Three Quarters of This Century

Abstract

The distribution and motion of stars in the Galaxy, spectral classification and the Hertzsprung-Russell diagram, work on the restricted three-body problem, first extragalactic studies with the new Mt. Wilson telescope, the laws of stellar interiors, and the impact of relativity theory upon astronomy — these and other early highlights of 20th-century work are so much connected with the present, that the historical outline can be said here to merge into the stream of current research. Similarly, many results on double stars will have to be reported in later sections, rather than in the present survey.