K2-45 b

Astrophysical Synthesis & Habitability Characterization

K2-45 b is a confirmed gas giant exoplanet orbiting the star K2-45, located approximately 1615.5 light-years (495.32 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 1.911% across the stellar disk), this world measures 6.71 Earth radii (0.6 Jupiter radii) and has a measured mass of 36.4 Earth masses (0.11 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.66 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.81 g⊕ (7.94 m/s²), and an escape velocity of 26.1 km/s.

In its orbital architecture around K2-45, K2-45 b completes one full revolution every 1.729 Earth days at a semi-major axis of 0.0224 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 140.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1 carries the world between 0.0202 AU at periapsis and 0.0246 AU at apoapsis, driving measurable seasonal insolation cycles.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1074 K (+801°C / +1474°F) and receiving 100.00 S⊕ (~136,100 W/m²), K2-45 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star K2-45 is classified as a stellar host with an effective photospheric temperature of 4,103 K, a radius of 0.445 R☉, a mass of 0.503 M☉, an estimated bolometric luminosity of 0.05 L☉. From Earth, K2-45 shines at apparent V-band magnitude 15.746 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.

Discovery Facility: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).