HD 208897 b
Astrophysical Synthesis & Habitability Characterization
HD 208897 b is a confirmed gas giant exoplanet orbiting the star HD 208897, located approximately 220.1 light-years (67.49 parsecs) from the Solar System. First announced in 2017 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.7 Earth radii (1.22 Jupiter radii) and has a measured mass of 379.487 Earth masses (1.19 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.81 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.02 g⊕ (19.81 m/s²), and an escape velocity of 58.9 km/s.
In its orbital architecture around HD 208897, HD 208897 b completes one full revolution every 358.27 Earth days at a semi-major axis of 1.063 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 32.3 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.02 (ranging from 1.0417 AU at periapsis to 1.0843 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 507 K (+234°C / +453°F) and receiving 10.89 S⊕ (~14,818 W/m²), HD 208897 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 208897 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 4,860 K, a radius of 4.98 R☉, a mass of 1.25 M☉, an estimated bolometric luminosity of 12.413 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.21 dex (metal-rich relative to the Sun). From Earth, HD 208897 shines at apparent V-band magnitude 6.508 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere.
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 208897 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 4,860 K |
| Stellar Radius | 4.9800 R☉ |
| Stellar Mass | 1.2500 M☉ |
| Bolometric Luminosity | 12.413 L☉ |
| Metallicity [Fe/H] | 0.210 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 6.508 · G: 6.237 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.063000 AU |
| Orbital Period | 358.27 days |
| Mean Orbital Velocity | 32.3 km/s |
| Orbital Eccentricity (e) | 0.02000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.81 g/cm³ (58.9 km/s vesc) |
| Insolation Flux | 10.8876 S⊕ (~14,818 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 220.100 LY (67.487 pc) |