HD 152581 b
Astrophysical Synthesis & Habitability Characterization
HD 152581 b is a confirmed gas giant exoplanet orbiting the star HD 152581, located approximately 540.6 light-years (165.76 parsecs) from the Solar System. First announced in 2011 by W. M. Keck Observatory 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 594.024 Earth masses (1.87 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.36 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.31 g⊕ (32.46 m/s²), and an escape velocity of 74.5 km/s.
In its orbital architecture around HD 152581, HD 152581 b completes one full revolution every 686.5 Earth days (1.88Julian years) at a semi-major axis of 1.66 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 26.3 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.04 (ranging from 1.5936 AU at periapsis to 1.7264 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 427 K (+154°C / +309°F) and receiving 5.41 S⊕ (~7,359 W/m²), HD 152581 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 152581 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 5,027 K, a radius of 5.14 R☉, a mass of 1.3 M☉, an estimated bolometric luminosity of 15.137 L☉. Stellar evolution modeling indicates an estimated stellar age of 12 Gyr and a metallicity of [Fe/H] = -0.46 dex (metal-poor relative to the Sun). From Earth, HD 152581 shines at apparent V-band magnitude 8.38 (accessible to binoculars and small amateur telescopes) 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 152581 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 5,027 K |
| Stellar Radius | 5.1400 R☉ |
| Stellar Mass | 1.3000 M☉ |
| Bolometric Luminosity | 15.137 L☉ |
| Metallicity [Fe/H] | -0.460 dex |
| Stellar Age | 12.000 Gyr |
| Apparent Magnitude | V: 8.380 · G: 8.127 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.660000 AU |
| Orbital Period | 686.5 days |
| Mean Orbital Velocity | 26.3 km/s |
| Orbital Eccentricity (e) | 0.04000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.36 g/cm³ (74.5 km/s vesc) |
| Insolation Flux | 5.4072 S⊕ (~7,359 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 540.600 LY (165.760 pc) |