Our editors will review what you’ve submitted and determine whether to revise the article.Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work!
Centaur object, any of a population of small bodies, similar to asteroids in size but to comets in composition, that revolve around the Sun in the outer solar system, mainly between the orbits of Jupiter and Neptune. The first known member of the group, Chiron, was discovered in 1977, although its close affinity with icy comet nuclei was not recognized until more than a decade later. Since the discovery of the second known representative, Pholus, in 1992, hundreds of Centaur objects, or Centaurs, have been reported, and astronomers have speculated that thousands more may exist.
Centaur objects, which are as large as about 250 km (160 miles) in diameter, are thought to have originated beyond the orbits of Neptune and Pluto, in a vast, disk-shaped reservoir of comet nuclei called the Kuiper belt. Having been perturbed inward by Neptune’s gravitational influence, they presently travel in unstable orbits that cross the paths of the giant planets. Because of the likelihood that they will collide with a planet or be flung by a planet’s gravity out of the solar system or toward the inner planets, these objects are thought to spend a short lifetime, in astronomical terms, as Centaurs. This implies that the population of Centaurs is being continually replenished from the Kuiper belt.
At the large distances of the Centaurs from the Sun, customary distinctions between comets and asteroids can become blurred. By traditional definition, comets contain more frozen water and other volatile compounds than rocky material, and they give off gases when these ices vaporize. At the very low temperatures in the outer solar system, however, icy bodies such as the Centaurs may never show this activity.
Learn More in these related Britannica articles:
solar system: Composition of the solar systemThe Centaur objects, a population of comet nuclei having diameters as large as 200 km (125 miles), orbit the Sun between Jupiter and Neptune, probably having been gravitationally perturbed inward from the Kuiper belt. The interplanetary medium—an exceedingly tenuous plasma (ionized gas) laced with concentrations of…
Kuiper belt…years, and for the icy Centaur objects, which have orbits in the region of the giant planets. (Some of the Centaurs may represent the transition from Kuiper belt objects [KBOs] to short-period comets.) Although its existence had been assumed for decades, the Kuiper belt remained undetected until the 1990s, when…
small body: Populations… while closely approaching Earth’s, (3) Centaur objects, icy bodies that are thought to have been gravitationally perturbed out of the Kuiper belt and now travel mainly between the orbits of Jupiter and Neptune, and (4) individual idiosyncratic planet-crossing objects such as the asteroid Hidalgo, which travels between the inner edge…