The Star That Does Not Move

If you photograph the sky in a long exposure, all the stars will smear into arcs. Except for one. It will stay a point.

That is the North Star, and by its foreign name Polaris. And the reason it looks as if it is standing still is not that it is special — it is that it happens to be almost exactly in the direction to which the axis of rotation of the earth points. The line that connects it and us makes a very small angle with that axis.

The earth rotates, and so all the other stars appear to move around us during the night. But a star that is exactly on the continuation of the axis does not appear to move. It is the axis.

And so, if you have found it — you have found north. Not roughly: the direction toward it is north, and it stays north all night and all year. A compass can be deflected near metal; the North Star cannot.

And here is a surprise. Many people are sure that the North Star is the brightest star in the sky. It is not. There are dozens of stars brighter than it. It stands out only in its immediate surroundings, where it is indeed the brightest. That is, the most important star in the sky is not the most prominent star in it — it is only the one that is in the right place.

And how do you find it? Not by brightness, as we have seen. You find it by shape. In the constellation of the Great Bear — the one that looks like a pan with a handle — the two stars at the end of the pan stand on one line. You extend that line outward, you carry on with it, and you arrive at a prominent star that has no competitors around it. That is it.

And the moment you have found it, you have all the directions at once. Face toward it — north. Your back — south. Your right hand — east.

One more thing worth knowing: it is visible only from the northern hemisphere. Whoever travels far enough south loses it below the horizon, and uses other stars.

And it is far away. About 390 light years, that is, the light you see from it set out hundreds of years ago.

Until the compass was invented, and afterwards navigation by satellites, the North Star was the main aid for finding your way at sea. And today too people learn to find it in lessons of maritime navigation — because a device can run out of battery, and the sky cannot.