HIP 56640 b
Astrophysical Synthesis & Habitability Characterization
HIP 56640 b is a confirmed gas giant exoplanet orbiting the star HIP 56640, located approximately 399 light-years (122.32 parsecs) from the Solar System. First announced in 2021 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 2151.698 Earth masses (6.77 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.79 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 13.34 g⊕ (130.82 m/s²), and an escape velocity of 145.6 km/s.
In its orbital architecture around HIP 56640, HIP 56640 b completes one full revolution every 2675.576 Earth days (7.33Julian 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 18.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.118 carries the world between 4.0131 AU at periapsis and 5.0869 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.700 R⊕, HIP 56640 b 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 56640 is classified as an orange K-type star of spectral type K1 III with an effective photospheric temperature of 4,769 K, a radius of 4.93 R☉, a mass of 1.75 M☉, an estimated bolometric luminosity of 11.28 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.15 Gyr and a metallicity of [Fe/H] = -0.03 dex (near-solar heavy-element abundance). From Earth, HIP 56640 shines at apparent V-band magnitude 7.94 (accessible to binoculars and small amateur telescopes) in the Southern 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 56640 |
| Spectral Type | K1 III |
| Effective Temp (Teff) | 4,769 K |
| Stellar Radius | 4.9300 R☉ |
| Stellar Mass | 1.7500 M☉ |
| Bolometric Luminosity | 11.28 L☉ |
| Metallicity [Fe/H] | -0.030 dex |
| Stellar Age | 9.150 Gyr |
| Apparent Magnitude | V: 7.940 · G: 7.650 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 4.550000 AU |
| Orbital Period | 2675.576 days |
| Mean Orbital Velocity | 18.5 km/s |
| Orbital Eccentricity (e) | 0.11800 |
| Orbital Inclination (i) | 85.0930° |
| Mean Bulk Density | 5.79 g/cm³ (145.6 km/s vesc) |
| Insolation Flux | 0.5420 S⊕ (~738 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 399.000 LY (122.324 pc) |