HD 4732 b
Astrophysical Synthesis & Habitability Characterization
HD 4732 b is a confirmed gas giant exoplanet orbiting the star HD 4732, located approximately 178.7 light-years (54.78 parsecs) from the Solar System. First announced in 2012 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.4 Earth radii (1.2 Jupiter radii) and has a measured mass of 631.207 Earth masses (1.99 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.45 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.52 g⊕ (34.52 m/s²), and an escape velocity of 76.8 km/s.
In its orbital architecture around HD 4732, HD 4732 b completes one full revolution every 371.74 Earth days (1.02Julian years) at a semi-major axis of 1.129 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 33 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.266, swinging from 0.8287 AU at periapsis out to 1.4293 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 499 K (+226°C / +439°F) and receiving 10.30 S⊕ (~14,020 W/m²), HD 4732 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 4732 is classified as an orange K-type star of spectral type K0 IV with an effective photospheric temperature of 4,898 K, a radius of 5.03 R☉, a mass of 1.39 M☉, an estimated bolometric luminosity of 13.065 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.47 Gyr and a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, HD 4732 shines at apparent V-band magnitude 5.9 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The HD 4732 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 4732 b sharing its stellar neighborhood alongside HD 4732 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 | HD 4732 |
| Spectral Type | K0 IV |
| Effective Temp (Teff) | 4,898 K |
| Stellar Radius | 5.0300 R☉ |
| Stellar Mass | 1.3900 M☉ |
| Bolometric Luminosity | 13.065 L☉ |
| Metallicity [Fe/H] | -0.010 dex |
| Stellar Age | 1.470 Gyr |
| Apparent Magnitude | V: 5.900 · G: 5.651 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.129000 AU |
| Orbital Period | 371.74 days |
| Mean Orbital Velocity | 33 km/s |
| Orbital Eccentricity (e) | 0.26600 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.45 g/cm³ (76.8 km/s vesc) |
| Insolation Flux | 10.3009 S⊕ (~14,020 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 178.700 LY (54.784 pc) |