Kepler-859 b
Astrophysical Synthesis & Habitability Characterization
Kepler-859 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-859, located approximately 2739.4 light-years (839.9 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1354% across the stellar disk), this world measures 3.09 Earth radii (0.28 Jupiter radii) and has a measured mass of 9.75 Earth masses. Combining its mass and radius yields a mean bulk density of 1.82 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.02 g⊕ (10 m/s²), and an escape velocity of 19.9 km/s.
In its orbital architecture around Kepler-859, Kepler-859 b completes one full revolution every 20.382 Earth days at a semi-major axis of 0.13157 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 70.2 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 528 K (+255°C / +491°F) and receiving 14.90 S⊕ (~20,275 W/m²), Kepler-859 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-859 is classified as a stellar host with an effective photospheric temperature of 5,020 K, a radius of 0.77 R☉, a mass of 0.81 M☉, an estimated bolometric luminosity of 0.338 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.57 Gyr and a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-859 shines at apparent V-band magnitude 15.977 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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-859 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,020 K |
| Stellar Radius | 0.7700 R☉ |
| Stellar Mass | 0.8100 M☉ |
| Bolometric Luminosity | 0.338 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | 4.570 Gyr |
| Apparent Magnitude | V: 15.977 · G: 15.881 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.131570 AU |
| Orbital Period | 20.382 days |
| Mean Orbital Velocity | 70.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.5900° |
| Mean Bulk Density | 1.82 g/cm³ (19.9 km/s vesc) |
| Insolation Flux | 14.8970 S⊕ (~20,275 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2739.400 LY (839.903 pc) |