WASP-77 A b
Astrophysical Synthesis & Habitability Characterization
WASP-77 A b is a confirmed gas giant exoplanet orbiting the star WASP-77 A, located approximately 343 light-years (105.17 parsecs) from the Solar System. First announced in 2012 by SuperWASP using the Transit detection technique (producing an estimated primary transit depth of 1.8663% across the stellar disk), this world measures 13.56 Earth radii (1.21 Jupiter radii) and has a measured mass of 529.311 Earth masses (1.67 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.17 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.88 g⊕ (28.24 m/s²), and an escape velocity of 69.9 km/s.
In its orbital architecture around WASP-77 A, WASP-77 A b completes one full revolution every 1.36 Earth days at a semi-major axis of 0.023234 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 185.9 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.01353 (ranging from 0.0229 AU at periapsis to 0.0235 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1674 K (+1401°C / +2554°F) and receiving 1,440.00 S⊕ (~1,959,840 W/m²), WASP-77 A b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star WASP-77 A is classified as a solar-type yellow star of spectral type G8 V with an effective photospheric temperature of 5,617 K, a radius of 0.91 R☉, a mass of 0.903 M☉, an estimated bolometric luminosity of 0.74 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.2 Gyr and a metallicity of [Fe/H] = -0.1 dex (near-solar heavy-element abundance). From Earth, WASP-77 A shines at apparent V-band magnitude 10.294 (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: SuperWASP · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | WASP-77 A |
| Spectral Type | G8 V |
| Effective Temp (Teff) | 5,617 K |
| Stellar Radius | 0.9100 R☉ |
| Stellar Mass | 0.9030 M☉ |
| Bolometric Luminosity | 0.74 L☉ |
| Metallicity [Fe/H] | -0.100 dex |
| Stellar Age | 6.200 Gyr |
| Apparent Magnitude | V: 10.294 · G: 10.097 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.023234 AU |
| Orbital Period | 1.36 days |
| Mean Orbital Velocity | 185.9 km/s |
| Orbital Eccentricity (e) | 0.01353 |
| Orbital Inclination (i) | 89.9900° |
| Mean Bulk Density | 1.17 g/cm³ (69.9 km/s vesc) |
| Insolation Flux | 1440.0000 S⊕ (~1,959,840 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 343.000 LY (105.166 pc) |