Looking Up: Kochabitation

Mar 20, 2017

past and present north stars
Credit earthsky.org

This week on Looking Up Hal reminds us that Polaris is not always the North Star.

Chances are, if there is anything you know about navigating around the night sky, it is that you can use the front two stars of the Big Dipper to find Polaris, the North Star. In the pre-GPS world, lots of navigation, from sailing ships to aircraft to even spacecraft, relied on celestial navigation to find their way home. And, for about the last 1500 years or so, Polaris has been the star everyone used. But did you know that this was not always the case?

The Earth, simply put, wobbles. Like a spinning top that is slowing down, the axis of the Earth, over a 26,000 year cycle, sweeps a large 47 degree circle in the sky. And that means that from about 1500 BC until about 500 AD, the North Star was, so to speak, the very interesting star Kochab (KOE-cab)!

Kochab is one of the two stars that make up the front end of the “Little Dipper,” which has Polaris at the end of the handle. Kochab is about 50 times bigger than our Sun, and is at least 500 times brighter. And in about 25,000 years or so, it will again be our North Star, so make a note on your calendar, so you won’t get lost.

If you’d like to take a closer look at Kochab or any of the wonderful and amazing things in the sky, please visit CSASTRO.org for a link to information on our monthly meetings and our free public star parties! 

This is Hal Bidlack for the Colorado Springs Astronomical Society, telling you to keep looking up, Southern Colorado!