Hydra

Authors: Susanne M Hoffmann, Youla Azkarrula, Doris Vickers, Roland Laffitte, IanRidpath

---

IAU Hydra chart

ʿˊΥδρος (Hydros)

Asterism Info
Native	ʿˊΥδρος
Romanisation	Hydros
Translation	Water Snake
Position (2000)
Right ascension	129.4140311 to 211.59290829999998
Declination	-33.90812978 to 6.41880152
Area	1124.77 sq. deg.
Stars
Bright stars	171
Bayer/Flamsteed stars	120
Stars brighter than 3.00m	6
Brightest star	Alphard (1.97m)
Taxonomy
category of asterism	Almagest constellation
IAU- constellations	Hya, Sex, Cra, Crv, Vir

Babylonian predecessor of Hydra: MUŠ, a creature with a snake-body with a wing, a dog-head and front legs; painting by Jessica Gullberg, in Stellarium by Susanne M Hoffmann

clay tablets VAT 7847+AO6448

Hydra (as a vessel) with Corvus and Crater on the Farnese Globe (2nd century CE), mapped to Stellarium by SMH 2021.

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 ^{mul (d)}MUŠ. For Aratos and Eratosthenes, the constellations Hydra, Corvus, and Crater belong together; they form a super-constellation consisting of several figures. They tell a star legend whose main character is the raven, who is said to have carried the Hydra to Apollo. However, this contradicts the figure in the sky: the raven is tiny compared to the Hydra and looks more like it is riding on it. This legend testifies to the actually foreign origin of the constellation: The giant snake and the raven were adopted as an image from Mesopotamia. The description or listing of these figures is already documented in MUL.APIN in the 2nd millennium BCE. It is one of the few constellations for which there is even evidence of an engraving from Mesopotamia – although only from the Seleucid period, i.e., under Greek rule.

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 Corvus, the Raven (or Crow) is mentioned at the tip of the tail of the huge creature in the sky.

Babylonian

see

• ^{mul (d)}MUŠ
• ^(mul)MUŠ.ḪUŠ

The Babylonian "serpent" has a dog's head, at least front legs (if not also hind legs), and wings.

Egyptian

In Ptolemaic times (1st century BCE), when Egypt was ruled by the Romans, new Egyptian temples were built: a Chnum temple in Esna and a Hathor temple Dendera (south and north of Thebes/ Luxor). They display a cultural mixture of Babylonian and Egyptian constellations.

• 
  Leo (and Com); rectangular zodiac of Dendera
• 
  Leo with Com, Hya, Crv, circular zodiac of Dendera (CC BY Musée du Louvre, Département des Antiquités égyptiennes)

Aratus

Constellation Hydra with Crater and Corvus on the Kugel Globe (1st century BCE), detail from drawing by SMH.

But yet another constellation sweeps across the horizon: they call it the Hydra. Like a living thing [445] it winds at great length, its head comes below the middle of the Crab, its coil under the Lion’s body, and its tail hangs over the Centaur himself. On its middle coil lies the Bowl, and on the last one the figure of a Raven that looks like one pecking the coil. [450] Yes, and there too Procyon shines brightly beneath the Twins. (Kidd 1997)

For Aratus Pi Hya is part of the snake which can be derived from the simultaneously setting constellations (663).

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.

Pamias and Zucker (2013, 121-125): Hydra to which also belongs the Cup and the Raven

Var. 1 (Περὶ τοῦ Ὕδρου, ἐφ ᾧ Κρατὴρ καὶ Κόραξ): This constellation has multiple meanings due to a remarkable event. The raven is associated with the cult of Apollo, as each god has a bird dedicated to them. As the gods were making a sacrifice, he was sent to fetch water from a spring to make a libation, for before the advent of wine, spring water was considered the most sacred of all; seeing a fig tree near the spring bearing unripe figs, he waited for them to ripen; after some time, when they were ripe and he had eaten the figs, realising that he had committed a sacrilege, he also seized the hydra that was in the spring and brought it along with the cup, claiming that the hydra had drunk the water from the spring day after day. But Apollo discovered the truth and imposed upon the raven a punishment commensurate with his fault: to be thirsty amongst men during this time of year, as Aristotle says in his books On the Animals; and Archelaus says much the same in his On the Particular Natures.

