LIKE tiny versions of Saturn, asteroids can deck themselves out with glittering rings. A space rock called 10199 Chariklo is the first asteroid known to have a ring system, revealing an unexpected possibility for small bodies in the solar system. Until now, rings have been found only around giant planets. Colin Snodgrass of the Max Planck Institute for Solar System Research in Göttingen, Germany, and his colleagues found the rings in June 2013 during an occultation. This is when an object crosses in front of a star as seen from Earth, causing it to briefly wink out. Seen from sites across South America, the star’s brightness dipped in a distinctive pattern, indicating a set of twin rings (Nature, DOI: 10.1038/ nature13155). Chariklo orbits between the paths of Saturn and Uranus, and the asteroid has shown mysterious behaviour in the past. The tiny body was seen dimming and brightening, and its spectrum held hints of water ice disappearing and reappearing. A pair of icy, reflective rings seen from different angles would explain this. The rings could have formed in a number of ways, including impacts flinging up debris, or small moons colliding or being broken up by gravity if they spiralled too close to the asteroid.
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