Umbriel
Moon· orbits Uranus
Umbriel is the darkest of Uranus's major moons — an old, uniformly dim, heavily cratered ice world, oddly marked by one bright ring of material ('Wunda').
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Key facts
Mass
1.27 × 10²¹ kg
0.0174 Moon masses
Radius
585 km
34% of our Moon's radius
Surface gravity
0.249 m/s²
3% of Earth's
Day length
4.1 days
Orbit around Uranus
4.14 Earth days
Science
Physical
- Mass
- 1.27 × 10²¹ kg · 0.0174 Moon masses
- Radius
- 585 km · 34% of our Moon's radius
- Density
- 1,523 kg/m³ · 1.5× water
- Surface gravity
- 0.249 m/s² · 3% of Earth's
- Escape velocity
- 540 m/s · 5% of Earth's
Orbit around Uranus
- Distance from Uranus
- 209,856 km
- Orbital period
- 4.1 days
- Eccentricity
- 0.004
- Inclination
- 0.10 °
Rotation
- Rotation period
- 4.1 days
- Tidal locking
- Tidally locked to its parent
Temperature
- Mean
- 75 K (-198 °C)
Composition
- Bulk composition
- Water ice and rock with a dark, carbon-rich coating of uncertain origin.
Radiation & temperature
- Insolation
- 0.00264 S⊕ · 1/378 of the sunlight Earth receives
- Bond albedo
- 0.10 · reflects 10% of incoming sunlight
- Equilibrium temperature
- 61 K (-212 °C)
- Measured mean temperature
- 75 K (-198 °C)
- Greenhouse warming
- +14 K
Discovery & history
- Discovered
- October 24, 1851
- By
- William Lassell
- Method
- Visual discovery (telescopic)
- Name
- Umbriel, a dusky, melancholy sprite in Pope's 'The Rape of the Lock'.
Lassell found Umbriel on the same night as Ariel in 1851. The darkest of Uranus's large moons, it is an ancient, cratered world marked by a mysterious bright ring nicknamed the 'fluorescent Cheerio'.
Images
Images from open archives · credit shown per image