47 UMa b
Astrophysical Synthesis & Habitability Characterization
47 UMa b 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 1996 by Lick Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.2 Earth radii (1.18 Jupiter radii) and has a measured mass of 804.08 Earth masses (2.53 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.93 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 4.61 g⊕ (45.21 m/s²), and an escape velocity of 87.3 km/s.
In its orbital architecture around 47 UMa, 47 UMa b completes one full revolution every 1078 Earth days (2.95Julian years) at a semi-major axis of 2.1 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 21.2 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.032 (ranging from 2.0328 AU at periapsis to 2.1672 AU at apoapsis), the planet experiences minimal orbital distance variation.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.200 R⊕, 47 UMa 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 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 b sharing its stellar neighborhood alongside 47 UMa c, 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) | 2.100000 AU |
| Orbital Period | 1078 days |
| Mean Orbital Velocity | 21.2 km/s |
| Orbital Eccentricity (e) | 0.03200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.93 g/cm³ (87.3 km/s vesc) |
| Insolation Flux | 0.3576 S⊕ (~487 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 45.000 LY (13.797 pc) |