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( Bayer designation)
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 scientific names by the German astronomer Johann Bayer during the early 17th Century, in 1603, in his star atlas Uranometria (named after Urania, the Greek Muse of Astronomy, along with Uranus, the Greek god of the sky and heavens). Johann Bayer traveled by sailing ship to various parts of the world, including the southern hemisphere, to conduct his astronomical observations and apply his data. Bayer assigned a lower-case Greek letter, such as alpha (a), beta (ß), gamma (?), etc, to each star he cataloged. Bayer then attached to each star’s Greek letter the Latin name of the star’s parent constellation in genitive form (or possessive form) to indicate that the star belonged exclusively to that constellation. (See List of constellations for a list of constellations and the genitive forms of their names) For example, Bayer assigned the Greek letter alpha (a) to a specific star in the constellation Taurus (the Bull), and added to the star’s Greek letter (a) the name Tauri, which is the genitive form of the Latin name Taurus, to indicate that the star belongs exclusively to Taurus the Bull. As a result, the star’s scientific name turned out to be a Tauri (that is to say Alpha Tauri), which means "Alpha of Taurus" or "Alpha of the Bull". A single constellation may contain fifty or more stars, but there are only twenty-four letters of the Greek alphabet, so, when he ran out of Greek letters to use for identifying the stars of a specific constellation, Bayer began using lower-case Latin letters. For example, Bayer assigned three stars in the constellation Carina as s Carinae, and another star in Centaurus as d Centauri, to indicate "s of the Keel" and "d of the Centaur", respectively. Within constellations having an extremely large number of stars, Bayer eventually advanced to upper-case Latin letters, ending with the upper-case letter "Q". For example, Bayer assigned a star in Scorpius the Scorpion the scientific name G Scorpii, which means "G of Scorpius" or "G of the Scorpion". Another example is a star in Vela the Sails, called N Velorum, which means "N of Vela" or "N of the Sails". For the most part, Bayer assigned Greek and Latin letters to stars in order of apparent brightness, from brightest to dimmest, within a particular constellation. The brightest star in a particular constellation was assigned alpha (a), the second brightest beta (ß), the third brightest gamma (?), and so on. Since the brightest star in many constellations is designated as Alpha (a), many people wrongly assume that Bayer meant to put the stars exclusively in order of their brightness, but in his day there was no way to measure stellar brightness precisely. Traditionally, the stars were assigned to one of six magnitude classes, and Bayer's catalog lists all the first-magnitude stars, followed by all the second-magnitude stars, and so on. However within each magnitude class, there was no attempt to arrange stars by relative brightness. Bayer did not always assign Greek and Latin letters to stars in this manner. Bayer sometimes assigned letters to stars according to their location within a constellation (for example the northern, southern, eastern, or western part of a constellation), according to the order in which a constellation’s stars rise in the east, according to the historical or mythological information on specific stars within a constellation, or according to his own random choosing. Usually the stars were roughly ordered from the head to the feet (or tail) of the figure (like the stars in the Big Dipper). The conclusion is that Alpha (a) is NOT always the brightest star in a constellation; in fact, of the 88 modern constellations, there are at least 30 constellations in which alpha (a) is not the brightest star, and 4 of those 30 lack an alpha (a) star altogether. He then repeated the procedure for the stars of the 2nd-magnitude. As is evident from the map and chart, he again followed a "top-down" ("north-south") route.
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