Hydra


Hydra - west part
Hydra - east part


English nameHydra

Major
stars
alpha HydraeAlphardmagn. 2,2RA: 09h 27m 35.26s Dec: -08 39' 31.2"
gamma Hydraemagn. 3,3RA: 13h 18m 55.30sDec: -23 10' 17.5"
epsilon Hydraemagn. 3,5RA: 08h 46m 46.61sDec: +06 25' 07.6"
zeta Hydraemagn. 3,3RA: 08h 55m 23.64sDec: +05 56' 43.8"
ny Hydraemagn. 3,3RA: 10h 49m 37.48sDec: -16 11' 37.6"
pi Hydraemagn. 3,5RA: 14h 06m 22.29sDec: -26 40' 56.3"

DescriptionEven though it is rather weak, Hydra is the biggest constellation of the sky, which extends for well seven hours of right ascension. The most evident part is a small group of stars that draw the head and that are on the border with Cancer, to the south-west of Leo: from there, the tail stretches toward Centaurus, finally touching Libra.

There are no very bright stars, except Alphard ("the solitary one", in Arab), an orange giant. Remarkable is also epsilon Hydrae, a double composed by a yellow star and a blue star, respectively of third and seventh magnitude.

M83Among the other interesting heavenly objects there are: M48, an open cluster of about eighty stars, situated on the border with Monoceros; NGC 3242, a planetary nebula of ninth magnitude, known as Ghost of Jupiter because it resembles the planet Jupiter; M68, a globular cluster to observe with instruments of a certain power; and finally M83 (reproduced here on the right), a frontally seen spiral galaxy, among the brightest galaxies of the southern sky.


Mythology
and history
The constellation represents the monstrous snake wiht nine heads (but in the sky it has only one head) that lived in the Lerna swamp, from which it went out to devastate the surrounding country. During the second of his labours, Hercules attached it: with the cudgel he broke its heads, but they immediately regrew in double number. Then the hero asked for help his coachman Iolao, who burned with an ardent brand the stump of every cut head. So the monster was defeated and killed.

Another legend associates this constellation with Crater and Corvus (see the mythology of this latter).


Back to constellations page.