Var. 2 (Ὕδρου ἐν ᾧ Κρατ<ὴρ καὶ Κόραξ>): This constellation is plural [a super-constellation] because of one remarkable event. The raven is associated with the cult of Apollo, as a bird is dedicated to each of the gods. As the gods were performing a sacrifice, he was sent to fetch water from a spring for a libation; seeing a fig tree near the spring bearing unripe figs, he waited for them to ripen; after some time, when they were ripe and he had eaten the figs, realising that he had committed a sacrilege, he also seized the hydra that was in the fountain and brought it along with the cup, claiming that the hydra had drunk the water from the spring day after day. But Apollo discovered what had happened and imposed upon the raven a punishment commensurate with his offence: to be thirsty amongst men during this time of year, as Aristotle states in his books On Animals. To leave a clear reminder of the sacrilege that had been committed against the gods, Apollo depicted and placed among the constellations the Hydra, the Crater, and the Raven, which cannot drink from it nor approach it.

The Hydra has three bright stars at the tip of its head, six on its first coil, the last of which is bright, three on the second coil, four on the third, two on the fourth, and nine dim stars stretching from the fifth coil to the tail. Twenty-seven in all.

Corvus is situated on the tail of Hydra and faces west. It has one dim star on its beak, two on its wing, two on its rump, and one at the tips of its legs. Seven in all.

Crater is situated on Hydra, some distance from the coil, and is tilted towards the knees of Virgo. Crater has two dim stars on the rim, two in the centre of the Bowl, and two at the base. Six in total.

Eratosthenes's star catalogue can be reconstructed from the list of stars he mentions in the last section of each of the constelllation descriptions. Hoffmann (2017) made such a catalogue and used it for computational comparison with Hipparchus's, Ptolemy's and Babylonian data; it is based on the edition and translation by Pamias and Geus (2007) and presented here in English translation.

erat.Cat.ID	constStarID	starName	ident.Bayer	ident.HIP	certainty
655	1	three bright stars at the tip of the head [of the Water Serpent]	zeta Hya	43813	1
656	2	three bright stars at the tip of the head [of the Water Serpent]	eps Hya	43109	1
657	3	three bright stars at the tip of the head [of the Water Serpent]	delta Hya	42313	1
658	4	six on the first coil [of the Water Serpent]	omega Hya	44659	1
659	5	six on the first coil [of the Water Serpent]	theta Hya	45336	1
660	6	six on the first coil [of the Water Serpent]	tau1 Hya	46509	1
661	7	six on the first coil [of the Water Serpent]	tau2 Hya	46776	1
662	8	six on the first coil [of the Water Serpent]	iota Hya	47431	1
663	9	six on the first coil [of the Water Serpent]; of these, the last is bright	alpha Hya	46390	1
664	10	three on the second coil [of the Water Serpent]	lambda Hya	49841	1
665	11	three on the second coil [of the Water Serpent]	ups1 Hya	48356	1
666	12	three on the second coil [of the Water Serpent]	26 Hya	45751	1
667	13	four on the third [coil of the Water Serpent]		48615	2
668	14	four on the third [coil of the Water Serpent]	mu Hya	51069	2
669	15	four on the third [coil of the Water Serpent]	phi Hya	52085	2
670	16	four on the third [coil of the Water Serpent]	nu Hya	52943	2
671	17	two on the fourth [coil of the Water Serpent]	xi Hya	56343	2
672	18	two on the fourth [coil of the Water Serpent]	chi1 Hya	54204	2
673	19	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail		57047	2
674	20	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail		55756	2
675	21	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail		55588	2
676	22	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail	omikron Hya	56922	2
677	23	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail	beta Hya	57936	2
678	24	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail	alpha Crv	59199	2
679	25	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail	beta Crv	61359	2
680	26	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail	gam Hya	64962	1
681	27	nine dim stars on the fifth coil [of the Water Serpent] extending to the tail	pi Hya	68895	1
682	1	the Raven on its tail [of the Water Serpent] has a dim star on its beak [facing west]	alpha Crv	59199	2
683	2	the Raven[…] two on the wing	eps Crv	59316	2
684	3	the Raven[…] two on the wing	gam Crv	59803	2
685	4	the Raven[…] two on the tail	delta Crv	60965	2
686	5	the Raven[…] two on the tail	eta Crv	61174	2
687	6	the Raven[…] one on each tip of the foot	beta Crv	61359	2
688	7	the Raven[…] one on each tip of the foot	6 Crv	60425	2
689	1	the Cup [at a considerable distance from the first coil of the Hydra, inclined toward the knees of Virgo] has two dim stars on the rim	eps Crt	55687	2
690	2	the Cup has two dim stars on the rim	zeta Crt	57283	2
691	3	two in the middle [of the Cup]	delta Crt	55282	1
692	4	two in the middle [of the Cup]	gam Crt	55705	1
693	5	two near the bottom [of the Cup]	beta Crt	54682	2
694	6	two near the bottom [of the Cup]	alpha Crt	53740	2

