Prismtect › Constellations › Hydra
the Water Snake
Hydra is the largest constellation, so long it takes hours to rise. Its head is a small group of stars south of Cancer, and its brightest star, orange Alphard, stands alone in an empty part of the sky.
Hydra is often the many-headed serpent killed by Hercules, or the water snake that guarded the cup in the story of Apollo's crow.
Alphard means 'the solitary one' in Arabic, for it has no bright neighbours.
The Greek Hydra comes from a Babylonian serpent constellation listed in the MUL.APIN star catalogue.
The Greek writers did not agree on the snake's sex.
The Arabs called the stars of the head "belonging to the uninhabited spot".
Three of China's 28 lunar mansions were named after star groups in Hydra.
The Greek Hydra comes from a Babylonian serpent constellation listed in the MUL.APIN star catalogue. It was a mixed creature: part serpent, part lion, part bird. The scholar John H. Rogers links it with Ningishzida, a Babylonian god of the underworld. In ancient times the serpent stretched along the celestial equator, which made it a useful landmark.
The Greek writers did not agree on the snake's sex. Aratus used the female form, Hydra, while Eratosthenes and Ptolemy used the male form, Hydros. In the story of the many-headed monster, every head Hercules cut off grew back as two. His nephew Iolaus helped by searing each neck with a torch so no new heads could grow.
The Arabs called the stars of the head "belonging to the uninhabited spot". Alphard was also called "the backbone of the serpent", and one catalogue called it "the bright solitary one". The 10th-century Persian astronomer al-Sufi gave another name meaning "neck of the serpent".
Three of China's 28 lunar mansions were named after star groups in Hydra. The head was Liu, "willow", which marked the head of the Red Bird of the South. It was also seen as a chef, standing next to an outer kitchen where animals were made ready for sacrifice. A chain of seven stars around Alphard was Xing, "star", also called "seven stars". Zhang was an outstretched net, perhaps for catching birds. Near the tail, faint stars stood for trials and for executioners.
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