HD 12661 c
Astrophysical Synthesis & Habitability Characterization
HD 12661 c is a confirmed gas giant exoplanet orbiting the star HD 12661, located approximately 123.4 light-years (37.85 parsecs) from the Solar System. First announced in 2002 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.2 Earth radii (1.18 Jupiter radii) and has a measured mass of 899.454 Earth masses (2.83 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.16 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 5.16 g⊕ (50.6 m/s²), and an escape velocity of 92.3 km/s.
In its orbital architecture around HD 12661, HD 12661 c completes one full revolution every 1708 Earth days (4.68Julian years) at a semi-major axis of 2.8145 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 17.9 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.031 (ranging from 2.7273 AU at periapsis to 2.9017 AU at apoapsis), the planet experiences minimal orbital distance variation.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 174 K (-99°C / -146°F) and an incident flux of 0.15 S⊕ (~199 W/m²), surface water and volatile species on HD 12661 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 12661 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 5,748 K, a radius of 1.11 R☉, a mass of 1.02 M☉, an estimated bolometric luminosity of 1.207 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.39 Gyr and a metallicity of [Fe/H] = 0.36 dex (metal-rich relative to the Sun). From Earth, HD 12661 shines at apparent V-band magnitude 7.43 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 12661 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 12661 c sharing its stellar neighborhood alongside HD 12661 b.
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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 12661 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 5,748 K |
| Stellar Radius | 1.1100 R☉ |
| Stellar Mass | 1.0200 M☉ |
| Bolometric Luminosity | 1.207 L☉ |
| Metallicity [Fe/H] | 0.360 dex |
| Stellar Age | 6.390 Gyr |
| Apparent Magnitude | V: 7.430 · G: 7.247 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.814500 AU |
| Orbital Period | 1708 days |
| Mean Orbital Velocity | 17.9 km/s |
| Orbital Eccentricity (e) | 0.03100 |
| Orbital Inclination (i) | 136.0000° |
| Mean Bulk Density | 2.16 g/cm³ (92.3 km/s vesc) |
| Insolation Flux | 0.1459 S⊕ (~199 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 123.400 LY (37.848 pc) |