HD 148156 b
Astrophysical Synthesis & Habitability Characterization
HD 148156 b is a confirmed gas giant exoplanet orbiting the star HD 148156, located approximately 186.3 light-years (57.13 parsecs) from the Solar System. First announced in 2009 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.9 Earth radii (1.24 Jupiter radii) and has a measured mass of 270.144 Earth masses (0.85 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.55 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.4 g⊕ (13.73 m/s²), and an escape velocity of 49.3 km/s.
In its orbital architecture around HD 148156, HD 148156 b completes one full revolution every 1027 Earth days (2.81Julian years) at a semi-major axis of 2.45 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 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.52, swinging from 1.176 AU at periapsis out to 3.724 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.900 R⊕, HD 148156 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 148156 is classified as a solar-type yellow star of spectral type G0/2 V with an effective photospheric temperature of 6,308 K, a radius of 1.21 R☉, a mass of 1.22 M☉, an estimated bolometric luminosity of 2.08 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.29 dex (metal-rich relative to the Sun). From Earth, HD 148156 shines at apparent V-band magnitude 7.69 (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 148156 |
| Spectral Type | G0/2 V |
| Effective Temp (Teff) | 6,308 K |
| Stellar Radius | 1.2100 R☉ |
| Stellar Mass | 1.2200 M☉ |
| Bolometric Luminosity | 2.08 L☉ |
| Metallicity [Fe/H] | 0.290 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 7.690 · G: 7.555 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.450000 AU |
| Orbital Period | 1027 days |
| Mean Orbital Velocity | 26 km/s |
| Orbital Eccentricity (e) | 0.52000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.55 g/cm³ (49.3 km/s vesc) |
| Insolation Flux | 0.2965 S⊕ (~404 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 186.300 LY (57.129 pc) |