Kepler-171 b
Astrophysical Synthesis & Habitability Characterization
Kepler-171 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-171, located approximately 2817.5 light-years (863.86 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0654% across the stellar disk), this world measures 2.34 Earth radii and has a measured mass of 6.08 Earth masses. Combining its mass and radius yields a mean bulk density of 2.62 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.11 g⊕ (10.89 m/s²), and an escape velocity of 18 km/s.
In its orbital architecture around Kepler-171, Kepler-171 b completes one full revolution every 4.167 Earth days at a semi-major axis of 0.05 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 130.5 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 1053 K (+780°C / +1436°F) and receiving 304.18 S⊕ (~413,986 W/m²), Kepler-171 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-171 is classified as a stellar host with an effective photospheric temperature of 5,642 K, a radius of 0.839 R☉, a mass of 0.978 M☉, an estimated bolometric luminosity of 0.64 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.4 Gyr and a metallicity of [Fe/H] = 0.17 dex (metal-rich relative to the Sun). From Earth, Kepler-171 shines at apparent V-band magnitude 15.101 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-171 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-171 b sharing its stellar neighborhood alongside Kepler-171 c, Kepler-171 d.
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-171 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,642 K |
| Stellar Radius | 0.8390 R☉ |
| Stellar Mass | 0.9780 M☉ |
| Bolometric Luminosity | 0.64 L☉ |
| Metallicity [Fe/H] | 0.170 dex |
| Stellar Age | 2.400 Gyr |
| Apparent Magnitude | V: 15.101 · G: 14.905 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.050000 AU |
| Orbital Period | 4.167 days |
| Mean Orbital Velocity | 130.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.8900° |
| Mean Bulk Density | 2.62 g/cm³ (18 km/s vesc) |
| Insolation Flux | 304.1780 S⊕ (~413,986 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2817.500 LY (863.855 pc) |