HIP 67851 b
Astrophysical Synthesis & Habitability Characterization
HIP 67851 b 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 13.7 Earth radii (1.22 Jupiter radii) and has a measured mass of 365.503 Earth masses (1.15 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.78 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.95 g⊕ (19.12 m/s²), and an escape velocity of 57.8 km/s.
In its orbital architecture around HIP 67851, HIP 67851 b completes one full revolution every 89.23 Earth days at a semi-major axis of 0.42 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 51.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.13 carries the world between 0.3654 AU at periapsis and 0.4746 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 841 K (+568°C / +1054°F) and receiving 83.22 S⊕ (~113,262 W/m²), HIP 67851 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
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 b sharing its stellar neighborhood alongside HIP 67851 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: 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) | 0.420000 AU |
| Orbital Period | 89.23 days |
| Mean Orbital Velocity | 51.2 km/s |
| Orbital Eccentricity (e) | 0.13000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.78 g/cm³ (57.8 km/s vesc) |
| Insolation Flux | 83.2200 S⊕ (~113,262 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 209.100 LY (64.118 pc) |