Beta Centauri

Encyclopedia : B : BE : BET : Beta Centauri

Agena, Hadar, Khadar, HR 5267, HD 122451, CD−59°5365, LHS 51, SAO 252582, HIP 68702, GC 18971, CCDM J14038-6022

|} Beta Centauri (β Cen / β Centauri), also known as Hadar or Agena, is the second brightest star in the constellation Centaurus and the eleventh brightest star in the nighttime sky. Beta Centauri is a blue-white giant star that is approximately 525 light-years from the Solar system.

In 1935 J.G. Voute identified Beta Centauri as a double star, giving it the identifier VOU 31. The companion is separated from the primary by 1.3", and has remained so since the discovery, although the position angle has changed slightly. This would indicate that the orbital period is very long, if the pair are actually gravitationally associated. The primary is also a spectroscopic binary, having at least one companion with an orbital period of 352 days, and possibly other companions.

The name hadar comes from the Arabic word for "ground", while the name agena comes from Latin words for "the knee".

Hadar is also useful as a guide star, making an imaginary line with Rigil Kentaurus that passes within a few degrees of Gacrux, in the constellation Crux. Using Gacrux, a navigator can draw a line with Acrux to effectively determine south.

The star is not actually shown officially on the Australian flag, although the Commonwealth Star is placed in a manner suggesting that it is.

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