Astronomers usually call the Little Bear Ursa Minor (Latin for little bear). In America, the shape is called the Little Dipper.

By far the most important and famous star in Ursa Minor is the North or Pole Star, Polaris. This is the star at the very end of the bear’s long tail.

The reason Polaris is so important is that it is almost directly above the North Pole. This means you can use it like a compass to find north. Also, the angle of the star above the horizon gives you your 'latitude’ (north-south position on the Earth's surface). For years, sailors relied on the Pole Star for navigating at sea, with the help of instruments like quadrants and astrolabes.

Finding the Pole Star

You can find the Pole Star, Polaris, by following a line drawn through Dubhe and Merak, the two end stars in the bowl part of Ursa Major (Great Bear) – see diagram.

The ancient Greeks realized that Polaris did not mark the pole exactly. We now know that the earth’s axis moves slowly backwards and forwards over thousands of years, so the star nearest the pole changes over time. About 5000 years ago a star called Thuban was the Pole Star. In about 5000 years’ time, a star called Alderamin in the constellation Cepheus will be nearest the pole. Eventually, in about 28,000 years, Polaris will be the Pole Star again – for a time.

Supergiant

The Great and Little Bear from a 17th-century pocket globe. Click image to find out more about this object.

Polaris is interesting to astronomers because it is a pulsating supergiant. Supergiants are the largest and brightest stars, often many hundred times larger (and much brighter) than our Sun.

However, Polaris does not look very bright to us because it is so far away. Polaris is 431 light years away from Earth: over 6400 million million kilometres (4000 million million miles).

Legends

There are many different legends about the Pole Star in different cultures:

• In Arabic mythology, it is an evil star who killed the great warrior of the sky. The dead warrior now lies in the coffin of the 'Funeral Bier' constellation – the Arabic name for the Great Bear.
• In Norse mythology the Pole Star is the jewel on the end of the spike which the gods stuck through the universe and round which the sky revolves.
• To the Moguls (Mongolian empire) it was the peg holding the world together.

Great Bear | Little Bear | The two bears