Jason Taylor, of Balclutha School, asks :-

Why do stars stay in the same place?

Frank Andrews, then an astronomer educator at Wellington's Carter Observatory, responded.

All the stars you can see in the night sky are part of the Milky Way Galaxy. This is a huge disk-like association of billions of stars that orbit around a massive black hole at its centre. Our Sun takes 220,000,000 years to make one complete orbit. This is known as a Galactic Year. Relative movement of stars can be detected with powerful telescopes as well as specially designed artificial satellites and is called Proper Motion.

The reason that stars seem to stay in the same place is that they are so far away. Most of the stars, including our Sun, are moving through space at tens of kilometres per second. Even though they are actually moving at speeds that seem fast by earthly standards we would have to live for tens of thousands of years before any changes in their relative positions would become easily noticeable to the unaided eye. If you could come back to Earth in 2500BC, when many of the constellations we know so well today were named, you would not see any noticeable changes. However if you could come back in two million years time, the night sky would have changed beyond recognition.