Kepler-309 b
Astrophysical Synthesis & Habitability Characterization
Kepler-309 b is a confirmed super-earth exoplanet orbiting the star Kepler-309, located approximately 1776.1 light-years (544.57 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0393% across the stellar disk), this world measures 1.56 Earth radii and has a measured mass of 3.05 Earth masses. Combining its mass and radius yields a mean bulk density of 4.43 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.25 g⊕ (12.26 m/s²), and an escape velocity of 15.6 km/s.
In its orbital architecture around Kepler-309, Kepler-309 b completes one full revolution every 5.924 Earth days at a semi-major axis of 0.059 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 108.4 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 531 K (+258°C / +496°F) and receiving 99.49 S⊕ (~135,410 W/m²), Kepler-309 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-309 is classified as a low-mass red dwarf of spectral type M0 V with an effective photospheric temperature of 4,713 K, a radius of 0.721 R☉, a mass of 0.816 M☉, an estimated bolometric luminosity of 0.23 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.02 Gyr and a metallicity of [Fe/H] = 0.27 dex (metal-rich relative to the Sun). From Earth, Kepler-309 shines at apparent V-band magnitude 15.418 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-309 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-309 b sharing its stellar neighborhood alongside Kepler-309 c.
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-309 |
| Spectral Type | M0 V |
| Effective Temp (Teff) | 4,713 K |
| Stellar Radius | 0.7210 R☉ |
| Stellar Mass | 0.8160 M☉ |
| Bolometric Luminosity | 0.23 L☉ |
| Metallicity [Fe/H] | 0.270 dex |
| Stellar Age | 3.020 Gyr |
| Apparent Magnitude | V: 15.418 · G: 15.126 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.059000 AU |
| Orbital Period | 5.924 days |
| Mean Orbital Velocity | 108.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.8500° |
| Mean Bulk Density | 4.43 g/cm³ (15.6 km/s vesc) |
| Insolation Flux | 99.4930 S⊕ (~135,410 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1776.100 LY (544.568 pc) |