K2-180 b
Astrophysical Synthesis & Habitability Characterization
K2-180 b is a confirmed sub-neptune exoplanet orbiting the star K2-180, located approximately 665 light-years (203.9 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0989% across the stellar disk), this world measures 2.466 Earth radii and has a measured mass of 11.41 Earth masses. Combining its mass and radius yields a mean bulk density of 4.2 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.88 g⊕ (18.44 m/s²), and an escape velocity of 24.1 km/s.
In its orbital architecture around K2-180, K2-180 b completes one full revolution every 8.866 Earth days at a semi-major axis of 0.0756 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 92.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.075 carries the world between 0.0699 AU at periapsis and 0.0813 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 798 K (+525°C / +977°F) and receiving 48.30 S⊕ (~65,736 W/m²), K2-180 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-180 is classified as an orange K-type star of spectral type K2 V with an effective photospheric temperature of 5,365 K, a radius of 0.719 R☉, a mass of 0.735 M☉, an estimated bolometric luminosity of 0.384 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.5 Gyr and a metallicity of [Fe/H] = -0.578 dex (metal-poor relative to the Sun). From Earth, K2-180 shines at apparent V-band magnitude 12.557 (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 | K2-180 |
| Spectral Type | K2 V |
| Effective Temp (Teff) | 5,365 K |
| Stellar Radius | 0.7190 R☉ |
| Stellar Mass | 0.7350 M☉ |
| Bolometric Luminosity | 0.384 L☉ |
| Metallicity [Fe/H] | -0.578 dex |
| Stellar Age | 7.500 Gyr |
| Apparent Magnitude | V: 12.557 · G: 12.404 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.075600 AU |
| Orbital Period | 8.866 days |
| Mean Orbital Velocity | 92.8 km/s |
| Orbital Eccentricity (e) | 0.07500 |
| Orbital Inclination (i) | 89.1500° |
| Mean Bulk Density | 4.2 g/cm³ (24.1 km/s vesc) |
| Insolation Flux | 48.3000 S⊕ (~65,736 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 665.000 LY (203.896 pc) |