Moon of Uranus
Umbriel
The darkest of Uranus's major moons.
Umbriel circles Uranus every 4.14 days, keeping one face toward the planet. Its orbit lies in Uranus's sideways equatorial plane. Its ancient, heavily cratered surface reflects only a small share of the sunlight that reaches it.
How it moves
- Umbriel orbits Uranus every 4.144 days at about 266,000 km.
- Its orbit is nearly circular (eccentricity 0.0039) and close to Uranus's equator.
- It is tidally locked to Uranus.
- Like Uranus's other large moons, it orbits nearly perpendicular to the planets' orbital plane.
Facts
- Mean radius
- 584.7 km
- Mass
- 1.220e+21 kg
- Surface gravity
- 0.249 m/s²
- Rotation period
- 99.46 hours
- Orbital period
- 4.144 days
- Average orbital distance
- 266,000 km
- Eccentricity
- 0.0039
- Discovered
- October 24, 1851, by William Lassell
Umbriel reflects only about 16% of the light that hits it, the darkest of Uranus's large moons.
Sources: nssdc.gsfc.nasa.gov, ssd.jpl.nasa.gov, ssd.jpl.nasa.gov