HD 38801 b
Astrophysical Synthesis & Habitability Characterization
HD 38801 b is a confirmed gas giant exoplanet orbiting the star HD 38801, located approximately 298.2 light-years (91.44 parsecs) from the Solar System. First announced in 2009 by Subaru Telescope using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.5 Earth radii (1.12 Jupiter radii) and has a measured mass of 3082.315 Earth masses (9.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 8.7 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 19.73 g⊕ (193.49 m/s²), and an escape velocity of 175.7 km/s.
In its orbital architecture around HD 38801, HD 38801 b completes one full revolution every 685.25 Earth days (1.88Julian years) at a semi-major axis of 1.623 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 25.8 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.017 (ranging from 1.5954 AU at periapsis to 1.6506 AU at apoapsis), the planet experiences minimal orbital distance variation.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.500 R⊕, HD 38801 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star HD 38801 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 5,338 K, a radius of 2.029 R☉, a mass of 1.207 M☉, an estimated bolometric luminosity of 2.999 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.072 Gyr and a metallicity of [Fe/H] = 0.25 dex (metal-rich relative to the Sun). From Earth, HD 38801 shines at apparent V-band magnitude 8.26 (accessible to binoculars and small amateur telescopes) in the Southern 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: Subaru Telescope · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 38801 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 5,338 K |
| Stellar Radius | 2.0290 R☉ |
| Stellar Mass | 1.2070 M☉ |
| Bolometric Luminosity | 2.999 L☉ |
| Metallicity [Fe/H] | 0.250 dex |
| Stellar Age | 6.072 Gyr |
| Apparent Magnitude | V: 8.260 · G: 8.034 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.623000 AU |
| Orbital Period | 685.25 days |
| Mean Orbital Velocity | 25.8 km/s |
| Orbital Eccentricity (e) | 0.01700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 8.7 g/cm³ (175.7 km/s vesc) |
| Insolation Flux | 1.7311 S⊕ (~2,356 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 298.200 LY (91.435 pc) |