HD 74156 c
Astrophysical Synthesis & Habitability Characterization
HD 74156 c 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 12.5 Earth radii (1.12 Jupiter radii) and has a measured mass of 2753.983 Earth masses (8.66 Jupiter masses). Combining its mass and radius yields a mean bulk density of 7.77 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 17.63 g⊕ (172.89 m/s²), and an escape velocity of 166 km/s.
In its orbital architecture around HD 74156, HD 74156 c completes one full revolution every 2448.487 Earth days (6.7Julian years) at a semi-major axis of 3.678 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 16.3 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.377, swinging from 2.2914 AU at periapsis out to 5.0646 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.500 R⊕, HD 74156 c 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 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 c sharing its stellar neighborhood alongside HD 74156 b.
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) | 3.678000 AU |
| Orbital Period | 2448.487 days |
| Mean Orbital Velocity | 16.3 km/s |
| Orbital Eccentricity (e) | 0.37700 |
| Orbital Inclination (i) | 120.1620° |
| Mean Bulk Density | 7.77 g/cm³ (166 km/s vesc) |
| Insolation Flux | 0.1860 S⊕ (~253 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 187.900 LY (57.603 pc) |