HAT-P-45 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-45 b is a confirmed gas giant exoplanet orbiting the star HAT-P-45, located approximately 974 light-years (298.64 parsecs) from the Solar System. First announced in 2014 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.2343% across the stellar disk), this world measures 15.984 Earth radii (1.43 Jupiter radii) and has a measured mass of 283.492 Earth masses (0.89 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 1.11 g⊕ (10.89 m/s²), and an escape velocity of 47.1 km/s.
In its orbital architecture around HAT-P-45, HAT-P-45 b completes one full revolution every 3.129 Earth days at a semi-major axis of 0.0452 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 157.2 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.049 (ranging from 0.043 AU at periapsis to 0.0474 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1652 K (+1379°C / +2514°F) and receiving 1,052.24 S⊕ (~1,432,097 W/m²), HAT-P-45 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-45 is classified as a stellar host with an effective photospheric temperature of 6,330 K, a radius of 1.319 R☉, a mass of 1.259 M☉, an estimated bolometric luminosity of 2.506 L☉. Stellar evolution modeling indicates an estimated stellar age of 2 Gyr and a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, HAT-P-45 shines at apparent V-band magnitude 12.783 (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: HATNet · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HAT-P-45 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,330 K |
| Stellar Radius | 1.3190 R☉ |
| Stellar Mass | 1.2590 M☉ |
| Bolometric Luminosity | 2.506 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | 2.000 Gyr |
| Apparent Magnitude | V: 12.783 · G: 12.398 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.045200 AU |
| Orbital Period | 3.129 days |
| Mean Orbital Velocity | 157.2 km/s |
| Orbital Eccentricity (e) | 0.04900 |
| Orbital Inclination (i) | 87.8000° |
| Mean Bulk Density | 0.38 g/cm³ (47.1 km/s vesc) |
| Insolation Flux | 1052.2390 S⊕ (~1,432,097 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 974.000 LY (298.640 pc) |