Beta Centauri

Bayer name	β Centauri
Cordoba Survey	CD −59 ° 5054
Bright Star Catalog	HR 5267 [1]
Henry Draper Catalog	HD 122451 [2]
SAO catalog	SAO 252582 [3]
Tycho catalog	TYC 9005-3919-1 [4]
Hipparcos catalog	HIP 68702 [5]
Further designations:	Hadar, Agena, FK5 518

β Cen A is itself a spectroscopic double star, which is not further differentiated here.

Beta Centauri (abbreviated to β Cen ) is the second brightest star of the distinctive Centaurus constellation in the southern sky (0.6 mag ). In addition to the Bayer designation (β = second brightest in the constellation), it also has the proper names Agena and Hadar . The former is Latin and means knee (of the centaur), while the Arabic hadar stands for ground; this is also the name of a landscape in Ethiopia .

The star is about 530 light years away from the solar system and has long been believed to be a single blue-white supergiant , whose luminosity exceeds that of the sun by at least 10,000 times. It was not until 1935 that JG Voute was able to reveal it as a double star whose components (A, B) are only 1.3 "apart. Nevertheless, the position angle changes only slowly, so that the orbital period must be around 300 years. The smaller star ( Hadar B ) has the brightness 4.1 likes and shines 1500 times brighter than the sun, but is almost outshone by the brighter central star.

Three blue stars

Small discrepancies in the spectral analysis finally led to the discovery that the “central star ” ( β Cen A or Hadar A ) is a narrow, spectroscopic binary star . The two stars were called A1 and A2 and are almost identical: both have 8 times the solar size and 15 times the solar mass , spectral class B1 and 50,000 times the solar luminosity each - especially in high-energy blue light. They circle each other at a distance of 2.6 AU (half the distance between Sun and Jupiter) (according to other information in 23 AU), but due to the huge masses in only 355 days.

Stars that are so big and hot (approx. 30,000 ° C) "burn up" their nuclear fuel much faster than dwarf stars (like the sun) and only remain in a stable state for a relatively short time (see main sequence ). Depending on the mass of the stars, they expand into red giants or supergiants after about 5 to 500 million years . The central stars Hadar A1 and A2 are probably only 12 million years old. They could be orbited by planets in the outer space , but no Earth-like conditions are conceivable.

Constellations Centaurus (southern part) and cross, in between the "coal sack"

Location in the starry sky

Beta Centauri is the second brightest star in the constellation Centaurus (second from top left).

Beta Centauri is the eleventh brightest star in the firmament and forms a pair of stars with its slightly brighter neighboring star Alpha Centauri (α Cen) - which is, however, much closer (4.3 ly). Also nearby is the Southern Cross , so that within just 15 ° there are a total of five 1st magnitude stars ( there are 22 in the entire starry sky ).

Data of the system center β Cen A1 + A2

Apparent brightness: 0.66 ^m
Absolute brightness: −5.42 ^M
Spectral type: B1 II
Radial speed: −12 km / s
Apparent Movement : 0.042 "/ year
Position (2000.0): right ascension 14 h 3 m 49.40 s, declination −60 ° 22 '23.0 "
Position (1970.0): right ascension 14 h 1 m 41.4 s, declination −60 ° 13 '45 "(difference above precession )

Web links

http://stars.astro.illinois.edu/sow/hadar.html

Individual evidence

↑ ^a ^b Simbad

[simbad-1] Simbad