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Alpha Centauri is the brightest star system in the southern constellation of Centaurus, and is the third brightest in the entire night sky (although too far south to be visible in most of the northern hemisphere).

It is also the closest star system to Earth, at 4.2-4.4 light-years. That makes it a logical choice as "first port of call" for science fiction and computer game speculation about space travel.

1 Names

It bears the proper name Rigil Kentaurus (often shortened to Rigil Kent), derived from the Arabic phrase for "foot of the centaur," but is nonetheless usually referred to by its Bayer designation Alpha Centauri. Another alternative name is Toliman. It and the nearby Beta Centauri are the "Pointers" to the Southern Cross.

2 System components

Alpha Centauri is a triple star system. It consists of two main stars, Alpha Centauri A and Alpha Centauri BAlpha Centauri B (also Rigel Kentaurus B — the foot of the centaur in Arabic) is a star of the Alpha Centauri star system. It is approximately 4. 40 light years from Earth's Solar System. Some facts about Alpha Centauri B Parallax: 0. 742 arcsecs Spectral (which form a binary starA binary star system consists of two stars both orbiting around their barycenter. The term "binary star" was apparently first coined by Sir William Herschel in 1802 to designate "a real double star the union of two stars that are formed together in one sy together) at a distance of 4.36 ly, and a dimmer red dwarfThis article is about red dwarfs, the type of star. Red Dwarf is also the name of a British television series. According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spe named Proxima CentauriThe red dwarf Proxima Centauri (also Alpha Centauri C , part of the Alpha Centauri star system, is the nearest star to Earth, other than the Sun. As the name suggests, it is located in the constellation of Centaurus. Based on the parallax of 772. 42 milli at a distance of 4.22 ly. The larger member of the binary star, Alpha Centauri A, is similar to the SunThe Sun (also called Sol is the star in our solar system. Planet Earth orbits the Sun. Other bodies that orbit the Sun include other planets, asteroids, meteoroids, comets and dust. Not all objects passing through the solar system have been orbitally capt, but a little larger and brighter. Like the sun, its spectral typeStars can be classified by using Wien's Displacement Law; but this poses difficulties for distant stars. Stellar spectroscopy offers a way to classify stars according to their absorption lines; particular absorption lines can be observed only for a certai is G2 V. The smaller of the two, Alpha Centauri BAlpha Centauri B (also Rigel Kentaurus B — the foot of the centaur in Arabic) is a star of the Alpha Centauri star system. It is approximately 4. 40 light years from Earth's Solar System. Some facts about Alpha Centauri B Parallax: 0. 742 arcsecs Spectral, is dimmer, with a spectral type of K1 V. The two orbit one another elliptically (e=0.52), approaching as close as 11.2 astronomical unitThe astronomical unit AU is a unit of distance, approximately equal to the mean distance between Earth and Sun. The currently accepted value of the AU is 149,597,870,691+-30 metres (about 150 million kilometres or 93 million miles). Earth's orbit is not as (0.000,2 ly) and receding to 35.6 AU (0.000,6 ly)with a period of just under 80 years. Hence the sum of the two masses is times that of the Sun (see formulaIn mechanics, the two-body problem is a special case of the n-body problem that admits a closed form solution. The most commonly encountered version of the problem, involving an inverse square law force, is encountered in celestial mechanics and the Bohr).

These two stars are about 5 to 6 billion years old.

The red dwarf Proxima Centauri is about 13,000 astronomical units away from Alpha Centauri (1 ly = 63,241 AU, hence this is 0.2 ly, about 1/20 of the distance between Alpha Centauri and the Sun, it is 0.14 ly closer to us) and may be in orbit about it, with a period on the order of 500,000 years or more. For this reason, Proxima is sometimes referred to as Alpha Centauri C. However, it is not clear if it really is in orbit, although the association is unlikely to be entirely accidental as it shares approximately the same motion through space as the larger star system.

Seen from Earth, Proxima is separated by 2 degrees from Alpha Centauri A and B (about 4 times the angular diameter of the full Moon), and the latter are at an angular distance of up to 40" from each other.