Hydrus

Origin

Hydrus, a small southern constellation, represents a lesser-known male water snake.Hydrus was invented in the early 1600s with a prehistory in the 1590s. When Dutch navigators first extended the ancient constellation of the River (now: Eri) further south and used its curley line for star hopping to the south pole (as depicted in Bayer’s Uranometria 1603), but later noticed that Ptolemy states the brightest star is at the end of the River. As the extended River-constellation ended at Achernar, the rest of the curley line to the south pole needed another name: Hydrus. It was originally translated “Lesser Water Snake” in Dutch but later coined “Male Watersnake” by Lacaille in the 1750s. Lacaille, placing a contemporary invention for navigators, the octant, at the south pole cut off the tail tip of the original Hydrus definition. However, because of its position in the southern hemisphere, Hydrus is often challenging to observe from northern latitudes.

Bright Stars

In terms of bright stars, Beta Hydri is a yellow star of magnitude 2.8. It shines as the constellation's brightest, located around 24 light-years away, and Gamma Hydri is another notable bright star which varies between magnitude 3.26 and 3.33.

Photo of the constellation Hydrus produced by NOIRLab in collaboration with Eckhard Slawik, a German astrophotographer. The annotations are from a standardized set of 88 western IAU constellations and stick figures from Sky & Telescope. Please find here a non-annotated version of the image.

Credit: E. Slawik/NOIRLab/NSF/AURA/M. Zamani