Visible this month, all through the evening hours, is a long, faint constellation, Hydra, the female water snake. With the Moon not much of a hindrance, you may be able to spot it toward the southern part of the sky. Hydra is stretched out, with its head over in the southwest, while over in the southeast is the end of its tail. It’s the largest of the recognized 88 constellations—meandering across 95 degrees of the sky—and it takes nearly 7 hours to rise each night!
There’s a male snake bearing the name Hydrus, but it’s visible only in Southern Hemisphere skies. Some think Hydra commemorates the fabled hundred-headed serpent that was ultimately overcome by Hercules.
The Stars of the Hydra Constellation
Hydra’s head is a rough box of five stars between the stars Procyon and Regulus, and south of the faint Cancer, the Crab. Its scraggly stream of dim stars then wriggles southeastward past its lone bright star—the ruddy, second-magnitude Alphard, which appears brighter than it is because it has no competition star. Hydra’s trail of faint stars finally ends in a distant tail below Virgo. Hydra is slithering underneath faint Sextans, the Sextant, Crater, the Cup, and brighter Corvus, the Crow.
The star, Epsilon Hydrae, located in the snake’s head, is a multiple star system: a close pair 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!
So head outside from around 9:30 p.m. to 11:30 p.m. this month to see Hydra slithering across the cosmos.