South Star
The modern term South Star, also called southern pole star, refers to the star that happens to lie closest to the south celestial pole (SCP) and which appears (approximately) directly overhead to an observer at the Earth's South Pole. At present, the naked-eye star nearest to this imaginary point is Sigma Octantis, whose angular separation from the pole is about 1° (as of 2000). Its apparent magnitude is a very faint 5.45, and as such it is not very useful for general navigational purposes. This is in contrast to the much brighter 2nd magnitude North Star, Polaris, which marks the approximate position of the north celestial pole.
Although the south celestial pole currently lacks a bright star like Polaris to mark its position, slow changes over time (due to the effects of precession) mean that other stars will become southern pole stars. For example, in the next 7500 years, the south celestial pole will pass close to the stars Gamma Chamaeleontis (4200 CE), I Carinae, Omega Carinae (5800 CE), Upsilon Carinae, Iota Carinae (Aspidiske, 8100 CE) and Delta Velorum (9200 CE).[1]
A similar concept applies to other planets; see pole star for details.