A Ringed Minor Planet
03 April 2014

An artist’s rendition showing the ringed minor planet Chariklo
Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)

Astronomers using telescopes in Argentina, Brazil and Chile, have discovered a ring system around a minor planet known as Chariklo. Before the discovery of the rings of Chariklo, the four giant Jovian planets were the only known ringed members of the solar system. This discovery is really surprising, as it has been thought that small solar system objects cannot retain ring systems. It is speculated that the presence of small unseen moons around Chariklo may help preserve these rings.  

Chariklo (260 km across) belongs to a category of minor planets, known as the Centaurs, which orbit the Sun, between the orbits of Jupiter and Neptune. They are believed to be similar in composition to comets, but their sizes are similar to those of the asteroids. Chariklo orbits the Sun every 63 years, and its distance from the Sun varies between 1,960 million km and 2,791 million km. Its orbit lies between the orbits of Saturn and Uranus.

The rings of Chariklo were detected when the minor planet occulted (eclipsed) a star, on 3 June 2013. There were two slight dips in the light of the star, observed shortly before, and shortly after the occultation. The observations revealed two small, narrow rings circling Chariklo. These rings seem to be composed of icy particles. The occultation is an interesting astronomical phenomenon, similar to solar eclipses, in which the Moon crosses directly between the Earth and the Sun. It occurs when a solar system object passes in front of a celestial object.

European Southern Observatory
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Aymen Mohamed Ibrahem
Senior Astronomy Specialist
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