Space · Moons
Umbriel
A moon of Uranus — The darkest of Uranus's major moons — covered in a bright ring (Wunda) at the equator.
Quick facts
Parent planet
Diameter (mean)
1169 km
Mass
1.28 × 10²¹ kg
0.0174 Moon masses
Mean orbital radius
266,000 km
Orbital period
4.144 Earth days
Discovery year
1851
Discoverer
William Lassell
Naming origin
Sprite in The Rape of the Lock by Alexander Pope
Surface conditions
Umbriel is the darkest of Uranus's major moons (albedo 0.21), heavily cratered. The dominant feature is Wunda, a 131-km-wide bright ring near the equator — the floor of a crater partially filled with bright material whose origin is unsettled (frost? ejecta from a younger impact?). The dark surface composition is thought to result from radiation darkening over geological time.
Missions and observations
Every Uranus-system mission has had an opportunity to image or characterize Umbriel. The list below is the Uranus-system mission catalog; specific Umbriel encounters are documented in mission archives.
| Mission | Year at Uranus | Status |
|---|---|---|
|
Voyager 2 NASA |
1986 | Completed |
Naming etymology
Umbriel was a sprite in Alexander Pope's The Rape of the Lock (1712), associated with melancholy and shade — a name fitting for the darkest Uranian moon. Named by John Herschel in 1852.
Methodology & sources
Diameter, mass, and orbital parameters from JPL Solar System Dynamics — Physical Parameters. Discovery year and discoverer from the JPL Satellite Discovery Circumstances. Naming etymology from the IAU Working Group for Planetary System Nomenclature. Agent-matched moon pages use the matching Mungomash team avatar in the hero; non-agent moons are text-only.