HD 125390 b
Astrophysical Synthesis & Habitability Characterization
HD 125390 b is a confirmed gas giant exoplanet orbiting the star HD 125390, located approximately 501.1 light-years (153.65 parsecs) from the Solar System. First announced in 2019 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 11.9 Earth radii (1.06 Jupiter radii) and has a measured mass of 8646.204 Earth masses (27.2 Jupiter masses). Combining its mass and radius yields a mean bulk density of 28.29 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 61.06 g⊕ (598.79 m/s²), and an escape velocity of 301.5 km/s.
In its orbital architecture around HD 125390, HD 125390 b completes one full revolution every 1757.392 Earth days (4.81Julian years) at a semi-major axis of 3.496 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 21.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.597, swinging from 1.4089 AU at periapsis out to 5.5831 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 11.900 R⊕, HD 125390 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 125390 is classified as a solar-type yellow star of spectral type G7 III with an effective photospheric temperature of 4,882 K, a radius of 6.47 R☉, a mass of 1.82 M☉, an estimated bolometric luminosity of 21.335 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, HD 125390 shines at apparent V-band magnitude 8.21 (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 125390 |
| Spectral Type | G7 III |
| Effective Temp (Teff) | 4,882 K |
| Stellar Radius | 6.4700 R☉ |
| Stellar Mass | 1.8200 M☉ |
| Bolometric Luminosity | 21.335 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 8.210 · G: 7.941 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.496000 AU |
| Orbital Period | 1757.392 days |
| Mean Orbital Velocity | 21.6 km/s |
| Orbital Eccentricity (e) | 0.59700 |
| Orbital Inclination (i) | 84.6850° |
| Mean Bulk Density | 28.29 g/cm³ (301.5 km/s vesc) |
| Insolation Flux | 1.0874 S⊕ (~1,480 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 501.100 LY (153.647 pc) |