HD 75289 b
Astrophysical Synthesis & Habitability Characterization
HD 75289 b is a confirmed gas giant exoplanet orbiting the star HD 75289, located approximately 95 light-years (29.12 parsecs) from the Solar System. First announced in 1999 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14.2 Earth radii (1.27 Jupiter radii) and has a measured mass of 155.737 Earth masses (0.49 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.3 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.77 g⊕ (7.55 m/s²), and an escape velocity of 37 km/s.
In its orbital architecture around HD 75289, HD 75289 b completes one full revolution every 3.509 Earth days at a semi-major axis of 0.05 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 155 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.03 (ranging from 0.0485 AU at periapsis to 0.0515 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1260 K (+987°C / +1809°F) and receiving 821.35 S⊕ (~1,117,856 W/m²), HD 75289 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 75289 is classified as a solar-type yellow star of spectral type G0 with an effective photospheric temperature of 6,117 K, a radius of 1.23 R☉, a mass of 1.29 M☉, an estimated bolometric luminosity of 1.9 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.6 Gyr and a metallicity of [Fe/H] = 0.26 dex (metal-rich relative to the Sun). From Earth, HD 75289 shines at apparent V-band magnitude 6.35 (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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 75289 |
| Spectral Type | G0 |
| Effective Temp (Teff) | 6,117 K |
| Stellar Radius | 1.2300 R☉ |
| Stellar Mass | 1.2900 M☉ |
| Bolometric Luminosity | 1.9 L☉ |
| Metallicity [Fe/H] | 0.260 dex |
| Stellar Age | 5.600 Gyr |
| Apparent Magnitude | V: 6.350 · G: 6.210 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.050000 AU |
| Orbital Period | 3.509 days |
| Mean Orbital Velocity | 155 km/s |
| Orbital Eccentricity (e) | 0.03000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.3 g/cm³ (37 km/s vesc) |
| Insolation Flux | 821.3488 S⊕ (~1,117,856 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 95.000 LY (29.116 pc) |