Mysterious Ring Spotted Around Minor Planet

Ring around Quaoar 'should not be possible'
By Rob Quinn,  Newser Staff
Posted Feb 9, 2023 4:45 PM CST
Mysterious Ring Spotted Around Minor Planet
An artist's impression of Quaoar with its ring and its moon, Weywot.   (ESA)

Astronomers have made a puzzling discovery in the deep reaches of the solar system, far beyond Neptune. Quaoar, a minor planet in the Kuiper belt, has a ring like those around Saturn, but it is further from the planet than the zone where current models say rings are possible. The ring is more than seven planetary radiii away from Quaoar, more than twice as far as the Roche limit, which was thought to be the maximum distance that rings could form, the Guardian reports. "This is the discovery of a ring located in a place that should not be possible," says astronomer Bruno Morgado, per Reuters. Morgano is the lead author of a study published in the journal Nature.

Inside the Roche limit, tidal forces prevent particles from becoming a moon. Morgado says that according to the calculations of 19th-century French astronomer Edouard Roche, the particles that form Quaoar's ring should have formed a moon within just 10 or 20 years, with denser regions clumping together and attracting more particles, the New York Times reports. "It really shouldn’t be there," he says. "We should look at this limit again and better understand how the satellites are formed." Quaoar—named after the creation god of the Indigenous Tongva people of southern California—also has a moon, further out than the ring. When Quaoar was discovered in 2002, it was the biggest object detected in the solar system since Pluto, a fellow Kuiper belt object.

"These are the most unusual rings we’ve seen," study co-author Vik Dhillon tells the Guardian. He says one theory is that the icy debris around Quaoar is "less sticky" than that around other planets. "If they have a really frosty ice coating then you can get quite an elastic collision, like hailstones colliding rather than snowflakes," Dhillon says. (More dwarf planet stories.)

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