HD 104985 b
Astrophysical Synthesis & Habitability Characterization
HD 104985 b is a confirmed gas giant exoplanet orbiting the star HD 104985, located approximately 328 light-years (100.58 parsecs) from the Solar System. First announced in 2003 by Okayama Astrophysical 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 1766.808 Earth masses (5.56 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.65 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 10.78 g⊕ (105.72 m/s²), and an escape velocity of 131.4 km/s.
In its orbital architecture around HD 104985, HD 104985 b completes one full revolution every 199.68 Earth days at a semi-major axis of 0.715 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 39 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.047 (ranging from 0.6814 AU at periapsis to 0.7486 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 901 K (+628°C / +1162°F) and receiving 115.15 S⊕ (~156,726 W/m²), HD 104985 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 104985 is classified as a solar-type yellow star of spectral type G9 III with an effective photospheric temperature of 4,738 K, a radius of 11.12 R☉, a mass of 1.22 M☉, an estimated bolometric luminosity of 55.909 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.32 dex (metal-poor relative to the Sun). From Earth, HD 104985 shines at apparent V-band magnitude 5.794 (visible to the unaided human eye under dark skies) 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: Okayama Astrophysical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 104985 |
| Spectral Type | G9 III |
| Effective Temp (Teff) | 4,738 K |
| Stellar Radius | 11.1200 R☉ |
| Stellar Mass | 1.2200 M☉ |
| Bolometric Luminosity | 55.909 L☉ |
| Metallicity [Fe/H] | -0.320 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 5.794 · G: 5.497 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.715000 AU |
| Orbital Period | 199.68 days |
| Mean Orbital Velocity | 39 km/s |
| Orbital Eccentricity (e) | 0.04700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.65 g/cm³ (131.4 km/s vesc) |
| Insolation Flux | 115.1548 S⊕ (~156,726 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 328.000 LY (100.576 pc) |