Main Page | See live article | Alphabetical index Hydra 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. Despite its size, Hydra contains only one reasonably bright star (Alphard, α Hya). It also contains the radio source Hydra A. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.