A circumpolar star or constellation is one that never sets as seen from a given location, but always stays above the observer’s horizon and can be viewed all year round (see Circumpolar Stars). The area of sky depicted here shows stars which are circumpolar as seen from roughly mid-southern latitudes and includes the constellations that surround Octans (the Octant), the group which contains the south celestial pole. Unlike its northern counterpart, which is marked by the relatively bright Polaris in Ursa Minor (see North Circumpolar Stars) there is no particularly bright star indicating the position of the south celestial pole.
Many of the groups in this region of sky are rather faint, including Hydrus (the Little Water Snake), Tucana (the Toucan), Mensa (the Table Mountain) and Dorado (the Goldfish) although this quartet of obscure constellations can at least lay claim to the fact that they host the two nearby dwarf irregular galaxies the Large and Small Magellanic Clouds. The Large Magellanic Cloud lies on the border between Mensa and Dorado, the Small Magellanic Cloud straddling the region between the two constellations Hydrus and Tucana.
The Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are members of the Local Group of Galaxies (see Glossary). They resemble detached portions of the Milky Way and are plainly visible to the unaided eye. Located at a distance of over 160,000 light years, the LMC is a sizeable system measuring around 14,000 light years across. Somewhat further away is the SMC which, at a distance of around 190,000 light years, has a diameter of around 7,000 light years.
Early navigators referred to the Magellanic Clouds as the Cape Clouds, being as they were a pair of prominent celestial objects seen as they approached the Cape of Good Hope. They were also known to many ancient civilizations, although it was only following accounts of the circumnavigation of the Earth by the Portuguese explorer Ferdinand Magellan in the early-16th century that their presence became more widely known. Magellan’s contribution eventually resulted in both objects being named in his honour.
Lying quite close to the triangle of stars forming Hydrus is the bright star Achernar in Eridanus (the River). Achernar is fairly easy to pick out and acts as an effective finding aid for the relatively obscure constellations that lie in the same region of sky including Phoenix (the Phoenix), Horologium (the Pendulum Clock) and Reticulum (the Net). Slightly to the north of Phoenix we see the dim Sculptor (the Sculptor) and the prominent Fomalhaut, the leading star in Piscis Austrinus (the Southern Fish).
Bordering Piscis Austrinus to the south we have the reasonably prominent Grus (the Crane) with the fainter and more obscure Microscopium (the Microscope) nearby. Indus (the Indian) borders Microscopium, this forming a triangle of constellations with Pavo (the Peacock) and Telescopium (the Telescope).
Slightly more noticeable are Ara (the Altar) and Triangulum Australe (the Southern Triangle) both of which, along with the fainter trio Norma (the Level), Circinus (the Compasses) and Lupus (the Wolf) can be tracked down by using the bright pair of stars Alpha and Beta Centauri in Centaurus (the Centaur) as a location finder.
The southern regions of Centaurus surround the bright constellation Crux (the Cross) while immediately to the south of Crux we find the tiny but conspicuous Musca (the Fly). Lying close to the south celestial pole is the less prominent trio Chamaeleon (the Chamaeleon), Apus (the Bird of Paradise) and Volans (the Flying Fish).
Located close to the bright star Canopus in Carina (the Keel) is the bent line of three faint stars forming Pictor (the Painter’s Easel). Carina itself, along with adjoining Vela (the Sail) are considerably more prominent, as is the asterism the ‘False Cross’ which is formed from two stars in Carina and two in Vela. This pattern is often confused with nearby Crux which is located some way to the east.
In spite of this area of sky containing mainly faint and relatively obscure groups, the region is ringed by the bright stars Alpha and Beta Centauri in Centaurus, Canopus in Carina and Achernar in Eridanus. Using these stars as a framework and arming yourself with the accompanying chart, you should be able to identify the south circumpolar constellations.