K2-159 b
Astrophysical Synthesis & Habitability Characterization
K2-159 b is a confirmed sub-neptune exoplanet orbiting the star K2-159, located approximately 557.7 light-years (171 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0623% across the stellar disk), this world measures 2.26 Earth radii and has a measured mass of 5.73 Earth masses. Combining its mass and radius yields a mean bulk density of 2.74 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.12 g⊕ (10.98 m/s²), and an escape velocity of 17.8 km/s.
In its orbital architecture around K2-159, K2-159 b completes one full revolution every 12.422 Earth days at a semi-major axis of 0.1013 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 88.7 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 684 K (+411°C / +772°F) and receiving 49.29 S⊕ (~67,088 W/m²), K2-159 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-159 is classified as a stellar host with an effective photospheric temperature of 5,425 K, a radius of 0.83 R☉, a mass of 0.9 M☉, an estimated bolometric luminosity of 0.535 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.07 dex (near-solar heavy-element abundance). From Earth, K2-159 shines at apparent V-band magnitude 11.995 (faint and requiring research-grade or CCD telescopic photometry) in the Southern 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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-159 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,425 K |
| Stellar Radius | 0.8300 R☉ |
| Stellar Mass | 0.9000 M☉ |
| Bolometric Luminosity | 0.535 L☉ |
| Metallicity [Fe/H] | -0.070 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 11.995 · G: 11.640 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.101300 AU |
| Orbital Period | 12.422 days |
| Mean Orbital Velocity | 88.7 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.0646° |
| Mean Bulk Density | 2.74 g/cm³ (17.8 km/s vesc) |
| Insolation Flux | 49.2934 S⊕ (~67,088 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 557.700 LY (170.998 pc) |