HATS-40 b
Astrophysical Synthesis & Habitability Characterization
HATS-40 b is a confirmed gas giant exoplanet orbiting the star HATS-40, located approximately 4378 light-years (1342.29 parsecs) from the Solar System. First announced in 2018 by HATSouth using the Transit detection technique (producing an estimated primary transit depth of 0.5161% across the stellar disk), this world measures 17.71 Earth radii (1.58 Jupiter radii) and has a measured mass of 505.35 Earth masses (1.59 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.5 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.61 g⊕ (15.79 m/s²), and an escape velocity of 59.8 km/s.
In its orbital architecture around HATS-40, HATS-40 b completes one full revolution every 3.264 Earth days at a semi-major axis of 0.04997 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 166.5 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.312, swinging from 0.0344 AU at periapsis out to 0.0656 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2101 K (+1828°C / +3322°F) and receiving 3,163.38 S⊕ (~4,305,355 W/m²), HATS-40 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HATS-40 is classified as a stellar host with an effective photospheric temperature of 6,460 K, a radius of 2.26 R☉, a mass of 1.561 M☉, an estimated bolometric luminosity of 7.981 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.07 Gyr and a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, HATS-40 shines at apparent V-band magnitude 13.478 (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-40 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,460 K |
| Stellar Radius | 2.2600 R☉ |
| Stellar Mass | 1.5610 M☉ |
| Bolometric Luminosity | 7.981 L☉ |
| Metallicity [Fe/H] | 0.010 dex |
| Stellar Age | 2.070 Gyr |
| Apparent Magnitude | V: 13.478 · G: 13.284 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.049970 AU |
| Orbital Period | 3.264 days |
| Mean Orbital Velocity | 166.5 km/s |
| Orbital Eccentricity (e) | 0.31200 |
| Orbital Inclination (i) | 85.8000° |
| Mean Bulk Density | 0.5 g/cm³ (59.8 km/s vesc) |
| Insolation Flux | 3163.3762 S⊕ (~4,305,355 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4378.000 LY (1342.290 pc) |