K2-312 c
Astrophysical Synthesis & Habitability Characterization
K2-312 c is a confirmed gas giant exoplanet orbiting the star HD 80653, located approximately 358.3 light-years (109.86 parsecs) from the Solar System. First announced in 2023 by Roque de los Muchachos Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.8 Earth radii (1.14 Jupiter radii) and has a measured mass of 1681.312 Earth masses (5.29 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.42 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 10.26 g⊕ (100.62 m/s²), and an escape velocity of 128.2 km/s.
In its orbital architecture around HD 80653, K2-312 c completes one full revolution every 871.32 Earth days (2.39Julian years) at a semi-major axis of 1.882 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 23.5 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.8435, swinging from 0.2945 AU at periapsis out to 3.4695 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.800 R⊕, K2-312 c 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 80653 is classified as a solar-type yellow star of spectral type G0 V with an effective photospheric temperature of 5,959 K, a radius of 1.199 R☉, a mass of 1.15 M☉, an estimated bolometric luminosity of 1.626 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.3 Gyr and a metallicity of [Fe/H] = 0.255 dex (metal-rich relative to the Sun). From Earth, HD 80653 shines at apparent V-band magnitude 9.452 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 80653 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-312 c sharing its stellar neighborhood alongside HD 80653 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: Roque de los Muchachos Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 80653 |
| Spectral Type | G0 V |
| Effective Temp (Teff) | 5,959 K |
| Stellar Radius | 1.1990 R☉ |
| Stellar Mass | 1.1500 M☉ |
| Bolometric Luminosity | 1.626 L☉ |
| Metallicity [Fe/H] | 0.255 dex |
| Stellar Age | 3.300 Gyr |
| Apparent Magnitude | V: 9.452 · G: 9.307 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.882000 AU |
| Orbital Period | 871.32 days |
| Mean Orbital Velocity | 23.5 km/s |
| Orbital Eccentricity (e) | 0.84350 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.42 g/cm³ (128.2 km/s vesc) |
| Insolation Flux | 0.4596 S⊕ (~626 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 358.300 LY (109.860 pc) |