V-band magnitude 15.31 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-47 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-47 c sharing its stellar neighborhood alongside Kepler-47 b, Kepler-47 d.
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-47 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,636 K |
| Stellar Radius | 0.9360 R☉ |
| Stellar Mass | 0.9570 M☉ |
| Bolometric Luminosity | 0.793 L☉ |
| Metallicity [Fe/H] | -0.250 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 15.310 · G: 15.163 |
| System Architecture | 2 Stars, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.963800 AU |
| Orbital Period | 303.227 days |
| Mean Orbital Velocity | 34.6 km/s |
| Orbital Eccentricity (e) | 0.04400 |
| Orbital Inclination (i) | 90.1925° |
| Mean Bulk Density | 0.17 g/cm³ (9.2 km/s vesc) |
| Insolation Flux | 0.9037 S⊕ (~1,230 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3343.200 LY (1025.020 pc) |