Alpha Centauri, the brightest "star" in the constellation of Centaurus is, when seen through a telescope, actually three stars orbiting around one another. This trinary star system consists of two Sun-like stars, Alpha Centauri A and Alpha Centauri B, and a red dwarf, Alpha Centauri C, or Proxima Centauri. Its distance from Earth is approximately 4.37 light years, making it the closest star system in the galaxy to the Solar System.
Alpha Centauri is a trinary star system, meaning that it has three stars. It is Earth's closest stellar neighbor outside the solar system.
Its largest member, Alpha Centauri A (Rigil Kentaurus), (or "ACA" to astronomers), is about twenty percent larger than the sun, but otherwise very similar. ACA would be unremarkable were it not for the fact that it serves as the sun for Pandora, a large moon that orbits Polyphemus. It was on Pandora that explorers encountered the Na'vi, the only intelligent species yet discovered in outer space. Pandora is also the only known source for unobtanium, a high temperature superconductor essential for many of Earth's technologies.
Alpha Centauri B (Toliman), (ACB) is about fifteen percent smaller than the sun, and noticeably orange because it is 500 Kelvin cooler than its neighboring star.
Alpha Centauri C (ACC), also known as Proxima Centauri, is a red dwarf, only twenty percent of the size of the Sun and less than half its temperature. ACC gives off only a dim red glow instead of the bright yellow glare of the Sun and ACA.
The three gas giant planets orbiting Alpha Centauri B were discovered by terrestrial observatories. The five rocky planets were discovered two decades later. Since the arrangement of the planets resembled our own solar system, they were named for their counterparts: Vulcan (inside Mercury's orbit), Hermes (Mercury), Aphrodite (Venus), Gaea (Earth), Ares (Mars), Zeus (Jupiter), Cronus (Saturn), and Poseidon (chosen instead of another name for Uranus, because it occupies the equivalent of Neptune's orbit).
Two inner rocky planets and three outer gas giants are orbiting ACA.  The three gas giants around ACA were not found until after the co-orbiting synchronized telescopic interferometer network (COSTIN) went into full operation. Upon their discovery, they were named Oceanus, Coeus, and Crius. Coeus was later renamed, or perhaps nicknamed, Polyphemus.
Three planets orbit Alpha Centauri C: a close-in gas giant and two rocky planets. 
The astronomical coordinates for the Centaurus star system are right ascension 14h 39.6m; declination -60 degrees 50'. Alpha Centauri A and B are located approximately 4.37 light years or 277,600 Astronomical units from Earth (one AU is the average distance of Earth from the Sun, about 93,000,000 miles or 1.496 Gm). Alpha Centauri C (also called "Proxima Centauri" because it is the closest of the three stars to Earth) is about 0.15 light years closer.
- James Cameron's Avatar: The Game - Ingame Pandorapedia