Definition of Eridanus
: a southern constellation that is visible stretching between the constellations of Orion and Phoenix and that is represented by the figure of a river How can you tell whether a galaxy is turned on or not? A team of astronomers set out to answer that question by making a series of detailed radio, infrared, optical, and spectroscopic observations of an unusual spiral galaxy in Eridanus. — Astronomy, August 1990
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First Known Use of eridanus
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