Star
Polaris
Also called the North Star, the Pole Star
The North Star. It sits almost directly above Earth's north pole, so the whole sky seems to turn around it.
Where the name comes from
Polaris is simply Latin for “of the pole”. It is the pole star, the one that marks true north.
Why it barely moves
Earth spins on an axis, and right now that axis happens to point almost exactly at Polaris. So while every other star wheels across the night, Polaris sits nearly still and the whole sky turns around it. Find Polaris and you have found north, which is why it guided travellers and sailors for thousands of years. It is not quite perfect. Polaris sits about three quarters of a degree off the true pole, so even it traces a tiny circle through the night.
It has not always held the job
Earth’s axis slowly wobbles like a spinning top, a motion called precession that takes about twenty six thousand years to come full circle. Five thousand years ago, when the pyramids were built, the pole star was Thuban in the dragon, Draco. In another twelve thousand years it will be brilliant Vega. Polaris is only the north star for this stretch of history, and the title keeps getting passed around.
It is not even that bright
People expect the North Star to be the brightest thing in the sky. It is not, not by a long way. Its whole value is where it sits, not how it shines. Look closely through a telescope and Polaris turns out to be three stars travelling together, the brightest of them a Cepheid, a kind of star that slowly pulses brighter and dimmer like a lighthouse set to a very slow dial.
Questions
Is Polaris the brightest star?
No, that is Sirius. Polaris is useful rather than bright. It ranks only around the 48th brightest star in the sky, which surprises most people.
How do I find Polaris?
Find the Big Dipper. The two stars on the outer edge of its bowl, the Pointers, aim straight at Polaris.
Is there a South Star?
Not a bright one. The south celestial pole has only a dim star near it, so southern navigators use the Southern Cross to find south instead.
Sources: Precession and distance figures from standard astronomical references.