K2-275 b

Astrophysical Synthesis & Habitability Characterization

K2-275 b is a confirmed sub-neptune exoplanet orbiting the star K2-275, located approximately 402.6 light-years (123.44 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0967% across the stellar disk), this world measures 2.34 Earth radii and has a measured mass of 6.08 Earth masses. Combining its mass and radius yields a mean bulk density of 2.62 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.11 g⊕ (10.89 m/s²), and an escape velocity of 18 km/s.

In its orbital architecture around K2-275, K2-275 b completes one full revolution every 3.281 Earth days at a semi-major axis of 0.0277 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 91.8 km/s (compared to Earth's 29.8 km/s).

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1166 K (+893°C / +1639°F) and receiving 161.25 S⊕ (~219,458 W/m²), K2-275 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star K2-275 is classified as a stellar host with an effective photospheric temperature of 4,841 K, a radius of 0.69 R☉, a mass of 0.77 M☉, an estimated bolometric luminosity of 0.235 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, K2-275 shines at apparent V-band magnitude 11.974 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-275 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-275 b sharing its stellar neighborhood alongside K2-275 c.

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