HAT-P-54 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-54 b is a confirmed gas giant exoplanet orbiting the star HAT-P-54, located approximately 468.5 light-years (143.65 parsecs) from the Solar System. First announced in 2015 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 2.4719% across the stellar disk), this world measures 10.581 Earth radii (0.94 Jupiter radii) and has a measured mass of 241.551 Earth masses (0.76 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.12 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.16 g⊕ (21.18 m/s²), and an escape velocity of 53.4 km/s.
In its orbital architecture around HAT-P-54, HAT-P-54 b completes one full revolution every 3.8 Earth days at a semi-major axis of 0.04117 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 117.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.074 carries the world between 0.0381 AU at periapsis and 0.0442 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 818 K (+545°C / +1013°F) and receiving 88.67 S⊕ (~120,682 W/m²), HAT-P-54 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-54 is classified as an orange K-type star of spectral type K7 with an effective photospheric temperature of 4,390 K, a radius of 0.617 R☉, a mass of 0.645 M☉, an estimated bolometric luminosity of 0.127 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.9 Gyr and a metallicity of [Fe/H] = -0.127 dex (metal-poor relative to the Sun). From Earth, HAT-P-54 shines at apparent V-band magnitude 13.398 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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-54 |
| Spectral Type | K7 |
| Effective Temp (Teff) | 4,390 K |
| Stellar Radius | 0.6170 R☉ |
| Stellar Mass | 0.6450 M☉ |
| Bolometric Luminosity | 0.127 L☉ |
| Metallicity [Fe/H] | -0.127 dex |
| Stellar Age | 3.900 Gyr |
| Apparent Magnitude | V: 13.398 · G: 13.017 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041170 AU |
| Orbital Period | 3.8 days |
| Mean Orbital Velocity | 117.9 km/s |
| Orbital Eccentricity (e) | 0.07400 |
| Orbital Inclination (i) | 87.0400° |
| Mean Bulk Density | 1.12 g/cm³ (53.4 km/s vesc) |
| Insolation Flux | 88.6713 S⊕ (~120,682 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 468.500 LY (143.651 pc) |