47 UMa c
Astrophysical Synthesis & Habitability Characterization
47 UMa c is a confirmed gas giant exoplanet orbiting the star 47 UMa, located approximately 45 light-years (13.8 parsecs) from the Solar System. First announced in 2001 by Lick Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14.2 Earth radii (1.27 Jupiter radii) and has a measured mass of 171.621 Earth masses (0.54 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.33 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.85 g⊕ (8.34 m/s²), and an escape velocity of 38.9 km/s.
In its orbital architecture around 47 UMa, 47 UMa c completes one full revolution every 2391 Earth days (6.55Julian years) at a semi-major axis of 3.6 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 16.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.098 carries the world between 3.2472 AU at periapsis and 3.9528 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 164 K (-109°C / -164°F) and an incident flux of 0.12 S⊕ (~166 W/m²), surface water and volatile species on 47 UMa c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star 47 UMa is classified as a solar-type yellow star of spectral type G0V with an effective photospheric temperature of 5,872 K, a radius of 1.2133 R☉, a mass of 1.06 M☉, an estimated bolometric luminosity of 1.57 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.48 Gyr and a metallicity of [Fe/H] = 0.04 dex (near-solar heavy-element abundance). From Earth, 47 UMa shines at apparent V-band magnitude 5.034 (visible to the unaided human eye under dark skies) in the Northern celestial hemisphere. The 47 UMa system is a multi-planet architecture hosting 3 confirmed worlds, with 47 UMa c sharing its stellar neighborhood alongside 47 UMa b, 47 UMa d.
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: Lick Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | 47 UMa |
| Spectral Type | G0V |
| Effective Temp (Teff) | 5,872 K |
| Stellar Radius | 1.2133 R☉ |
| Stellar Mass | 1.0600 M☉ |
| Bolometric Luminosity | 1.57 L☉ |
| Metallicity [Fe/H] | 0.040 dex |
| Stellar Age | 6.480 Gyr |
| Apparent Magnitude | V: 5.034 · G: 4.878 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.600000 AU |
| Orbital Period | 2391 days |
| Mean Orbital Velocity | 16.4 km/s |
| Orbital Eccentricity (e) | 0.09800 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.33 g/cm³ (38.9 km/s vesc) |
| Insolation Flux | 0.1217 S⊕ (~166 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 45.000 LY (13.797 pc) |