Hydra

IAU Hydra chart

One of the 88 IAU constellations. The name "Hydra" refers to a watersnake from Greek mythology. Still, the underlying constellation originally referred to a Babylonian creature that consisted of a dog-headed snake with wings, the MUŠ.

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 as early as 2nd millennium BCE; it occurs in lexical texts and texts of the Three Stars Each-genre. It is also mentioned in the first list (uranology) of MUL.APIN, where the Raven (or Crow) is mentioned at the tip of tail of the huge creature in the sky.

Aratus

The Greek poet Aratus has many Babylonian references; some of them hidden. For him, this constellation is a (Greek) watersnake.

• [443] Another constellation trails beyond, which men call the Hydra. Like a living creature it winds afar its coiling form. Its head comes beneath the middle of the Crab, its coil beneath the body of the Lion, and its tail hangs above the Centaur himself. Midway on its coiling form is set the Crater, and at the tip the figure of a Raven [Corvus] that seems to peck at the coil.
• [449] There, too, by the Hydra beneath the Twins brightly shines Procyon.
• [51x] and the coil of the gleaming Hydra: in it, too, the dim-lit Crater and the Crow and the scanty-starred Claws and the knees of Ophiuchus are borne.
• [595] Up rises the Hydra’s head and the bright-eyed Hare and Procyon and the forefeet of the flaming dog.
• [600] The Hydra rises higher as far as Crater, and before her the Dog brings up his hind feet, dragging behind him the stern of Argo of many stars.
• [607] Nor can the rising Claws [Libra], though faintly shining, pass unremarked, when at a bound the mighty sign of Boötes rises, jeweled with Arcturus. Aloft is risen all of Argo, but the Hydra, shed as she is afar over the heavens, will lack her tail.
• [663] So she is borne towards the West, but other signs in the East the vault of heaven brings from below, the remaining half of the Crown and the tail of the Hydra, and uplifts the body and head of the Centaur and the Beast that the Centaur holds in his right hand. But the fore-feet of the Centaur-Knight await the rising of the Bow. => pi Hya gehört für Aratus dazu But she sinks beneath the verge the coiling neck and all the brow of the gleaming Hydra.
• [700] Yet many a coil of the Hydra remains, but Night engulfs her wholly with the Centaur, when the Fishes [Pisces] rise; with the Fishes the Fish which is placed beneath azure Aegoceros rises

Eratosthenes

Eratosthenes in his Catasterismi gives two sections per constellation: First, he describes the story that led to the object/ animal/ god becoming a constellation. Then, he describes the positions of the stars in the figure.

English (our translation)

Hydra to which also belongs the Cup and the Raven

This constellation is plural [a super-constellation] because of one event. The raven is associated with the cult of Apollo, as a bird is dedicated to each of the gods. As the gods were making a sacrifice, he was sent to a fountain to collect a libation; seeing a fig tree near the fountain bearing figs that were unripe, he waited for them to ripen. At the time, when they were ripe and he had eaten the figs. Realising that he had committed a sacrilege, he also seized the watersnake (hydra) that was in the fountain and brought it with the cup, claiming that the hydra had been drinking day after day from the spring. But Apollo discovered what had happened and imposed on the raven punishment commensurate with his fault: to be thirsty among men at this time of the year, as Aristotle says in his books On the Animals. For the sacrilege that had been committed against the gods, Apollo placed the Hydra, the Crater, and the Raven, who cannot drink or bath among the constellations.

The Hydra has three bright stars on the tip of its head, six on its first fold, the last of which is bright, three on the second fold, four on the third, two on the fourth, and nine stars without brilliance which go from the fifth fold to the tail. In all, twenty-seven. The Raven is located on the tail of Hydra and looks towards the setting sun. It has a star without luster on the beak, two on the wing, two on the rump, and one on the tip of the legs. In all, seven. The Crater is located on the Hydra, at a certain distance from the fold, and is inclined towards the knees of the Virgin. The Crater has two stars without luster on the rim, two in the centre of the Cup, and two at the base.

