Binary Star
Spectroscopic Binaries
Spectroscopic binaries are pairs which are too close to each other as seen from the earth to be resolved into two stars. However, when the light from the star is analyzed with a spectrograph, which spreads the light into a continuous spectrum of colors with dark absorption lines superimposed, the spectral lines are alternately shortened or lengthened indicating Doppler motion, a to-andfro motion as seen from Earth. This shift in the wavelengths results from the periodic motion, in the line of sight, of the visible star revolving around the center of mass of the system. When only the brighter component has sufficient light to show on the spectrogram the system
Binary star systems contain two stars held by mutual gravitational attraction. The stars orbit a common center of mass.
Additional topics
Science EncyclopediaScience & Philosophy: Bilateral symmetry to Boolean algebraBinary Star - Importance, Visual Binaries, Study Of Orbital Motion, Astrometric Binaries, Spectroscopic Binaries, Eclipsing Binaries - Techniques of observation