In the Northern Hemisphere some of the stars of Ursa Major are easy to see on clear nights.
They make a pattern sometimes called the Big Dipper or the Plough.
Ursa Major and Ursa Minor are the 'Great Bear' and the 'Little Bear'.
The two brightest stars of Ursa Major are known as the Pointers, because they point at the brightest star of Ursa Minor, Polaris, the Pole Star.
The Pole Star, or North Star, has always been used for navigation.
Photographs show that as the Earth turns, Polaris is almost fixed in the centre of the turning star pattern.
Like many stars, the stars of the Plough have Arabic names.
One star, Mizar, is actually a double star.
Alcor probably orbits Mizar, taking around 750,000 years to complete one orbit.
Some people with good eyesight can see Alcor and Mizar as two stars on a clear night.
They can certainly be seen very easily with binoculars.