2060 Chiron

Chiron is a special object in space that orbits the Sun between the planets Saturn and Uranus. It was discovered in 1977 by Charles Kowal and was the first of its kind to be found. These objects are called centaurs because they travel between the asteroid belt and the Kuiper belt. Chiron is named after a wise character from Greek mythology.

At first, Chiron was thought to be just an asteroid, a rocky object in space. But in 1989, scientists noticed that it behaved like a comet, which are icy bodies that can develop a tail when they get close to the Sun. Because of this, Chiron is now known both as a minor planet and as a comet, with the comet name 95P/Chiron.

More recently, between the 2010s and early 2020s, scientists observed Chiron during events called occultations. These events helped discover that Chiron has rings around it, just like some planets do. Chiron is one of only four minor planets known to have rings, along with 10199 Chariklo, Haumea, and Quaoar. It is also the only known comet with rings.

History

Discovery

Chiron was found on November 1, 1977, by Charles Kowal using pictures taken on October 18 at Palomar Observatory. At that time, it was the farthest known small planet from the Sun and some news reports called it the tenth planet. Later, scientists found older pictures of Chiron from 1895. This helped them learn more about its path around the Sun.

Naming

This small planet was named after Chiron, a wise character from Greek mythology who was half-human and half-horse. Chiron was known for teaching many famous Greek heroes. The official naming was announced on April 1, 1978. Most planets do not have special symbols, but some people use a symbol that looks like a key for Chiron.

Orbit

Chiron moves in a stretched path around the Sun. It gets closest to the Sun near the orbit of Saturn and farthest out near Uranus, but it does not reach Uranus’s usual distance.

Chiron was exciting because it was the first object found in such a special path, far beyond the asteroid belt. It belongs to a group called centaurs, which travel between the outer planets. These paths are not stable and will change due to the pull of the giant planets over millions of years. Chiron probably started in the Kuiper belt and may become a comet in about a million years. It was closest to the Sun in 1996 and farthest in May 2021.

Physical characteristics

The light from Chiron looks neutral, similar to some asteroids and comets. It shows gases like carbon dioxide, carbon monoxide, ethane, propane, and acetylene, along with water ice.

Chiron rotates once every about 5.9 hours. Its size is estimated to be between about 150 km and 218 km in diameter, but this is hard to know exactly because Chiron sometimes acts like a comet. In 1988, Chiron became brighter and developed a fuzzy atmosphere, which is typical comet behavior. Unlike most comets, water isn’t a big part of Chiron’s atmosphere because it’s too far from the Sun. Instead, small amounts of carbon monoxide and other gases were found. Chiron is special because it’s both a comet (95P/Chiron) and a minor planet, showing how some objects can belong to more than one group.

Rings

Chiron has rings, just like the rings around 10199 Chariklo. These rings were found when scientists saw strange changes in starlight as Chiron moved in front of stars. The rings are about 324 kilometers wide and look different from various angles, which can make Chiron seem brighter or dimmer at times.

New observations in 2018 and 2022 showed that Chiron's rings change over time. In 2018, there was less material, but a new partial ring was starting to form. By 2022, the rings had more material and the new ring was complete. Scientists believe these changes happen in cycles. The rings of Chiron and Chariklo are very similar and stay in place because they are within a certain distance from their centers.

Exploration

Scientists wanted to send a spacecraft to visit Chiron. They suggested a mission called the Chiron Orbiter Mission for NASA's New Frontiers program or Flagship program. This idea was shared in May 2010. The spacecraft could have been launched between 2023 and 2025, depending on money and the type of engine used.

Another mission idea was part of the Discovery Program and was called Centaurus. If chosen, this mission could have launched between 2026 and 2029 to fly by Chiron and another similar object in the 2030s.