Beta Centauri
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation | Centaurus |
| Right ascension | 14h03m49.4s |
| Declination | −60°22′23″ |
| Apparent magnitude (V) | 0.60 |
| Characteristics | |
| Spectral type | B1III |
| B-V color index | −0.22 |
| U-B color index | −0.98 |
| Variable type | β Cep |
| Astrometry | |
| Radial velocity (Rv) | 5.9 km/s |
| Proper motion (μ) | RA: −33.96 mas/yr Dec.: −2.506 mas/yr |
| Parallax (π) | 6.21 ± 0.56 mas |
| Distance | 530 ± 50 ly (160 ± 10 pc) |
| Absolute magnitude (MV) | −5.42 |
| Other designations | |
| Database references | |
| SIMBAD | data |
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. The name Hadar comes from the Arabic word for "ground", while the name Agena comes from Latin words for "the knee".
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.
Beta Centauri is well-known in the Southern Hemisphere as the inner of the two "Pointers" to the Southern Cross. A line made from the other pointer, Alpha Centauri, through Beta Centauri leads to within a few degrees of Gacrux, the star at the top of the cross. Using Gacrux, a navigator can draw a line with Acrux to effectively determine south.
The star is not actually shown on the Australian flag, although the Commonwealth Star is placed in a manner suggesting that it is.[citation needed]
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