GJ 504 b

Astrophysical Synthesis & Habitability Characterization

GJ 504 b is a confirmed gas giant exoplanet orbiting the star GJ 504, located approximately 57.2 light-years (17.53 parsecs) from the Solar System. First announced in 2013 by Subaru Telescope using the Imaging detection technique (resolved directly via high-contrast coronagraphic or interferometric imaging), this world measures 12.106 Earth radii (1.08 Jupiter radii) and has a measured mass of 1271.3 Earth masses (4 Jupiter masses). Combining its mass and radius yields a mean bulk density of 3.95 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 8.67 g⊕ (85.02 m/s²), and an escape velocity of 114.6 km/s.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 510 K (+237°C / +459°F) and receiving 0.00 S⊕ (~1 W/m²), GJ 504 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star GJ 504 is classified as a solar-type yellow star of spectral type G0 V with an effective photospheric temperature of 6,234 K, a radius of 1.26 R☉, a mass of 1.22 M☉, an estimated bolometric luminosity of 2.151 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.16 Gyr and a metallicity of [Fe/H] = 0.28 dex (metal-rich relative to the Sun). From Earth, GJ 504 shines at apparent V-band magnitude 5.188 (visible to the unaided human eye under dark skies) in the Northern celestial hemisphere.

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