Moons · Space Codex
Umbriel
An old, dark, heavily cratered moon.
The darkest of Uranus's large moons
At a glance
Key points
A single bright ring about 140 km across, near its pole, stands out against the gloom.
- Darkest of Uranus's five major moons
- One bright 140 km ring stands out on its surface
- Named after a spirit in Pope's The Rape of the Lock
Surface
Umbriel is almost uniformly dark and saturated with craters, the oldest-looking surface among Uranus's large moons. The bright ring, possibly frost on a crater floor, is the only prominent light feature Voyager 2 saw.
Exploration
Voyager 2 is the only spacecraft to have visited, passing on 24 January 1986. Uranus was near solstice, so only the southern hemispheres of its moons were in sunlight; the northern halves have never been seen up close.
What we still don't know
Why Umbriel is so much darker than its neighbours, and what the bright ring is made of.
Missions
- 1977–
The only spacecraft to visit Uranus (1986) and Neptune (1989); interstellar since 5 Nov 2018.
First-hand · our 3D model
How we render it
Umbriel is a sphere wrapped in a global map built from USGS and NASA spacecraft mosaics. Voyager 2 imaged only one hemisphere, so the unseen side is a feathered procedural fill.
It is drawn at about 7.5% of Uranus's radius, enlarged from its true 2.3% so it stays visible. It orbits in Uranus's equatorial frame, inclined 0.1°, with a 4.14-day period kept in true ratio to its neighbours, and keeps one face towards Uranus.
Moon sizes and orbits are compressed so a whole system fits on screen, but never reordered: each moon is drawn at 0.72 × (true size ratio)^0.6 of its planet, capped so no large moon is drawn bigger than it really is, and orbit distances are log-compressed into a band that clears the planet's rings. Orbital periods keep their true ratios, every moon is tidally locked, and on lighter devices only the two largest moons of each planet are drawn.
Related entries
- UranusIce giant tipped on its side
Sources
- JPL Solar System Dynamics: satellite physical parameters (opens in a new tab)
- JPL Solar System Dynamics: satellite mean orbital elements (opens in a new tab)
- NASA NSSDC Uranian Satellite Fact Sheet (opens in a new tab)
- NASA Science: Umbriel (opens in a new tab)
Last reviewed against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.