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The Constellation Hydra, the Sea Serpent
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Hydra

Hydra is the longest constellation in the sky (>90 degrees) and is also the largest in terms of area. It is so long that it takes more than six hours to rise completely. Along its northern side are the zodiacal signs of Cancer, Leo, Virgo and Libra.

The serpent's head (south of Cancer and east of Canis Minor) is not a star cluster but a chance grouping of stars, which are at greatly different distances (100-400 lightyears away). The northernmost of the six, Epsilon Hydrae, is a quintuple star - a system of five stars. M48 is a fairly faint, but large, open cluster of about 80 stars easily observed with binoculars. It has an apparent diameter bigger than the disc of the full Moon.

This famous sea serpent is one of the most ancient constellations. In Greek mythology, Hercules slew Hydra, a horrible serpent with many heads that grew back as soon as they were cut off. Killing the Hydra was one of Hercules' twelve labors, during which he also defeated Leo, the lion, and Draco, the dragon.

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