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2060 Chiron
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2060 Chiron ( , or as in ) is a planetoid in the outer solar system. Discovered in 1977 by Charles T. Kowal (precovery images have been found as far back as 1895), it was the first known member of a new class of objects now known as centaurs, with an orbit between those of Saturn and Uranus.
Although it was initially classified as an asteroid, later dispute arose as to whether it was an asteroid or actually a comet. Today it is classified as both, and accordingly it is also known by the cometary designation 95P/Chiron.
Chiron is named after the centaur Chiron in Greek mythology.
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Encyclopedia
2060 Chiron ( , or as in ) is a planetoid in the outer solar system. Discovered in 1977 by Charles T. Kowal (precovery images have been found as far back as 1895), it was the first known member of a new class of objects now known as centaurs, with an orbit between those of Saturn and Uranus.
Although it was initially classified as an asteroid, later dispute arose as to whether it was an asteroid or actually a comet. Today it is classified as both, and accordingly it is also known by the cometary designation 95P/Chiron.
Chiron is named after the centaur Chiron in Greek mythology. It should not be confused with the dwarf planet partner of Pluto named Charon, discovered in 1978.
Orbit
Chiron's orbit was found to be highly eccentric, with perihelion just inside the orbit of Saturn and aphelion distance just outside the perihelion of Uranus (it does not reach the average distance of Uranus, however). Chiron's closest approach to Saturn in modern times was in May 720, at just under 30 Gm. It does not come nearly as close to Uranus; Chiron crosses Uranus' orbit where the latter is farther than average from the Sun. It attracted considerable interest because it was the first object discovered in such an orbit, well outside the asteroid belt. Chiron is classified as a centaur, the first of a class of objects orbiting between the outer planets. Chiron is a SU object since its perihelion lies within Saturn's zone of control and its aphelion lies within Uranus' zone of control. Centaurs are not in stable orbits and over millions of years will eventually be removed by gravitational perturbation by the giant planets, moving to different orbits or leaving the solar system altogether. Chiron is probably a refugee from the Kuiper belt and will likely become a short period comet in about a million years.
Physical characteristics
In February 1988, at 12 AU from the Sun, Chiron brightened by 75 percent. This is behaviour typical of comets but not asteroids. Further observations in April 1989 showed that Chiron had developed a cometary coma. At the time of its discovery, Chiron was close to aphelion, whereas the observations showing a coma were done closer to perihelion, perhaps explaining why no cometary behavior had been seen earlier. The fact that Chiron is still active likely means it has not been in this orbit that long.
Chiron is officially designated as both a comet and an asteroid, an indication of the sometimes fuzzy dividing line between the two classes of object. The term proto-comet has also been used. At approximately 150 km across, it is unusually large for a comet nucleus.
Since the discovery of Chiron, other centaurs have been discovered, and nearly all are currently classified as asteroids but are being observed for possible cometary behavior. 60558 Echeclus has displayed a cometary coma and now also has the cometary designation 174P/Echeclus. After passing perihelion in early 2008, centaur 52872 Okyrhoe significantly brightened.
There are other non-centaur asteroids that are also classified as main-belt comets: 4015 Wilson-Harrington, 7968 Elst-Pizarro, and 118401 LINEAR.
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