Hipparchus

Rising & Setting

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.

Star at the Tip of the Tail

• 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°.

Hipparchus's "lost" star Catalogue

The star catalogue of Hipparchus is not preserved. Yet, several scholars have reconstructed it in the past century: Vogt (1925), Grasshoff (1990), Hoffmann (2017) and Glover (2026). Grasshoff's catalogue and computations are not published digitally, Hoffmann published three versions of the Manitius+Hoffmann star lists in the CDS VizieR "catalog of catalogs", and Glover printed the star lists constellationwise in his book.

Hipparchus's star in Aquarius (Glover 2026)

hipp.Cat.ID	constStarID	starName	ident.Bayer	ident.HIP	concordance
322	1		α Hya	46390	CPAE
323	2		β Hya	57936	CPAE
324	3		γ Hya	64962	CPAE
325	4		δ Hya	42313	CPAE
326	5		ε Hya	43109	CPAE
327	6		ζ Hya	43813	CPAE
328	7		η Hya	42799	CPAE
329	8		θ Hya	45336	CPAE
330	9		ι Hya	47431	CPAE
331	10		κ Hya	47452	CPAE
332	11		λ Hya	49841	CPAE
333	12		μ Hya	51069	CPAE
334	13		ν Hya (Crt)	52943	CPAE
335	14		ξ Hya	56343	CPAE
336	15		ο Hya	56922	CPAE
337	16		π Hya	68895	CPAE
338	17		ρ Hya	43234	CPAE
339	18		σ Hya	42402	CPAE
340	19		τ Hya (τ1)*	46509	CPAE
341	20		τ Hya (τ2)*	46776	CPAE
342	21		υ Hya (υ1)*	48356	CPAE
343	22		υ Hya (υ2)*	49402	CPAE
344	23		χ1 Hya	54204	CPAE
345	24		ψ Hya	64166	CPAE
346	25		ω Hya	44659	CPAE
347	26		k Hya	70306	CPAE

Hyginus, Astronomica

This is the sign on which the Crow sits and over which the Bowl is placed. The following reason has been handed down: When Apollo was sacrificing, the crow, who was under his guardianship, was sent to a spring to get some pure water. Seeing several trees with their figs not yet ripe, he perched on one of them waiting for them to ripen. After some days when the figs had ripened and the crow had eaten some, Apollo, who was waiting, saw him come flying in haste with the bowl full of water. For this fault of tardiness Apollo, who had had to use other water because of the crow's delay, punished him in this way. As long as the figs are ripening, the crow cannot drink, because on those days he has a sore [?] throat,. So when the god wished to illustrate the thirst of the crow, he put the bowl among the constellations, and placed the water-snake underneath to delay the thirsty crow. For the crow seems to peck at the end of its tail to be allowed to go over to the bowl.

Istros and several others have said that the Crow was Coronis, daughter of Phlegyas. She bore Aesculapius to Apollo, but after Ischys, son of Elatus, had lain with her, the crow, which had noted it, reported it to Apollo. For his unpleasant news Apollo changed him to black instead of his former white color, and transfixed Ischys with his arrows.

