Scientists have found that a new ring of debris found orbiting Uranus is blue. The ring has a small moon in it called Mab, thought to be the source of the particles, and is “strikingly similar” to Saturn's outer ring.

The American team, reporting in Science, say only the smallest particles lost by Mab during meteor impacts are not reclaimed by its gravity. The unusual blue colour is caused by their tiny size reflecting only the blue end of the visible spectrum in a effect similar to that which makes the sky blue.

Team leader Professor Imke de Pater from the University of California said: “The blue colour says that this ring is predominantly submicron-sized material, much smaller than the material in most other rings, which appear red."

The ring was discovered in December using the Hubble Space Telescope. Previous studies of Uranus' rings missed it because they used infra-red radiation. ®