HD 203387 b
Astrophysical Synthesis & Habitability Characterization
HD 203387 b 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 13.1 Earth radii (1.17 Jupiter radii) and has a measured mass of 1106.043 Earth masses (3.48 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.71 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 6.45 g⊕ (63.25 m/s²), and an escape velocity of 102.8 km/s.
In its orbital architecture around HD 203387, HD 203387 b completes one full revolution every 512.535 Earth days (1.4Julian years) at a semi-major axis of 1.771 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 37.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.732, swinging from 0.4746 AU at periapsis out to 3.0674 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 610 K (+337°C / +639°F) and receiving 23.10 S⊕ (~31,436 W/m²), HD 203387 b 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 b sharing its stellar neighborhood alongside HD 203387 c.
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) | 1.771000 AU |
| Orbital Period | 512.535 days |
| Mean Orbital Velocity | 37.6 km/s |
| Orbital Eccentricity (e) | 0.73200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.71 g/cm³ (102.8 km/s vesc) |
| Insolation Flux | 23.0974 S⊕ (~31,436 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 201.400 LY (61.748 pc) |