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Hydra (constellation)

 
Hydra (constellation)

 
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Hydra (constellation)
 
 
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Hydra is the largest of the 88 modern constellation
Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
s, measuring 1303 square degrees. It has a long history, having been included among the 48 constellations listed by the 1st century astronomer Ptolemy
Ptolemy

Claudius Ptolemaeus , known in English as Ptolemy , was a Roman Greek mathematics, Greek astronomy, geographer and astrologer. He lived in History of Roman Egypt, and was probably born there in a town in the Thebaid called Ptolemais Hermiou; he died in Alexandria around 168 AD....
. It is commonly represented as a water snake
Water snake

Different snakes are called water snakes. Most are colubrids. Examples include:* Helicops species, including:** Helicops angulatus* Liophis species, including:...
.

ite its size, Hydra contains only one reasonably bright star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
, Alphard
Alphard

name=Alpha Hydrae }}Alphard is the brightest star in the constellation Hydra , marking the heart of the snake.Alphard is an orange giant star....
 (a Hya, 30 Hya), which is of apparent magnitude
Apparent magnitude

The apparent magnitude of a celestial body is a measurement of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the Earth's atmosphere....
 1.98. Alphard
Alphard

name=Alpha Hydrae }}Alphard is the brightest star in the constellation Hydra , marking the heart of the snake.Alphard is an orange giant star....
 ("the solitary one") is actually a double star.






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Hydra is the largest of the 88 modern constellation
Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
s, measuring 1303 square degrees. It has a long history, having been included among the 48 constellations listed by the 1st century astronomer Ptolemy
Ptolemy

Claudius Ptolemaeus , known in English as Ptolemy , was a Roman Greek mathematics, Greek astronomy, geographer and astrologer. He lived in History of Roman Egypt, and was probably born there in a town in the Thebaid called Ptolemais Hermiou; he died in Alexandria around 168 AD....
. It is commonly represented as a water snake
Water snake

Different snakes are called water snakes. Most are colubrids. Examples include:* Helicops species, including:** Helicops angulatus* Liophis species, including:...
.

Notable features


Stars

Despite its size, Hydra contains only one reasonably bright star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
, Alphard
Alphard

name=Alpha Hydrae }}Alphard is the brightest star in the constellation Hydra , marking the heart of the snake.Alphard is an orange giant star....
 (a Hya, 30 Hya), which is of apparent magnitude
Apparent magnitude

The apparent magnitude of a celestial body is a measurement of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the Earth's atmosphere....
 1.98. Alphard
Alphard

name=Alpha Hydrae }}Alphard is the brightest star in the constellation Hydra , marking the heart of the snake.Alphard is an orange giant star....
 ("the solitary one") is actually a double star. The other main named star in Hydra is Sigma, s, Hydrae, which also has the name of Minaruja, from the Arabic for snake's nose. At magnitude 4.54, it is rather dim. The head of the snake corresponds to the Ashlesha nakshatra
Nakshatra

A nakshatra or lunar mansion is one of the 27 or 28 divisions of the sky, identified by the prominent star in them, that the Moon passes through during its monthly cycle, as used in Hindu astronomy and Jyotisha....
, the lunar zodiacal constellation in Indian astronomy.

R Hydrae
R Hydrae

R Hydrae is a Mira variable in the constellation Hydra .The apparent magnitude of R Hydrae varies over a orbital period of 389 days, between 3.21 and 11.00....
 is a Mira variable
Mira variable

Mira variables, named after the star Mira , are a class of pulsating variable stars characterized by very red colors, pulsation periods longer than 100 days, and light amplitudes greater than one Apparent magnitude....
 star that ranges in magnitude between 3.5, when it can be visible to the naked eye, to 10.9, when a telescope
Telescope

A telescope is an instrument designed for the observation of remote objects by the collection of electromagnetic radiation. The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century....
 is required to see it.

There are several double star
Double Star

Double Star is a science fiction novel by Robert A. Heinlein, first serialized in Astounding Science Fiction and published in hardcover the same year....
s of interest in Hydra. Epsilon Hydrae
Epsilon Hydrae

Epsilon Hydrae is a Stellar classification, third-magnitude star in the constellation Hydra . The Vedic Sanskrit name Ashlesha , meaning "The Embracing One", is sometimes applied to this star....
 (e Hya) is a binary star
Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star or secondary....
 with components of magnitudes 3.3 and 6.8, separated by 2.7 arcseconds. N Hydrae (N Hya) is a pair of stars of magnitudes 5.8 and 5.9. Struve 1270 (S1270) consists of a pair of stars, magnitudes 6.4 and 7.4.

