Polaris

August 09, 2019

Here in the northern hemisphere, we’re lucky to have a bright pole star. There is a star that marks the south pole, but it’s so dim that it’s barely visible to the naked eye even under dark skies.

Polaris or, the North Star, is the brightest star in Ursa Minor, the little dipper. Nitpicky observers will note that it’s not perfectly centered with the north pole, but almost everyone would agree it’s close enough.

Polaris is a great navigational star for obvious reasons. Escaped slaves using the Underground Railroad would travel under the darkness of night and use Polaris as their guide north. The folk song “Follow The Drinkin’ Gourd” references the legend of using the big dipper to point to the north star on the way to freedom.

Polaris is actually a system of three stars. The Polaris we can easily see, Polaris Aa is a big star. A yellow supergiant more than five times as massive as our sun, and more than 35 times larger. Its orbital companion, Polaris Ab is about the same size as our sun, and its more distant companion, Polaris B is about 40% larger. 

To find Polaris… just look north! Or, find the big dipper and use the two stars at the end of the cup to draw a straight line up. The bright star that line connects with is Polaris. You can confirm it by then looking for the little dipper. Polaris marks the end of the Little Dipper’s handle.

Polaris hasn’t always been the north star, nor will it keep that designation. The next star in line is Gamma Cephei (SEE-fee-eye), the tip of the constellation Cepheus. But that won’t happen for another 22-hundred years.