Alpha Centauri (or Rigel Kentaurus, as it is also known) is actually a system composed of three gravitationally bound stars. The two main stars are Alpha Centauri A and Alpha Centauri B. The tiniest star in the system is a red dwarf known as Alpha Centauri C.

The Alpha Centauri system is a special one. At an average distance of 4.3 light-years, these stars are our nearest known neighbors in space beyond the solar system.

Centauri A and B are remarkably Sun-like, with Centauri A being a near twin of the Sun (both are yellow G stars). In comparison to the Sun, Alpha Centauri A is 1.5 times as luminous and shines at magnitude -0.01 while Alpha Centauri B is half as luminous and shines at magnitude 1.3.

Alpha Centauri C, is 7,000 times fainter and shines at 11^th magnitude.

Because of its position in the sky, the Alpha Centauri system is not easily visible in much of the Northern Hemisphere. An observer must be at latitudes south of 28 degrees north (or roughly from Naples, Florida and locations further south) to see the closest stellar system to us.

The two brighter components of the system make a wonderful double star to observe in a small telescope.

Naked-eye Alpha Centauri appears so bright because it is so close. This also means that it has a large proper motion – the drifting of stars relative to each other due to their actual motion and direction in space. In another 4,000 years Alpha Centauri will have moved near enough to Beta Centauri for the two to form an apparent double star. [Alpha Centauri Map]