HD 204941 b
Astrophysical Synthesis & Habitability Characterization
HD 204941 b is a confirmed gas giant exoplanet orbiting the star HD 204941, located approximately 93.7 light-years (28.72 parsecs) from the Solar System. First announced in 2011 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 10.1 Earth radii (0.9 Jupiter radii) and has a measured mass of 73.101 Earth masses (0.23 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.39 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.72 g⊕ (7.06 m/s²), and an escape velocity of 30.1 km/s.
In its orbital architecture around HD 204941, HD 204941 b completes one full revolution every 1733 Earth days (4.74Julian years) at a semi-major axis of 2.55 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 16 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.37, swinging from 1.6065 AU at periapsis out to 3.4935 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 134 K (-139°C / -218°F) and an incident flux of 0.05 S⊕ (~65 W/m²), surface water and volatile species on HD 204941 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 204941 is classified as an orange K-type star of spectral type K1/2V with an effective photospheric temperature of 5,026 K, a radius of 0.78 R☉, a mass of 0.58 M☉, an estimated bolometric luminosity of 0.348 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.67 Gyr and a metallicity of [Fe/H] = -0.19 dex (metal-poor relative to the Sun). From Earth, HD 204941 shines at apparent V-band magnitude 8.45 (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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 204941 |
| Spectral Type | K1/2V |
| Effective Temp (Teff) | 5,026 K |
| Stellar Radius | 0.7800 R☉ |
| Stellar Mass | 0.5800 M☉ |
| Bolometric Luminosity | 0.348 L☉ |
| Metallicity [Fe/H] | -0.190 dex |
| Stellar Age | 6.670 Gyr |
| Apparent Magnitude | V: 8.450 · G: 8.191 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.550000 AU |
| Orbital Period | 1733 days |
| Mean Orbital Velocity | 16 km/s |
| Orbital Eccentricity (e) | 0.37000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.39 g/cm³ (30.1 km/s vesc) |
| Insolation Flux | 0.0477 S⊕ (~65 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 93.700 LY (28.717 pc) |