Hydra constellation is the largest constellation in the sky and is located in the southern celestial hemisphere. It was first catalogued by the Greek astronomer Ptolemy in the 2nd century.
There are 13 stars with known planets and seven named stars in the constellation of Hydra. The names, as approved by the International Astronomical Union (IAU), are Alphard, Ashlesha, Felis, Lerna, Minchir, Ukdah and Zhang. The brightest star in Hydra constellation is Alphard with an apparent magnitude of 1.98.
Two meteor showers associated with the constellation of Hydra — the Alpha Hydrids and the Sigma Hydrids. The Sigma Hydrids peak on December 6 and are a very active shower with an unknown parent body. The Alpha Hydrids are a minor shower that peaks between January 1 and 7. Hyrda also contains three Messier objects — Messier 48, Messier 68 and Messier 83.
History and Mythology of the Hydra Constellation
The Greek constellation of Hydra is an adaptation of the Babylonian constellation MUL.DINGIR.MUŠ, which was one of the two Babylonian constellations that represented a serpent and loosely corresponded to Hydra.
The shape of Hydra represents a twisting snake, and so it features as such in some Greek myths. It is usually associated with the second of Heracles’ labours in Greek mythology. Hydra was a giant multi-headed creature fathered by Typhon and Echidna, who was half-woman, half-serpent. The dragon Ladon was Hydra’s brother and is represented by the constellation of Draco.
According to legend, if one of the Hydra’s heads was cut off, two more would grow in its place. However, Hercules’ nephew, Iolaus, seared the necks with a torch to prevent them from growing back and thus enabled Hercules to overcome Hydra.
In another myth, Hydra is associated with a water snake that a crow served Apollo 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.
Location of the Hydra Constellation
The constellation of Hydra is the largest of the 88 modern constellations, occupying an area of 1303 square degrees in the night sky. The constellation lies in the second quadrant of the southern hemisphere (SQ2) and can be seen at latitudes between +54° and -83°. Its right ascension is 8h –15h and its declination is −20°. It is best seen at 9pm during the month of April.
Hyra’s neighboring constellations are Antlia, Cancer, Canis Minor, Centaurus, Corvus, Crater, Leo, Libra, Lupus, Monoceros, Puppis, Pyxis, Sextans and Virgo. It belongs to the Hercules family of constellations, along with Aquila, Ara, Centaurus, Corona Australis, Corvus, Crater, Crux, Cygnus, Hercules, Lupus, Lyra, Ophiuchus, Sagitta, Scutum, Sextans, Serpens, Triangulum Australe and Vulpecula.
Alphard, also known as Alpha Hydrae, is the brightest star in the constellation of Hydra and has an apparent magnitude of 2.0. It has the stellar classification K3 II-III, which makes it halfway between an orange giant and bright giant.
Alphard has a mass that is three times that of the Sun and a radius that is 50 times that of the Sun. It is located 177 light years away from the Sun and is believed to be around 420 million years old.
The name Alphard is derived from the Arabic al-fard, which means “the solitary one.”
Gamma Hydrae is the second brightest star in Hyrda and has an apparent magnitude of 2.993. It is a yellow giant, with the stellar classification of G8 III. It has a mass that is three times that of the Sun and a radius that is 13 times that of the Sun. Gamma Hydrae is also 115 times more luminous than the Sun, although it is much younger.
Gamma Hydrae is thought to be around 372 million years old and is located 133.8 light years away from Earth.
Zeta Hydrae is the third brightest star in Hydra and has an apparent magnitude of 3.10. It is located around 167 light years away from us and is believed to be around 400 million years old.
Zeta Hydrae has the stellar classification G9 II-III and is an evolved giant in the luminosity class between a giant and bright giant. Its mass is 4.2 times that of the Sun and its radius is 18 times that of the Sun. It is also 132 times more luminous than the Sun.
Beta Hydrae is a binary star with a combined apparent magnitude of 4.276, although it varies by 0.04 magnitudes over a period of 2.344 days. The star is located around 370 light years away from the Solar System. The primary component in Beta Hydrae is a giant Bp star classified as an alpha-2 Canum Venaticorum type variable.
