The Centaurs are a classification of minor celestial bodies in our solar system, named after the mythological centaurs. Chiron is probably the best known of the astronomical centaurs and the one most often used by astrologers.
The orbits of the Centaurs stretch between the inner and outer planets. They are a very new demographic in our solar system. Although the first was discovered in 1920, the classification of Centaurs wasn't established until the discovery of Chiron in 1977. This classification is so new that astronomers are still trying to understand how they fit in the massive composite of our solar system.
Mythologically, the centaurs were half-man and half-horse.