HD 125612 c
Astrophysical Synthesis & Habitability Characterization
HD 125612 c is a confirmed sub-neptune exoplanet orbiting the star HD 125612, located approximately 187.9 light-years (57.62 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 4.07 Earth radii (0.36 Jupiter radii) and has a measured mass of 15.574 Earth masses. Combining its mass and radius yields a mean bulk density of 1.27 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.94 g⊕ (9.22 m/s²), and an escape velocity of 21.9 km/s.
In its orbital architecture around HD 125612, HD 125612 c completes one full revolution every 4.155 Earth days at a semi-major axis of 0.051 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 133.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.149 carries the world between 0.0434 AU at periapsis and 0.0586 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1303 K (+1030°C / +1886°F) and receiving 441.43 S⊕ (~600,783 W/m²), HD 125612 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 125612 is classified as a solar-type yellow star of spectral type G3 V with an effective photospheric temperature of 5,900 K, a radius of 1.07 R☉, a mass of 1.05 M☉, an estimated bolometric luminosity of 1.245 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.77 Gyr and a metallicity of [Fe/H] = 0.23 dex (metal-rich relative to the Sun). From Earth, HD 125612 shines at apparent V-band magnitude 8.31 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 125612 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 125612 c sharing its stellar neighborhood alongside HD 125612 b, HD 125612 d.
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 125612 |
| Spectral Type | G3 V |
| Effective Temp (Teff) | 5,900 K |
| Stellar Radius | 1.0700 R☉ |
| Stellar Mass | 1.0500 M☉ |
| Bolometric Luminosity | 1.245 L☉ |
| Metallicity [Fe/H] | 0.230 dex |
| Stellar Age | 1.770 Gyr |
| Apparent Magnitude | V: 8.310 · G: 8.156 |
| System Architecture | 2 Stars, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.051000 AU |
| Orbital Period | 4.155 days |
| Mean Orbital Velocity | 133.5 km/s |
| Orbital Eccentricity (e) | 0.14900 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.27 g/cm³ (21.9 km/s vesc) |
| Insolation Flux | 441.4278 S⊕ (~600,783 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 187.900 LY (57.621 pc) |