About the Bowl Phylarchus writes this tale: In the Chersonnese near Troy where many have said the tomb of Protesilaus is located, there is a city, Elaeusa by name. When a certain Demophon was ruling there, a sudden plague fell on the land with a strange death-rate among the citizens. Demophon, greatly disturbed by this, sent to the oracle of Apollo seeking a remedy, and was told that every year one girl of noble rank should be sacrificed to their household gods. Demophon, passing over his own daughters, would choose by lot one of the daughters of the nobles, and kept doing this until his scheme offended a certain man of highest rank. He said he wouldn't allow his daughter to be entered in the drawing unless the daughters of the king were included. The king, angered by this, killed the noble's daughter without drawing of lots. This deed Mastusius, father of the girl, for a time out of patriotism pretended he did not resent, for the girl might have perished if the lots had been taken. Little by little, time led the king to forget. When the girl's father had shown himself to be on most friendly terms with the king, he said he was going to make a solemn sacrifice and invited the king and his daughters to join the celebration. The king, suspecting nothing, sent his daughters ahead; since he was busy with a state affair, he would come later. When this happened as Mastusius wished, he killed the king's daughters, and mixing their blood with wine in a bowl, bade it be given as a drink to the king on his arrival. The king asked for his daughters, and when he learned what had happened, he ordered Mastusius and the bowl to be thrown into the sea. The cape where he was thrown, to memorialize him is called Mastusian; the harbour still is called the Bowl. Astronomers of old pictured it in the stars, so that men might remember that no one can profit from an evil deed with impunity, nor can hostilities often be forgotten. Some, with Eratosthenes, say that it is the bowl Icarus used when he showed wine to men; others the jar into which Mars was thrown by Otus and Ephialtes. (Mary Ward 1960)

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 the rear of these, 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 rearmost of all, about on the cheek	zet Hya
τῶν ἐv τῇ έκφύσει του τραχήλου β ὁ ἡγούμενος	6	The more advanced of the 2 stars in the place where the neck joins [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 together 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 of the 3 stars to the rear, after 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 advanced of the next 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 after [i.e.  to the rear of]  the base of Crater	beta Crt
ὁ νοτιώτερος αυτῶν	20	The southernmost of them	chi1 Hya
τῶv μετα τούτους γ ὡς ἐν τριγώνῳ ὁ ἡγούμενος	21	The most advanced of the 3 stars after these, as it were in a triangle	xi Hya
ὁ μέσος αὐτῶν και νοτιώτερος	22	The middle and southernmost one	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 section 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. 6-15]	epsilon Sex