Hipparchus

Greek (Manitius 1894)	German (Manitius 1894)	English
	weiter giebt Eudoxos auch die auf den sogenannten Kolurkreisen gelegenen Sterne an und behauptet, auf dem einen derselben liege die Mitte des Großen Bären, die Mitte des Kreises, der Nacken der Wasserschlange und von der Argo das Stück zwischen dem Hinterteil und dem Mastbaum; alsdann nach dem unsichtbaren Pol der Schwanz des südlichen Fisches, die Mitte des Steinbocks und die Mitte des Pfeils; endlich gehe er durch den Hals und den rechten Flügel des Schwans, durch die linke Hand des Kepheus, durch die Windung der Schlange und vorbei am Schwanze des Kleinen Bären.	Eudoxus also gives the stars situated on the so-called circles of Colur and claims that on one of them lies the centre of the Great Bear, the centre of the circle, the neck of the watersnake and the part of the Argo between the rump and the mast; then, after the invisible pole, the tail of the southern fish, the centre of Capricorn and the centre of the arrow; finally, it passes through the neck and the right wing of the swan, through the left hand of Cepheus, through the coil of the Snake and past the tail of the Little Bear.	Lib. I. Cap. XL § 9 .
	Ersichtlich macht er dies auch bei dem Aufgange der Fische, wo er sich also ausdrückt; nachdem er nämlich von der Wasserschlange gesagt, daß das Stück vom Kopfe bis zur ersten Windung, wenn der Wassermann im Aufgange begriffen ist, nicht mehr über dem Horizont sei, während den Rest ihres Körpers die Fische hinabführen.	He also makes this evident in the rising of the fishes, where he expresses himself thus; for after he has said of the watersnake that the part from the head to the first coil, when the Aquarius is in the act of rising, is no longer above the horizon, while the rest of its body is led down by the fishes.	Lib. II. Cap. I. § 24
	Untergang des Perseus, mitkulminierend: Leo 5 1/2: Von der Wasserschlange der vierte von den vier hinter dem hellen nach Osten gelegenen (λ2), 1 Mbr. westlich des Meridians.	Setting of Perseus, co-culminating: Leo 5 1/2: Of the watersnake the fourth of the four behind the bright one to the east (λ2), 1 moon width west of the meridian.	Lib. II, Cap.VI. §15
	Aufgang des Kentaur, mitkulminierend: Cnc 12°: Von der Wasserschlange der nachfolgende in der südlichen Kinnlade (η)	Rising of the centaur, co-culminating: Cnc 12°: From the watersnake of the following in the southern jaw (η)	Lib. III. Cap. I. § 4.
	Untergang Kleiner Hund, mitkulminierend: 3 . Von der Wasserschlange der am Ende des Schwanzes (π).	Downfall Small dog, co-culminating: 3 . From the watersnake at the end of the tail (π).	Lib. III. Cap. n. § 13
	Aufgang der Jungfrau, mitkulminierend: 2. Von der Wasserschlange der nördlichere von denen im Rachen (δ) , 1 Mbr. östlich des Meridians.	Rising of Virgo, co-culminating: 2. of the watersnake the more northerly of those in the throat (δ), 1 moon width east of the meridian.	Lib. III. Cap. III. § 3
	Aufgang des Skorpions, mitkulminierend: Von der Wasserschlange von den vieren nach dem hellsten [vor dem Becher] der dritte von Westen (ν2 Hydrae)	Rising of the scorpion, co-culminating: Of the watersnake of the four after the brightest [before the cup] the third from the west (ν2 Hydrae)	Lib. III. Cap. III. § 5.

The mathematical astronomer mentions this constellation rising and setting.

