More than One Sun

Abstract

On a clear, dark night several thousand stars can be seen at any one time. They form familiar patterns such as the Great Bear and Cygnets in the northern hemisphere and Scorpio and Crux in the south. The distances are so great that we see the constellation patterns essentially unchanged from those seen by the Ancient Egyptians for instance. This is partly due to the fact that some of the bright stars in constellations are in what are called moving groups—a loose association of stars moving through space together. More tightly bound are clusters of stars such as the Pleaders or Seven Sisters which appears in the northern sky in the late summer. Eventually the moving groups and clusters of stars will gradually disperse because the distance between the stars is such that the gravitational attraction between the members is relatively weak.