Kepler-25 c
Astrophysical Synthesis & Habitability Characterization
Kepler-25 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-25, located approximately 793.4 light-years (243.25 parsecs) from the Solar System. First announced in 2011 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1321% across the stellar disk), this world measures 5.217 Earth radii (0.47 Jupiter radii) and has a measured mass of 15.2 Earth masses. Combining its mass and radius yields a mean bulk density of 0.59 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.56 g⊕ (5.49 m/s²), and an escape velocity of 19.1 km/s.
In its orbital architecture around Kepler-25, Kepler-25 c completes one full revolution every 12.721 Earth days at a semi-major axis of 0.1117 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 95.5 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.0061 (ranging from 0.111 AU at periapsis to 0.1124 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 934 K (+661°C / +1222°F) and receiving 210.17 S⊕ (~286,044 W/m²), Kepler-25 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-25 is classified as a warm F-type star of spectral type F8 with an effective photospheric temperature of 6,354 K, a radius of 1.316 R☉, a mass of 1.165 M☉, an estimated bolometric luminosity of 2.533 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.75 Gyr and a metallicity of [Fe/H] = 0.11 dex (metal-rich relative to the Sun). From Earth, Kepler-25 shines at apparent V-band magnitude 10.769 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-25 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-25 c sharing its stellar neighborhood alongside Kepler-25 b, Kepler-25 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-25 |
| Spectral Type | F8 |
| Effective Temp (Teff) | 6,354 K |
| Stellar Radius | 1.3160 R☉ |
| Stellar Mass | 1.1650 M☉ |
| Bolometric Luminosity | 2.533 L☉ |
| Metallicity [Fe/H] | 0.110 dex |
| Stellar Age | 2.750 Gyr |
| Apparent Magnitude | V: 10.769 · G: 10.632 |
| System Architecture | 2 Stars, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.111700 AU |
| Orbital Period | 12.721 days |
| Mean Orbital Velocity | 95.5 km/s |
| Orbital Eccentricity (e) | 0.00610 |
| Orbital Inclination (i) | 92.7640° |
| Mean Bulk Density | 0.59 g/cm³ (19.1 km/s vesc) |
| Insolation Flux | 210.1720 S⊕ (~286,044 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 793.400 LY (243.249 pc) |