Stars within the Constellation Area

id	Label	IAU design.	description	Vmag
1	Alphard	HIP 46390	Constellation lines	1.97
2	Gienah	HIP 59803	Inside the hull	2.58
3	Kraz	HIP 61359	Inside the hull	2.64
4	Algorab	HIP 60965	Inside the hull	2.94
5	ϵ Corvi	HIP 59316	Inside the hull	2.98
6	γ Hydrae	HIP 64962	Constellation lines (Vertex)	3
7	ζ Hydrae	HIP 43813	Constellation lines	3.1
8	ν Hydrae	HIP 52943	Constellation lines (Vertex)	3.11
9	π Hydrae	HIP 68895	Constellation lines (Vertex)	3.28
10	Ashlesha	HIP 43109	Constellation lines	3.38
11	δ Crateris	HIP 55282	Inside the hull	3.56
12	λ Hydrae	HIP 49841	Inside the hull	3.61
13	μ Hydrae	HIP 51069	Constellation lines	3.81
14	θ Hydrae	HIP 45336	Constellation lines (Vertex)	3.91
15	Ukdah	HIP 47431	Inside the hull	3.91
16	Alchiba	HIP 59199	Inside the hull	4.01
17	γ Crateris	HIP 55705	Inside the hull	4.06
18	Alkes	HIP 53740	Inside the hull	4.07
19	Zhang	HIP 48356	Constellation lines	4.11
20	δ Hydrae	HIP 42313	Constellation lines (Vertex)	4.131
21	η Hydrae	HIP 42799	Constellation lines (Vertex)	4.3
22	ρ Hydrae	HIP 43234	Inside the hull	4.337
23	Minchir	HIP 42402	Constellation lines (Vertex)	4.43
24	β Crateris	HIP 54682	Inside the hull	4.449
25	τ 2 Hydrae	HIP 46776	Constellation lines (Vertex)	4.548
26	υ 2 Hydrae	HIP 49402	Constellation lines (Vertex)	4.588
27	τ 1 Hydrae	HIP 46509	Constellation lines	4.6
28	ζ Crateris	HIP 57283	Inside the hull	4.706
29	ϵ Crateris	HIP 55687	Inside the hull	4.802
30	U Hya	HIP 52009	Inside the hull	4.82
31	ϕ 3 Hydrae	HIP 52085	Constellation lines	4.903
32	ψ Hydrae	HIP 64166	Inside the hull	4.934
33	R Hya	HIP 65835	Inside the hull	4.97
34	ω Hydrae	HIP 44659	Constellation lines	4.981
35	κ Hydrae	HIP 47452	Constellation lines	5.052
36	λ Crateris	HIP 55598	Inside the hull	5.09
37	II Hya	HIP 57613	Inside the hull	5.11
38	η Crateris	HIP 58188	Inside the hull	5.16
39	ζ Corvi	HIP 60189	Inside the hull	5.21
40	23 Hya	HIP 45527	Inside the hull	5.23
41	ϵ Sextantis	HIP 50414	Inside the hull	5.24
42	-	HIP 53252	Inside the hull	5.24
43	31 Crt	HIP 58587	Inside the hull	5.264
44	303 G. Hya	HIP 58082	Inside the hull	5.272
45	200 G. Hya	HIP 49809	Inside the hull	5.296
46	-	HIP 46404	Inside the hull	5.32
47	328 G. Hya	HIP 61621	Inside the hull	5.41
48	* gam Sex A	HIP 48437	Inside the hull	5.43
49	-	HIP 52737	Inside the hull	5.44
50	330 G. Hya	HIP 62131	Inside the hull	5.454
51	* bet Hya B	HIP 57936	Constellation lines	5.47
52	3 Crv	HIP 59394	Inside the hull	5.47
53	ι Crateris	HIP 56802	Inside the hull	5.48
54	-	HIP 54029	Inside the hull	5.511
55	33 Hya	HIP 46982	Inside the hull	5.548
56	-	HR 3750	Inside the hull	5.56
57	-	HIP 51046	Inside the hull	5.56
58	28 Hya	HIP 46221	Inside the hull	5.579
59	225 G. Hya	HIP 51491	Inside the hull	5.58
60	* 17 Crt A	HIP 56280	Inside the hull	5.58
61	195 G. Hya	HIP 49569	Inside the hull	5.582
62	18 Sex	HIP 49865	Inside the hull	5.618
63	92 G. Hya	HIP 44356	Inside the hull	5.627
64	-	HIP 61015	Inside the hull	5.63
65	-	HIP 53316	Inside the hull	5.651
66	6 Crv	HIP 60425	Inside the hull	5.658
67	333 G. Hya	HIP 62500	Inside the hull	5.658
68	* 17 Crt B	HIP 56280	Inside the hull	5.671
69	236 G. Hya	HIP 51933	Inside the hull	5.71
70	351 G. Hya	HIP 66400	Inside the hull	5.78
71	41 Sex	HIP 52980	Inside the hull	5.791
72	357 G. Hya	HIP 67143	Inside the hull	5.795
73	-	HIP 59728	Inside the hull	5.807
74	-	HIP 56078	Inside the hull	5.813
75	-	HIP 52948	Inside the hull	5.842
76	300 G. Hya	HIP 57841	Inside the hull	5.85
77	-	HIP 53778	Inside the hull	5.857
78	329 G. Hya	HIP 61720	Inside the hull	5.866
79	-	HIP 53723	Inside the hull	5.879
80	-	HIP 58158	Inside the hull	5.893
81	17 Sex	HIP 49812	Inside the hull	5.901
82	κ Crateris	HIP 55874	Inside the hull	5.923
83	25 Sex	HIP 50885	Inside the hull	5.97