Delta Hydrae is a binary star with the stellar classification of A1V, which makes it a white dwarf. It has an apparent magnitude of 4.14 and is about 17 times more luminous than the Sun. It is also approximately 179 light years away from Earth and is sometimes known as Lisan al Shudja or Lingua Hydri, which means “the tongue of the snake”.
Epsilon Hydrae is a multiple star system that consists of at least four stars, located around 129 light years distant from Earth.
The main component is the binary star Epsilon Hydrae AB, with the stellar classification of G5 III + F0V making it a yellow giant and a yellow white dwarf. It has an apparent magnitude of 3.38 and the stars have an orbital period of 15 years. They are also separated by 0.2 arc seconds.
The primary component is Epsilon Hydrae A and is 67 times more luminous than the Sun. Epsilon Hydrae C is a spectroscopic binary star of the spectral type F5. It is separated from the main pair by 3 arc seconds and has an apparent magnitude of 7.5. It has a period of 9.9047 days and orbits the main pair with a period of 870 years.
Epsilon Hydrae D is believed to be gravitationally bound to the Epsilon Hydrae system because it shares a common proper motion with the other stars. It is separated from the main pair by 19 arc seconds and has an estimated orbital period of 10,000 years.
27 Hydrae is an evolved yellow giant star with the stellar classification G8III-IV. It has an apparent magnitude of 4.82 and is located 243.4 light years away from the Sun. It is thought to have a low-mass companion, an M class dwarf, and a substellar companion orbiting it with a period of 9.3 years.
Minchir, also known as Sigma Hydrae, is an orange giant of the stellar classification K1III with an apparent magnitude of 4.44. Its name is derived from the Arabic Minkhir al-Shuja, which means “the nostril of Hydra”. It is located 353 light years away from the Sun.
R Hydrae is a red giant located 410 light years away. It has an apparent magnitude that changes from 3.5 to 10.9 over a period of 389 days. It is a Myra-type variable star, which is a red pulsating variable star in the late stage of evolution, with the stellar classification of M7IIIe.
V Hydrae is one of the reddest stars in the night sky with a B-V colour index of +5.5. It is a carbon star with the stellar classification C9I and is classified as a semi-regular variable, with its apparent magnitude ranging from 7.0 to 11.5 over a period of about 18 years, with a sub-period of 530 days. The star is located around 1,300 light years away from us.
U Hydrae is a carbon star and one of the few carbon stars that can be seen without binoculars. A variable star, its magnitude ranges from 4.8 and 5.06 over a period of 114.8 days. It is approximately 677 light years away from Earth and belongs to the spectral class C.
Nu Hydrae is an orange giant star with an apparent magnitude of 3.115. It has a radius 21 times that of the Sun and is 151 times more luminous than the Sun. It is located 144 light years from the solar system, near the border with Crater constellation. Nu Hydrae is also a known x-ray source.
Pi Hydrae is an orange star halfway between the subgiant and giant stage of evolution, giving it the stellar classification of K1 III-IV. It can be seen without binoculars and has a visual magnitude of 3.25. It has a mass that is 2.45 that of the Sun and 12-13 times the Sun’s radius. This star is located 101 light years away from Earth.
Deep Sky Objects
Messier 48, also known as M48 or NGC 2548, is an open star cluster that was discovered by Charles Messier in 1771. It has an apparent magnitude of 5.5 and can be seen without binoculars under good conditions. It is thought to be about 300 million years old and is approximately 1,500 light years distant from Earth.
Messier 68, also known as M68 or NGC 4590, is a globular cluster that discovered by Charles Messier in 1780. It has an apparent magnitude of 9.67 and is approximately 33,600 light years distant from the Solar System.
The Hydra Cluster is a galaxy cluster that is 190.1 million light years away from the Solar System. It contains 157 bright galaxies, the largest of which are the ellipticals NGC 3309 and NGC 3311 and the spiral galaxy NGC 3312. It spans 10 million light years and the galaxies are all about 150,000 light years in diameter.
Hydra Cluster is part of the larger Hydra-Centaurus Supercluster, which is approximately 158 million light years distant from the Sun. It contains galaxies from the constellations of Hydra, Norma and Centaurus.
