Kepler-26 c
Astrophysical Synthesis & Habitability Characterization
Kepler-26 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-26, located approximately 1093.6 light-years (335.31 parsecs) from the Solar System. First announced in 2011 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2372% across the stellar disk), this world measures 2.72 Earth radii and has a measured mass of 6.2 Earth masses. Combining its mass and radius yields a mean bulk density of 1.7 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.84 g⊕ (8.24 m/s²), and an escape velocity of 16.9 km/s.
In its orbital architecture around Kepler-26, Kepler-26 c completes one full revolution every 17.256 Earth days at a semi-major axis of 0.10725 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 67.6 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.013 (ranging from 0.1059 AU at periapsis to 0.1086 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 385 K (+112°C / +234°F) and receiving 4.82 S⊕ (~6,560 W/m²), Kepler-26 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-26 is classified as a low-mass red dwarf of spectral type M0 V with an effective photospheric temperature of 3,914 K, a radius of 0.512 R☉, a mass of 0.544 M☉, an estimated bolometric luminosity of 0.055 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.95 Gyr and a metallicity of [Fe/H] = -0.13 dex (metal-poor relative to the Sun). From Earth, Kepler-26 shines at apparent V-band magnitude 15.853 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-26 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-26 c sharing its stellar neighborhood alongside Kepler-26 d, Kepler-26 b, Kepler-26 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-26 |
| Spectral Type | M0 V |
| Effective Temp (Teff) | 3,914 K |
| Stellar Radius | 0.5120 R☉ |
| Stellar Mass | 0.5440 M☉ |
| Bolometric Luminosity | 0.055 L☉ |
| Metallicity [Fe/H] | -0.130 dex |
| Stellar Age | 2.950 Gyr |
| Apparent Magnitude | V: 15.853 · G: 15.409 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.107250 AU |
| Orbital Period | 17.256 days |
| Mean Orbital Velocity | 67.6 km/s |
| Orbital Eccentricity (e) | 0.01300 |
| Orbital Inclination (i) | 89.0900° |
| Mean Bulk Density | 1.7 g/cm³ (16.9 km/s vesc) |
| Insolation Flux | 4.8200 S⊕ (~6,560 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1093.600 LY (335.307 pc) |