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 The asteroid, known as Chariklo, is more than 621 million miles (1
billion km) from Earth, circling the sun in an orbit between Saturn
and Uranus.
On June 3, 2013, astronomers at seven different locations in Chile,
Brazil, Uruguay and Argentina were standing by to observe the
asteroid as it passed in front of star, relative to the telescopes'
lines of sight. They hoped the dips in starlight, caused by the
asteroid passing in front of the star, would reveal details of the
154-mile (248-km) asteroid's size and shape.
They ended up with much more. Analyzing flickers of light during the
occultation revealed two dense rings circling Chariklo.
Previously, only the giant planets Saturn, Jupiter, Uranus and
Neptune were known to have rings.
"We weren't looking for a ring and didn't think small bodies like
Chariklo had them at all," lead astronomer Felipe Braga-Ribas, with
Brazil's National Observatory in Rio de Janeiro, said in a
statement. "The discovery ... came as a complete surprise."
Chariklo's rings have crisp edges, a feature typically caused by the
gravitational effects of a small embedded moon or moons.
"It's likely that Chariklo has at least one small moon still waiting
to be discovered," Braga-Ribas said.
Chariklo's inner ring is 4.3 miles wide and the outer ring is 1.9
miles wide. The bands are separated by a 5.6 mile wide gap.
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"It was quite amazing to realize that we were able not only to
detect a ring system, but also pinpoint that it consists of two
clearly distinct rings," astronomer Uffe Grae Jorgensen, with the
University of Copenhagen in Denmark, said in a statement.
The origin of the rings is not known, but scientists suspect they
formed after another body crashed into Chariklo, forming a debris
disk of icy particles.
The research is published in this week's issue of the journal
Nature.
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