84	-	HIP 60157	Inside the hull	5.97
85	-	HIP 61688	Inside the hull	5.982
86	136 G. Hya	HIP 46288	Inside the hull	5.985
87	ϕ 2 Hydrae	HIP 51905	Inside the hull	6.012
88	6 Sex	HIP 48341	Inside the hull	6.016
89	209 G. Hya	HIP 50536	Inside the hull	6.027
90	-	HIP 61951	Inside the hull	6.03
91	-	HIP 51302	Inside the hull	6.032
92	-	HIP 56364	Inside the hull	6.044
93	243 G. Hya	HIP 52113	Inside the hull	6.045
94	-	HIP 59895	Inside the hull	6.07
95	-	HIP 50292	Inside the hull	6.075
96	322 G. Hya	HIP 60603	Inside the hull	6.081
97	-	HIP 54214	Inside the hull	6.086
98	-	HIP 49293	Inside the hull	6.097
99	ψ Crateris	HIP 54742	Inside the hull	6.105
100	157 G. Hya	HIP 46869	Inside the hull	6.113
101	155 G. Hya	HIP 46840	Inside the hull	6.12
102	-	HIP 57732	Inside the hull	6.122
103	153 G. Hya	HIP 46744	Inside the hull	6.123
104	154 G. Hya	HIP 46768	Inside the hull	6.124
105	146 G. Hya	HIP 46529	Inside the hull	6.126
106	10 Hya	HIP 42931	Inside the hull	6.127
107	217 G. Hya	HIP 50790	Inside the hull	6.13
108	81 G. Hya	HIP 43902	Inside the hull	6.131
109	105 G. Hya	HIP 45167	Inside the hull	6.131
110	MO Hya	HIP 62788	Inside the hull	6.141
111	-	HIP 56293	Inside the hull	6.16
112	NS Hya	HIP 44738	Inside the hull	6.17
113	TU Crv	HIP 61496	Inside the hull	6.184
114	LV Hya	HIP 58272	Inside the hull	6.189
115	VX Crt	HIP 56899	Inside the hull	6.19
116	-	HIP 56901	Inside the hull	6.198
117	-	HIP 51490	Inside the hull	6.2
118	-	HIP 57079	Inside the hull	6.2
119	356 G. Hya	HIP 67071	Inside the hull	6.205
120	-	HIP 49900	Inside the hull	6.225
121	245 G. Hya	HIP 52391	Inside the hull	6.228
122	-	HIP 56245	Inside the hull	6.228
123	199 G. Hya	HIP 49802	Inside the hull	6.23
124	197 G. Hya	HIP 49689	Inside the hull	6.244
125	159 G. Hya	HIP 46893	Inside the hull	6.25
126	* psi Crt A	HIP 54742	Inside the hull	6.25
127	-	HIP 61270	Inside the hull	6.254
128	-	HIP 58574	Inside the hull	6.255
129	147 G. Hya	HIP 46543	Inside the hull	6.257
130	144 G. Hya	HIP 46504	Inside the hull	6.27
131	-	HIP 60809	Inside the hull	6.294
132	-	HR 4935	Inside the hull	6.3
133	337 G. Hya	HIP 63243	Inside the hull	6.303
134	-	HIP 50584	Inside the hull	6.308
135	37 Hya	HIP 47427	Inside the hull	6.32
136	-	HIP 51490	Inside the hull	6.32
137	-	HR 4935	Inside the hull	6.32
138	-	HIP 48413	Inside the hull	6.329
139	-	HIP 53259	Inside the hull	6.34
140	-	HIP 54048	Inside the hull	6.343
141	71 G. Hya	HIP 43570	Inside the hull	6.35
142	172 G. Hya	HIP 47454	Inside the hull	6.356
143	-	HIP 53849	Inside the hull	6.36
144	-	HIP 50552	Inside the hull	6.361
145	50 G. Hya	HIP 42854	Inside the hull	6.362
146	-	HIP 54749	Inside the hull	6.378
147	34 Hya	HIP 47249	Inside the hull	6.39
148	-	HIP 61208	Inside the hull	6.39
149	* gam Sex B	HIP 48437	Inside the hull	6.4
150	332 G. Hya	HIP 62448	Inside the hull	6.405
151	308 G. Hya	HIP 58436	Inside the hull	6.416
152	-	HIP 48351	Inside the hull	6.42
153	-	HIP 50893	Inside the hull	6.42
154	-	HIP 56830	Inside the hull	6.42
155	320 G. Hya	HIP 60468	Inside the hull	6.42
156	364 G. Hya	HIP 68224	Inside the hull	6.42
157	54 G. Hya	HIP 42981	Inside the hull	6.43
158	274 G. Hya	HIP 54703	Inside the hull	6.43
159	294 G. Hya	HIP 57001	Inside the hull	6.44
160	258 G. Hya	HIP 53387	Inside the hull	6.444
161	166 G. Hya	HIP 47242	Inside the hull	6.46
162	-	HIP 48839	Inside the hull	6.46
163	299 G. Hya	HIP 57749	Inside the hull	6.477
164	348 G. Hya	HIP 65969	Inside the hull	6.478
165	233 G. Hya	HIP 51852	Inside the hull	6.479
166	297 G. Hya	HIP 57507	Inside the hull	6.48
167	-	HIP 59742	Inside the hull	6.49
168	346 G. Hya	HIP 65682	Inside the hull	6.49
169	-	HIP 50693	Inside the hull	6.499
170	-	HIP 51656	Inside the hull	6.5
171	342 G. Hya	HIP 64375	Inside the hull	6.5

