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Hydra, The Water Monster Constellation Facts and Mythology

Hydra Constellation Star Map

Hydra (Pronounciation:Hi-dra, Abbrev:Hya, Latin:Hydrae) is a constellation, one of 88 constellations that the night sky is divided into. The sky is not divided up equally between the constellations. Hydra takes up 1302.844 sq. degrees of the night sky which equates to 3.16% of the night sky. Hydra is the 1st largest in terms of size in the night sky.

The constellation name means The Water Monster . The constellation is one of the original constellations that was devised by the Ancient Greco-Egyptian astronomer Ptolemy who lived between 90 A.D. and 168 A.D.

There are 20 stars that make up the main constellation. The hipparcos satellite scanned and detailed 3038 stars. There are 121 stars that can be seen with the naked eye in the constellation on a very clear night sky.

Hydra is not a member of the Zodiac group of twelve constellations that appear when the Sun sets. Hydra is a northern hemispheric constellation which means it can't be seen easily or at all from the southern hemisphere.

The distance to Hydra is not calculable because all the stars that make up the constellation are at various distances. The best answer for distance to Hydra is to calculate the average distance of the stars.

There are 32 Extrasolar Planets (Exoplanets) in this constellation that are detailed on this site. There is a dedicated page for exoplanets in Hydra. The current largest star so far identified in the constellation of Hydra is W Hydrae.

There are 3 deep space objects that were identified by Charles Messier in this constellation. There are no non-Messier deep space objects in this constellation that are covered at present on this site.

The image at the top right of this page was generated using Night Vision, a free to use and download application by Brian Simspon.

Hydra Star Facts

The caveat of these stars are that they are catalogued on this site. If you know of a star that is nearer or further then do let me know in the comments and I'll add it to the site. The stars mentioned are from the Hipparcos catalogue or have been added because of their special status.

Wise 0855-0714, Nearest Star

The nearest star to Earth is Wise 0855-0714 which is roughly about 2.31 Light Years from the Earth. The nearest star to the Earth with an exoplanet is HD 90156 which is about 72.9 Light Years.

S Hydrae, Furthest Star

The furthest star that is located in the constellation is S Hydrae and it is 108721.1 light years away from the Sun. The furthest figure is derived from either the 1997 or 2007 Hipparcos star catalogue parallax figure and it has been known to produce distances that are wrong.

Alphard, Brightest Star in Hydra

The brightest star in Hydra is Alphard and is located about 59.00 light years from the Sun. The star has a apparent magnitude of 1.99 but an absolute magnitude of -1.72 when the star is viewed from a distance of 10 Parsecs or 32.6 Light Years. The star is recognised as being the brightest in the constellation as it has the Bayer status of Alpha.

HD 100623, Dimmest Visible Star

The dimmest star that can be seen in Hydra with the naked eye is HD 100623. The dim star has an apparent magnitude of 5.96. The dimmest star that a person is able to see with their naked eye is 6.0 magnitude based on the table in the reference. Ref: University of Michigan.

R, U, V Hydrae

The constellation has a number of interesting variable stars labelled with a single letter. The brightest of these stars is U Hydrae which is a Magnitude 4 star and therefore is easy to see without visual aids. R Hydrae is on the cusp of visibility at Magnitude 6.4. V Hydrae is the only one of the three that can't be seen by the naked eye, you will need a good pair of binoculars to see.

All three stars are too far away for anyone to see the variability in the stars, you would need a very good telescope in order to see the star varying in size.

SDSS 0907-0245

The snappily named SDSS 0907-0245 is an example of a Hypervelocity Stars, a star that is moving at above normal speed for a star. It is a star that got too close to the centre of the galaxy and thrown out. It will eventually become a rogue star, a star that is not within a galaxy.

Size and Location of Hydra

Hydra is the undefeated largest constellation in the sky by area. It accounts for just over 3% which might seem a small amount but you need to take into account it is one of 88 constellations so it takes up more than its fair share of space. Hydra is a southern constellation lying south of the equator.

Hydra Constellation

Hydra was a multi-headed sea creature that inhabited the lake near Lerna in the Argoid. It was alleged the lake had an entrance to the Underworld which it guarded. When one head was chopped off, another two would grow in its place. The only way of killing it was to chop off its head and setting fire to the severed neck. Hercules would chop off the head and Iolaus, a companion would set fire. During the fight, Hera set Cancer the crab to make things harder for Hercules.

Hydra Facts

Is a Zodiac Sign No
Largest StarW Hydrae
Brightest StarAlphard
Area1302.844 sq. deg.
Percentage of Night Sky3.16%
Size Position1st
Hemisphere Northern
Site Exoplanet Count32
Meteor Shower Count16
Nearest StarWise 0855-0714
Nearest Star with Exoplanet(s)HD 90156
Largest StarW Hydrae
Brightest StarAlphard
Dimmest StarHD 100623
Furthest StarS Hydrae
Bright Star Count121
Hipparcos Star Count3038
Main Star Count20
Messier Deep Space Object Count3
*Non-Messier Deep Space Object Count0
Bordering / Neighbouring / Surrounding ConstellationsCrater
Canis Minor

*Note: The number of Non-Messier Deep Space Object Count relates to how many are covered on this site not how many there are.

List of Deep Space Objects (Galaxies, Nebulas, Supernovas, etc) in Hydra

NameTypeDistanceDeclinationRight Ascension
Messier 48 (NGC2548)Globular Cluster1500-05:4808h 13m 8
Messier 68 (NGC4590)Globular Cluster33600-26:4512h 39m 5
Messier 83 (NGC5236)Spiral Galaxy14700000-29:5213h 37m 0
NGC 4993Elliptical or Lenticular Galaxy130 Million LY-23d 23` 413h 09m 47m 2
Penguin Galaxy (NGC 2936)Galaxy326 Million LY+2d 46` 0009h 37m 41

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