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For The First Time, Astronomers Find Asteroids Can Have Rings

Astronomers studying a 250 kilometer wide asteroid-like object named Chariklo have come to a surprising conclusion: By analyzing dips in the object's brightness, they've found that Chariklo is surrounded by a ring system.

Their findings are published in today's edition of Nature and this is the first time rings have been found on a body this small. In the past, scientists thought only giant planets — like Jupiter, Saturn, Uranus and Neptune — had the gravitational heft to support rings.

What this finding tells us is if rings can be found on this small object, orbiting between Saturn and Uranus, perhaps the celestial features are common across the universe.

Nature explains:

"'We thought that maybe having rings was linked with the mass of the object. So finding them on a small object was very unexpected,' [lead author Felipe Braga-Ribas] says.

"Chariklo belongs to a class of objects called Centaurs, which traverse the outer Solar System in unstable orbits and can share characteristics with both asteroids and comets. Because they are small, dark and far away, studying them is a challenge, Braga-Ribas says. His team discovered the rings while observing the way in that the asteroid blocked out light from a distant star as it passed between the star and Earth on 3 June 2013.

"The researchers found a dip in brightness, as expected, when the asteroid traversed the star. But they also detected two much smaller dips, both before Chariklo passed in front of the star, and after. Piecing together results from telescopes at seven sites across South America, the team deduced that the blips were caused by two distinct, narrow rings that were respectively 7 and 3 kilometres wide. The same technique was used to discover the rings around Uranus in 1977."

NBC News reports on another oddity scientists suspect about Chariklo:

"Astronomers suggest that the rings (nicknamed Oiapoque and Chu', after rivers in Brazil) are made up of debris left over from a cosmic collision (like the one thought to have given rise to Earth's moon). The fact that the rings are so sharply confined suggests that "shepherd moons" may be keeping them in line.

'It's likely that Chariklo has at least one small moon still waiting to be discovered,' Braga-Ribas said."

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Eyder Peralta is NPR's East Africa correspondent based in Nairobi, Kenya.