Kepler-1889 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1889 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1889, located approximately 4550.3 light-years (1395.13 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1091% across the stellar disk), this world measures 2.944 Earth radii and has a measured mass of 8.98 Earth masses. Combining its mass and radius yields a mean bulk density of 1.94 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.5 km/s.

In its orbital architecture around Kepler-1889, Kepler-1889 b completes one full revolution every 37.304 Earth days at a semi-major axis of 0.2082 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 60.7 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 493 K (+220°C / +428°F) and receiving 14.00 S⊕ (~19,054 W/m²), Kepler-1889 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1889 is classified as a stellar host with an effective photospheric temperature of 5,646 K, a radius of 0.817 R☉, a mass of 0.864 M☉, an estimated bolometric luminosity of 0.609 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.28 dex (metal-poor relative to the Sun). From Earth, Kepler-1889 shines at apparent V-band magnitude 15.715 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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