Alpha Centauri

:This article is about the star system. For the computer game, see Sid Meier's Alpha Centauri.

System components

Alpha Centauri is a triple star system. It consists of two main stars, Alpha Centauri A and Alpha Centauri B (which form a binary star together) at a distance of 4.36 ly, and a dimmer red dwarf named Proxima Centauri at a distance of 4.22 ly. The larger member of the binary star, Alpha Centauri A, is similar to the Sun, but a little larger and brighter. Like the Sun, its spectral type is G2 V. The smaller of the two, Alpha Centauri B, 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 units (2×10−4 ly) and receding to 35.6 AU (6×10−4 ly), with a period of just under 80 years. Hence the sum of the two masses is 23.4^3/80^2=2.0 times that of the Sun (see formula).

Related Topics:
Alpha Centauri A - Alpha Centauri B - Binary star - Ly - Red dwarf - Proxima Centauri - Sun - Spectral type - E - Astronomical unit - Formula

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

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The red dwarf Proxima Centauri is about 13,000 astronomical units away from Alpha Centauri (1 ly = 63,241 AU, hence this is 0.21 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.

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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.

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The closest neighbours to the Alpha Centauri system are the Sun and Barnard's star (1.98 pc or 6.47 ly), which is also the next nearest star from Earth, at a distance of 5.96 ly.

Related Topics:
Barnard's star - Pc

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