A team of international astronomers published a discovery in Nature about a ring system surrounding Quaoar, a dwarf planet that is roughly half the size of Pluto and lies beyond Neptune’s orbit around the Sun. The researchers utilized HiPERCAM, an ultra-sensitive high-speed camera developed by scientists at the University of Sheffield and mounted on the world’s largest optical telescope, the Gran Telescopio Canarias.
The ring system was identified not by direct observation, but by observing an occultation, where the light from a star was blocked by Quaoar. The event lasted a mere minute, but was preceded and followed by two dips in light, signifying the presence of rings.
While ring systems are scarce in the Solar System, with only Saturn, Jupiter, Uranus, and Neptune’s well-known rings and two minor planets, Chariklo and Haumea, possessing them, Quaoar’s ring system is particularly noteworthy because it lies beyond seven planetary radii, twice as far as the previously thought maximum radius according to the Roche limit, where ring systems were thought to be able to persist. For comparison, Saturn’s main rings are located within three planetary radii. This discovery necessitates a rethinking of ring formation theories.
According to Professor Vik Dhillon, a co-author of the study from the University of Sheffield, this new ring system was unexpected and its location so far from Quaoar challenges previous ideas of how ring systems form. The use of HiPERCAM was crucial in making the discovery, as the event was short-lived and the rings are too small and faint to observe directly. The study was led by the Federal University of Rio de Janeiro and involved 59 researchers from all over the world, including six UK universities and was partly funded by the Science and Technology Facilities Council.