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 variable to be identified.) Astronomers use them in their calculations of stellar distances. Polaris is puzzling because its rate of change does not fit stellar evolution models. I reckon it's also a mite annoying because it's so bright, it's hard to get a fix on it. Mayhaps if secularists admitted that the universe was created much more recently than they dream of in their philosophies, they'd have fewer difficulties.

The north celestial pole is a projection of the earth’s rotation axis onto the sky. Polaris lies within ¾ of a degree of the north celestial pole, so to the naked eye Polaris appears to remain fixed. However, a telescope will reveal that Polaris goes through a tiny circle each sidereal day (a sidereal day is about four minutes shorter than a solar day). This is why we call Polaris the North Star—its location so close to the north celestial pole fixes its position within ¾ degree of true north above the horizon.

To read the entire article, click on "Polaris: A Brief History of the Current North Star".




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