HD 47186 b
Astrophysical Synthesis & Habitability Characterization
HD 47186 b is a confirmed sub-neptune exoplanet orbiting the star HD 47186, located approximately 122.2 light-years (37.46 parsecs) from the Solar System. First announced in 2008 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 5.02 Earth radii (0.45 Jupiter radii) and has a measured mass of 22.248 Earth masses. Combining its mass and radius yields a mean bulk density of 0.97 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.88 g⊕ (8.63 m/s²), and an escape velocity of 23.5 km/s.
In its orbital architecture around HD 47186, HD 47186 b completes one full revolution every 4.085 Earth days at a semi-major axis of 0.05 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 133.2 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.04 (ranging from 0.048 AU at periapsis to 0.052 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1268 K (+995°C / +1823°F) and receiving 441.61 S⊕ (~601,027 W/m²), HD 47186 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 47186 is classified as a solar-type yellow star of spectral type G6 V with an effective photospheric temperature of 5,657 K, a radius of 1.08 R☉, a mass of 0.96 M☉, an estimated bolometric luminosity of 1.072 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.5 Gyr and a metallicity of [Fe/H] = 0.24 dex (metal-rich relative to the Sun). From Earth, HD 47186 shines at apparent V-band magnitude 7.63 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 47186 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 47186 b sharing its stellar neighborhood alongside HD 47186 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 47186 |
| Spectral Type | G6 V |
| Effective Temp (Teff) | 5,657 K |
| Stellar Radius | 1.0800 R☉ |
| Stellar Mass | 0.9600 M☉ |
| Bolometric Luminosity | 1.072 L☉ |
| Metallicity [Fe/H] | 0.240 dex |
| Stellar Age | 6.500 Gyr |
| Apparent Magnitude | V: 7.630 · G: 7.449 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.050000 AU |
| Orbital Period | 4.085 days |
| Mean Orbital Velocity | 133.2 km/s |
| Orbital Eccentricity (e) | 0.04000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.97 g/cm³ (23.5 km/s vesc) |
| Insolation Flux | 441.6068 S⊕ (~601,027 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 122.200 LY (37.457 pc) |