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© Copyright 1999, Jim Loy
The above picture is the north sky, just a few minutes ago, as shown by a popular planetarium program. Can you find the North Star (Polaris)?
People think that the North Star is very bright. It is not. It is moderately bright, and it is surrounded by very dim stars. So, it stands out, a little. But, the main clue to where the North Star is, is the Big Dipper. Can you find the Big Dipper in that picture?
The Big Dipper normally stands out better
than it does in the above picture. Here, on the left, I have drawn blue lines
from star to star, to show you the Big Dipper, and the Little Dipper. The North
Star is at the end of the handle of the Little Dipper. It is hard to find the
Little Dipper, without first finding the North Star. Normally, you find the Big
Dipper, and then sight along the two stars at the end of the bowl of the Big
Dipper, and the North Star is almost in line with those two stars (but not
exactly).
Once you have found the North Star a few times, it becomes easy to find.
The North Star is not exactly North. It is a little less than one degree from being directly over the Earth's North Pole. One degree may not seem like much. But, the apparent diameter of the moon is about a half degree.
Addendum:
Polaris (Alpha Ursae Minoris because it is the brightest star in Ursa Minor) is a type II pulsating Cepheid variable, of color F8 (white, slightly yellowish). Its average magnitude is 1.99 (making it the 49th brightest star in the sky), varying by about .1 magnitudes (which is not much) over a period of 3.9696 days. It has a small companion star, of magnitude 9; they orbit each other over a period of many thousands of years. The brighter star has an unseen companion, with an orbital period of 30.5 years. These stars are about 360 light years from us. Polaris itself is about 1600 times brighter than our sun.
Because of the wobble of the Earth's axis, Polaris was not always the pole star, and will not be in the distant future. About 5000 years ago, Thuban (Alpha Draconis) was the pole star. About 3000 years ago, Kochab (Beta Ursae Minoris) was the pole star. This wobble is the cause of the Precession of the Equinoxes.