Hydra, the water snake, is the largest of all the 88 constellations. It winds about a quarter of the way around the entire sky. And right now, the whole thing is in view after about 11 p.m., when its tail snakes into view in the southeast.
In this case, though, bigger doesn't mean brighter or more prominent. In fact, it's just about impossible to pick out the sinuous path of the snake without dark skies and a good starchart.
Even so, many cultures outlined a twisting pathway in Hydra's stars. In some cultures it was a river, in others a snake or dragon.
In Greek mythology, it represented a multi-headed monster that Hercules was required to kill as one of his 12 labors. The chore was complicated by the fact that every time he cut off one of the heads, two others grew in its place. So Herc recruited some help: his nephew, Iolaus. Each time Hercules cut off a head, Iolaus burned the stump with a torch to prevent new heads from growing -- a ploy that helped Hercules kill the monster.
The head -- there's just one in the astronomical version of the beast -- is Hydra's most prominent feature. It's outlined by about a half-dozen modest stars well to the east of the "twins" of Gemini. The brightest members of the group are Zeta and Epsilon Hydrae, which are a little behind the snake's glowing eyes.
And a little to the east of the head is Hydra's brightest star, Alphard -- "the solitary one" -- which we'll talk about tomorrow.
Script by Damond Benningfield, Copyright 2011
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