- Hydra is the largest of the 88 constellations, winding over a quarter of the way around the sky. Its head is south of the constellation Cancer, the crab, while the tip of its tail lies between Libra, the scales, and Centaurus, the centaur. The total length from its westernmost boundary to the easternmost one is 102°.5. Yet for all its size there is nothing prominent about Hydra. Its only star of note is second-magnitude Alphard, a name that comes from the Arabic al-fard appropriately meaning ‘the solitary one’. Bode on his Uranographia atlas gave it the alternative name Unuk es Schudscha, from the Arabic unuk al-shujā, neck of the serpent. Both names were originally given by al-Ṣūfī in his Book of the Fixed Stars (AD 964).
- Star Tales - Hydrus (ianridpath.com)
A small southern counterpart of the great water-snake, Hydra, with which it is not to be confused. This is one of several examples of the repetition of constellation figures in the sky, as in the Great and Little Bear, the Great and Little Dog, the two lions, the horses Pegasus and Equuleus, the Northern and Southern Crown, and the Northern and Southern Triangle.
