HD 147018 c
Astrophysical Synthesis & Habitability Characterization
HD 147018 c is a confirmed gas giant exoplanet orbiting the star HD 147018, located approximately 131.9 light-years (40.43 parsecs) from the Solar System. First announced in 2009 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.7 Earth radii (1.13 Jupiter radii) and has a measured mass of 2080 Earth masses (6.54 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.6 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 12.9 g⊕ (126.51 m/s²), and an escape velocity of 143.2 km/s.
In its orbital architecture around HD 147018, HD 147018 c completes one full revolution every 1008 Earth days (2.76Julian years) at a semi-major axis of 1.922 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 20.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.133 carries the world between 1.6664 AU at periapsis and 2.1776 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.700 R⊕, HD 147018 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 147018 is classified as a solar-type yellow star of spectral type G9 V with an effective photospheric temperature of 5,441 K, a radius of 0.9379 R☉, a mass of 0.927 M☉, an estimated bolometric luminosity of 0.692 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.36 Gyr and a metallicity of [Fe/H] = 0.1 dex (metal-rich relative to the Sun). From Earth, HD 147018 shines at apparent V-band magnitude 8.3 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 147018 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 147018 c sharing its stellar neighborhood alongside HD 147018 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 147018 |
| Spectral Type | G9 V |
| Effective Temp (Teff) | 5,441 K |
| Stellar Radius | 0.9379 R☉ |
| Stellar Mass | 0.9270 M☉ |
| Bolometric Luminosity | 0.692 L☉ |
| Metallicity [Fe/H] | 0.100 dex |
| Stellar Age | 6.360 Gyr |
| Apparent Magnitude | V: 8.300 · G: 8.111 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.922000 AU |
| Orbital Period | 1008 days |
| Mean Orbital Velocity | 20.7 km/s |
| Orbital Eccentricity (e) | 0.13300 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.6 g/cm³ (143.2 km/s vesc) |
| Insolation Flux | 0.1927 S⊕ (~262 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 131.900 LY (40.426 pc) |