HD 129445 b
Astrophysical Synthesis & Habitability Characterization
HD 129445 b is a confirmed gas giant exoplanet orbiting the star HD 129445, located approximately 220 light-years (67.44 parsecs) from the Solar System. First announced in 2009 by Las Campanas Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.3 Earth radii (1.19 Jupiter radii) and has a measured mass of 797.749 Earth masses (2.51 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.87 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 4.51 g⊕ (44.23 m/s²), and an escape velocity of 86.6 km/s.
In its orbital architecture around HD 129445, HD 129445 b completes one full revolution every 1840 Earth days (5.04Julian years) at a semi-major axis of 2.9 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 17.1 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.7, swinging from 0.87 AU at periapsis out to 4.93 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 173 K (-100°C / -148°F) and an incident flux of 0.15 S⊕ (~199 W/m²), surface water and volatile species on HD 129445 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 129445 is classified as a solar-type yellow star of spectral type G6 V with an effective photospheric temperature of 5,646 K, a radius of 1.1758 R☉, a mass of 0.99 M☉, an estimated bolometric luminosity of 1.26 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.25 dex (metal-rich relative to the Sun). From Earth, HD 129445 shines at apparent V-band magnitude 8.8 (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: Las Campanas Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 129445 |
| Spectral Type | G6 V |
| Effective Temp (Teff) | 5,646 K |
| Stellar Radius | 1.1758 R☉ |
| Stellar Mass | 0.9900 M☉ |
| Bolometric Luminosity | 1.26 L☉ |
| Metallicity [Fe/H] | 0.250 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 8.800 · G: 8.618 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.900000 AU |
| Orbital Period | 1840 days |
| Mean Orbital Velocity | 17.1 km/s |
| Orbital Eccentricity (e) | 0.70000 |
| Orbital Inclination (i) | 52.0000° |
| Mean Bulk Density | 1.87 g/cm³ (86.6 km/s vesc) |
| Insolation Flux | 0.1462 S⊕ (~199 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 220.000 LY (67.439 pc) |