The European Southern Observatory (ESO) recently announced that a large asteroid known as 10199 Chariklo has two narrow rings which encircle it. Chariklo is the largest asteroid in a class of what are called Centaurs. Centaurs are essentially asteroids, or minor planets, orbiting the sun primarily between Neptune and Jupiter. Centaurs are comprised of asteroids ranging from a mere one kilometer in diameter to approximately 250 kilometers in size. Because Chariklo is at the top of the Centaur size scale and has now been observed to have rings, some astronomers would like to see it reclassified as a dwarf planet, such as Pluto is now designated. New information has provided astronomers with the discovery that this asteroid, or minor planet, Chariklo, has not just one, but two rings.
From what astronomers previously understood, it did not appear possible for an object this small to have a stable ring system. The other planets with rings, Saturn, Jupiter, Neptune, and Uranus, each have their own ring systems but these planets are much larger. Scientists were actually observing the occlusion of a star by Chariklo when they noticed an extra dip in the star’s light both before Chariklo eclipsed the star and again afterward. The observation occurred on June 3, 2013 during investigations from South America. While a total of seven sites witnessed the signature dips in star brightness, originally they did not understand the cause. Upon further investigation, the new discovery was made that Chariklo, an asteroid of only 248 kilometers across, has rings. The rings themselves are only between three and seven kilometers wide and have a distance of approximately nine kilometers between them.
The rings could have been formed from a collision between the asteroid and a smaller object which resulted in debris. The ability of just how the asteroid is maintaining the stability of the rings still remains unknown. The gravitational pull from Chariklo is most likely not great enough to shape the debris and have it retained as a stable ring system. Scientists theorize that there is at least one small moon orbiting this celestial body. The moon, or possibly multiple moons, would exert an additional force which would help to sustain the rings.
One of the rings is only three kilometers wide while the other is approximately seven kilometers wide. Scientists believe that the rings are at least partially composed of water ice. The presence of the rings may serve to provide information on the evolution and origin of Chariklo. At this time, project leaders have provisionally designated the rings Chuí and Oiapoque which are the names of actual rivers in Brazil located at both the northern and southern extremes.
The discovery of the rings around the Centaur designated as 10199 Chariklo has been of particular interest to astronomers. A collaboration of international researchers led by Felipe Braga-Ribas from Brazil’s National Observatory was formed to analyze the information. While there is no direct, visual observation of the rings circling Chariklo, the data retrieved rules out other possibilities and points to rings as the source of the star’s dips in brightness during the asteroid occlusion. Researchers are confident that this new discovery is, in fact, showing that an asteroid can be encircled with rings, just like our larger planets.
By Dee Mueller
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