jeudi 4 septembre 2008

Centaurus 4

Beta Centauri

Distance (Light Years) 525 ± 47
Visual Magnitude 0.61
Color (B-V) -0.23

Names For This Star

Hadar is an Arabic word meaning "Ground."
Another name for the star is Agena. According to a note in Allen, this name appears to be a compound of the letter "A" for alpha and "gena" meaning knee. (See the note on p. 154 of the 1963 Dover.) The root of the name would presumably be Latin. However, the only meaning that I have been able to find for the word "gena" is "cheek" rather than "knee".

Description of the Star

Hadar is a blue, hot B1III giant star, maybe 13,000 times as luminous as the sun. There is a companion star lying at an angular separation of 0.871 sec of arc, that is, at a projected distance of 140 AU.
The spectrum of the star seems to indicate further companions revolving with respective periods of 3.7 hours and 352 days.

Theta Centauri

Distance (Light Years) 60.9 ± 0.9
Visual Magnitude 2.06
Color (B-V) 1.01

Names For This Star

The name Menkent for Theta Centauri is not found in Allen, but "Gibson" and "Dolan" offer the translation "The Shoulder of the Centaur" for the name. If Gibson and Dolan are correct then "Menkent" would probably be a mixture of Arabic (Men-, see Menkalinan) and Greek (Kentauros).
Description of the Star

Menkent is a cool, orange K0-IIIb giant having a luminosity about 45 times that of the sun. The spectral type suggests a temperature of around 4500 K, a mass at least 4 times that of the sun, and a diameter at least 16 times larger than the sun.

Rigel kentaurus
Alpha Centauri

Distance (Light Years) 4.395 ± 0.008
Visual Magnitude -0.01
Color (B-V) 0.71

Names For This Star

Rigel Kentaurus derives from the Arabic Al Rijl al Kentaurus, "The Centaur's Foot." This is often shortened to Rigil Kent.
The The Bright Star Catalog lists Toliman as an alternative name for this star.

Description of the Star

The stars of the Rigel Kentaurus system represent the nearest stars to the earth other than the sun.
A Triple Star System

The Rigel Kentaurus system is a triple star system. The A star primary is of spectral type G2V, that is yellow star of the same type as our sun. This star is slightly larger in mass and diameter than the sun, and slightly more luminous.
The B component of the system is separated by about 24 AU from A (that is somewhat greater than the distance between the sun and planet Uranus) and revolves with a period of 79.9 years.

Rigel Kentaurus C is a cool red M5.5Ve main sequence dwarf with a Visual Magnitude of 11.1, corresponding to a luminosity of about 1/17,000 that of the sun. This star is known as Proxima Centauri.

The Nearest Star

Proxima is separated from the other two stars of the system by about 1/6 of a ly. At 4.22 ly from the earth, Proxima is actually the nearest single star to the earth.
See this German site for a nice three-dimensional representation of our nearby neighbor stars.

See this page for more information on the Rigel Kentaurus system.

Rigel Kentaurus B
Alpha2 Centauri

Distance (Light Years) 4.395± 0.008
Visual Magnitude 1.33
Color (B-V) 0.88

Description of the Star

Rigel Kentaurus B is an orange K1V main sequence star having about 46% of the luminosity of the sun. The spectral type implies a temperature of 4750 K, a mass of 70% of that of the sun, and a 83% of the sun's diameter. See this page for more information on this star and the Rigel Kentaurus system.

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