HATS-45 b
Astrophysical Synthesis & Habitability Characterization
HATS-45 b is a confirmed gas giant exoplanet orbiting the star HATS-45, located approximately 2518.3 light-years (772.11 parsecs) from the Solar System. First announced in 2018 by HATSouth using the Transit detection technique (producing an estimated primary transit depth of 1.01% across the stellar disk), this world measures 14.415 Earth radii (1.29 Jupiter radii) and has a measured mass of 222.481 Earth masses (0.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.41 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 43.9 km/s.
In its orbital architecture around HATS-45, HATS-45 b completes one full revolution every 4.188 Earth days at a semi-major axis of 0.05511 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 143.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.24 carries the world between 0.0419 AU at periapsis and 0.0683 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1518 K (+1245°C / +2273°F) and receiving 811.35 S⊕ (~1,104,248 W/m²), HATS-45 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HATS-45 is classified as a stellar host with an effective photospheric temperature of 6,450 K, a radius of 1.315 R☉, a mass of 1.272 M☉, an estimated bolometric luminosity of 2.685 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.52 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, HATS-45 shines at apparent V-band magnitude 13.325 (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-45 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,450 K |
| Stellar Radius | 1.3150 R☉ |
| Stellar Mass | 1.2720 M☉ |
| Bolometric Luminosity | 2.685 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 1.520 Gyr |
| Apparent Magnitude | V: 13.325 · G: 13.239 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.055110 AU |
| Orbital Period | 4.188 days |
| Mean Orbital Velocity | 143.2 km/s |
| Orbital Eccentricity (e) | 0.24000 |
| Orbital Inclination (i) | 85.6100° |
| Mean Bulk Density | 0.41 g/cm³ (43.9 km/s vesc) |
| Insolation Flux | 811.3504 S⊕ (~1,104,248 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2518.300 LY (772.110 pc) |