Constellation

a group of stars. One observing the sky on a clear night cannot fail to observe that the bright stars form more or less noticeable groups. The best known to young people is perhaps that of the Great Dipper, the outer stars of which point to the pole star. The belt of stars through which the sun appears to move annually was divided into twelve groups or constellations, probably by the Babylonians, certainly prior to the earliest extant history. The earliest works on the subject, of which we have any knowledge, were written in the fourth century before Christ. The earliest astronomical writing that has been preserved is a star catalog called the Almagest. It was prepared by Ptolemy, the Greek professor of astronomy at Alexandria, about 120-150 A. D. His catalog contains over a thousand stars divided into forty-eight constellations. This ancient grouping has never been disturbed seriously. Astronomical maps of the present day adopt the groups and use the names given by Ptolemy. The principal additions are those in the southern hemisphere, which were not known to the Greek writer. The entire sky has now been plotted off and given names. In all, the additions have brought up the number of constellations to eighty-nine. Most of the names adopted by Ptolemy were derived from the Greek mythology. See Orion; Cassiopeia; Charles'S Wain; Berenice'S Locks