This week, take the opportunity to identify Polaris, the north star. From many northern latitudes, the constellation of Ursa Major, the Great Bear, never sets and it can act as a pointer. The brightest, most recognisable part of that constellation, is the asterism known as the Plough. Finding the two stars that mark the end of the Plough allows a line to be drawn upwards to Polaris, which is the brightest star in Ursa Minor, the little bear. It lies around 400 light years away.
The chart shows the view looking north from London at midnight tonight. Earth’s rotation axis currently points almost exactly at Polaris, meaning that from northern latitudes the entire sky appears to pivot around the north star throughout the night. Because Earth wobbles like a spinning top, completing a full circle every 26,000 years, Polaris has not always been the north star. Around the time of the ancient Egyptians, it was Thuban in Draco, the dragon. In the coming 41st century, Errai, in Cepheus, the King, will assume the role.