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Rings Aren’t Supposed To Form This Far Away From A Planet—Astronomers Found Them There Anyway

Forbes 2/8/2023 Brian Bushard, Forbes Staff


Astronomers discovered a ring around a distant dwarf planet beyond Neptune at a distance from the dwarf planet that was previously thought to be impossible, defying astronomers’ understanding of how planetary rings form as researchers continue to discover rare planetary phenomena, even in the solar system.

Astronomers observed a ring system around a distant dwarf planet at a distance previously thought impossible. ESA, CC BY-SA 3.0 IGO © Provided by Forbes Astronomers observed a ring system around a distant dwarf planet at a distance previously thought impossible. ESA, CC BY-SA 3.0 IGO

Key Facts

Astronomers at University of Sheffield observed rings around a Pluto-sized dwarf planet called Quaoar, beyond Neptune, with rings farther from the dwarf planet than Saturn’s iconic rings.

Unlike Saturn’s rings, the rings around Quaoar are too faint to be seen under normal conditions using a telescope, according to the paper published Wednesday morning in the journal Nature.

Astronomers instead discovered the rings using a camera called a HiPERCAM mounted on a telescope in La Palma, in Spain’s Canary Islands by observing the light of a distant star blocked by Quaoar on its orbit around the sun.

Ring systems—which form when other space objects like meteors or small moons collide and leave behind tiny particles of ice, rocks and dust within a planet’s orbit—are rare in the solar system, despite large well-known rings around Saturn, Jupiter and Uranus, with only two other dwarf planets having them, according to astronomers.

Big Number

4,100. That’s how many kilometers Quaoar’s rings are from the dwarf planet’s core. That puts its rings at a distance of roughly 7.4 of the dwarf planet’s radii from its core—twice as far as the maximum distance, called a “Roche limit,” astronomers previously thought possible for a ring system to survive. Saturn’s rings, by contrast, are within three of the gas giant’s radii.


The discovery comes less than a month after astronomers observed another ring system around a giant icy asteroid more than two billion miles from Earth using NASA’s James Webb Telescope, bringing the Grand Canyon-sized asteroid’s rings into much clearer view more than 25 years after the asteroid was discovered.

Further Reading

Welcome To Chariklo, A Ringed World In The Solar System Just Examined By The Webb Telescope (Forbes)

NASA’s James Webb Telescope Captures Stunning Cosmic Hourglass (Forbes)

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