The Hydrus constellation is home to four stars with known planets and no named stars. The brightest star in the constellation is Beta Hydri, with an apparent magnitude of 2.80, and is also the closest star in the constellation to Earth, located only 24.38 light years away.
There are no Messier objects in Hydrus nor are any meteor showers associated with the constellation.
History and Mythology Of The Hydrus Constellation
The constellation of Hydrus was created by Plancius from the observations of Dutch sailors Frederick de Houtman and Pieter Dirkszoon Keyser in the late 16th century. It represents the sea snakes they would have seen on their voyages.
Nicolas Louis de Lacaille gave the constellation the name l’Hydre Mâle to emphasize the difference in gender between Hydrus and Hydra on his planisphere of the southern skies.
Because Hydrus is a southern constellation, it wasn’t visible to the ancient Greeks or Romans.
Location Of The Hydrus Constellation
Hydrus is the 61st largest constellation in the night sky and occupies an area of 243 square degrees. It is located in the first quadrant of the southern hemisphere (SQ1) and can be seen at latitudes between +8° and -90°.
Its right ascension is 00h 06.1m to 04h 35.1m and its declination is −57.85° to −82.06°. It is best seen at 9pm, during the month of November.
Hydrus’ neighboring constellations are Dorado, Eridanus, Horologium, Mensa, Octans, Phoenix, Reticulum and Tucana and it belongs to the Johann Bayer family of constellations, along with Apus, Chamaeleon, Dorado, Grus, Indus, Musca, Pavo, Phoenix, Tucana and Volans.
Beta Hydri is the brightest star in the constellation and has an apparent magnitude of 2.80. It is a yellow subgiant, with the stellar classification of G2 IV, and is located around 24.33 light years away from the Sun. It is one of the oldest star in the Sun’s neighbourhood, as well as the nearest subgiant star to the solar system.
Beta Hydri has a mass that is 108 percent of the Sun’s and a radius that is 181 percent. It is also 3.494 times more luminous than the Sun.
Alpha Hydri also known as the Head of Hydrus, is the second brightest star in the constellation and has an apparent magnitude of 2.90. It is a yellow-white subgiant with the stellar classification of F0 IV and is located around 71.8 light years away from us, to the south-west of Achernar, the ninth brightest star in the sky.
Alpha Hydri is twice as massive and 80 percent larger than the Sun. It is thought to be around 810 million years old. It is 32 times more luminous than the Sun.
Gamma Hydri is the third brightest star in Hydrus and has an apparent magnitude of 3.24. It is a luminous red giant belonging to the spectral class M2III and is located around 214 light years away from Earth, lying at the southeastern apex of the triangle asterism that dominates the constellation.
It has a radius that is 60 times that of the Sun and is 655 times more luminous.
Delta Hydri is a white dwarf of the spectral type A3V and has an apparent magnitude of 4.08. It is located around 140 light years away from us.
Epsilon Hydri is a a blue-white giant with the stellar classification of B9III and an apparent magnitude of 4.06.
Nu Hydri is an orange giant star with the stellar classification K3III and a visual magnitude of 4.75. It is located approximately 339 light years away from Earth.
Zeta Hydri is located around 284 light years away from the Solar System and has an apparent magnitude of 4.83. It belongs to the spectral class A2IV-V, which means that it is a white star halfway between the subgiant and dwarf stage of evolution.
Eta-2 Hydri is a yellow giant of the spectral type G8.5III, with an an apparent magnitude of 4.68. It is located around 219 light years distant away the Solar System. In 2005, an extrasolar planet, Eta-2 Hydri b, was discovered orbiting the star with an orbital period of 711 days.
GJ 3021, also known as 2 G. Hydri, is a double star with an apparent magnitude of 6.59. It is located around 57 light years away from us. The primary component in the system, GJ 3021 A, is a solar analogue. It is a yellow dwarf with the stellar classification of G6 V. The secondary component in the system, GJ 3021 B, is a class M4 red dwarf.
In 2000, an extrasolar planet, GJ 3021 b, was confirmed to be orbiting the primary with a period of 133.71 days. It is a Jovian planet with a mass at least 3.37 times that of Jupiter.
HD 10180 is a yellow dwarf with the stellar classification of G1V and an apparent magnitude of 7.33. It is located approximately 127 light years away from the Solar System. It is a Sun-like star, a mass about 6 percent greater than the Sun’s and a radius that is 120 percent of the Sun’s. HD 10180 is also 149 percent more luminous than the Sun.
This Yellow Dwarf has a large planetary system, with at least seven planets observed orbiting the star, making it the largest exoplanetary system known.
Deep Sky Objects
NGC 1511 is a spiral galaxy with an apparent magnitude of 11.0. It was discovered by the British astronomer John Herschel on November 2, 1834.
NGC 1466 is a globular cluster with an apparent magnitude of 11.4. It is located around 14,000 light years away from us and was also discovered by John Herschel in 1834. It is notable for the large number of RR Lyrae type variable stars it contains, the brightest of which are magnitude 19.
NGC 1473 is an irregular galaxy with an apparent magnitude of 13.0. It was also discovered by John Herschel in 1834.
IC 1717 was discovered by the Danish astronomer John Louis Emil Dreyer and was described as an excessively small and faint, much extended object located near the yellow giant star Eta-2 Hydri. Despite the fact he gave coordinates, the object can no longer be seen. It was thought possibly to be a supernova or the site of a planet that was destroyed.
- The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is “Hyi”.
- The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 12 segments.
- As one of the deep southern constellations, Hydrus remains below the horizon at latitudes north of the 30th parallel in the Northern Hemisphere, and is circumpolar at latitudes south of the 50th parallel in the Southern Hemisphere.
- Hydrus culminates at midnight around 26 October.
- 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/
- Hydrus 1 – https://starregistration.net/constellations/hydrus-constellation.html
- NGC 1511 – https://cgs.obs.carnegiescience.edu/CGS/object_html_pages/NGC1511.html
- Hydrus 2 – https://in-the-sky.org/data/constellation.php?id=44
- NGC 1466 – https://en.wikipedia.org/wiki/NGC_1466
- NGC 1473 – https://theskylive.com/sky/deepsky/ngc1473-object