Cyrix 6x86

History

The constellation of Hydre is rather old and Ptolémée had indexed it in its Almageste .

It represents the Hydre de Lerne, killed by Hercules within the framework of its twelve work.

In the ancient Mésopotamie, it is associated to the god Ningishzida.

Observation of stars

The constellation can be located only per pieces. It is a not very brilliant and rather scattered star constellation, whose forms are seldom suggestive. The hydre is a little the monster of the Log Born stellar.

; Head of the hydre The head of Hydre is located halfway between Procyon of the Puppy and Régulus of the Lion. One rather easily locates (Mag 3) his two eyes, ε Hya and ζ Hya, enough close relations and of appreciably equivalent luminosity. When the conditions of visibility are good, one sees taking shape the two nostrils parallel with the eyes, and a fifth small star which closes the head.

In the alignment of the two eyes, side of Procyon, one finds with 10° an average star (mag 3) which is most brilliant of the constellation of the Cancer. The body of the hydre is prolonged other side of this alignment, towards the East.

With right angle of this first direction, in the alignment of the head which leaves the eyes towards the nostrils, one also finds with 10° an average star (mag 4) which is ζ My, fourth of the Licorne, followed to 10° in the same direction (a little on the left) by α My, and this alignment continues until Sirius (α CMa), of the Large Dog, 15° further.

; Heart of the hydre The heart of Hydre is Alphard, star relatively brilliant (mag 2) and isolated located at the south from Régulus, on the way of Canopus. Alphard is used as central benchmark for this area of the sky. It is halfway on alignment between Régulus and the beginning of the compass, γ Pyxidis.

; Higher trunk of Hydre The beginning of the body of Hydre follows in two pieces the head office of the axis Procyon - Alphard. On the basis of the Head, one meets two small fairly brilliant stars (mag 4), with regular interval, then the body forms a right angle towards the left in direction of Alphard. So instead of forking one continues straight over the length of a third interval, one falls on a not very spangled zone which is the constellation of the Sextan, located between Alphard and the constellation of the Lion.

The continuation of the body of Hydre continues along the axis Procyon - Alphard, in direction of the Corbeau. One meets on this axis two average stars, λ Hya and ν Hya. On this level, the body of the hydre " disparaît" to yield the place to the constellation of the Cut. The zone of the constellation continues more in the south, but without hardly of brilliant star guiding the glance.

; Tail of Hydre The tail of the hydre leaves the figure. It can be admired around the constellation of the Corbeau, small easily locatable constellation in the south of the Vierge.

Principal stars

Alphard (α Hydrae)

The the most brilliant star of Hydre and only with a name is called Alphard (α Hydrae) and is with the neck of the monster. It is a distant of 180 light-years, shining like 400 Sun, broad orange giant star of a half of ua.

Other stars

ε Hydrae is a multiple star having at least five members: in the center is a formed couple of a yellow giantess and a white under-giantess distant of 10,5 ua and orbiting in 15,05 years. With 190 ua of the couple, a yellow star carries out a revolution in 900 years. It is also about a star couple, extremely close one to the other (approximately 0,09 ua and they turn one around the other in 9 days). Lastly, 800 ua further, a small red star closes walk.

σ Hydrae, the 18th star of the constellation, bears a proper name curiously: Al Minliar Al Shuja

R Hydrae is a variable star of the type Mira (ο Ceti) and evolves/moves between the magnitudes 4,97 and 10,9 over one 388,87 days period.

Two stars of Hydre at least have two planets: HD 74156, with two planets 1,86 and 6,17 times more massive than Jupiter, orbiting to 0,294 and 3,40 ua into 51,643 and 2 025,0 days, and HD 82943, with two planets also, 0,88 and 1,63 times more massive than Jupiter, orbiting to 0,73 and 1,16 ua into 221,6 and 444,6 days.

Celestial objects

Because its length, the constellation of Hydre contains several astral objects, like the open Amas M48, the globular Amas M68 and the spiral galaxies NGC 3621 and M83, the latter being among most brilliant visible Galaxie S of the Southern hemisphere.

See too

List of stars of Hydre

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