HD 65216 c
Astrophysical Synthesis & Habitability Characterization
HD 65216 c is a confirmed gas giant exoplanet orbiting the star HD 65216, located approximately 114.5 light-years (35.12 parsecs) from the Solar System. First announced in 2013 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.4 Earth radii (1.2 Jupiter radii) and has a measured mass of 645.195 Earth masses (2.03 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.48 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.59 g⊕ (35.21 m/s²), and an escape velocity of 77.6 km/s.
In its orbital architecture around HD 65216, HD 65216 c completes one full revolution every 5370 Earth days (14.7Julian years) at a semi-major axis of 5.75 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 11.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.17 carries the world between 4.7725 AU at periapsis and 6.7275 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 106 K (-167°C / -269°F) and an incident flux of 0.02 S⊕ (~29 W/m²), surface water and volatile species on HD 65216 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 65216 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,612 K, a radius of 0.88 R☉, a mass of 0.874 M☉, an estimated bolometric luminosity of 0.689 L☉. Stellar evolution modeling indicates an estimated stellar age of 4 Gyr and a metallicity of [Fe/H] = -0.169 dex (metal-poor relative to the Sun). From Earth, HD 65216 shines at apparent V-band magnitude 7.97 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 65216 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 65216 c sharing its stellar neighborhood alongside HD 65216 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 65216 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,612 K |
| Stellar Radius | 0.8800 R☉ |
| Stellar Mass | 0.8740 M☉ |
| Bolometric Luminosity | 0.689 L☉ |
| Metallicity [Fe/H] | -0.169 dex |
| Stellar Age | 4.000 Gyr |
| Apparent Magnitude | V: 7.970 · G: 7.794 |
| System Architecture | 3 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.750000 AU |
| Orbital Period | 5370 days |
| Mean Orbital Velocity | 11.6 km/s |
| Orbital Eccentricity (e) | 0.17000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.48 g/cm³ (77.6 km/s vesc) |
| Insolation Flux | 0.0214 S⊕ (~29 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 114.500 LY (35.121 pc) |