Kepler-865 c
Astrophysical Synthesis & Habitability Characterization
Kepler-865 c is a confirmed terrestrial exoplanet orbiting the star Kepler-865, located approximately 1911.7 light-years (586.14 parsecs) from the Solar System. First announced in 2023 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0085% across the stellar disk), this world measures 0.89 Earth radii and has a measured mass of 0.64 Earth masses. Combining its mass and radius yields a mean bulk density of 5.01 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.81 g⊕ (7.94 m/s²), and an escape velocity of 9.5 km/s.
In its orbital architecture around Kepler-865, Kepler-865 c completes one full revolution every 6.209 Earth days at a semi-major axis of 0.061 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 106.9 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 914 K (+641°C / +1186°F) and receiving 164.98 S⊕ (~224,538 W/m²), Kepler-865 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-865 is classified as a stellar host with an effective photospheric temperature of 5,440 K, a radius of 0.885 R☉, a mass of 0.782 M☉, an estimated bolometric luminosity of 0.615 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.27 Gyr and a metallicity of [Fe/H] = -0.24 dex (metal-poor relative to the Sun). From Earth, Kepler-865 shines at apparent V-band magnitude 14.635 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-865 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-865 c sharing its stellar neighborhood alongside Kepler-865 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-865 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,440 K |
| Stellar Radius | 0.8850 R☉ |
| Stellar Mass | 0.7820 M☉ |
| Bolometric Luminosity | 0.615 L☉ |
| Metallicity [Fe/H] | -0.240 dex |
| Stellar Age | 4.270 Gyr |
| Apparent Magnitude | V: 14.635 · G: 14.504 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.061000 AU |
| Orbital Period | 6.209 days |
| Mean Orbital Velocity | 106.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.1100° |
| Mean Bulk Density | 5.01 g/cm³ (9.5 km/s vesc) |
| Insolation Flux | 164.9800 S⊕ (~224,538 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1911.700 LY (586.137 pc) |