Kepler-125 c
Astrophysical Synthesis & Habitability Characterization
Kepler-125 c is a confirmed sub-earth exoplanet orbiting the star Kepler-125, located approximately 598.1 light-years (183.37 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0176% across the stellar disk), this world measures 0.74 Earth radii and has a measured mass of 0.33 Earth masses. Combining its mass and radius yields a mean bulk density of 4.49 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.6 g⊕ (5.88 m/s²), and an escape velocity of 7.5 km/s.
In its orbital architecture around Kepler-125, Kepler-125 c completes one full revolution every 5.774 Earth days at a semi-major axis of 0.051 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 96.1 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 529 K (+256°C / +493°F) and receiving 16.81 S⊕ (~22,878 W/m²), Kepler-125 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-125 is classified as a low-mass red dwarf of spectral type M1 V with an effective photospheric temperature of 3,810 K, a radius of 0.512 R☉, a mass of 0.5421 M☉, an estimated bolometric luminosity of 0.05 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.09 Gyr and a metallicity of [Fe/H] = -0.14 dex (metal-poor relative to the Sun). From Earth, Kepler-125 shines at apparent V-band magnitude 15.431 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-125 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-125 c sharing its stellar neighborhood alongside Kepler-125 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-125 |
| Spectral Type | M1 V |
| Effective Temp (Teff) | 3,810 K |
| Stellar Radius | 0.5120 R☉ |
| Stellar Mass | 0.5421 M☉ |
| Bolometric Luminosity | 0.05 L☉ |
| Metallicity [Fe/H] | -0.140 dex |
| Stellar Age | 1.090 Gyr |
| Apparent Magnitude | V: 15.431 · G: 14.768 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.051000 AU |
| Orbital Period | 5.774 days |
| Mean Orbital Velocity | 96.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.9400° |
| Mean Bulk Density | 4.49 g/cm³ (7.5 km/s vesc) |
| Insolation Flux | 16.8100 S⊕ (~22,878 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 598.100 LY (183.365 pc) |