Southern Cross is a constellation in the southern celestial hemisphere, its declination being about 60° S., and its right ascension 180°. It consists of five principal stars arranged as a somewhat irregular cross, and numerous smaller stars. The shape of the cross is gradually, but very slowly, changing, owing to the proper motion of the stars themselves. The cross is first seen by travellers voyaging southwards in the Atlantic when they reach the twentieth parallel, and it is as noticeable a constellation in the southern hemisphere as the Great Bear is in the northern. Its form is used as a decoration on the Brazilian stamps instead of the usual head.