Polaris is the star that is always almost directly above the North Pole. It is also called the Pole Star. For many years sailors and explorers in the Northern Hemisphere have used this star to find directions. When a person faces Polaris, he is facing true north. Polaris is sometimes called the North Star.
Polaris is not one of the brightest stars in the sky. It can be found easily, however, with the help of the "pointer stars." The pointers are two stars in the Big Dipper that point to Polaris. They are the two stars that form the side of the dipper which is farthest from the handle. A line through these two stars leads to Polaris. Polaris is the last star in the handle of the Little Dipper. The dippers are parts of the constella-tion Ursa Majar and Ursa Minor.
Polaris cannot be seen at all in the Southern Hemisphere. In the Northern Hemisphere it is visible the year round. Polaris is not exactly above the North Pole. If it were, it would not seem to move at all. As the earth rotates, however, Polaris traces a very small circle around the celestial North Pole. The constellations near Polaris are called circumpolar constellations. They seem to move in a circle around Polaris.
Besides helping to find directions, Polaris can tell a person in the Northern Hemisphere what latitude he is in. The degree of the angle from the horizon to Polaris is about the same degree of latitude that the observer is írom tbe equatoi. At tiie equator this angle is zero for Polaris is on the horizon. At the North Pole, the angle is 90 de-grees. Polaris is directly overhead.
Polaris has not always been the pole star. Many years ago, Thuban was the star used to find the north direction. The earth's axis changes its direction very slowly. It is moving away from Polaris now. In about 12,000 years Vega, a very bright star, will be the north star.
