HD 74156 b
Astrophysical Synthesis & Habitability Characterization
HD 74156 b is a confirmed gas giant exoplanet orbiting the star HD 74156, located approximately 187.9 light-years (57.6 parsecs) from the Solar System. First announced in 2003 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 532.363 Earth masses (1.67 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.19 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.92 g⊕ (28.64 m/s²), and an escape velocity of 70.2 km/s.
In its orbital architecture around HD 74156, HD 74156 b completes one full revolution every 51.636 Earth days at a semi-major axis of 0.28 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 59 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.636, swinging from 0.1019 AU at periapsis out to 0.4581 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 680 K (+407°C / +765°F) and receiving 32.10 S⊕ (~43,681 W/m²), HD 74156 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 74156 is classified as a solar-type yellow star of spectral type G0 with an effective photospheric temperature of 6,068 K, a radius of 1.5106 R☉, a mass of 1.1 M☉, an estimated bolometric luminosity of 2.776 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.7 Gyr and a metallicity of [Fe/H] = 0.131 dex (metal-rich relative to the Sun). From Earth, HD 74156 shines at apparent V-band magnitude 7.61 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 74156 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 74156 b sharing its stellar neighborhood alongside HD 74156 c.
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 74156 |
| Spectral Type | G0 |
| Effective Temp (Teff) | 6,068 K |
| Stellar Radius | 1.5106 R☉ |
| Stellar Mass | 1.1000 M☉ |
| Bolometric Luminosity | 2.776 L☉ |
| Metallicity [Fe/H] | 0.131 dex |
| Stellar Age | 3.700 Gyr |
| Apparent Magnitude | V: 7.610 · G: 7.469 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.280000 AU |
| Orbital Period | 51.636 days |
| Mean Orbital Velocity | 59 km/s |
| Orbital Eccentricity (e) | 0.63600 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.19 g/cm³ (70.2 km/s vesc) |
| Insolation Flux | 32.0951 S⊕ (~43,681 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 187.900 LY (57.603 pc) |