HATS-25 b
Astrophysical Synthesis & Habitability Characterization
HATS-25 b is a confirmed gas giant exoplanet orbiting the star HATS-25, located approximately 1536.7 light-years (471.16 parsecs) from the Solar System. First announced in 2016 by HATSouth using the Transit detection technique (producing an estimated primary transit depth of 1.368% across the stellar disk), this world measures 14.123 Earth radii (1.26 Jupiter radii) and has a measured mass of 194.83 Earth masses (0.61 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.38 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.98 g⊕ (9.61 m/s²), and an escape velocity of 41.5 km/s.
In its orbital architecture around HATS-25, HATS-25 b completes one full revolution every 4.299 Earth days at a semi-major axis of 0.05163 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 130.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.176 carries the world between 0.0425 AU at periapsis and 0.0607 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1277 K (+1004°C / +1839°F) and receiving 454.87 S⊕ (~619,081 W/m²), HATS-25 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HATS-25 is classified as a solar-type yellow star of spectral type G with an effective photospheric temperature of 5,715 K, a radius of 1.107 R☉, a mass of 0.994 M☉, an estimated bolometric luminosity of 1.173 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.5 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, HATS-25 shines at apparent V-band magnitude 13.172 (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-25 |
| Spectral Type | G |
| Effective Temp (Teff) | 5,715 K |
| Stellar Radius | 1.1070 R☉ |
| Stellar Mass | 0.9940 M☉ |
| Bolometric Luminosity | 1.173 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 7.500 Gyr |
| Apparent Magnitude | V: 13.172 · G: 12.935 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.051630 AU |
| Orbital Period | 4.299 days |
| Mean Orbital Velocity | 130.7 km/s |
| Orbital Eccentricity (e) | 0.17600 |
| Orbital Inclination (i) | 86.9300° |
| Mean Bulk Density | 0.38 g/cm³ (41.5 km/s vesc) |
| Insolation Flux | 454.8721 S⊕ (~619,081 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1536.700 LY (471.158 pc) |