HIP 67851 c
Astrophysical Synthesis & Habitability Characterization
HIP 67851 c is a confirmed gas giant exoplanet orbiting the star HIP 67851, located approximately 209.1 light-years (64.12 parsecs) from the Solar System. First announced in 2015 by Multiple Observatories 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 2204.776 Earth masses (6.94 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.93 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 13.67 g⊕ (134.06 m/s²), and an escape velocity of 147.4 km/s.
In its orbital architecture around HIP 67851, HIP 67851 c completes one full revolution every 3128.41 Earth days (8.57Julian years) at a semi-major axis of 4.55 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 15.8 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.3, swinging from 3.185 AU at periapsis out to 5.915 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.700 R⊕, HIP 67851 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 HIP 67851 is classified as an orange K-type star of spectral type K0 III with an effective photospheric temperature of 4,840 K, a radius of 5.45 R☉, a mass of 1.28 M☉, an estimated bolometric luminosity of 14.624 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.46 Gyr and a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, HIP 67851 shines at apparent V-band magnitude 6.17 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The HIP 67851 system is a multi-planet architecture hosting 2 confirmed worlds, with HIP 67851 c sharing its stellar neighborhood alongside HIP 67851 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 67851 |
| Spectral Type | K0 III |
| Effective Temp (Teff) | 4,840 K |
| Stellar Radius | 5.4500 R☉ |
| Stellar Mass | 1.2800 M☉ |
| Bolometric Luminosity | 14.624 L☉ |
| Metallicity [Fe/H] | 0.010 dex |
| Stellar Age | 5.460 Gyr |
| Apparent Magnitude | V: 6.170 · G: 5.893 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 4.550000 AU |
| Orbital Period | 3128.41 days |
| Mean Orbital Velocity | 15.8 km/s |
| Orbital Eccentricity (e) | 0.30000 |
| Orbital Inclination (i) | 89.8630° |
| Mean Bulk Density | 5.93 g/cm³ (147.4 km/s vesc) |
| Insolation Flux | 0.7091 S⊕ (~965 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 209.100 LY (64.118 pc) |