HD 42012 b
Astrophysical Synthesis & Habitability Characterization
HD 42012 b is a confirmed gas giant exoplanet orbiting the star HD 42012, located approximately 120 light-years (36.8 parsecs) from the Solar System. First announced in 2017 by Haute-Provence Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.5 Earth radii (1.2 Jupiter radii) and has a measured mass of 508.528 Earth masses (1.6 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.14 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.79 g⊕ (27.36 m/s²), and an escape velocity of 68.7 km/s.
In its orbital architecture around HD 42012, HD 42012 b completes one full revolution every 857.5 Earth days (2.35Julian years) at a semi-major axis of 1.67 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 21.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.2 carries the world between 1.336 AU at periapsis and 2.004 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.500 R⊕, HD 42012 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star HD 42012 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 5,405 K, a radius of 0.82 R☉, a mass of 0.83 M☉, an estimated bolometric luminosity of 0.515 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.1 Gyr and a metallicity of [Fe/H] = -0.09 dex (near-solar heavy-element abundance). From Earth, HD 42012 shines at apparent V-band magnitude 8.44 (accessible to binoculars and small amateur telescopes) 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: Haute-Provence Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 42012 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 5,405 K |
| Stellar Radius | 0.8200 R☉ |
| Stellar Mass | 0.8300 M☉ |
| Bolometric Luminosity | 0.515 L☉ |
| Metallicity [Fe/H] | -0.090 dex |
| Stellar Age | 4.100 Gyr |
| Apparent Magnitude | V: 8.440 · G: 8.229 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.670000 AU |
| Orbital Period | 857.5 days |
| Mean Orbital Velocity | 21.2 km/s |
| Orbital Eccentricity (e) | 0.20000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.14 g/cm³ (68.7 km/s vesc) |
| Insolation Flux | 0.1927 S⊕ (~262 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 120.000 LY (36.798 pc) |