Sigma Octantis (σ Oct) is a magnitude 5.5 star in the constellation Octans, located at roughly RA 21h 09m, decl. −88° 57'
Its position near the southern celestial pole makes it the southern hemisphere's pole star and counterpart to Polaris, the current North Star. To an observer standing at the South Pole, Sigma Octantis would appear almost motionless and all the other stars in the Southern sky would appear to rotate around it.
Sigma Octantis is sometimes called Polaris Australis, or South Star. However, it is a faint star—at magnitude 5.5 it is barely visible to the naked eye—which makes it a rather poor pole star, especially by comparison to the much brighter and easily visible Polaris.
At present, Polaris is slightly under 1° away from the pole of rotation (about twice the apparent diameter of the Moon) and hence revolves around the pole in a small circle almost 2° in diameter.
Polaris is due to become an even more accurate pole star in the near future — the distance between Polaris and the pole will reach a minimum (of just under 1/2 degree) in 2100.
Although Polaris is a relatively bright star and is conspicuous since no other stars of similar brightness are close to it, it is nowhere near the brightest; it is actually the 47th brightest star.
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