Uranus may have two tiny, previously undiscovered moons orbiting near two of the planet’s rings, researchers using data from NASA’s Voyager 2 spacecraft have found. Rob Chancia, a doctoral student at University of Idaho in the US, spotted key patterns in the rings while examining decades-old images of Uranus’ icy rings taken by Voyager 2 which flew by the planet 30 years ago. He noticed the amount of ring material on the edge of the alpha ring – one of the brightest of Uranus’ multiple rings -varied periodically. A similar, even more promising pattern occurred in the same part of the neighbouring beta ring.
Researchers analysed radio occultations – made when Voyager 2 sent radio waves through the rings to be detected back on Earth – and stellar occultations, made when the spacecraft measured the light of background stars shining through the rings, which helps show how much material they contain.
They found the pattern in Uranus’ rings was similar to moon-related structures in Saturn’s rings called moonlet wakes. The researchers estimate the hypothesised moonlets in Uranus’ rings would be four to 14 kilometres in diameter – as small as some identified moons of Saturn, but smaller than any of Uranus’ known moons.