K2-88 b

Astrophysical Synthesis & Habitability Characterization

K2-88 b is a confirmed terrestrial exoplanet orbiting the star K2-88, located approximately 360.6 light-years (110.56 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.194% across the stellar disk), this world measures 1.23 Earth radii and has a measured mass of 2.04 Earth masses. Combining its mass and radius yields a mean bulk density of 6.04 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.35 g⊕ (13.24 m/s²), and an escape velocity of 14.4 km/s.

In its orbital architecture around K2-88, K2-88 b completes one full revolution every 4.612 Earth days at a semi-major axis of 0.0345 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 81.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.26, swinging from 0.0255 AU at periapsis out to 0.0435 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 465 K (+192°C / +378°F) and receiving 7.80 S⊕ (~10,616 W/m²), K2-88 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star K2-88 is classified as a stellar host with an effective photospheric temperature of 3,537 K, a radius of 0.256 R☉, a mass of 0.258 M☉, an estimated bolometric luminosity of 0.00920 L☉. From Earth, K2-88 shines at apparent V-band magnitude 15.523 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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