Kepler-725 c
Astrophysical Synthesis & Habitability Characterization
Kepler-725 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-725, located approximately 2473.8 light-years (758.47 parsecs) from the Solar System. First announced in 2025 by Kepler using the Transit Timing Variations detection technique (producing an estimated primary transit depth of 0.103% across the stellar disk), this world measures 3.08 Earth radii (0.27 Jupiter radii) and has a measured mass of 9.7 Earth masses. Combining its mass and radius yields a mean bulk density of 1.83 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.02 g⊕ (10 m/s²), and an escape velocity of 19.9 km/s.
In its orbital architecture around Kepler-725, Kepler-725 c completes one full revolution every 207.541 Earth days at a semi-major axis of 0.6744 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 35.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.436, swinging from 0.3804 AU at periapsis out to 0.9684 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 3.080 R⊕, Kepler-725 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-725 is classified as a solar-type yellow star of spectral type G with an effective photospheric temperature of 5,395 K, a radius of 0.88 R☉, a mass of 0.95 M☉, an estimated bolometric luminosity of 0.589 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.6 Gyr and a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, Kepler-725 shines at apparent V-band magnitude 15.145 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-725 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-725 c sharing its stellar neighborhood alongside Kepler-725 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-725 |
| Spectral Type | G |
| Effective Temp (Teff) | 5,395 K |
| Stellar Radius | 0.8800 R☉ |
| Stellar Mass | 0.9500 M☉ |
| Bolometric Luminosity | 0.589 L☉ |
| Metallicity [Fe/H] | 0.140 dex |
| Stellar Age | 1.600 Gyr |
| Apparent Magnitude | V: 15.145 · G: 14.993 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.674400 AU |
| Orbital Period | 207.541 days |
| Mean Orbital Velocity | 35.4 km/s |
| Orbital Eccentricity (e) | 0.43600 |
| Orbital Inclination (i) | 89.6966° |
| Mean Bulk Density | 1.83 g/cm³ (19.9 km/s vesc) |
| Insolation Flux | 1.4000 S⊕ (~1,905 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2473.800 LY (758.469 pc) |