HATS-54 b
Astrophysical Synthesis & Habitability Characterization
HATS-54 b is a confirmed gas giant exoplanet orbiting the star HATS-54, located approximately 2441.6 light-years (748.59 parsecs) from the Solar System. First announced in 2019 by HATSouth using the Transit detection technique (producing an estimated primary transit depth of 0.7191% across the stellar disk), this world measures 11.377 Earth radii (1.01 Jupiter radii) and has a measured mass of 239.325 Earth masses (0.75 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.9 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.85 g⊕ (18.14 m/s²), and an escape velocity of 51.3 km/s.
In its orbital architecture around HATS-54, HATS-54 b completes one full revolution every 2.544 Earth days at a semi-major axis of 0.037 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 158.2 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 1429 K (+1156°C / +2113°F) and receiving 476.97 S⊕ (~649,149 W/m²), HATS-54 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HATS-54 is classified as a solar-type yellow star of spectral type G6 V with an effective photospheric temperature of 5,621 K, a radius of 1.23 R☉, a mass of 1.05 M☉, an estimated bolometric luminosity of 1.355 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.96 Gyr and a metallicity of [Fe/H] = 0.37 dex (metal-rich relative to the Sun). From Earth, HATS-54 shines at apparent V-band magnitude 13.937 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: HATSouth · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HATS-54 |
| Spectral Type | G6 V |
| Effective Temp (Teff) | 5,621 K |
| Stellar Radius | 1.2300 R☉ |
| Stellar Mass | 1.0500 M☉ |
| Bolometric Luminosity | 1.355 L☉ |
| Metallicity [Fe/H] | 0.370 dex |
| Stellar Age | 7.960 Gyr |
| Apparent Magnitude | V: 13.937 · G: 13.776 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.037000 AU |
| Orbital Period | 2.544 days |
| Mean Orbital Velocity | 158.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 83.6700° |
| Mean Bulk Density | 0.9 g/cm³ (51.3 km/s vesc) |
| Insolation Flux | 476.9650 S⊕ (~649,149 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2441.600 LY (748.585 pc) |