Ara, the Altar

Ara is a small southern constellation, one of Ptolemy's forty-eight, representing an altar. In Greek myth it is the altar on which the gods of Olympus swore their alliance before the war against the Titans, or the altar upon which the centaur bears its offering; the smoke of its sacrifice was sometimes identified with the Milky Way, which runs close by. It lies deep in the southern sky, below the tail of Scorpius, too far south to be seen from much of the northern hemisphere. Its stars are modest and set within a rich Milky Way field. In astronomical tradition the constellation is a pattern of stars rather than a zodiac sign. These are the features of Ara as the classical and modern traditions describe it, distinct from any astrological reading of the southern region of sky it occupies.

Ara sits beside Telescopium, introduced by Lacaille in the 1750s and named, appropriately for a region of sky otherwise carrying an altar's smoke and a centaur's sacrifice, for the instrument that made the systematic eighteenth-century survey of the far southern sky possible in the first place. Norma and Circinus, the level and the compasses, are two more of Lacaille's instrument names carved from the same general stretch of sky in the 1750s.