K2-119 b
Astrophysical Synthesis & Habitability Characterization
K2-119 b is a confirmed sub-neptune exoplanet orbiting the star K2-119, located approximately 1192.4 light-years (365.58 parsecs) from the Solar System. First announced in 2017 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1067% across the stellar disk), this world measures 2.53 Earth radii and has a measured mass of 6.94 Earth masses. Combining its mass and radius yields a mean bulk density of 2.36 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.08 g⊕ (10.59 m/s²), and an escape velocity of 18.5 km/s.
In its orbital architecture around K2-119, K2-119 b completes one full revolution every 7.727 Earth days at a semi-major axis of 0.0698 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 98.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.07 carries the world between 0.0649 AU at periapsis and 0.0747 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 666 K (+393°C / +739°F) and receiving 54.90 S⊕ (~74,719 W/m²), K2-119 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-119 is classified as a stellar host with an effective photospheric temperature of 4,740 K, a radius of 0.71 R☉, a mass of 0.76 M☉, an estimated bolometric luminosity of 0.228 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.05 dex (near-solar heavy-element abundance). From Earth, K2-119 shines at apparent V-band magnitude 14.818 (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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-119 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,740 K |
| Stellar Radius | 0.7100 R☉ |
| Stellar Mass | 0.7600 M☉ |
| Bolometric Luminosity | 0.228 L☉ |
| Metallicity [Fe/H] | -0.050 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.818 · G: 14.510 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.069800 AU |
| Orbital Period | 7.727 days |
| Mean Orbital Velocity | 98.3 km/s |
| Orbital Eccentricity (e) | 0.07000 |
| Orbital Inclination (i) | 89.4000° |
| Mean Bulk Density | 2.36 g/cm³ (18.5 km/s vesc) |
| Insolation Flux | 54.9000 S⊕ (~74,719 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1192.400 LY (365.581 pc) |