Astronomers run rings round Saturn

This is how the the sky might look from within one of Saturn's most unusual rings, the sixth and outermost "F-ring".

Astronomers at Queen Mary & Westfield College in London have analysed data from the Voyager spacecraft and found that the F-ring consists of not one, but four interwoven strands of dust and ice. It also exhibits strange phenomena, such as "kinks" in the tidy lines, as well as clumps and braids - unlike the other rings.

The scientists now reckon that the F-ring is kept together by an unknown number of "shepherding moons" about a kilometre in diameter which orbit near and even within it. Otherwise, the ring would be broken up by the intrusion of the moon Prometheus - whose elliptical orbit brings it into the ring every 19 years, causing huge disruption. It is believed the small moons cause the "kinks".

Astronomers remain perplexed by the F-ring, because it is also the thickest. One of the main purposes of the Cassini craft, to be launched this October, will be to unravel more of its secrets. Kevin Beurle of QMW said: "It's incredibly complex, so we want to know more. It really is very strange."