HATS-38 b

Astrophysical Synthesis & Habitability Characterization

HATS-38 b is a confirmed gas giant exoplanet orbiting the star HATS-38, located approximately 1120.4 light-years (343.53 parsecs) from the Solar System. First announced in 2020 by HATSouth using the Transit detection technique (producing an estimated primary transit depth of 0.326% across the stellar disk), this world measures 6.882 Earth radii (0.61 Jupiter radii) and has a measured mass of 23.519 Earth masses. Combining its mass and radius yields a mean bulk density of 0.4 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.5 g⊕ (4.9 m/s²), and an escape velocity of 20.7 km/s.

In its orbital architecture around HATS-38, HATS-38 b completes one full revolution every 4.375 Earth days at a semi-major axis of 0.05036 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 125.2 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 1294 K (+1021°C / +1870°F) and receiving 464.70 S⊕ (~632,457 W/m²), HATS-38 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star HATS-38 is classified as a stellar host with an effective photospheric temperature of 5,732 K, a radius of 1.105 R☉, a mass of 0.89 M☉, an estimated bolometric luminosity of 1.183 L☉. Stellar evolution modeling indicates an estimated stellar age of 11.89 Gyr and a metallicity of [Fe/H] = -0.102 dex (metal-poor relative to the Sun). From Earth, HATS-38 shines at apparent V-band magnitude 11.967 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.

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