Kepler-26 d
Astrophysical Synthesis & Habitability Characterization
Kepler-26 d is a confirmed terrestrial exoplanet orbiting the star Kepler-26, located approximately 1093.6 light-years (335.31 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0295% across the stellar disk), this world measures 1.07 Earth radii and has a measured mass of 1.24 Earth masses. Combining its mass and radius yields a mean bulk density of 5.58 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.08 g⊕ (10.59 m/s²), and an escape velocity of 12 km/s.
In its orbital architecture around Kepler-26, Kepler-26 d completes one full revolution every 3.544 Earth days at a semi-major axis of 0.039 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 119.7 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 652 K (+379°C / +714°F) and receiving 31.79 S⊕ (~43,266 W/m²), Kepler-26 d 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 4,486 K, a radius of 0.571 R☉, a mass of 0.593 M☉, an estimated bolometric luminosity of 0.118 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.95 Gyr and a metallicity of [Fe/H] = -0.21 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 d sharing its stellar neighborhood alongside Kepler-26 b, Kepler-26 c, 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) | 4,486 K |
| Stellar Radius | 0.5710 R☉ |
| Stellar Mass | 0.5930 M☉ |
| Bolometric Luminosity | 0.118 L☉ |
| Metallicity [Fe/H] | -0.210 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) | 0.039000 AU |
| Orbital Period | 3.544 days |
| Mean Orbital Velocity | 119.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.9100° |
| Mean Bulk Density | 5.58 g/cm³ (12 km/s vesc) |
| Insolation Flux | 31.7900 S⊕ (~43,266 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1093.600 LY (335.307 pc) |