Kepler-65 c
Astrophysical Synthesis & Habitability Characterization
Kepler-65 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-65, located approximately 990.6 light-years (303.73 parsecs) from the Solar System. First announced in 2012 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0281% across the stellar disk), this world measures 2.58 Earth radii and has a measured mass of 5.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.73 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.81 g⊕ (7.94 m/s²), and an escape velocity of 16.2 km/s.
In its orbital architecture around Kepler-65, Kepler-65 c completes one full revolution every 5.86 Earth days at a semi-major axis of 0.068 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 126.2 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.02 (ranging from 0.0666 AU at periapsis to 0.0694 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1246 K (+973°C / +1783°F) and receiving 609.99 S⊕ (~830,199 W/m²), Kepler-65 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-65 is classified as a stellar host with an effective photospheric temperature of 6,211 K, a radius of 1.41 R☉, a mass of 1.25 M☉, an estimated bolometric luminosity of 2.654 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.9 Gyr and a metallicity of [Fe/H] = 0.17 dex (metal-rich relative to the Sun). From Earth, Kepler-65 shines at apparent V-band magnitude 10.922 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-65 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-65 c sharing its stellar neighborhood alongside Kepler-65 b, Kepler-65 d, Kepler-65 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-65 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,211 K |
| Stellar Radius | 1.4100 R☉ |
| Stellar Mass | 1.2500 M☉ |
| Bolometric Luminosity | 2.654 L☉ |
| Metallicity [Fe/H] | 0.170 dex |
| Stellar Age | 2.900 Gyr |
| Apparent Magnitude | V: 10.922 · G: 10.966 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.068000 AU |
| Orbital Period | 5.86 days |
| Mean Orbital Velocity | 126.2 km/s |
| Orbital Eccentricity (e) | 0.02000 |
| Orbital Inclination (i) | 92.3300° |
| Mean Bulk Density | 1.73 g/cm³ (16.2 km/s vesc) |
| Insolation Flux | 609.9920 S⊕ (~830,199 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 990.600 LY (303.728 pc) |