An eclipsing binary is a binary star oriented so that one component passes in front of the other as seen by the observer. The changing blocked light produces repeated minima in the light curve. Eclipse depths depend on surface brightness and size as well as on the geometry, while durations constrain stellar radii relative to orbital separation and the orbital inclination.
When both components also have measured Doppler shifts, their velocity amplitudes supply a binary mass ratio and orbital scale. Combining these with the eclipse geometry can determine individual masses and stellar radii, providing direct tests of stellar structure. A deeper eclipse usually means more light was hidden; it does not by itself identify the more massive component.
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