WikiPortallus: 2060 Chiron.html

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 G m. 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.⁷ 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.⁸ Chiron is probably a refugee from the Kuiper belt and will likely become a short period comet in about a million years.⁷

Physical characteristics

In February 1988, at 12 AU from the Sun, Chiron brightened by 75 percent.⁹ This is behaviour typical of comets but not asteroids. Further observations in April 1989 showed that Chiron had developed a cometary coma.⁹ 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.⁶

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.¹⁰

References

^ Marc W. Buie (2007-08-18). "Orbit Fit and Astrometric record for 2060". SwRI (Space Science Department). Retrieved on 2008-10-13.
^ ^a ^b ^c ^d "JPL Small-Body Database Browser: 2060 Chiron (1977 UB)" (2008-09-04 last obs). Retrieved on 2007-01-11.
^ ^a ^b John Stansberry, Will Grundy, Mike Brown, Dale Cruikshank, John Spencer, David Trilling, Jean-Luc Margot (2007). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope". University of Arizona, Lowell Observatory, California Institute of Technology, NASA Ames Research Center, Southwest Research Institute, Cornell University. Retrieved on 2008-10-18.
^ ^a ^b Groussin (January 2004). "Properties of the nuclei of Centaurs Chiron and Chariklo". Astronomy and Astrophysics, v.413, p.1163-1175 (2004). Retrieved on 2007-10-18.
^ Meech, Karen (19 February 1994). "THE STRUCTURE OF THE INNER COMA OF COMET CHIRON: IMAGING THE EXOPAUSE". INSTITUTE FOR ASTRONOMY, UNIVERSITY OF HAWAII. Retrieved on 2007-10-19.
^ ^a ^b Grayzeck, Ed (2003-12-11). "The Chiron Perihelion Campaign". NASA Goddard Space Flight Center. Retrieved on 2007-10-18.
^ ^a ^b Horner, J.; Evans, N.W.; Bailey, M. E. (2004). Simulations of the Population of Centaurs II: Individual Objects, http://arxiv.org/abs/astro-ph/0408576. Retrieved on 28 August 2008.
^ Jewitt, David C.; A. Delsanti (2006). "The Solar System Beyond The Planets", Solar System Update : Topical and Timely Reviews in Solar System Sciences. Springer-Praxis Ed.. ISBN 3-540-26056-0. (Preprint version (pdf))
^ ^a ^b Ken Croswell (Harvard University) (1990-08-25). "The changing face of Chiron". New Scientist issue 1731. Retrieved on 2008-10-13.
^ Trigo-Rodríguez, Melendo, García-Hernández, Davidsson, Sánchez (2008). "A continuous follow-up of Centaurs, and dormant comets: looking for cometary activity." (PDF). European Planetary Science Congress. Retrieved on 2008-10-12.

2060 Chiron.html

Contents

Orbit

Physical characteristics

References

External links