WASP-42 b
Astrophysical Synthesis & Habitability Characterization
WASP-42 b is a confirmed gas giant exoplanet orbiting the star WASP-42, located approximately 578.2 light-years (177.29 parsecs) from the Solar System. First announced in 2012 by SuperWASP using the Transit detection technique (producing an estimated primary transit depth of 1.6707% across the stellar disk), this world measures 12.576 Earth radii (1.12 Jupiter radii) and has a measured mass of 167.496 Earth masses (0.53 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.46 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 40.8 km/s.
In its orbital architecture around WASP-42, WASP-42 b completes one full revolution every 4.982 Earth days at a semi-major axis of 0.0561 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 122.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.062 carries the world between 0.0526 AU at periapsis and 0.0596 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1021 K (+748°C / +1378°F) and receiving 137.12 S⊕ (~186,618 W/m²), WASP-42 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star WASP-42 is classified as a stellar host with an effective photospheric temperature of 5,315 K, a radius of 0.892 R☉, a mass of 0.951 M☉, an estimated bolometric luminosity of 0.57 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.4 Gyr and a metallicity of [Fe/H] = 0.29 dex (metal-rich relative to the Sun). From Earth, WASP-42 shines at apparent V-band magnitude 12.169 (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-42 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,315 K |
| Stellar Radius | 0.8920 R☉ |
| Stellar Mass | 0.9510 M☉ |
| Bolometric Luminosity | 0.57 L☉ |
| Metallicity [Fe/H] | 0.290 dex |
| Stellar Age | 4.400 Gyr |
| Apparent Magnitude | V: 12.169 · G: 11.969 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.056100 AU |
| Orbital Period | 4.982 days |
| Mean Orbital Velocity | 122.5 km/s |
| Orbital Eccentricity (e) | 0.06200 |
| Orbital Inclination (i) | 88.0000° |
| Mean Bulk Density | 0.46 g/cm³ (40.8 km/s vesc) |
| Insolation Flux | 137.1180 S⊕ (~186,618 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 578.200 LY (177.291 pc) |