An infrared view from Hubble Space Telescope reveals features in the clouds of the planet Uranus, plus the planet's rings and many of its moons (labeled at right). Uranus is the third-largest planet in the solar system, but is so remote that its rings and moons are difficult to see and study. [NASA/JPL/STScI]
The planet Saturn stands high in the southwest as darkness falls this month. It looks like a bright golden star. A telescope reveals its best-known feature: its beautiful rings.
Two other "ringed" planets climb into view about the time that Saturn drops from the sky: Jupiter and Uranus. They're in the east at first light. Jupiter looks like a brilliant star. Uranus is quite close to Jupiter, but you need binoculars to see it.
The rings of these giant worlds are much fainter than Saturn's -- so faint that they weren't discovered until the 1970s.
So far, astronomers have counted 15 rings around Uranus. Most of them are only a few miles wide, and they're about as dark as charcoal.
The rings may be the debris from several small moons that were blasted apart by collisions. Much of this debris is rocky -- from the size of pebbles to boulders. Other bits consist of ices that were darkened by radiation.
The rings are probably no more than a few hundred million years old. Collisions between the planet's moons and big space rocks may supply them with fresh material. And powerful collisions may occasionally pulverize another moon, creating a new ring.
Over the last three years, the rings have turned edge-on as seen from Earth three times. That's allowed astronomers to look for ripples or clumps in the rings, and to hunt for small moons embedded within them. Their observations will shed a little more light on Uranus's dark rings.
Script by Damond Benningfield, Copyright 2010
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