What is "hydrus"

Hydrus \Hy"drus\, n. [L., a water serpent; also, a certain constellation, Gr. "y`dros.] (Astron.) A constellation of the southern hemisphere, near the south pole.

Hydrus is a small constellation in the deep southern sky. It was first depicted on a celestial atlas by Johann Bayer in his 1603 Uranometria. The French explorer and astronomer Nicolas Louis de Lacaille charted the brighter stars and gave their Bayer designations in 1756. Its name means "male water snake", as opposed to Hydra, a much larger constellation that represents a female water snake. It remains below the horizon for most Northern Hemisphere observers.

The brightest star is the 2.8- magnitude Beta Hydri, also the closest reasonably bright star to the south celestial pole. Pulsating between magnitude 3.26 and 3.33, Gamma Hydri is a variable red giant some 60 times the diameter of our Sun. Lying near it is VW Hydri, one of the brightest dwarf novae in the heavens. Four star systems have been found to have exoplanets to date, most notably HD 10180, which could bear up to nine planetary companions.

Hydrus is a suite of Windows-based modeling software that can be used for analysis of water flow, heat and solute transport in variably saturated porous media (e.g., soils). HYDRUS suite of software is supported by an interactive graphics-based interface for data-preprocessing, discretization of the soil profile, and graphic presentation of the results. While HYDRUS-1D simulates water flow, solute and heat transport in one-dimension, and is a public domain software, HYDRUS 2D/3D extends the simulation capabilities to the second and third dimensions, and is distributed commercially.

The Hydrus (also known as Enhydros, Enidros, Hildris, Hydra, Idra, Idres, Ydre, Ydris, and Ydrus) is a creature from Medieval bestiaries. They were said to be found in the Nile River. While in the Nile, a crocodile would roll the hydrus in the mud before eating the smaller creature. However, once inside the crocodile's stomach, the hydrus would burst free from the stomach lining. In medieval Christian tradition, this bursting free from the crocodile became an emblem of the resurrection of Christ bursting free from Hell.

There is considerable confusion in applying the name hydrus and its variations to beasts. The root of the word itself refers to water, and this led to several beasts, mostly serpents, being so labeled. Isidore of Seville lists the hydros, a water snake that causes those bitten to swell up, the cure for which is the dung of an ox. The hydrus was also confused with the Hydra of the Hercules legend, some texts saying that it was a many-headed water dragon, living in the swamp of Lerna, that could grow new heads.

The modern constellation Hydrus is not included in the Three Enclosures and Twenty-Eight Mansions system of traditional Chinese uranography because its stars are too far south for observers in China to know about them prior to the introduction of Western star charts. Based on the work of Xu Guangqi and the German Jesuit missionary Johann Adam Schall von Bell in the late Ming Dynasty, this constellation has been classified under the 23 Southern Asterisms (近南極星區, Jìnnánjíxīngōu) with the names Snake's Tail (蛇尾, Shéwěi), Snake's Abdomen (蛇腹, Shéfù), Snake's Head (蛇首, Shéshǒu) and White Patched Nearby (附白, Fùbái).

The name of the western constellation in modern Chinese is 水蛇座 (shuǐ shé zuò), which means "the water snake constellation".

Hydrus is a small constellation in the southern sky.

Hydrus may also refer to:

• Hydrus (Chinese astronomy), constellations recognized in China
• Hydrus (legendary creature), a creature from Medieval bestiaries
• Hydrus (software), a software suite for simulating subsurface water flow
• SS Hydrus, a Great Lakes freighter