HATS-2 b
Astrophysical Synthesis & Habitability Characterization
HATS-2 b is a confirmed gas giant exoplanet orbiting the star HATS-2, located approximately 1115.2 light-years (341.93 parsecs) from the Solar System. First announced in 2013 by HATSouth using the Transit detection technique (producing an estimated primary transit depth of 1.7323% across the stellar disk), this world measures 12.576 Earth radii (1.12 Jupiter radii) and has a measured mass of 435.425 Earth masses (1.37 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.21 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.75 g⊕ (26.97 m/s²), and an escape velocity of 65.8 km/s.
In its orbital architecture around HATS-2, HATS-2 b completes one full revolution every 1.354 Earth days at a semi-major axis of 0.02317 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 186.1 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 1550 K (+1277°C / +2331°F) and receiving 950.06 S⊕ (~1,293,027 W/m²), HATS-2 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HATS-2 is classified as an orange K-type star of spectral type K with an effective photospheric temperature of 5,227 K, a radius of 0.876 R☉, a mass of 0.904 M☉, an estimated bolometric luminosity of 0.514 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.2 Gyr and a metallicity of [Fe/H] = 0.15 dex (metal-rich relative to the Sun). From Earth, HATS-2 shines at apparent V-band magnitude 13.565 (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-2 |
| Spectral Type | K |
| Effective Temp (Teff) | 5,227 K |
| Stellar Radius | 0.8760 R☉ |
| Stellar Mass | 0.9040 M☉ |
| Bolometric Luminosity | 0.514 L☉ |
| Metallicity [Fe/H] | 0.150 dex |
| Stellar Age | 7.200 Gyr |
| Apparent Magnitude | V: 13.565 · G: 13.342 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.023170 AU |
| Orbital Period | 1.354 days |
| Mean Orbital Velocity | 186.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.8300° |
| Mean Bulk Density | 1.21 g/cm³ (65.8 km/s vesc) |
| Insolation Flux | 950.0563 S⊕ (~1,293,027 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1115.200 LY (341.925 pc) |