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Alpha Centauri

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Alpha Centauri or Alpha Centauri or Rigil Kentaurus or Rigil Kentarus or Toliman or Bungula is a system of three stars very close: Alpha Centauri A and Alpha Centauri B are the two main stars that form a double star and Proxima Centauri is a red dwarf far less luminous star that is closest to the Sun . To the naked eye, this system appears to be the brightest star in the constellation Centaurus and the third brightest of the whole sky. Alpha Centauri is too far south to be visible in most parts of the northern hemisphere .

Summary 1 A double star 2 Possibility of planet formation 3 References 4 Internal Links 5 External Links

A double star

comparative sizes of star system Alpha Centauri with Sun

Alpha Centauri A is a star of spectral type G2, very similar to the Sun , although slightly larger and brighter. Alpha Centauri B is somewhat less luminous and spectral type K1. They orbit around each other over a period of 80 years, remoteness ranging from 11.2 to 35.6 AU .

Of the three stars is Proxima Centauri is the closest to us, 4.22 light years, or 270,000 times the distance between the Earth and Sun. Proxima is a red dwarf apparent magnitude of 11, far too faint to see with the naked eye. It is distant by Alpha Centauri 13 000 AU and though its orbit around the central couple is not directly known, the association between these three stars is not fully Proxima and accidental because the couple move together along the main. For this reason, Proxima is sometimes called Alpha Centauri C .
The period of the orbit was estimated between 500 000 years and 2 million years.

Possibility of planet formation

Computer models of planetary formation suggest that terrestrial planets could be formed around Alpha Centauri A and B but that gaseous planets like Jupiter and Saturn could not be formed because the gravitational effects caused by the double star would prevent the formation ^{[ 1]} . Given the similarities of this stellar system in terms of star type, age, stability of the orbit, it was suggested that may hold the greatest potential to hold a extraterrestrial life ^{[2 ]} .

Some believe that a planet that is formed in the Alpha Centauri system would be very dry because it is believed that the presence of gaseous planets far more massive, is essential to attract comets and thus provide the terrestrial planets in water. This would not be a problem though if Alpha Centauri B played the same role as the gas planets to the Sun to Alpha Centauri A, and vice versa. The two stars have a good spectral type to harbor life on a planet potential.

For a temperature of the Earth, a planet orbiting Alpha Centauri A is expected to be 1.25 AU or midway between the orbit of the Earth and Mars in the solar system. It should be at 0.7 AU , equivalent to the orbit of Venus for Alpha Centauri B is cooler and less luminous.

References

1. ↑ M. Barbier, F. Marzari, H. Scholl, Formation of terrestrial planets in close binary systems : The case of α Centauri A, Astronomy & Astrophysics, 2002, pages=219–224.
2. ↑ P.A. Wigert and M.J. Holman, The stability of planets in the Alpha Centauri system  [ archive ] , The Astronomical Journal, 1997 ,volume 113, pages=1445–1450.

 

Liens internes

• Alpha Centauri A
• Alpha Centauri B
• Proxima Centauri
• constellation Centaurus
• List of nearest stars
• List of brightest stars
• stargazing
• Star