Spectroscopic Double Stars
In the measurement of the radial velocity of the 800 stars on the first programme it was found that in about 180 stars successive plates did not give constant velocities, the stars at one time approaching at another receding from us. This phenomenon is practically certain proof that we are measuring the velocity of a star revolving around an invisible companion and such stars are generally called spectroscopic binaries to distinguish them from visual binaries which can be seen double in the telescope. Over 200 spectroscopic binaries have been discovered at this observatory as compared with about 700 discovered elsewhere, again a considerable addition. In about 20 of these binaries, observations were continued until the period of revolution, the form of the orbit, the separation of the two stars and in some cases, their masses were determined. In a particular class of spectroscopic binaries, the eclipsing variables, which allow from the combination of spectroscopic and photometric measurements the absolute dimensions to be obtained, we were able to determine the separation of the two stars, their diameters, densities, masses and brightnesses and the probable distances. Such complete information has been obtained here about seven systems, while only seven other systems have been determined elsewhere.