Johann Bayer (1572 – March 7, 1625) was a German lawyer and uranographer (celestial cartographer). He was born in Rain, Lower Bavaria, in 1572. At twenty, in 1592 he began his study of philosophy and law at the University of Ingolstadt, after which he moved to Augsburg to begin work as a lawyer, becoming legal adviser to the city council in 1612. Bayer had several interests outside his work, including archaeology and mathematics. However, he is primarily known for his work in astronomy; particularly for his work on determining the positions of objects on the celestial sphere. 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 constellations Latin name. The original list of Bayer designations contained 1,564 stars. Most of the brighter stars were assigned their first systematic names by 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 cataloged, combined with the Latin name of the star’s parent constellation in genitive (possessive) form. For example, Aldebaran is designated α Tauri (pronounced Alpha Tauri and abbreviated α Tau), which means Alpha of the constellation Taurus (even though the star merely happens to lie along the same line of sight as the Hyades in Taurus). For the most part, Bayer assigned Greek and Latin letters to stars in rough order of apparent brightness, from brightest to dimmest, within a particular constellation. Since in a majority of constellations the brightest star is designated Alpha (α), 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 Bayers catalog lists 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. Bayer did not always follow this rule; he 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 either the order in which they rise in the east, to his own arbitrary choosing, or to historical or mythological information on specific stars within a constellation.
Posted on: Sat, 16 Aug 2014 03:30:48 +0000
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