Editing Beta Centauri (section)

==Stellar system==
The Beta Centauri system is made up of three [[star]]s: Beta Centauri Aa, Beta Centauri Ab, and Beta Centauri B. All the spectral lines detected are consistent with a B1-type star, with only the line profiles varying, so it is thought that all three stars have the same spectral type.

In 1935, [[Joan Voûte]] identified Beta Centauri B, giving it the identifier VOU 31. The companion is separated from the primary by 1.3 [[seconds of arc]], and has remained so since the discovery, although the position angle has changed six degrees since. Beta Centauri B is a B1 dwarf with an apparent magnitude of 4.

In 1967, Beta Centauri's observed variation in [[radial velocity]] suggested that Beta Centauri A is a [[binary star]].<ref>{{cite journal | last = Breger | first = M. | title = A Spectroscopic Study of Two Southern B-Type Variables | date = May 1967| journal = Monthly Notices of the Royal Astronomical Society | volume = 136 | issue = 1 | pages = 51–59 | doi = 10.1093/mnras/136.1.51| doi-access =  free}}</ref><ref name=Robertson/> This was confirmed in 1999.<ref name=Robertson>{{cite journal | last1 = Robertson | first1 = J.G. | last2= Bedding | first2=T.G. | last3= Aerts | first3= C.| last4= Waelkens | first4= C. | last5= Marson | first5= R.G. | last6= Barton | first6= J.R. | title = Interferometry and spectroscopy of β Cen: a β Cephei star in a binary system| date = January 1999| journal = Monthly Notices of the Royal Astronomical Society | volume = 302 | issue = 1 | pages = 245–252 | doi =10.1046/j.1365-8711.1999.02068.x| arxiv = astro-ph/9809158 | bibcode = 1999MNRAS.302..245R | doi-access= free }}</ref> It consists of a pair of stars, β Centauri Aa and β Centauri Ab, of similar mass that orbit each other over a period of 357&nbsp;days with a large [[Orbital eccentricity|eccentricity]] of about 0.8245.<ref name=Pigulski16/>

The pair were calculated to be separated by a mean distance of roughly 4&nbsp;[[astronomical unit]]s (based on a distance to the system of 161 parsecs) in 2005.<ref name=aaa437_2_599/>

[[File:BetCenLightCurve.png|thumb|left|A [[light curve]] for Beta Centauri, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]] data.<ref name=MAST/>]]
Both Aa and Ab apparently have a [[stellar classification]] of B1&nbsp;III,<ref name=aaa437_2_599/> with the [[luminosity class]] of III indicating [[giant star]]s that are [[stellar evolution|evolving]] away from the [[main sequence]]. Component Aa rotates much more rapidly than Ab, causing its spectral lines to be broader, and so the two components can be distinguished in the [[stellar spectrum|spectrum]]. Component Ab, the slow-rotating star, has a strong magnetic field although no detected [[chemically peculiar star|abundance peculiarities]] in its spectrum. Multiple pulsations modes have been detected in component Aa, some of which correspond to brightness variations, so this star is considered to be variable. The detected pulsation modes correspond to those for both [[β Cephei variable]]s and [[slowly pulsating B star]]s. Similar pulsations have not been detected in component Ab, but it is possible that it is also a variable star.<ref name=Pigulski16/>

Aa is 12.02 times as massive as the Sun, while Ab is 10.58 times as massive.<ref name=Pigulski16/> Their [[angular diameter]]s are estimated at 0.77 and 0.72 [[milliarcsecond]]s.<ref name=Davis2006/> At the system's distance of {{val|110.6|0.5|ul=parsec}}, this derive liner radii of {{solar radius calculator|type=AD|0.77|0.1106|decimals=1}} and {{solar radius calculator|type=AD|0.72|0.1106|decimals=1}} [[solar radii]], respectively.{{efn|name=radius|group=note}}