On one of those, currently, rare winter evenings when the sky is cloudless, you can easily find the famous asterism we call the Big Dipper. When you do, find the star in the middle of the Dipper’s handle. Looking very closely, you’ll see 2 points of light. The larger point is named Mizar and its smaller companion is called Alcor. While these two stars look superb when viewed by a pair of binoculars, even people with poor eyesight should be able to discern both Mizar and Alcor in a dark sky. However, you would need to have a small telescope like the one used by an Italian astronomer who informed Galileo in 1617 that Mizar is a double star caused by a chance alignment of physically unrelated stars. This opinion was overruled in 1889 when a spectroscope revealed the brighter component of Mizar’s two stars consisted of two stars. Later, spectroscopic analysis of the dimmer component of Mizar’s two stars was also composed of two stars. Thus, Mizar is now believed to be a quadruple star. As for Alcor, in 2009 two groups of astronomers independently reported Alcor, as well, is a binary star. Moreover, astronomers now think Alcor A and Alcor B are gravitationally bound to Mizar’s quadruple system. Thus, the “double star” actually contains six stars.Mizar and Alcor in the Big Dipper