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.
• 
  Hydra with Crater and Corvus on the Mercator Globe (1551)
• 
  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.
• 
  (1952) H.A. Rey's stick figure of Hydra
• 
  (1988) O. Hlad's stick figure of Hydra

Arabic

Hydra in Laffitte (2025, 365). Fig. 77 : Ὕδρη / Hydrē, « l’Hydre », et Κρατήρ / Kratēr, « la Coupe »,

– al-Šuğā^c, « le Gros Serpent », et al-Bāṭiyya, « la Petite Jarre » (ap. Urania’s Mirror)

Dhanab al Shuja (γ Hya : 2,99) / ذنب الشجع

Recently introduced, this name is the Arabic Ḏanab al-Šuğā^c, ‘the Tail of the Hydra’, in an Arabic or Persian catalogue using Greek formatting and as yet unidentified. NB : We have fī aṣal al-ḏanab, ‘at the root of the tail,’ and ^cand al-ḏanab, ‘at the tail,’ π/ γ Hya, and ^calā ṭaraf al-ḏanab, ‘at the tip of the tail,’ π/ γ Hya, c/ the translators of Ptolemy, then al-Ṣūfī and al-Battānī, but Ṭarf al-ḏanab, ‘the tip of the tail’, c/ al-Bīrūnī. However, this name does not appear in any known text. Abs. c/ Allen. Dhanab al-Shuja, Pultar, Dhanab al-Shuja and Cauda Hydrae.

Mythology

Greek/ Greco-Roman folklore

Eratosthenes recounts that the raven was sent by the gods to fetch water for a sacrifice. As long as there was no wine, spring water was considered the most sacred drink. However, on its way, the raven saw a fig tree with green fruit, waited there until they ripened, and ate its fill of the delicious figs. In order to have an excuse for the delay to the gods, he grabbed the water snake in the spring, carried it together with the crater to the gods, and claimed that it had drunk the water he had been sent to fetch.

Apollo, a god of light, divination, and truth, saw through the deception. He punished the raven by condemning it to live among humans and suffer from thirst for a similar length of time. He also placed the image of the raven in the sky, together with the crater and the water snake, as a warning against deception and slander.

While the water snake is innocent in Eratosthenes' version, according to another legend, the Hydra is the monster that was fought and defeated by Heracles. The story is part of the Hercules myth, but the constellation Hercules is far away from the Hydra and has nothing to do with either the raven or the crater. This seems to be a later ancient (Roman?) reinterpretation, because Eratosthenes' version does not seem particularly convincing when looking at the sky.

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 "highest" which doesn't apply here).

Weblink

• Warburg Institute Iconographic Database – Hydra
• Ian Ridpath's Star Tales – Hydra

References

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