Star Tales – Coma Berenices

Between Boötes and Leo lies an attractive little swarm of stars that was known to the Greeks but was not classed by them as a separate constellation, being considered part of Leo. Eratosthenes referred to it as the hair of Ariadne under his entry on the Northern Crown (Corona Borealis), but under Leo he said it was the hair of Queen Berenice of Egypt, which is as we know it today. Ptolemy referred to these stars as ‘a nebulous mass, called the lock’ (i.e. of hair) in his Almagest of c. AD 150, and it was occasionally illustrated as such thereafter.

The group was first shown as separate constellation in 1536, under the name Berenices Crinis, on a globe by the German mathematician and cartographer Caspar Vopel (1511–61). He was followed in 1551 by the Dutch cartographer Gerardus Mercator, who termed the constellation Cincinnus or Circinnus. In 1602 Tycho Brahe included Coma Berenices in his influential star catalogue, thus ensuring its widespread adoption.

Coma Berenices, the flowing tresses of an Egyptian queen, from the Uranographia of Johann Bode (1801).

Berenice was a real person who, in the third century BC, married her brother, Ptolemy III Euergetes, as was the tradition of the Egyptian royal family. Berenice was reputedly a great horsewoman who had already distinguished herself in battle. Hyginus, who deals with the star group under Leo in his Poetic Astronomy, tells the following story.

It seems that a few days after their marriage Ptolemy set out to attack Asia. Berenice vowed that if he returned victorious she would cut off her hair in gratitude to the gods. On Ptolemy’s safe return, the relieved Berenice carried out her promise and placed her hair in the temple dedicated to her mother Arsinoë (identified after her death with Aphrodite) at Zephyrium near the modern Aswan. But the following day the tresses were missing. What really happened to them is not recorded, but Conon of Samos, a mathematician and astronomer who worked at Alexandria, pointed out the group of stars near the tail of the lion, telling the king that the hair of Berenice had gone to join the constellations.

Chinese astronomers plotted 15 stars of the Coma Star Cluster which they called Langwei, a group of court officials that included various scholars, advisors and bodyguards. To the north was a single star called Langjiang, captain of the bodyguards, most likely Gamma Comae Berenices although it is also identified as 31 Com or even Alpha Canum Venaticorum. Beta, 37 and 41 Com formed Zhouding, representing a three-legged bronze food vessel (although an earlier tradition placed Zhouding in Boötes).

Alpha Comae Berenices was the northernmost star in a chain of five that extended southwards into Virgo; this chain marked the eastern wall of Taiwei, a court where the Emperor met with his privy council. Five faint stars in southern Coma Berenices, identities uncertain, formed Nei wuzhuhou, representing five feudal lords or princes who governed various outlying states, here seen gathered within the court of Taiwei. Other constellations within the court were in present-day Virgo and Leo.