Hydra

IAU Hydra chart

One of the 88 IAU constellations.

Etymology and History

The Greek constellation of the Water Snake is a derivative of the Babylonian constellation of the MUŠ-Dragon, a dog-headed creature with the body of a gigantic snake with front legs and wings.

Origin of Constellation

The Babylonian constellation is mentioned ...

Aratus

Hipparchus mentions the constellation rising and setting. The first star rising is , the last star rising is the oneat the tip of the tail (ὁ ἐν ἄκρᾳ τῇ οὐρᾷ)

Transfer and Transformation of the Constellation

• 
  the Babylonian version of the "Hydra and Corvus" super-constellation does not contain a cup or jar. visualized in Stellarium (drawing by Jessica Gullberg)
• 
  the lonely star in front of the dragon-head (Procyon) rised simultaneously with the faint stars of The Crab in ancient Babylon. Procyon and the head / foot of the dragon may serve as a replacement for Cancer
• 
  The Greeks introduced a Crater atop the snake. On the Farnese Globe, the body of the snake forms a vessel for Corvus and Crater.
• 
  In early modern time, some scholars extended the snake-body of Hydra beyond pi Hydrae and placed a second bird (Solitaire or Noctua) at this new end.

IAU WGSN

The star pi Hydrae is very important in history as it is one of the keywitnesses for transfer from Hipparchus to Ptolemy.

• name in Hipparchus: ὁ ἐν ἄκρᾳ τῇ οὐρᾷ (the one at the farthest point of the tail)
• name in the Almagest: ὁ ἐπ᾽ἄκρας τῆς οὐρᾶς (the one at the end of the tail)

The Greek term ἄκρᾳ can be translated as "at the farthest point" or "at the end" or "hightest".

References

• References (general)
• References (Babylonian)
• References (ancient Greco-Roman)
• References (medieval)