Hydra (constellation)

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Hydra
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Abbreviation	Hya
Genitive	Hydrae
Symbology	the Hydra
Right ascension	10 h
Declination	−20°
Area	1303 sq. deg. Ranked 1st
Number of stars (magnitude < 3)	2
Brightest star	Alphard (α Hya) (App. magnitude 1.98)
Meteor showers	????? ?????
Bordering constellations	Antlia Cancer Canis Minor Centaurus Corvus Crater Leo Libra Lupus (corner) Monoceros Puppis Pyxis Sextans Virgo
Visible at latitudes between +54° and −83° Best visible at 21:00 (9 p.m.) during the month of April

Hydra (IPA: /ˈhʌɪdrə/) is the largest of the 88 modern constellations, and was also one of the 48 constellations listed by Ptolemy. It should not be confused with Hydrus.

1 Notable features
2 Stars
3 Mythology
4 External links

[edit] Notable features

Hydra is the largest modern constellation, at 1303 square degrees. Despite its size, Hydra contains only one reasonably bright star, Alphard (α Hya, 30 Hya), which is of apparent magnitude 1.98.

R Hydrae is a Mira variable star that ranges in magnitude between 3.5, when it is easily visible to the naked eye, to 10.9, when a telescope is required to see it.

There are several double stars of interest in Hydra. Epsilon Hydrae (ε Hya) is a binary star 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 (Σ1270) consists of a pair of stars, magnitudes 6.4 and 7.4.

The constellation also contains the radio source Hydra A.

[edit] Stars

Stars with proper names:

Alphard [Alfard, Kalbelaphard] or Cor Hydrae (30/α Hya) 1.99

< قلب الفرد qalb al-fard Heart of the solitary one

(46/γ Hya) 2.99 Dhanab al Shuja or Cauda Hydrae

< ذنب الشجاع dhanab aš-šuga Tail of the Snake (lit. brave)

< Latin for Tail of Hydra

(4/δ Hya) 4.14 Mautinah or Mawtinah

< الموتنة am-mawtinah Circlet of Pearls (referring to the Hydra's head)

(11/ε Hya) 3.38 Ashlesha

< Vedic for "the Embracing One"

(16/ζ Hya) 3.11 Hydrobius

< υδροβιος hydrobios water-dweller (aquatic creature)

(43/ν Hya) 3.11 Sherasiph or Pleura

< ﻑالشراﺴ al-sharāsif The Ribs [of Hydra] (together with β Crt)

< πλευρά pleura side or ribs (of Hydra)

(49/π Hya) 3.25 Sataghni

< Sanskrit for a cannon-like weapon of war used in medieval India

(5/σ Hya) 4.45 Minhar al Shija [Al Minliar al Shuja, Minchir]

< منخر الشجاع minxar aš-šuga^c: Nostril of the snake (lit. brave)

(τ Hya) Ukdah (31/τ¹ Hya) 4.59 or (32/τ² Hya) 4.54

< عقدة ^cuqdah Knot

Stars with Bayer designation:

β Hya 4.29; 22/θ Hya 3.89; 7/η Hya 4.30; 35/ι Hya 3.90; 38/κ Hya 5.07; 41/λ Hya 3.61; 42/μ Hya 3.83; ξ Hya 3.54; ο Hya 4.70; 13/ρ Hya 4.35; 39/υ¹ Hya 4.11; 40/υ² Hya 4.60; χ¹ Hya 4.92; χ² Hya 5.69; φ Hya 4.91; φ¹ Hya 7.81; φ² Hya 6.01; 45/ψ Hya 4.94; 18/ω Hya 4.99; 6/a Hya 4.98; b¹ Hya 5.44; b³ Hya 5.23; 51/k Hya 4.78; 52/l Hya 4.97; 54/m Hya 5.15; 33/A Hya 5.56; C Hya 3.91; 12/D Hya 4.32; 58/E Hya 4.42; F Hya 4.63; G Hya 4.72; I Hya 4.76; 27/P Hya 4.80

Stars with Flamsteed designation:

1 Hya 5.61; 2 Hya 5.60; 3 Hya 5.72; 9 Hya 4.87; 10 Hya 6.13; 14 Hya 5.30; 15 Hya 5.55; 17 Hya 6.07; 17 Hya 6.67; 19 Hya 5.60; 20 Hya 5.47; 21 Hya 6.10; 23 Hya 5.24; 24 Hya 5.49; 25 Hya 7.35; 26 Hya 4.77; 28 Hya 5.60; 29 Hya 6.53; 34 Hya 6.40; 37 Hya 6.31; 44 Hya 5.08; 47 Hya 5.20; 48 Hya 5.77; 50 Hya 5.07; 55 Hya 5.61; 56 Hya 5.23; 57 Hya 5.76; 59 Hya 5.65; 60 Hya 5.83

Other notable stars:

HD 74156 7.62 – has 2 planets
HD 82943 6.54 – has 2 planets

[edit] Mythology

The constellation Hydra resembles a twisting snake, and features as such in some Greek myths. In Greek mythology, a crow serves Apollo. It is sent to fetch water, but it rests lazily on the journey, and after finally obtaining the water in a cup, takes back a water snake as well, as an excuse. According to the myth, 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, and Corvus, in the area of the sky known as the Sea.

The Hydra was also considered to be the Lernaean Hydra (as defeated by Heracles for one of his Twelve Labours) by the Greeks. Its position in the sky (below the ecliptic), together with the constellation Cancer (which lies near its head) may be the origin of parts of the myth.

The 48 Constellations listed by Ptolemy