K2-280 b
Astrophysical Synthesis & Habitability Characterization
K2-280 b is a confirmed gas giant exoplanet orbiting the star K2-280, located approximately 1277 light-years (391.54 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.2886% across the stellar disk), this world measures 7.5 Earth radii (0.67 Jupiter radii) and has a measured mass of 37.1 Earth masses (0.12 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.48 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.66 g⊕ (6.47 m/s²), and an escape velocity of 24.9 km/s.
In its orbital architecture around K2-280, K2-280 b completes one full revolution every 19.895 Earth days at a semi-major axis of 0.1461 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 79.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.35, swinging from 0.095 AU at periapsis out to 0.1972 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 787 K (+514°C / +957°F) and receiving 69.50 S⊕ (~94,590 W/m²), K2-280 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-280 is classified as a stellar host with an effective photospheric temperature of 5,500 K, a radius of 1.28 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 1.345 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.96 Gyr and a metallicity of [Fe/H] = 0.33 dex (metal-rich relative to the Sun). From Earth, K2-280 shines at apparent V-band magnitude 12.524 (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 | K2-280 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,500 K |
| Stellar Radius | 1.2800 R☉ |
| Stellar Mass | 1.0300 M☉ |
| Bolometric Luminosity | 1.345 L☉ |
| Metallicity [Fe/H] | 0.330 dex |
| Stellar Age | 8.960 Gyr |
| Apparent Magnitude | V: 12.524 · G: 12.360 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.146100 AU |
| Orbital Period | 19.895 days |
| Mean Orbital Velocity | 79.9 km/s |
| Orbital Eccentricity (e) | 0.35000 |
| Orbital Inclination (i) | 89.5300° |
| Mean Bulk Density | 0.48 g/cm³ (24.9 km/s vesc) |
| Insolation Flux | 69.5000 S⊕ (~94,590 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1277.000 LY (391.537 pc) |