Zeta Aurigae (ζ Aur, ζ Aurigae) is the Bayer designation for a binary star system in the northern constellation of Auriga. It has the traditional names Haedus and Sadatoni. Based upon parallax measurements made during the Hipparcos mission, this system is approximately 790 light-years (240 parsecs) distant from the Earth. It has a combined apparent visual magnitude of 3.75, which is bright enough to be seen with the naked eye.
This is an eclipsing binary system with the orbital plane being oriented close to the line of sight from the Earth; the inclination of this system is estimated as 87.0°. As a result, an eclipse of one star by the other occurs during each orbit, causing the magnitude to decrease to +3.99. The pair have an orbital period of 972 days (2.66 years) and an eccentricity of 0.4. The primary component has been categorized as a K-type bright giant or supergiant star. Its companion is a B-type main sequence star of stellar classification B5 V or B7 V.
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