Double Stars and the Masses of the Stars

Abstract

In 1803 F. W. Herschel discovered that a Gem = Castor is a visual double star whose components move round each other under the influence of their mutual attraction. Thus the observation of double stars offers the possibility of determining the masses of stars or at anyrate of making quantitative assertions about them. Since the masses of stars are detectable only through their gravitational interaction, the investigation of double stars is even now of fundamental significance for the whole of astrophysics.