Space: Astronomy is astonished. Asteroid with Rings found.Video.
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Astronomers used seven telescopes, but just one revealed the pair of rings orbiting the rocky Chariklo. The asteroid's 155-mile diameter (250 kilometers) is dwarfed by the giant gas planets, the only other bodies known to have rings.
"This discovery shows that size is not important in order to have — or not have — rings," Felipe Braga-Ribas, of the National Observatory in Brazil, told Space.com by email.
An asteroid among giants
On June 3, 2013, Braga-Ribas led a team of astronomers in observing Chariklo as it passed in front of a distant star — a process known as an occultation. As the asteroid traveled, it blocked light from the star, enabling scientists to learn more about it.
The astronomers were surprised to discover that a few seconds before and after the main occultation, the light dimmed slightly, indicating that something circled the rocky asteroid. By comparing the data gathered from seven different telescopes, the team was able to identify the shape, size and orientation of the rings.
The system consists of a dense, 4-mile-wide (7 km) ring near the planet, and a smaller 2-mile-wide (3 km) ring farther out.
From the surface of the asteroid, "they would be two spectacular sharp and really bright rings, crossing all the sky," Braga-Ribas said. "They would be noticeably close, as they are at about 1/1,000 of the moon's distance from us," he added.
He went on to say that the larger, inner ring would block the view of the outer ring from the ground. The rings are similar to those around Saturn, in that both are very dense, bright and possibly formed by rock and water ice. But their scales are quite different.
"The whole Chariklo system would fit about 12 times in the Cassini Division," Braga-Ribas said, referring to the largest gap in Saturn's rings.
Particles orbiting Chariklo also travel more slowly — only tens of meters per second, compared with tens of kilometers per second in the rings of Saturn.
While Saturn is the most well-known ringed body in the solar system, Jupiter, Neptune and Uranus also have their own, fainter rings.