HD 134987 b
Astrophysical Synthesis & Habitability Characterization
HD 134987 b is a confirmed gas giant exoplanet orbiting the star HD 134987, located approximately 85.4 light-years (26.18 parsecs) from the Solar System. First announced in 1999 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 13.5 Earth radii (1.2 Jupiter radii) and has a measured mass of 511.706 Earth masses (1.61 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.15 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.81 g⊕ (27.56 m/s²), and an escape velocity of 68.9 km/s.
In its orbital architecture around HD 134987, HD 134987 b completes one full revolution every 258.18 Earth days at a semi-major axis of 0.81 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 34.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.23 carries the world between 0.6237 AU at periapsis and 0.9963 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.500 R⊕, HD 134987 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 HD 134987 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,736 K, a radius of 1.22 R☉, a mass of 1.1 M☉, an estimated bolometric luminosity of 1.446 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.4 Gyr and a metallicity of [Fe/H] = 0.28 dex (metal-rich relative to the Sun). From Earth, HD 134987 shines at apparent V-band magnitude 6.47 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 134987 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 134987 b sharing its stellar neighborhood alongside HD 134987 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 134987 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,736 K |
| Stellar Radius | 1.2200 R☉ |
| Stellar Mass | 1.1000 M☉ |
| Bolometric Luminosity | 1.446 L☉ |
| Metallicity [Fe/H] | 0.280 dex |
| Stellar Age | 8.400 Gyr |
| Apparent Magnitude | V: 6.470 · G: 6.290 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.810000 AU |
| Orbital Period | 258.18 days |
| Mean Orbital Velocity | 34.1 km/s |
| Orbital Eccentricity (e) | 0.23000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.15 g/cm³ (68.9 km/s vesc) |
| Insolation Flux | 2.7435 S⊕ (~3,734 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 85.400 LY (26.180 pc) |