WASP-123 b
Astrophysical Synthesis & Habitability Characterization
WASP-123 b is a confirmed gas giant exoplanet orbiting the star WASP-123, located approximately 645.8 light-years (198 parsecs) from the Solar System. First announced in 2016 by SuperWASP using the Transit detection technique (producing an estimated primary transit depth of 1.1655% across the stellar disk), this world measures 15.132 Earth radii (1.35 Jupiter radii) and has a measured mass of 285.729 Earth masses (0.9 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.45 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.25 g⊕ (12.26 m/s²), and an escape velocity of 48.6 km/s.
In its orbital architecture around WASP-123, WASP-123 b completes one full revolution every 2.978 Earth days at a semi-major axis of 0.04263 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 155.8 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1500 K (+1227°C / +2241°F) and receiving 758.32 S⊕ (~1,032,079 W/m²), WASP-123 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star WASP-123 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,740 K, a radius of 1.285 R☉, a mass of 1.166 M☉, an estimated bolometric luminosity of 1.608 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.9 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, WASP-123 shines at apparent V-band magnitude 11.03 (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-123 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,740 K |
| Stellar Radius | 1.2850 R☉ |
| Stellar Mass | 1.1660 M☉ |
| Bolometric Luminosity | 1.608 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 6.900 Gyr |
| Apparent Magnitude | V: 11.030 · G: 10.900 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.042630 AU |
| Orbital Period | 2.978 days |
| Mean Orbital Velocity | 155.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.2000° |
| Mean Bulk Density | 0.45 g/cm³ (48.6 km/s vesc) |
| Insolation Flux | 758.3240 S⊕ (~1,032,079 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 645.800 LY (197.996 pc) |