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Uranus: Rings

Dust particles in Uranian rings
Dust particles in Uranian rings
When two teams of scientists set up to watch Uranus pass in front of star SAO 158687 in 1977, they expected a rare chance to observe a distant planet. Instead, they made a major disovery: Uranus, like Saturn, is encircled with a band of rings.

As the observers in the Kuiper Airborne Observatory and the Perth Observatory in Australia watched, the star appeared to blink out briefly several times. The blinking was caused by the rings blocking the starlight. The Australian team was so surprised they missed three rings as they tried to figure out why the starlight signal kept disappearing.

The Kuiper team had a better vantage point and were first to publish the surprising news that Uranus was encircled by five narrow rings, which they named Alpha, Beta, Gamma, Delta and Epsilon in order of increasing distance from the planet. The Perth team identified six distinct dips in the starlight, which they named rings 1 through 6. More rings were discovered in 1986.

Observing distant planets is difficult, especially with complications due to daylight arriving before the planet completed its transit in front of the star. But, after careful analysis and a closer view courtesy of the Voyager 2 spacecraft in 1986, scientists have now identified 11 known rings around Uranus. In order of increasing distance from the planet, they are 1986U2R, 6, 5, 4, Alpha, Beta, Eta, Gamma, Delta, Lambda and Epsilon. Some of the larger rings are surrounded by belts of fine dust.


Uranus's Rings
Ring Name: 1986U2R
Distance*: 38,000 km
Width: ~2,500 km
Thickness: 0.1 km
Albedo: 0.03

Ring Name: 6
Distance*: 41,837 km
Width: 1 km - 3 km
Thickness: 0.1 km
Albedo: 0.03

Ring Name: 5
Distance*: 42,235 km
Width: 2 km - 3 km
Thickness: 0.1 km
Mass: 0.1 kg
Albedo: 0.03

Ring Name: 4
Distance*: 42,572 km
Width: 2 km - 3 km
Thickness: .1 km
Mass: .1 kg
Albedo: 0.03

Ring Name: Alpha
Distance*: 44,718 km
Width: 4 km - 13 km
Thickness: 0.1 km
Albedo: 0.03

Ring Name: Beta
Distance*: 45,661 km
Width: 7 km - 12 km
Thickness: 0.1 km
Albedo: 0.03

Ring Name: Eta
Distance*: 47,176 km
Width: 1 km - 2 km
Thickness: 0.1 km
Albedo: 0.03

Ring Name: Gamma
Distance*: 47,627 km
Width: 1 km - 4 km
Thickness: 0.1 km
Albedo: 0.03

Ring Name: Delta
Distance*: 48,300 km
Width: 3 km - 7 km
Thickness: 0.1 km
Albedo: 0.03

Ring Name: Lambda
Distance*: 50,024 km
Width: 2 km - 3 km
Thickness: 0.1 km
Albedo: 0.03

Ring Name: Epsilon
Distance*: 51,149 km
Width: 20 km - 95 km
Thickness: < 15 km
Albedo: 0.03

* The distance is measured from the planet center to the start of the ring.
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