HATS-75 b
Astrophysical Synthesis & Habitability Characterization
HATS-75 b is a confirmed gas giant exoplanet orbiting the star HATS-75, located approximately 635.9 light-years (194.96 parsecs) from the Solar System. First announced in 2021 by HATSouth using the Transit detection technique (producing an estimated primary transit depth of 2.4132% across the stellar disk), this world measures 9.909 Earth radii (0.88 Jupiter radii) and has a measured mass of 156.054 Earth masses (0.49 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.88 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.59 g⊕ (15.59 m/s²), and an escape velocity of 44.4 km/s.
In its orbital architecture around HATS-75, HATS-75 b completes one full revolution every 2.789 Earth days at a semi-major axis of 0.032742 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 127.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.064 carries the world between 0.0306 AU at periapsis and 0.0348 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 772 K (+499°C / +930°F) and receiving 59.26 S⊕ (~80,653 W/m²), HATS-75 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HATS-75 is classified as a stellar host with an effective photospheric temperature of 3,790 K, a radius of 0.5848 R☉, a mass of 0.6017 M☉, an estimated bolometric luminosity of 0.063 L☉. Stellar evolution modeling indicates an estimated stellar age of 14.9 Gyr and a metallicity of [Fe/H] = 0.522 dex (metal-rich relative to the Sun). From Earth, HATS-75 shines at apparent V-band magnitude 15.689 (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-75 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,790 K |
| Stellar Radius | 0.5848 R☉ |
| Stellar Mass | 0.6017 M☉ |
| Bolometric Luminosity | 0.063 L☉ |
| Metallicity [Fe/H] | 0.522 dex |
| Stellar Age | 14.900 Gyr |
| Apparent Magnitude | V: 15.689 · G: 14.903 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.032742 AU |
| Orbital Period | 2.789 days |
| Mean Orbital Velocity | 127.7 km/s |
| Orbital Eccentricity (e) | 0.06400 |
| Orbital Inclination (i) | 88.0700° |
| Mean Bulk Density | 0.88 g/cm³ (44.4 km/s vesc) |
| Insolation Flux | 59.2600 S⊕ (~80,653 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 635.900 LY (194.964 pc) |