HD 5388 b
Astrophysical Synthesis & Habitability Characterization
HD 5388 b is a confirmed gas giant exoplanet orbiting the star HD 5388, located approximately 173.1 light-years (53.07 parsecs) from the Solar System. First announced in 2010 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.1 Earth radii (1.17 Jupiter radii) and has a measured mass of 1017.051 Earth masses (3.2 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.49 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 5.93 g⊕ (58.15 m/s²), and an escape velocity of 98.6 km/s.
In its orbital architecture around HD 5388, HD 5388 b completes one full revolution every 772.5 Earth days (2.11Julian years) at a semi-major axis of 1.757 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 24.7 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.41, swinging from 1.0366 AU at periapsis out to 2.4774 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.100 R⊕, HD 5388 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 5388 is classified as a warm F-type star of spectral type F6 V with an effective photospheric temperature of 6,297 K, a radius of 1.91 R☉, a mass of 1.21 M☉, an estimated bolometric luminosity of 5.146 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.27 dex (metal-poor relative to the Sun). From Earth, HD 5388 shines at apparent V-band magnitude 6.73 (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 5388 |
| Spectral Type | F6 V |
| Effective Temp (Teff) | 6,297 K |
| Stellar Radius | 1.9100 R☉ |
| Stellar Mass | 1.2100 M☉ |
| Bolometric Luminosity | 5.146 L☉ |
| Metallicity [Fe/H] | -0.270 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 6.730 · G: 6.591 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.757000 AU |
| Orbital Period | 772.5 days |
| Mean Orbital Velocity | 24.7 km/s |
| Orbital Eccentricity (e) | 0.41000 |
| Orbital Inclination (i) | 38.7000° |
| Mean Bulk Density | 2.49 g/cm³ (98.6 km/s vesc) |
| Insolation Flux | 1.4901 S⊕ (~2,028 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 173.100 LY (53.066 pc) |