Chariklo was the first minor planet, or centaur, discovered with rings. Photo by NASA/ESO/YouTube/screenshot

KOBE, Japan, Sept. 16 (UPI) -- Scientists have determined the origin of the rings that surround a pair of minor planets orbiting between Jupiter and Neptune.

The minor planets are known as centaurs, and are just two of 44,000 such objects. Centaurs have a diameter of at least 1 kilometer and follow unstable orbits that cross or have crossed the orbits of one of the giant planets.


In 2014, astronomers discovered rings around two centaurs, Chariklo and Chiron. Up until then, scientists believed the four giants, Jupiter, Saturn, Uranus and Neptune, were the only ringed bodies in the solar system.

As part of the new study, published recently in Astrophysical Journal Letters, a team of scientists from Japan modeled the risk of collision with a giant planet faced by centaurs. Their analysis suggests centaurs have only a 10 percent chance of a close encounter with one of the four giants.

Their model also determined that a close encounter with a giant planet can yield a new set of rings.

"During the close encounter, the icy mantle of the passing object is preferentially ripped off by the planet's tidal force and the debris is distributed mostly within the Roche limit of the largest remnant body," researchers explained in their newly published paper.

In other words, the debris from a centaur partially destroyed by a close encounter can become organized in a ring form around what remains of the minor planet.

"Our numerical results suggest that ring formation would be a natural outcome of such extreme close encounters, and centaurs can naturally have such ring systems because they cross the orbits of the giant planets," researchers concluded.