Cepheus was the mythological king of Ethiopia. He was deemed worthy of a place in the sky because he was fourth in descent from the nymph Io, one of the loves of Zeus – and having Zeus as a relative was always an advantage when it came to being commemorated among the constellations. The kingdom of Cepheus was not the Ethiopia we know today, but stretched from the south-eastern shore of the Mediterranean southwards to the Red Sea, an area that contains parts of the modern Israel, Jordan and Egypt. Ptolemy described him as wearing the tiara-like head-dress of a Persian king.

Cepheus in the robes of a Persian king, depicted in the Atlas Coelestis
of John Flamsteed (1729).

Cepheus was married to Cassiopeia, an unbearably vain woman whose boastfulness caused Poseidon to send a sea monster, Cetus, to ravage the shores of Cepheus’s kingdom. Cepheus was instructed by the Oracle of Ammon to chain his daughter Andromeda to a rock in sacrifice to the monster. She was saved by the hero Perseus, who killed the monster and claimed Andromeda for his bride.

King Cepheus laid on a sumptuous banquet at his palace to celebrate the wedding. But Andromeda had already been promised to Phineus, brother of Cepheus. While the celebrations were in progress, Phineus and his followers burst in, demanding that Andromeda be handed over, which Cepheus refused to do. The dreadful battle that ensued is described in gory detail by Ovid in Book V of his Metamorphoses. Cepheus retired from the scene, muttering that he had done his best, and left Perseus to defend himself. Perseus cut down many of his attackers, turning the remainder to stone by showing them the Gorgon’s head.

The constellation of Cepheus lies near the north celestial pole. Its most celebrated star is Delta Cephei, a pulsating supergiant star that varies in brightness every 5.4 days. It is the prototype of the Cepheid variable stars that astronomers use for estimating distances in space.
Chinese associations
In the Chinese sky, Alpha, Eta, Theta, Xi, Iota and Omicron Cephei were members of a nine-star group called Tiangou, the celestial hook (also known as Gouxing, ‘hook star’); the stars in this group were associated with omens regarding earthquakes. To the south of Tiangou, the stars Delta, Epsilon, Zeta, Mu and Nu Cephei formed Zaofu (also spelt Zhaofu), named after the legendary charioteer of the emperor Mu Wang.

In northern Cepheus, near the borders with Cassiopeia and Camelopardalis, were five stars that formed Wudineizuo, the seats of five celestial emperors. These emperors are thought to be the deified rulers of the five directions in the sky, i.e. north, south, east, west and central. There is no certainty as to which five stars represented them, though.

Part of the eastern wall of the Purple Palace Enclosure, aka the Central Palace, passed through Cepheus on its way from Draco to Cassiopeia, but there is no agreement between sources as to which stars were involved. For more on this Central Palace, see Ursa Minor.

© Ian Ridpath. All rights reserved