Cosmic Snake Star Pattern Now Slithering Across Night Sky

A giant celestial snake is slithering into view in our current night sky this spring.

We can look to the south to trace it during the early evening hours. In fact, the snake is one of the most extensive of all star patterns: the long and mostly faint constellation of Hydra, the female water snake.

Interestingly, there is also a much shorter, male snake bearing the name Hydrus that is visible only in Southern Hemisphere skies.

A long stream of stars

Hydra begins just below Cancer with a boxy shape of five stars representing the snake’s head, between Procyon and Regulus, and south of the faint Cancer, the Crab. [Top 10 Star Mysteries]

Hydra’s scraggly stream of dim stars then wriggles southeastward past its lone bright star – ruddy second magnitude Alphard – which appears brighter than it is because it has no competition star (hence it’s sometimes called the “Solitary One”).

Hydra’s trail of faint stars finally ends in a distant tail below Virgo that reaches almost as far to the east as Libra, the Scales.  The entire snake, running from high in the southwest sky, over toward the south and finally down low to the southeast, is now in view as soon as it gets dark. [Skywatching Guide: Meteor Showers of 2011]

Hydra is slithering underneath faint Sextans, the Sextant; Crater, the Cup; and brighter Corvus, the Crow.

Despite meandering across 95 degrees of the sky (and taking nearly seven hours to fully rise into view), it doesn’t include much of general interest.  But the star Epsilon Hydrae is a multiple star system: a close pair that takes 15.3 years to orbit each other with a third star orbiting around the close pair and taking about 650 years to make one complete revolution.

One of the more famous Hercules stories is how he killed a hundred-headed serpent known as the Hydra.  Perhaps that’s why when the constellation of Hercules stands triumphantly overhead on warm summer evenings Hydra’s tail is slithering out of sight below the southwest horizon.  

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