An Etymological Dictionary of Astronomy and Astrophysics

The thirteenth of Uranus’s known satellites and the third largest. It has a diameter of 1170 km and orbits Uranus every 4.144 days at a mean distance of about 265,980 km. Umbriel is very dark, with an albedo of 0.18. It has a heavily cratered surface. Umbriel was discovered by William Lassell (1799-1880) in 1851.

See also: Umbriel named for an evil spirit in Alexander Pope’s (1688-1744) poem The Rape of the Lock. Moreover, Umbriel derives from L. → umbra “shadow,” which fits the satellite’s appearance.