In the northern sky in December is a beautiful cluster of stars known as the Pleiades, or the “seven sisters”. Look carefully and you will probably count six stars. So why do we say there are seven of them?

Many cultures around the world refer to the Pleiades as “seven sisters”, and also tell quite similar stories about them. After studying the motion of the stars very closely, we believe these stories may date back 100,000 years to a time when the constellation looked quite different.