R.H. Allen:
Star Names

Ian Ridpath:
Star Tales

Universe Guide

Sea and Sky:




Star Lore

Hydra is a constellation in the southern celestial hemisphere.

It is the largest one of all constellations.

Ancient Babylon

In the Babylonian star catalogues, the constellation later known as Hydra (including β Cancri, the bottom star of the constellation Cancer) was listed as MUL.DINGIR.MU.

In Sumerian and Babylonian Mythology, the constellation was related to Nirah, a snake god. On boundary stones (right), Nirah often appeared on the upper edge, "enclosing" the stone document (which usually was a real estate deed).

There were two "serpent" constellations in Babylonian astronomy, known as Muḫuu and Bamu. While Bamu later became the Greek Serpens, Muḫuu became the Hydra. The connection can be traced back to a Kassite boundary stone (right), on which Hydra and Leo are depicted in the same way as they later appear on the Dendera zodiac.

The Muḫuu was mythological hybrid; it is a scaly animal with hind legs resembling the talons of an eagle, lion-like forelimbs, a long neck and tail, a horned head, a snake-like tongue, and a crest. Legends about it date back to the sixth century BC, when it appeared on the famous Ishtar Gate in Babylon.

The fact, that the Muḫuu appear together with real life animals like lions and aurochs indicates that the Babylonians really believed in the existence of the creature. Even the archaeologists who excavated the Ishtar Gate in 1902 first believed that they found a picture of an extinct, ancient animal.

Now, how did a Babylonian snake turn unto a seven-headed monster?

There actually is a Seven-headed Serpent in Sumerian Mythology. The creature was slain by Ninurta, the Sumerian god of farming, healing, hunting, law, scribes, and war. The Seven-headed Serpent can be traced to both the Muḫuu and the Bamu. The fight between Ninurta and the Serpent can be seen as one of the roots of the legend of the Twelve Labors of Hercules, one of which was to slay the Lernaean Hydra.

Sources: Wikipedia and J.H. Rogers: Origins of the ancient constellations

Nirah on a Babylonian boundary stone
Source: Wikipedia

Hydra and Leo on a Kassite boundary stone
(highlight by the author)
Source: J.H. Rogers

Hydra and Leo as Muḫuu on an astronomical
tablet of the Persian period

Muḫuu at Babylon's Ishtar Gate
Picture taken by the author

Ancient Greece

Ian Ridpath tells us two stories about the Hydra:

"Hydra was the creature that Heracles fought and killed as the second of his famous labors. The Hydra was a multi-headed creature, the offspring of the monster Typhon and the half-woman, half-serpent called Echidna. Hydra was thus the sister of the dragon that guarded the golden apples, commemorated in the constellation Draco.

Hydra reputedly had nine heads, the middle one of which was immortal. In the sky, though, it is shown with one head only perhaps this is the immortal one. ...

Heracles rode up to the Hydras lair in his chariot and fired flaming arrows into the swamp to force the creature into the open, where he grappled with it. The Hydra wrapped itself around one of his legs; Heracles smashed at its heads with his club but no sooner had one head been destroyed than two grew in its place. To add to Heracless worries, a huge crab scuttled out of the swamp and attacked his other foot, but Heracles stamped on the crab and crushed it. The crab is commemorated in the constellation Cancer.

Heracles called for help to his charioteer Iolaus who burned the stump of each head as soon as it was struck off to prevent others growing in its place. Finally Heracles cut off the immortal head of the Hydra and buried it under a heavy rock by the roadside. He slit open the body of the Hydra and dipped his arrows in its poisonous gall."

Source:Ian Ridpath

Herakles, Iolaos, and the Hydra on an Etruscan vase
Ca. 525 BC; Source: Wikipedia

Herakles and the Hydra on a Roman mosaic
Ca. 250 AD; Source: Wikipedia

Continuing Ian Ridpath quote:

"A second legend associates the water-snake with the constellations of the Crow (Corvus) and the Cup (Crater) that lie on its back. In this story, the crow was sent by Apollo to fetch water in the bowl, but loitered to eat figs from a tree. When the crow eventually returned to Apollo it blamed the water-snake for blocking the spring. But Apollo knew that the crow was lying, and punished the bird by placing him in the sky, where the water-snake eternally prevents him from drinking out of the bowl."

Source:Ian Ridpath
Hydra, Corvus and Crater in Urania's_Mirror (1824)
Source: Wikipedia

Ancient India

In Hindu Astronomy, the asterism forming the head of the Hydra (consisting of
δ, ε, η, ρ and σ Hydrae) constitutes the 9th Nakashtra, called Āleṣā, meaning "Clinging Star" or "Nāga."

Nāga are semi-divine deities, or a semi-divine race of half-human half-serpent beings that reside in the netherworld.

