K2-291 b

Astrophysical Synthesis & Habitability Characterization

K2-291 b is a confirmed super-earth exoplanet orbiting the star K2-291, located approximately 293.7 light-years (90.06 parsecs) from the Solar System. First announced in 2019 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0263% across the stellar disk), this world measures 1.589 Earth radii and has a measured mass of 6.49 Earth masses. Combining its mass and radius yields a mean bulk density of 8.92 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 2.57 g⊕ (25.2 m/s²), and an escape velocity of 22.6 km/s.

In its orbital architecture around K2-291, K2-291 b completes one full revolution every 2.225 Earth days at a semi-major axis of 0.03261 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 159.4 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1278 K (+1005°C / +1841°F) and receiving 633.00 S⊕ (~861,513 W/m²), K2-291 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star K2-291 is classified as a stellar host with an effective photospheric temperature of 5,520 K, a radius of 0.899 R☉, a mass of 0.934 M☉, an estimated bolometric luminosity of 0.673 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.72 Gyr and a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, K2-291 shines at apparent V-band magnitude 10.014 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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