HATS-13 b
Astrophysical Synthesis & Habitability Characterization
HATS-13 b is a confirmed gas giant exoplanet orbiting the star HATS-13, located approximately 1375.9 light-years (421.86 parsecs) from the Solar System. First announced in 2015 by HATSouth using the Transit detection technique (producing an estimated primary transit depth of 1.9716% across the stellar disk), this world measures 13.585 Earth radii (1.21 Jupiter radii) and has a measured mass of 172.582 Earth masses (0.54 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 0.94 g⊕ (9.22 m/s²), and an escape velocity of 39.9 km/s.
In its orbital architecture around HATS-13, HATS-13 b completes one full revolution every 3.044 Earth days at a semi-major axis of 0.04057 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 145 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.181 carries the world between 0.0332 AU at periapsis and 0.0479 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1244 K (+971°C / +1780°F) and receiving 315.99 S⊕ (~430,059 W/m²), HATS-13 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HATS-13 is classified as a stellar host with an effective photospheric temperature of 5,523 K, a radius of 0.887 R☉, a mass of 0.962 M☉, an estimated bolometric luminosity of 0.657 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.5 Gyr and a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, HATS-13 shines at apparent V-band magnitude 13.911 (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-13 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,523 K |
| Stellar Radius | 0.8870 R☉ |
| Stellar Mass | 0.9620 M☉ |
| Bolometric Luminosity | 0.657 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | 2.500 Gyr |
| Apparent Magnitude | V: 13.911 · G: 13.680 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.040570 AU |
| Orbital Period | 3.044 days |
| Mean Orbital Velocity | 145 km/s |
| Orbital Eccentricity (e) | 0.18100 |
| Orbital Inclination (i) | 88.5500° |
| Mean Bulk Density | 0.38 g/cm³ (39.9 km/s vesc) |
| Insolation Flux | 315.9878 S⊕ (~430,059 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1375.900 LY (421.855 pc) |