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JOHANN BAYER (1572 - 1625)

Johann Bayer was born in Rain, Bavaria in 1592. He attended the university at Ingolstadt in 1592, studying philosophy. Bayer settled in Augsburg where he worked as a lawyer. He become interested in astronomy and set to work mapping the skies. In 1603 he published the first book of star charts, Uranometria. Bayer used Tycho Brahe’s catalogue of stars to find their positions. He then set to work assigning a Greek letter prefix to each star that indicated its brightness within its parent galaxy. The Greek letter was followed by the name of the galaxy in which the star was found.


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The Greek letter alpha (α) indicated the brightest star, beta (β) the second brightest, and so on. For example, the variable star Mira in the constellation of Cetus is named by the Bayer Designation as omicron (ο) Ceti. His charts did have some faults. There were stars that occurred in two constellations, for example, so that they were named twice and not necessarily with the same Greek letter prefix! However, the Bayer Designation (naming system) is still used today and Uranometria 2000 can be bought from Amazon.com.

Bayer’s Star Atlas included all forty eight of Ptolemy’s constellations as seen in the northern hemisphere. It also showed twelve new southern hemisphere constellations that had never been described before in Europe. Bayer used the information that the Dutch navigators Pieter Dirckz Keyser and Frederick de Houtmann brought back with them from their exploration of the East Indies in 1595.

Johann Bayer’s work is honoured by the naming of a Moon crater after him, the Bayer Crater.

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