Puzzing Polaris and Stellar Evolution
Many of us in the Northern Hemisphere began stargazing by finding the Big Dipper (or Plough) and using the stars as pointers, and the two on the end of the "bowl" would point to Polaris , the North Star. This was also the beginning of the Little Dipper's handle. While Polaris seems fixed in the sky, it is not that way in the long run. Credit: Flickr / DSS / Giuseppe Donatiello (public domain) At one time, the North Star was Thuban, but that changed because of the precession of the Earth. Ever spin a toy top? It wobbles, and if you could have a laser pointer attached to the top, you might see it draw circles on the ceiling. The same thing happens with the earth, but since it is much larger, the precession takes a mighty long time and would take about 26,000 years to complete one cycle. Polaris is also a Cepheid variable , a kind of star that changes its intensity. (The name came from a star in the constellation Cepheus, which was the first of this kind of variabl