Johann Bayer

Johann Bayer was a German astronomer and lawyer. He was born in Rain, Bavaria in 1572. He began his study of philosophy in Ingolstadt in 1592, and later moved to Augsburg to begin work as a lawyer. He grew interested in astronomy during his time in Augsburg. He ultimately became legal advisor to the Augsburg city council in 1612 and died in 1625. He is most famous for his star atlas Uranometria, published in 1603, which was the first atlas to cover the entire celestial sphere.

Bayer’s atlas included many innovations. Unlike previous astronomy texts, Uranometria portrayed the constellations as maps and not merely as pictures corresponding to mythology. Each plate has a carefully engraved grid so star positions can be determined precisely. He developed a star naming system that was adopted by later stellar cartographers. The stars are shown as they appeared from earth, a reversal from classical tradition where positioning was patterned from celestial globes and it included twelve southern constellations, newly discovered by 16th century voyagers. It was the first atlas to make use of Tycho Brahe's accurate measurements of stellar positions. Which were far better than Ptolemy's rather incomplete list. The system introduced a new system of star designation, which has become known as the Bayer designation, as well as some of the modern constellations.

When Bayer published his hugely influential catalog, Uranometria, in 1603, he included 12 new southern asterisms. Asterisms are informal yet distinctive groupings of stars. An example of a northern asterism is the Big Dipper in the constellation Ursa Major. In addition, Bayer added 12 southern constellations to Ptolemy's original 48. Bayer named the constellations of Apus, Chamaeleon, Dorado, Grus, Hydrus, Indus, Musca, Pavo, Phoenix, Triangulum Australe, Tucana, and Volans. When he published Uranometria he dedicated it to two leading citizens of Augsburg and received an honorarium of 150 gulden.

Bayer named the stars by assigning them Greek letters, in magnitude classes. In each constellation, every star is classified using the Bayer system by assigning then Greek letters in order of decreasing brightness. The Bayer system cannot go beyond 24, the number of letters in the Greek alphabet. The brightest star in a constellation is alpha, the second-brightest is beta, the third is gamma, etc. This system is still frequently used today.

Uranometria was the first of its kind. It represented a tremendous leap forward both esthetically and for its astronomical content, and became the standard for all later star atlases. As a tribute to him and his accomplishments in the field of astronomy there is a crater on the mooned named the Bayer crater after him.

Works Cited

Bayer, Johann." Encyclopædia Britannica. 2007. Encyclopædia Britannica Online. 13 Oct. 2007 <http://www.britannica.com/eb/article-9013868>.

"Johann Bayer." The Reader's Digest Great Encyclopedia. Pleasantville: Funk & Wagnalls, 1975.