HD 118203 c
Astrophysical Synthesis & Habitability Characterization
HD 118203 c is a confirmed gas giant exoplanet orbiting the star HD 118203, located approximately 300.9 light-years (92.26 parsecs) from the Solar System. First announced in 2024 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.4 Earth radii (1.11 Jupiter radii) and has a measured mass of 3747.197 Earth masses (11.79 Jupiter masses). Combining its mass and radius yields a mean bulk density of 10.84 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 24.37 g⊕ (238.99 m/s²), and an escape velocity of 194.5 km/s.
In its orbital architecture around HD 118203, HD 118203 c completes one full revolution every 5103 Earth days (13.97Julian years) at a semi-major axis of 6.28 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 13.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.26, swinging from 4.6472 AU at periapsis out to 7.9128 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 146 K (-127°C / -197°F) and an incident flux of 0.11 S⊕ (~153 W/m²), surface water and volatile species on HD 118203 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 118203 is classified as an orange K-type star of spectral type K0 IV with an effective photospheric temperature of 5,742 K, a radius of 2.04 R☉, a mass of 1.27 M☉, an estimated bolometric luminosity of 4.059 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.73 Gyr and a metallicity of [Fe/H] = 0.287 dex (metal-rich relative to the Sun). From Earth, HD 118203 shines at apparent V-band magnitude 8.05 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 118203 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 118203 c sharing its stellar neighborhood alongside HD 118203 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 118203 |
| Spectral Type | K0 IV |
| Effective Temp (Teff) | 5,742 K |
| Stellar Radius | 2.0400 R☉ |
| Stellar Mass | 1.2700 M☉ |
| Bolometric Luminosity | 4.059 L☉ |
| Metallicity [Fe/H] | 0.287 dex |
| Stellar Age | 4.730 Gyr |
| Apparent Magnitude | V: 8.050 · G: 7.893 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 6.280000 AU |
| Orbital Period | 5103 days |
| Mean Orbital Velocity | 13.4 km/s |
| Orbital Eccentricity (e) | 0.26000 |
| Orbital Inclination (i) | 93.7000° |
| Mean Bulk Density | 10.84 g/cm³ (194.5 km/s vesc) |
| Insolation Flux | 0.1122 S⊕ (~153 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 300.900 LY (92.259 pc) |