If Polaris is the North Star, is there a ‘south star’?
In the Northern Hemisphere, astronomers are fortunate to have a star, Polaris, very close to the north celestial pole. Polaris appears to stay fixed in position while the constellations rotate around it due to Earth’s spin about its axis. It’s a sensible assumption that there might be a similar guide at the south celestial pole, the point of sky around which the Southern Hemisphere stars appear to rotate. But Polaris is above the celestial pole purely by chance, and there’s no useful beacon marking the south celestial pole. The closest star, Sigma Octantis in Octans, is a very dim, fifth-magnitude star which is extremely hard to make out with the naked eye. While Sigma Octantis is the ‘south star’, it doesn’t have the same usefulness as Polaris for astronomers, so often falls by the wayside. To find the south celestial pole, one way is to find the Southern Cross to use ‘the pointers’ and the star Achernar.
If you’d like to see a southern equivalent of Polaris, you’ll have to wait a very long time. Earth undergoes a continuous change in the orientation of its rotational axis, known as axial precession. A consequence is the pole star changing due to the change in axial orientation. One cycle of precession is about 26,000 years, and in tens of thousands of years Sirius, the ‘Dog Star’, will be placed close to the south celestial pole. Astronomers certainly won’t have a hard time locating such a bright south star.