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A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. Most of the brighter stars were assigned their first systematic names by the German astronomer Johann Bayer in 1603, in his star atlas ''Uranometria''. Bayer assigned a lower-case Greek letter, such as alpha (α), beta (β), gamma (γ), etc., to each star he catalogued, combined with the Latin name of the star’s parent constellation in genitive (possessive) form. (See 88 modern constellations for the genitive forms.) For example, Aldebaran is designated ''α Tauri'' (pronounced ''Alpha Tauri''), which means "Alpha of the constellation Taurus".〔The letters of the Greek alphabet were used in antiquity as numerals, however in a different way.〕 A single constellation may contain fifty or more stars, but the Greek alphabet has only twenty-four letters. When these ran out, Bayer began using Latin letters: upper case ''A'', followed by lower case ''b'' through ''z'' (omitting ''j'' and ''v''), for a total of another 24 letters. Bayer never went beyond ''z'',〔 but later astronomers added more designations using both upper and lower case Latin letters, the upper case letters following the lower case ones in general. Examples include ''s Carinae'' (''s'' of the constellation Carina), ''d Centauri'' (''d'' of the constellation Centaurus), ''G Scorpii'' (''G'' of the constellation Scorpius), and ''N Velorum'' (''N'' of the constellation Vela). The last upper-case letter used in this way was ''Q''. Bayer did not catalog southern stars not visible from Germany, but later astronomers (notably Lacaille and Gould) supplemented Bayer's catalog with entries for southern constellations. == Order by magnitude class == In most constellations, Bayer assigned Greek and Latin letters to stars within a constellation in rough order of apparent brightness, from brightest to dimmest. Since the brightest star in a majority of constellations is designated Alpha (α), many people wrongly assume that Bayer meant to order the stars exclusively by brightness. In Bayer's day, however, stellar brightness could not be measured precisely. Stars were traditionally assigned to one of six magnitude classes (the brightest to first magnitude, the dimmest to sixth), and Bayer typically ordered stars within a constellation by class: all the first-magnitude stars, followed by all the second-magnitude stars, and so on. Within each magnitude class, Bayer made no attempt to arrange stars by relative brightness.〔 See p. 192.〕 As a result, the brightest star in each class did not always get listed first in Bayer's order. But in addition, Bayer did not always follow the magnitude class rule; he sometimes assigned letters to stars according to their location within a constellation, or the order of their rising, or to historical or mythological details. Occasionally the order looks quite arbitrary. Of the 88 modern constellations, there are at least 30 in which "Alpha" is not the brightest star, and four of those lack an alpha star altogether. (Constellations with no alpha include Vela and Puppis – both formerly part of Argo Navis, whose alpha is Canopus in Carina.) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bayer designation」の詳細全文を読む スポンサード リンク
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