Origin of minor planets’ rings discovered
22 Sep 2016 by qmtbqdmdjq.d qmtbqdmdjq.d
An international team of astronomers have proposed how rings around minor planets known as centaurs formed.
An international team of astronomers have proposed how rings around minor planets known as centaurs formed.
Centaurs orbit between Jupiter and Neptune and have crossed orbits with one or more giant planets. There are more than 40,000 of them, each with a diameter of more than one kilometre. The rings around two centaurs, Chiron and Chariklo, were the focus of this research.
In the study, published in Astrophysical Journal Letters, the authors put forward that the rings could have formed during a single extremely close encounter with one of the giant planets. They believe the centaurs would have been pulled apart by gravitational pull, with debris then accumulating in a disc shape around the largest fragment.
The astronomers found there was a one in 10 chance of centaurs passing close enough to be broken up by the gravitational pull of the giant planets. Computer simulations were carried out to understand what would happen in these instances. The researchers found the chances of a centaur break-up was dependent on variables such as the initial spin of the passing centaur, the size of its core and the distance of its closest approach to a giant planet.
If the passing centaur is differentiated — has separate, distinct layers — with a silicate core covered by an icy mantle, fragments of the partially disintegrated centaur would eventually form a ring around the largest piece of the centaur.
Ryuki Hyodo, lead author from Kobe University, said: “We have performed many different simulations and showed that in many cases the ring or moon/satellite formation naturally takes place. Thus, our simulations can already apply to other Centaurs and we estimated about 10% of Centaurs could have rings or small moon(s) as long as they are differentiated.”
It was previously thought the four giants — Jupiter, Saturn, Uranus and Neptune — were the only planets with rings in the Solar System. The team of researchers believe their findings show that there are many undiscovered centaurs with rings around them.
The researchers were from Kobe University, the Tokyo Institute of Technology and Institut de Physique du Globe de Paris. The next stage of research will be looking at the long-term evolution of rings or debris disks around centaurs.
