10199 Chariklo

10199 Chariklo

10199 Chariklo is a special object in space called a ringed asteroid and centaur. It moves in the outer part of our Solar System, between the planets Saturn and Uranus. Chariklo is the largest known centaur, about 250 kilometers or 160 miles across. Scientists found it on February 15, 1997, at the University of Arizona’s Spacewatch project at the Kitt Peak National Observatory.

What makes Chariklo special is its ring system. In 2013, astronomers found that Chariklo has two thin rings made of icy particles. It was the first tiny planet ever found to have rings. As of 2025, it is one of only four minor planets known to have rings, along with 2060 Chiron, Haumea, and Quaoar. Scientists are still learning why the rings stay in place. Some think tiny, unseen shepherd moons might be helping to keep the rings stable. The rings might have come from material thrown off Chariklo’s surface or from a moon that broke apart long ago.

Discovery and naming

Chariklo was found on February 15, 1997, by the University of Arizona’s Spacewatch project at Kitt Peak National Observatory. James V. Scotti helped make the discovery, though he is not listed as the discoverer. Observatories in Canada, the Czech Republic, and China also watched Chariklo. It was given the temporary name 1997 CU₂₆ and was the seventh centaur ever found.

Soon after, scientists studied Chariklo. By March 2, 1999, it received the official number 10199. It was named on September 28, 1999. The name comes from Chariclo, a figure in Greek mythology. She was the wife of Chiron. An astrologer later made a special symbol for Chariklo based on the symbol for another centaur named 2060 Chiron.

Orbit

Chariklo travels around the Sun between Saturn and Uranus. It is about 15.7 astronomical units from the Sun on average. It takes 62.5 years for Chariklo to go around the Sun once. Its path is tilted and stretched, coming as close as 13.1 astronomical units to the Sun and going as far as 18.4 astronomical units away.

Chariklo is called a centaur because its orbit is between Jupiter and Neptune. Centaurs have traits of both asteroids and comets. They are thought to come from far beyond Neptune, from places called the Kuiper belt and the scattered disc. Big planets like Jupiter and Neptune can change their paths in different ways. These changes can make centaurs leave their area, either by being thrown out of the Solar System, hitting a planet, or becoming a comet that moves closer to the Sun.

Chariklo’s orbit is more stable than other centaurs. It might leave the centaur region in about 7 to 10 million years. Uranus mostly affects Chariklo’s orbit, and it will likely come close to Uranus many times over the next 100 million years. Future meetings with Jupiter and Saturn could change Chariklo’s path and might affect its ring system.

Observation

Chariklo looks different in brightness from Earth, changing between 17 and 19 depending on its distance. It appeared brightest in 2003 when it was closest to both Earth and the Sun.

Chariklo and its rings are too small and distant for today's telescopes to see clearly. Special events, called stellar occultations, happen when Chariklo moves in front of stars. These events help scientists measure Chariklo's size and rings very accurately. These events led to the discovery of Chariklo's rings in 2013, and since then, many observations have been made by teams of professional and amateur astronomers working together.

Physical characteristics

Chariklo is a large asteroid shaped like an oval. It measures about 288 km × 270 km × 198 km (179 mi × 168 mi × 123 mi). Its average diameter is roughly 250 km (160 mi), making it the largest known centaur. A centaur is a type of object that orbits the Sun between Saturn and Uranus.

The surface of Chariklo looks dark and reddish. In certain types of light, its surface seems to contain water ice, minerals, and complex organic materials. Unlike some similar objects, Chariklo does not show signs of activity like a dusty tail or jets. This is likely because it is too cold and far from the Sun. However, in the past, it might have been closer to the Sun and more active.

Rings

Main article: Rings of Chariklo

In 2013, scientists found that the asteroid Chariklo has two rings. These rings are about 386 and 400 kilometers wide. The inner ring is about 6.9 kilometers wide and the outer ring is just 0.12 kilometers wide. The rings are about 14 kilometers apart.

Finding rings around a small object like Chariklo was a surprise because rings were thought to only exist around much larger objects. Scientists believe these rings might not stay for very long unless something is keeping them in place. They named the inner ring Oiapoque and the outer ring Chuí after rivers in Brazil. It’s also possible that another object, Chiron, might have rings too.

Exploration

Main article: Camilla (spacecraft)

There is a plan for a space mission named Camilla, first talked about in June 2018. This mission would send a robot spacecraft to fly past the asteroid Chariklo.

The mission would try to follow budget rules set by NASA. If it happens, the spacecraft would launch in September 2026. It would use the gravity of Venus and Earth to help it travel towards Jupiter.