Ask Space
ASTRONOMY
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.