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Western Slope Skies - May 13th Mizar and Alcor


Think of the farthest place you’ve ever been. When you arrived, how different was it from what you imagined? On Earth the farthest you could travel between two points is about 12,500 miles. This would be like going from central Chile to northwest China or from the highlands of Ecuador to the Klang Valley in Malaysia. The ideas we have of distant places often turn to feelings of surprise when we arrive and realize the detail our imaginations were lacking. The objects visible in the night sky offer similar experiences but on a much grander scale.

Take the second star from the end of the handle of the Big Dipper, Mizar. At first glance it appears alone, but with a relatively dark night and a few moments of staring, it’s possible to see another star emerge next to it, the much fainter Alcor. This fainter star was once known in old Arabic as, “the overlooked one” and has long been used as a test for eyesight- if you are unable to see Alcor with the naked eye, try using a pair of binoculars.

Mizar and Alcor are about 80 light years from Earth, but may be as close as 0.28 light years to each other. Just one light year translates to a whopping 5,878,625,373,183.6 miles! With distances like these, the night sky is full of surprises. With the aid of a telescope it’s possible to see that Mizar is not one, but two stars, Mizar A and B. To take it a step further, the two Mizars are in turn two stars themselves. And, in 2009 Alcor was discovered to be a two-star system. Due to the vast distances involved, what appear as two stars when viewing Mizar and Alcor are actually six!

Humans will not be visiting stars like Mizar and Alcor anytime soon, but we can take armchair trips and still be delighted at these far-flung objects. In a society where there is an abundance of information just a click away and travel from one extreme of the globe to the other is possible in a matter of hours, it may be difficult to be surprised at the world around us. Mizar and Alcor remind us that that couldn’t be further from the truth, sometimes all we have to do is look up.


Western Slope Skies is produced by members of the Black Canyon Astronomical Society and KVNF Community Radio. This episode was written and recorded by Jeremy Stringfield.