In Sanskrit, Āleṣā is written आश्लेषा.

Source: Wikipedia

6th century Naga at
Badami cave temples, Karnataka, India; Source: Wikipedia

Ancient China

In Chinese, Hydra is written 長 蛇 座.

In Chinese astronomy, the constellation stretches across seven Lunar Mansions.

The Hydra's tail is part of the First Lunar Mansion, called Jiǎo (Horn). The mansion extends into Virgo and Centaurus. It is the only Lunar Mansion in Hydra belonging to the quadrant of the Azure Dragon of the East.

The Hydra stars in this Lunar Mansion form three asterism.

Lunar Mansions in Hydra
Map based on

The stars γ and π Hydrae form an asterism called Ping, meaning "Justice." According to Ian Ridpath, these stars represent a senior law lord or appeal court judge. The two other asterisms, called Shwēi (meaning execution or executioners) and Zhènchē (meaning Battle Chariots) consist of very faint stars.

The other six Lunar Mansions are part of the Vermilion Bird of the South.

The 23rd Mansion, called Guǐ (Ghost) features only one very faint asterism called Wàich (The Outer Kitchen) in Hydra. Main star in this asterism is F Hydrae.
The asterism Liǔ, meaning "willow" gave its name to the 24th Lunar Mansion. It consists of the stars forming the "Head" of the Hydra, including δ, ε, η, ρ, σ, ζ, θ and ω Hydrae. In Chinese culture, the willow is a traditional symbol of mourning and of rebirth.

The next three asterisms too gave their names to their respective Lunar Mansions.

Xīng (Star) represents the 25th Lunar Mansion. The relatively bright stars Alphard (α Hya) and Ukdah (ι Hya) are part of that asterism. Ian Ridpath tells us that Xīng marks the neck of the Red Bird and Alphard itself was known as Niao, the Bird Star.

According to Wikipedia, another name for Alphard was Shshǒuyī, meaning the "leading" or the "stand alone" star.

Zhang, a name describing an outstretched net, is the name of the 26th Lunar Mansion. The asterism of the same name consists, among others, of λ, κ and φ Hydrae.

In ancient China, the star υ
1 Hydrae was called Zhāngsùyī. In 2017, the IAU officially named the star after the 26th Lunar Mansion, Zhang.

The 27th Lunar Mansion is called (Wing). It contains, among others, ν and χ Hydrae. The asterism by the same name may represent the wings of the Red Bird.

Zhn, the 28th Lunar Mansion represents a chariot. Much of that Lunar Mansion is located in the constellations Corvus and Centaurus. Only three faint asterisms, Jūnmn (Military Gate), Tǔ sīkōng (Master of Construction) and Qīngqiū (Green Hills) are part of Hydra. The main stars in the Hydra part of the 28th Lunar Mansion are β and ξ Hydrae.

Sources: Wikipedia and Ian Ridpath

Vermilion Bird of the South
Source: NIx's Mixed Bag

Vermilion Bird of the South
K. Herrmann


To the Navajo in the southwest of North America, the stars of the constellations Corvus and Hydra, together with the star Spica in the constellation Virgo form Hastiin Sik'ai', the "Squatting Man" or "The Man With His Legs Spread Apart."

Hastiin Sik'ai' is a leader in the sky, which is depicted in that three other constellations follow his trail in the sky: tse Etsoh, the "First Great One" (in the constellations Sagittarius and Libra), tse Ats'oos, the "First Slender One" (Orion) and Dilyehe, the "Planting Stars" (the Pleiades).

Source: Navajo Astronomy

Hastiin Sik'ai'
Source: Navajo Astronomy

Flags and other National Symbols

The center of the Brazilian flag presents the night sky as it would have been on November 15, 1889 at 08:30 over Rio de Janeiro. Each star corresponds to a Brazilian Federate Unit, sized in proportion relative to its geographic size.

Alphard, the brightest star in the constellation Hydra symbolizes the state of Mato Grosso do Sul, while
γ Hydrae symbolizes the state of Acre.

Source:Wikipedia, Flags of the World - Astronomy of the Brazilian Flag

Modern Day Fiction

In The Deadly Years, an episode of Star Trek:_The Original Series, the crew visits the (fictional) planet Gamma Hydra IV.

The planet is stated to be six light-years away from a binary star system where the first battle of the FederationKlingon War of 22562257 is fought.


Gamma Hydra IV

Modern Day Applications

The Toyota Alphard, manufactured since 2002, is a minivan named after the star Alphard (α Hyd).


Toyota Alphard
Source: Wikipedia

Back to Star Lore
Start Page

Back to Mythology
Start Page

Back to Space Page

Back to English
Main Page

Back to Start Page