The distant ice giant Uranus may not have been visited by a spacecraft since Voyager 2’s “Grand Tour” flyby in 1986 but the data gathered then is still being used today to make new discoveries. Most recently, researchers think they have found evidence of two previously unknown moons around Uranus, potentially bringing the planet’s count up to 29.
Saturn isn’t the only planet to have a ring system; Uranus also has a system of thin orbiting rings separated into 13 sections. Looking back into the data acquired by Voyager 2, researchers at the University of Idaho spotted faint periodic perturbations that resemble what would be created by the gravity from nearby moons.
But just because there are no moons located in Voyager images at the calculated locations doesn’t mean they aren’t there. Voyager’s cameras had resolution limitations, and it’s quite possible that the two proposed moons are just too small and too dark to have shown up in the pictures.
“Based on the observed structures in the rings, we estimate that the moonlets would need to be located about 100 km exterior to the rings’ semi-major axes and be 2-7 km in radius,” wrote researchers Robert Chancia and Matthew Hedman.
It will be quite some time before another mission like Voyager makes it all the way out to Uranus—located even further away than Saturn, over 1.6 billion miles from Earth—but it’s possible that observations with Hubble could help confirm the presence of these two tiny moons.