Why is the north star called the North Star include where it is in the sky and when viewed from the North pole your location and the equator also include what is meant by circumpolar stars?

Answer 1

(The references to "north", "overhead", and certain other references and statements in this answer are approximate as explained in the last paragraph.)

The North Star (Polaris) is called that because the direction to a point on the horizon directly below Polaris will be due north.

At the North Pole, Polaris will appear to be directly overhead. At the Equator, Polaris will appear to be on the horizon and due north. Polaris is not visible from the Southern Hemisphere.

So, in general, from the Northern Hemisphere, Polaris will always appear due north, and at an elevation above the horizon equal to your latitude.

Circumpolar stars are those which are always visible above the horizon (throughout the year) at your location, so Polaris itself is a circumpolar star. At the North Pole, all the stars you can see (half of the sky) are circumpolar. At the Equator, none of the stars are circumpolar, and you can see all of the stars in the sky at some point during the year.

Another way of looking at this is that the axis of rotation of the Earth points at Polaris. This changes over a long period of time due to precession of the axis of rotation, but that is beyond the scope of this discussion.

The reason why the references to exact directions (and certain other statements) given above are actually approximate is that the North Pole actually points at a spot in the sky about 3/4 of a degree away from Polaris. It is only a coincidence that there is a fairly bright star that close to the celestial north pole. In the Southern Hemisphere there is no "pole star".