New ring system in a remote Solar System object

8 Feb. () –

A new system of rings around a dwarf planet has been detected in the confines of the Solar System, much further than is usual for other ring systemschallenging theories.

The ring system is located around a dwarf planet, called Quaoar, which is about half the size of Pluto and orbits the Sun past Neptune.

The discovery, published in the journal ‘Nature’, was made by an international team of astronomers using HiPERCAM, an extremely 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 (GTC) on La Palma, 10.4 meters in diameter.

The rings are too small and faint to see directly in an image. Instead, the researchers made their discovery by observing an occultationwhen light from a background star was blocked by Quaoar in its orbit around the Sun. The event lasted less than a minute, but was unexpectedly preceded and followed by two dips in light, indicative of a ring system around Quaoar.

Ring systems are relatively rare in the Solar System: apart from the well-known rings around the giant planets Saturn, Jupiter, Uranus and Neptune, only two other minor planets have rings: Chariklo and Haumea. All ring systems known so far survive thanks to orbiting close to the parent body, so tidal forces prevent ring material from accreting and forming moons.

What makes the ring system around Quaoar extraordinary is that it is located at a distance of more than seven planetary radii, double what was believed to be the maximum radius according to the so-called “Roche limit”, which is the outer limit of where ring systems were thought to survive.

For comparison, the main rings around Saturn are within three planetary radii. Therefore, this discovery has forced a reconsideration of theories about the formation of rings.

Professor Vik Dhillon, co-author of the study from the Department of Physics and Astronomy at the University of Sheffield (UK), acknowledges it’s a statement that “it was unexpected to discover this new ring system in our Solar System, and it was doubly unexpected to find the rings so far from Quaoar, challenging our previous notions of how such rings form.”

“The use of our high-speed camera -HiPERCAM- was key to this discovery, since the event lasted less than a minute and the rings they are too small and faint to see in a direct image“, he highlights.

“Everyone learns about Saturn’s magnificent rings as a child, so we hope this new find will provide more information about how they came to be,” he says.