Alcor is a double star in the constellation Ursa Major. It is the fainter companion to Mizar, the middle star in the handle of the Big Dipper. Alcor has the Bayer designation g Ursae Majoris and the Flamsteed designation 80 Ursae Majoris. It lies at an approximate distance of 81.7 light years from Earth and has an apparent magnitude of 3.99.
Alcor is a member of the Ursa Major Moving Group, a group of stars formed in the same molecular cloud about 300 million years ago, that share common velocities and motion through space. Big Dipper stars Mizar, Alioth, Megrez, Phecda and Merak are also members of the group, as are many other relatively bright stars, including Menkalinan (Beta Aurigae), Alphecca (Alpha Coronae Borealis), Beta Serpentis, Skat (Delta Aquarii), Adhafera (Zeta Leonis) and Chi1 Orionis.
Alcor is one of the few stars that do not have a Bayer designation beginning with a Greek letter, but do have a proper name nonetheless. A great number of significantly brighter stars with Greek letter designations do not yet have a name.Many old Arabic texts refer to Mizar’s companion being an excellent test of eyesight. While it is easy enough to assume that the companion in question is Alcor, since one does not need to have perfect eyesight to see the star, the English amateur astronomer Sir Patrick Moore has suggested that the texts referred to Ludwig’s Star, a much fainter star (8th magnitude) that appears between Mizar and Alcor. Ludwig’s Star (Sidus Ludoviciana) has the spectral type A8/F0 III and is about five times more distant from us than Mizar and Alcor. The star was discovered (and mistaken for a planet) by the German astronomer Johann Georg Liebknecht in December 1722. Liebknecht named it after his patron, Louis V, Landgrave of Hesse-Darmstadt.Alcor was originally called Suhā or Sohā in Arabic, meaning “the forgotten one” or “the neglected one.” The name was a reference to the star’s faintness compared to the brighter Mizar. Alcor is also mentioned as al-Khawwar, or “the faint one,” on a list of Arabic names compiled by Professor Robert H. West of the Syrian Protestant College in Beirut, Lebanon and published in Popular Astronomy in 1895.
Alcor’s Latin name was Eques Stellula, or the Little Starry Horseman. Johann Bayer referred to it as Eques, the Cavalier.
Mizar and Alcor are sometimes known as the “Horse and Rider.”
The Japanese knew the star as jumyōboshi (寿命星), meaning “the lifespan star.” They believed that a person who could not see Alcor would not live another year. The legend is used in the Japanese manga Fist of the North Star.
In Indian astronomy, Alcor was known as Arundhati, the wife of Vashishtha, one of the Saptarishi (Seven Sages), represented by Mizar. Arundhati and Vashishtha symbolized marital closeness.
https://www.star-facts.com/alcor/
Alcor and Mizar, image: Wikisky
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