Southern Pinwheel Galaxy
The Southern Pinwheel Galaxy, also known as Messier 83, M83 or NGC 5236 is a barred spiral galaxy that bears a resemblance to the Pinwheel Galaxy in Ursa Major constellation. The galaxy was discovered by the French astronomer Nicolas Louis de Lacaille on February 23, 1752.
It has a visual magnitude of 7.54 and is one of the nearest and brightest barred spirals discovered. It is located 14.7 million light years away from the Sun and can be observed with binoculars. Six supernovae have been observed in the galaxy in the last century.
Ghost of Jupiter
Ghost of Jupiter, also known as NGC 3242 or Caldwell 59, is a planetary nebula that was discovered by the German-born British astronomer William Herschel on February 7, 1785. It has an apparent magnitude of 8.60 and can easily been seen in amateur telescopes. It is approximately 1,400 light years away from us.
Tombaugh’s Globular Cluster
Tombaugh’s Globular Cluster, also known as NGC 5694 or Caldwell 66, is one of the oldest known globular clusters, discovered by William Herschel in 1784. It is thought to have formed almost 12 million years ago and is located in the Milky Way galaxy. It has an apparent magnitude of 10.2.
NGC 3109 is a spiral or irregular galaxy that was discovered by John Herschel on March 24, 1835. It has an apparent magnitude of 10.4 and is approximately 4.3 million light years away from us.
It is a Magellanic type irregular galaxy, but could also be a small spiral galaxy. NGC 3109 is tidally interacting with the Antlia Dwarf — the dwarf elliptical galaxy located in Antlia constellation. As a result of the interaction, NGC 3109 has a warped disk. It is also notable for containing a large number of planetary nebulae and a considerable amount of dark matter.
NGC 3621 is a spiral galaxy with a flat disc permeated by dark lanes of material and with prominent spiral arms where young stars are forming in clusters. However, while most spiral galaxies have a central bulge — a large group of old stars packed in a compact, spheroidal region — NGC 3621 doesn’t. This makes it a pure-disc galaxy.
It has an apparent magnitude of 10.0 and is approximately 22 million light years distant from the Solar System. It is thought to have a small mass, around 20,000 times that of the Sun and can easily be observed in moderate-sized telescopes.
NGC 3054 is an intermediate spiral galaxy that was discovered by the German-American astronomer Christian Heinrich Friedrich Peters in 1859. It has an apparent magnitude of 12.4. In 2006, a supernova, SN 2006T, was observed in the galaxy.
NGC 5078 is a spiral galaxy with an apparent magnitude of 11.8. It is located around 94 million light years distant from the Solar System.
NGC 3314 is a pair of overlapping spiral galaxies which are not physically related. They have a visual magnitude of 12.5 and are 117 and 140 million light years distant. NGC 3314a is the galaxy in the foreground and appears face-on. The NGC 3314b is the galaxy in the background.
NGC 4980 is a spiral galaxy with a slightly deformed shape. However, here is no evidence of tidal interactions with another galaxy, as there are no other galaxies nearby. It is located around 80 million light years from Earth.
ESO 510-G13, also known as PGC 49473, is a spiral galaxy with an apparent magnitude of 13.4. It is located approximately 150 million light years distant from our Solar System.
ESO 510-G13 has a heavily warped cloud of dust around the equator. This suggests it may have interacted with another galaxy at some point in the past.
Some Images created with the NightVision app – https://www.nvastro.com/nvj.html
Some Images created with the Stelvision Sky Map https://www.stelvision.com/en/sky-map/
Hydra 1 – https://starregistration.net/constellations/hydra-constellation.html
Hydra 2 – https://www.universetoday.com/20930/hydra/
Alphard – http://www.astronomytrek.com/star-facts-alphard/
Gamma Hydrae – https://theskylive.com/sky/stars/gamma-hydrae-star
Zeta Hydrae – https://theskylive.com/sky/stars/zeta-hydrae-star
Minchir – https://theskylive.com/sky/stars/minchir-sigma-hydrae-star
Messier 48 – https://en.wikipedia.org/wiki/Messier_48
Hydra Cluster – https://apod.nasa.gov/apod/ap120512.html
Southern Pinwheel Galaxy – https://en.wikipedia.org/wiki/Messier_83
Ghost of Jupiter – https://www.nasa.gov/content/ghost-of-jupiter-nebula/