Greek	German (Manitius 1894)	English (from Manitius 1894)
	Die Wasserschlange (Hydra). Aufgang von Cnc 18 1/2 Grad bis Lib 15 1/2 Grad, Mitkulmination Ari 2 1/2 Grad bis Cnc 18 Grad. Anfang: Der nördlichere von denen im Rachen (δ). Ende: Der am Ende des Schwanzes (π). Ari 2 1/2° Vom Perseus der nebelförmige im Sichelschwert (χh). Der Knoten im Band der Fische (α), 1 Mbr. östlich des Meridians. Der nachfolgende von den drei hellen im Kopfe des Widders (α), 1 Mbr. östlich des Meridians. Cnc 18° Vom Löwen der südlichere der vorangehenden von denen im Kopfe (λ). Von der Argo der nördlichere von denen in der Mitte des Mastes ( o3 Argus = γ Pyxidis Nauticae) Dauer des Aufgangs: 7 1/15 St. = 424m = 106°.	The water snake (Hydra). Rising from Cnc 18 1/2 degrees to Lib 15 1/2 degrees, co-culmination Ari 2 1/2 degrees to Cnc 18 degrees. Beginning: The more northerly of those in the throat (δ). End: The one at the end of the tail (π). Ari 2 1/2° From Perseus the nebulous one in the crescent sword (χh). The node in the band of Pisces (α), 1 moon width east of the meridian. The next of the three bright ones in the head of Aries (α), 1 moon width east of the meridian. Cnc 18° Of Leo the more southerly of the preceding of those in the head (λ). Of the Argo the more northerly of those in the centre of the mast ( o3 Argus = γ Pyxidis Nauticae) Duration of the rise: 7 1/15 hours = 424m = 106°.	Lib III, Cap. I, §1
	Die Wasserschlange (Hydra). Untergang von Gem 29° bis Vir 11°; Mitkulmination Lib 18 1/2 Grad bis Sgr 18 1/2 Grad. Anfang: Der südlichere von denen im Raben (σ). Ende: Der am Ende des Schwanzes (π). Lib 18 1/2 Vom Drachen der drittletzte helle im Schwanze (α), 1 Mbr. westlich des Meridians. Vom Bootes der helle im Gürtel (ε). Von den Scheren der vor dem hellen am Ende der nördlichen Schere vorangehende (δ). Von der Wasserschlange der am Ende des Schwanzes (γ Librae ), 1 Mbr. westlich des Meridians. Sgr 18 1/2 Vom Drachen die südlichere Schläfe (γ). Von der Schlange des Ophiuchos der am Ende des Schwanzes (θ). Vom Schützen der vorangehende von denen im Obergewande (d). Dauer des Untergangs: 4 St. = 240m = 60°.	The watersnake (Hydra). Setting from Gem 29° to Vir 11°; co-culmination Lib 18 1/2 degrees to Sgr 18 1/2 degrees. Beginning: The more southerly of those in the raven (σ). End: The one at the end of the tail (π). Lib 18 1/2 Of the kite the third last light in the tail (α), 1 Mbr. west of the meridian. Of the Bootes the bright one in the belt (ε). Of the scissors, the one preceding the bright one at the end of the northern scissors (δ). Of the water snake the one at the end of the tail (γ Librae ), 1 Mbr. west of the meridian. Sgr 18 1/2 Of the dragon the more southern temple (γ). Of the serpent of Ophiuchus, that at the end of the tail (θ). Of the archer the preceding one of those in the upper garment (d). Duration of the setting: 4 hours = 240m = 60°.	Lib. III. Cap. II. § 1.

Greek	German	English
	Der nördlichere von denen im Rachen (δ).
	Der aro Ende des Schwanzes (π)

• The first star rising is ,
• the last star rising is the one at the tip of the tail (ὁ ἐν ἄκρᾳ τῇ οὐρᾷ).

Dauer des Aufgangs : 7 1/15 St. = 424m = 106°.

