They are discovered in many ways, which leads to many different classifications of binaries. Visual Binaries Visual Binaries can be seen in a telescope to be two separate stars. There are many beautiful visual binary stars, with stars of very different colors. A. A nice double star in binoculars is Epsilon Lyrae , which is within one degree of Vega. One beautiful pair is the blue and yellow Albireo , the star which is the bottom star of the the Northern Cross.
Some binaries are too close to see visually but can be discovered by red shifts in their spectra.
That is, one or both of the stars can be seen coming toward us or moving away from us. To have such a fast orbital motion always means that they are too close to be a visual binary. Both of the visual components of Mizar are also spectroscopic doubles. Eclipsing Binaries Eclipsing Binaries pass in front of each other, which dims the light coming from them. From the light curve one can deduce their relative sizes and positions.