Star Tales – Sagittarius

Sagittarius is depicted in the sky as a centaur, with the body and four legs of a horse but the upper torso of a man. He is shown wearing a cloak and drawing a bow, aimed in the direction of the neighbouring Scorpion. Aratus spoke of the Bow and the Archer as though they were separate constellations. Sagittarius is sometimes misidentified as Chiron. But Chiron is in fact represented by the other celestial centaur, the constellation Centaurus.

Sagittarius, the centaur-like archer, shown drawing his bow in the

Uranographia of Johann Bode (1801).

Sagittarius is a constellation of Sumerian origin, subsequently adopted by the Greeks, and this helps explain the confusion over its identity. Eratosthenes doubted that this constellation was a centaur, giving as one of his reasons the fact that centaurs did not use bows. Instead, Eratosthenes described Sagittarius as a two-footed creature with the tail of a satyr. He said that this figure was Crotus, son of Eupheme, the nurse to the Muses, who were nine daughters of Zeus. According to the Roman mythographer Hyginus, the father of Crotus was Pan, which confirms the view of Eratosthenes that he should be depicted as a satyr rather than a centaur.

Crotus invented archery and often went hunting on horseback. He lived on Mount Helicon among the Muses, who enjoyed his company. They sang for him, and he applauded them loudly. The Muses requested that Zeus place him in the sky, where he is seen demonstrating the art of archery. By his forefeet is a circle of stars that Hyginus said was a wreath thrown off by someone at play. This circlet of stars is the constellation Corona Australis.

Alpha Sagittarii is alternatively called Rukbat or Alrami, both from the Arabic rukbat al-rami, ‘knee of the archer’. Beta Sagittarii is called Arkab, from the Arabic name meaning ‘the archer’s Achilles tendon’. Gamma Sagittarii is Alnasl, from the Arabic meaning ‘the point’, referring to the tip of the archer’s arrow.

Delta, Epsilon and Lambda Sagittarii are respectively called Kaus Media, Kaus Australis and Kaus Borealis. The word Kaus comes from the Arabic al-qaus, ‘the bow’, while the suffixes are Latin words signifying the middle, southern and northern parts of the bow. Zeta Sagittarii is Ascella, a Latin word meaning ‘armpit’. All these names closely follow the descriptions of the stars’ positions given by Ptolemy in his Almagest.

Last, but not least, is Sigma Sagittarii, called Nunki. This name was applied relatively recently by navigators, but it was borrowed from a list of Babylonian star names. The Babylonian name NUN-KI was given to a group of stars representing their sacred city of Eridu on the Euphrates. The name has now been applied exclusively to Sigma Sagittarii, and is reputed to be the oldest star name in use.

Sagittarius contains a rich part of the Milky Way, lying towards the centre of our Galaxy. The exact centre of the Galaxy is believed to be marked by a radio-emitting source that astronomers call Sagittarius A. There are many notable objects in Sagittarius, including the Lagoon Nebula and the Trifid Nebula, two clouds of gas lit up by stars inside them.