Further stars mentioned

Greek (Manitius 1894)	German (Manitius 1894)	English (...)
	Von der Wasserschlange

Almagest

Greek (Heiberg 18xx)		English (Toomer 1984)	ident.
τῶν έν τῇ κεφαλῇ ε τῶν ἡγοvμένωv β ὁ vοτιώτερος ἐπὶ τῶv μυκτήρων	1	The 5 stars in the head: the southernmost_of the 2 advance ones, which is on the nostrils	sig  Hya
ὁ βορειότερος αὐτῶν καὶ ἐπάνω τοῦ ὀφθαλμοῦ	2	The 5 stars in the head: the northernmost of these [2], which is above the eye	delta Hya
τῶν ἑπομένων αὐτοῑς β ὁ βόρειος ῶς ἑπὶ τοῦ κρανίου	3	The 5 stars in the head: the northernmost of the 2 to tl1e rear ofthese, which is about on the skull	eps Hya
ὁ vοτιώτερος αύτῶν καὶ ἑπὶ τοῦ χάσματος	4	The 5 stars in the head: the southernmost of them, on the gaping jaws	eta Hya
ὁ πᾶσιv ἑπόμεvος ὡς ἑπὶ τῆς γένvος	5	The 5 stars in the head: the reannost of all, about on the cheek	zet Hya
τῶν ἐv τῇ έκφύσει του τραχήλου β ὁ ἡγούμενος	6	The more advanced ofthe 2 star~ in the place where the neckjoins [the head)	omega Hya
ὁ ἑπόμενος αὐτῶν	7	The rearmost of them	theta Hya
τῶν ἑξης ἐν τῇ καμπῇ τοῦ τραχήλου γ ὁ μέσος	8	The middle star of the following three in the bend of the neck	tau2 Hya
ὁ ἑπόμενος τῶν γ	9	The rearmost of the 3	iota Hya
ὁ νοτιώτατος αὐτῶν	10	The southernmost of them	tau1 Hya
τῶν ἀπο νότου β συνεχῶν δ άμαvρος καὶ βόρειος	11	The faint, northernmost star of the 2 close tagether to the south	BSC 3750
ὁ λαμρὸς τῶν β συνεχῶν	12	The bright one of these two close stars	alpha Hya
τῶν μετὰ τὴν καμπὴν ἑπομέvων γ ὁ ἡγούμενος	13	The most advanced ofthe 3 stars to the rear, afl:er the bend [in the neck	kappa Hya
ὁ μέσος αὐτῶν	14	The middle one	upsilon1 Hya
ὁ έπόμενος τῶν τριῶν	15	The rearmost of the three	upsilon2 Hya
τῶv ἑξῆς ὠς ἐπ' εὐθείας γ ὁ ἡγούμενος	16	The most advanccd of the ncxt 3 stars almost on a straight line	mu Hya
ὁ μέσος αυτῶν	17	The middle one	phi Hya
ὁ έπόμενος τῶv τριῶν	18	The rearmost of the three	nu Hya
τῶν μετὰ τὴν βάσιν τού Κρατῆρος β ὁ βορειότερος	19	The northernmost of the 2 stars aher [i.c.  to the rear o.t]  the base of Crater	beta Crt
ὁ νοτιώτερος αυτῶν	20	The southernmost of thcm	chi1 Hya
τῶv μετα τούτους γ ὡς ἐν τριγώνῳ ὁ ἡγούμενος	21	The most advanced of the 3 stars aller these, as it werc in a triangle	xi Hya
ὁ μέσος αὐτῶν και νοτιώτερος	22	The middle and southernmost onc	omicron Hya
ὁ έπόμενος τῶν τριῶv	23	The rearmost of the three	beta Hya
ὁ μετα τὸν Κόρκα ἐv τῷ παρούρῳ	24	The star after Corvus, in the scction by the tail	gamma Hya
ὁ ἐπ' ἄκρας τῆς οὐρᾶς	25	The star on the tip of the tail	pi Hya
Stars round Hydra outside the constellation:
ὁ ἐκ μεσημβρίας τῆς κεφαλῆς	26	The star to the south of the head	BSC 3314
ὁ ἐκ διαστήματος ἑπόμενος τοῑς ἐν τῷ τραχrjλῳ	27	The star some distance to the rear of those in the neck [ nos. 6-I5]	epsilon Sex

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

• 

  Leo and Virgo above the MUŠ-Dragon, two claytablet drawings from the Seleucid era (roughly 2nd century BCE), CC BY SMH based upon the drawings by E. Weidner (1967) and Thureau-Dangin (1922).

• 

  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" which doesn't apply here).

References

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