(Adds comment by astronomer, details of detection technique)
By Irene Klotz
CAPE CANAVERAL, Fla., March 26 It is not just
Saturn and the giant gas planets of the solar system that bear
rings. For the first time, rings have been found around an
asteroid, a study published on Wednesday shows.
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
They ended up with much more. Analyzing flickers of light
during the occultation revealed two dense rings circling
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
Chariklo's rings have crisp edges, a feature typically
caused by the gravitational effects of a small embedded moon or
"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 (7 km) wide and the outer
ring is 1.9 miles (3 km) wide. The bands are separated by a 5.6
mile (9 km) wide gap.
"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
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