GJ 422 b

Astrophysical Synthesis & Habitability Characterization

GJ 422 b is a confirmed sub-neptune exoplanet orbiting the star GJ 422, located approximately 41.3 light-years (12.66 parsecs) from the Solar System. First announced in 2014 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.33 Earth radii (0.3 Jupiter radii) and has a measured mass of 11.07 Earth masses. Combining its mass and radius yields a mean bulk density of 1.65 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1 g⊕ (9.81 m/s²), and an escape velocity of 20.4 km/s.

In its orbital architecture around GJ 422, GJ 422 b completes one full revolution every 20.129 Earth days at a semi-major axis of 0.111 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 60 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.11 carries the world between 0.0988 AU at periapsis and 0.1232 AU at apoapsis, driving measurable seasonal insolation cycles.

☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 3.330 R⊕, GJ 422 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.

The host star GJ 422 is classified as a low-mass red dwarf of spectral type M3.5 V with an effective photospheric temperature of 3,323 K, a radius of 0.3703 R☉, a mass of 0.35 M☉, an estimated bolometric luminosity of 0.015 L☉. From Earth, GJ 422 shines at apparent V-band magnitude 11.66 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.

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