Umbriel
What is Umbriel?
Moons· Diameter 1,169 km. The darkest of Uranus's large moons, an old cratered surface on which one bright ring, in Wunda crater, stands out.
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Orbit and size
| Diameter | 1,169 km |
|---|---|
| Distance from Uranus | 266,000 km |
| Orbit | 4.14 d |
| Note | bright ring in Wunda crater |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Parent planet and sibling moons
Wunda, the bright ring on dark Umbriel
Dark Umbriel has one bright spot: Wunda, a crater about 131 km wide near the equator. On its floor lies a ring of bright material that stands out against the dark surface like a doughnut. The name Wunda comes from a spirit of darkness in Australian Aboriginal mythology.
No one yet knows what the bright ring is. It may be material thrown out and piled up by an impact, or it may be a deposit of carbon dioxide ice. The only evidence is a few blurry pictures from Voyager 2, which imaged only about 40 percent of the surface. Umbriel's northern hemisphere has never been seen.
Why Umbriel is so dark is also unsolved. One explanation is that dark dust is mixed into its water ice. Another is that charged particles trapped in Uranus's magnetic field darkened material in the ice. But Ariel, which sits in the same environment, stays bright, so radiation alone cannot be the whole answer.
The moon in depth
Umbriel is a moon of Uranus discovered by William Lassell in 1851, together with Ariel. It is named after a gloomy sprite in Alexander Pope's poem The Rape of the Lock; the Latin word umbra means shadow. At 1,169 km across it is almost the same size as Ariel. It orbits 266,000 km from Uranus and goes around once every 4.14 days.
True to its name, Umbriel is the darkest of Uranus's large moons, reflecting less than half as much light as its neighbour Ariel. Voyager 2's pictures showed a surface crowded with large craters and almost no sign of new ground, so the surface appears to be very old. Its interior probably cooled early, ending any geological activity.
Why two neighbours of nearly equal size are so different has long been a puzzle: Ariel is young and bright, Umbriel old and dark. Scientists think Ariel alone was heated in the past while moving in step with another moon. In the orbit view you can find Umbriel circling outside Ariel and inside Titania.
Frequently asked
- How big is Umbriel?
- The diameter of Umbriel is 1,169 km.
- How far is Umbriel from Earth?
- The distance from uranus of Umbriel is 266,000 km.
- What is notable about Umbriel?
- The note of Umbriel is bright ring in Wunda crater.
- Which planet does Umbriel orbit?
- Umbriel orbits Uranus.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.