for Beta Aurigae, plotted from data published by Southworth
et al. (2007) Beta Aurigae is a binary star system, but it appears as a single star in the night sky. The two stars are
metallic-lined stars belonging to the
A-type stellar classification. Although the spectra have the
luminosity class of a
subgiant (IV), the components are still on the
main sequence stage of
evolution. This discrepancy arises from their nature as Am stars, which make them larger and more luminous than a "normal" star. A-type stars are hot and release a white hued light; these two stars burn brighter and with more heat than the
Sun, which is a G2-type
main sequence star. The pair constitute an
eclipsing spectroscopic binary; the combined
apparent magnitude varies over a period of 3.96
days between +1.89 and +1.94, as every 47.5
hours one of the stars partially
eclipses the other from
Earth's perspective. The two stars are designated Aa and Ab in modern catalogues, but have also been referred to as components
1 and
2 or
A and
B. There is an 11th magnitude optical companion with a separation of as of 2011, but increasing. It is also an A-class subgiant, but is an unrelated background star. At an
angular separation of along a position angle of 155° is a companion star that is 8.5 magnitudes fainter than the primary. It may be the source of the
X-ray emission from the vicinity. The Beta Aurigae system is believed to be a stream member of the
Ursa Major Moving Group. == See also ==