HD 5608 b
Astrophysical Synthesis & Habitability Characterization
HD 5608 b is a confirmed gas giant exoplanet orbiting the star HD 5608, located approximately 189.5 light-years (58.11 parsecs) from the Solar System. First announced in 2012 by Okayama Astrophysical Observatory 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 371.224 Earth masses (1.17 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.8 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.98 g⊕ (19.42 m/s²), and an escape velocity of 58.2 km/s.
In its orbital architecture around HD 5608, HD 5608 b completes one full revolution every 768.7 Earth days (2.1Julian years) at a semi-major axis of 1.79 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 25.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.11 carries the world between 1.5931 AU at periapsis and 1.9869 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 404 K (+131°C / +268°F) and receiving 4.46 S⊕ (~6,066 W/m²), HD 5608 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 5608 is classified as an orange K-type star of spectral type K0 IV with an effective photospheric temperature of 4,807 K, a radius of 5.43 R☉, a mass of 1.29 M☉, an estimated bolometric luminosity of 14.125 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.72 Gyr and a metallicity of [Fe/H] = 0.04 dex (near-solar heavy-element abundance). From Earth, HD 5608 shines at apparent V-band magnitude 6.003 (visible to the unaided human eye under dark skies) in the Northern celestial hemisphere.
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: Okayama Astrophysical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 5608 |
| Spectral Type | K0 IV |
| Effective Temp (Teff) | 4,807 K |
| Stellar Radius | 5.4300 R☉ |
| Stellar Mass | 1.2900 M☉ |
| Bolometric Luminosity | 14.125 L☉ |
| Metallicity [Fe/H] | 0.040 dex |
| Stellar Age | 1.720 Gyr |
| Apparent Magnitude | V: 6.003 · G: 5.727 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.790000 AU |
| Orbital Period | 768.7 days |
| Mean Orbital Velocity | 25.3 km/s |
| Orbital Eccentricity (e) | 0.11000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.8 g/cm³ (58.2 km/s vesc) |
| Insolation Flux | 4.4568 S⊕ (~6,066 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 189.500 LY (58.111 pc) |