The constellation also contains the radio source Hydra A.

Deep sky objects


Hydra contains three Messier objects. M83, also known as the Southern Pinwheel Galaxy, is located on the border of Hydra and Centaurus
Centaurus

Centaurus is a bright constellation in the celestial sphere. list of constellations by area constellations in the sky, Centaurus was included among the 48 constellations listed by of 1st century astronomer Ptolemy, and it remains one of the 88 modern constellations....
, M68
Messier 68

Messier 68 is a globular cluster in the Hydra constellation. It was discovered by Charles Messier in 1780. M68 is at a distance of about 33,000 light-years away from Earth....
 is a globular cluster
Globular cluster

A globular cluster is a sphere collection of stars that orbits a Galactic Center as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers....
 near M83, and M48
Messier 48

Messier 48 is an open cluster in the Hydra constellation. It was discovered by Charles Messier in 1771. M48 is visible to the naked eye under good atmospheric conditions. Its age is estimated to amount 300 million years....
 is an open star cluster in the western end of the serpent.

Mythology

The shape of Hydra resembles a twisting snake
Snake

Snakes are elongate legless carnivore reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears....
, and features as such in some Greek myths. One myth associates it with a water snake that a crow
Crow

The true crows are large passerine birds that form the genus Corvus in the family Corvidae. Ranging in size from the relatively small dove-sized jackdaws to the Common Raven of the Holarctic region and Thick-billed Raven of the highlands of Ethiopia, the 40 or so members of this genus occur on all temperate continents and several offsh...
 served Apollo
Apollo

In Greek mythology and Roman mythology, Apollo , is one of the most important and many-sided of the Twelve Olympians. The ideal of the kouros , Apollo has been variously recognized as a god of light and the sun; truth and prophecy; archery; medicine and healing; music, poetry, and the arts; and more....
 in a cup when it was sent to fetch water; Apollo saw through the fraud, and angrily cast the crow, cup, and snake, into the sky. The origin of this story is likely to be the juxtaposition of this constellation with those of Crater
Crater (constellation)

Crater is a constellation. Its name is Latin for cup, and in Greek mythology it is identified with the cup of the god Apollo . It was one of the 48 constellations listed by the 1st century astronomer Ptolemy, and remains one of the 88 modern constellations....
, and Corvus
Corvus (constellation)

Corvus is a small constellation in the southern sky. Its name is Latin for raven or crow. It includes only 11 stars visible to the naked eye . It was one of the 48 constellations listed by Ptolemy, who only counted 7 stars, and it remains one of the 88 modern constellations....
, in the area of the sky known as the Sea
Sea (astronomy)

The Sea or the Water is an area of the sky in which many water-related, and few land-related, constellations occur.Most of these constellations are named by Ptolemy:...
.

The Hydra was also considered to be the Lernaean Hydra
Lernaean Hydra

In Greek mythology, the Lernaean Hydra The Hydra was the offspring of Typhon and Echidna , noisome offspring of the earth goddess, Gaia. It was said to be the sibling of the Nemean Lion, the Stymphalian birds, the Chimera ,and Cerberus....
 (as defeated by Heracles
Heracles

In Greek mythology, Heracles or Herakles meaning "glory of Hera", or "Glorious through Hera" Alcides or Alcaeus " was a hero, the son of Zeus and Alcmene, foster son of Amphitryon and great-grandson of Perseus....
 for one of his Twelve Labours) by the Greeks. Its position in the sky (below the ecliptic
Ecliptic

The ecliptic is the apparent path that the Sun traces out in the sky during the year. As it appears to move in the sky in relation to the stars, the apparent path aligns with the planets throughout the course of the year....
), together with the constellation Cancer
Cancer (constellation)

Cancer is one of the twelve constellations of the zodiac. Its name is Latin for crab and it is commonly represented as such. Its symbol is . Cancer is small and its stars are faint....
 (which lies near its head) may be the origin of parts of the myth.

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