Kepler-51 c
Astrophysical Synthesis & Habitability Characterization
Kepler-51 c is a confirmed gas giant exoplanet orbiting the star Kepler-51, located approximately 2556.5 light-years (783.83 parsecs) from the Solar System. First announced in 2012 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.7705% across the stellar disk), this world measures 9 Earth radii (0.8 Jupiter radii) and has a measured mass of 4 Earth masses. Combining its mass and radius yields a mean bulk density of 0.03 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.05 g⊕ (0.49 m/s²), and an escape velocity of 7.5 km/s.
In its orbital architecture around Kepler-51, Kepler-51 c completes one full revolution every 85.312 Earth days at a semi-major axis of 0.384 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 49 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.014 (ranging from 0.3786 AU at periapsis to 0.3894 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 439 K (+166°C / +331°F) and receiving 4.33 S⊕ (~5,894 W/m²), Kepler-51 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-51 is classified as a stellar host with an effective photospheric temperature of 6,018 K, a radius of 0.94 R☉, a mass of 1.04 M☉, an estimated bolometric luminosity of 1.04 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.3 Gyr and a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-51 shines at apparent V-band magnitude 14.885 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-51 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-51 c sharing its stellar neighborhood alongside Kepler-51 b, Kepler-51 d, Kepler-51 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-51 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,018 K |
| Stellar Radius | 0.9400 R☉ |
| Stellar Mass | 1.0400 M☉ |
| Bolometric Luminosity | 1.04 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | 0.300 Gyr |
| Apparent Magnitude | V: 14.885 · G: 14.678 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.384000 AU |
| Orbital Period | 85.312 days |
| Mean Orbital Velocity | 49 km/s |
| Orbital Eccentricity (e) | 0.01400 |
| Orbital Inclination (i) | 89.4400° |
| Mean Bulk Density | 0.03 g/cm³ (7.5 km/s vesc) |
| Insolation Flux | 4.3310 S⊕ (~5,894 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2556.500 LY (783.831 pc) |