HD 203387 c
Astrophysical Synthesis & Habitability Characterization
HD 203387 c is a confirmed gas giant exoplanet orbiting the star HD 203387, located approximately 201.4 light-years (61.75 parsecs) from the Solar System. First announced in 2022 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.6 Earth radii (1.12 Jupiter radii) and has a measured mass of 2378.946 Earth masses (7.48 Jupiter masses). Combining its mass and radius yields a mean bulk density of 6.56 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 14.98 g⊕ (146.9 m/s²), and an escape velocity of 153.7 km/s.
In its orbital architecture around HD 203387, HD 203387 c completes one full revolution every 2481.072 Earth days (6.79Julian years) at a semi-major axis of 5.067 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 22.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.202 carries the world between 4.0435 AU at periapsis and 6.0905 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 361 K (+88°C / +190°F) and receiving 2.82 S⊕ (~3,840 W/m²), HD 203387 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 203387 is classified as a stellar host with an effective photospheric temperature of 5,174 K, a radius of 10.5852 R☉, a mass of 2.817 M☉, an estimated bolometric luminosity of 72.043 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, HD 203387 shines at apparent V-band magnitude 4.28 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The HD 203387 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 203387 c sharing its stellar neighborhood alongside HD 203387 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 203387 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,174 K |
| Stellar Radius | 10.5852 R☉ |
| Stellar Mass | 2.8170 M☉ |
| Bolometric Luminosity | 72.043 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 4.280 · G: 4.055 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.067000 AU |
| Orbital Period | 2481.072 days |
| Mean Orbital Velocity | 22.2 km/s |
| Orbital Eccentricity (e) | 0.20200 |
| Orbital Inclination (i) | 158.4620° |
| Mean Bulk Density | 6.56 g/cm³ (153.7 km/s vesc) |
| Insolation Flux | 2.8216 S⊕ (~3,840 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 201.400 LY (61.748 pc) |