THE DOLPHIN"), in astronomy, a constellation of the northern hemisphere, mentioned by Eudoxus (4th century B.C.) and Aratus (3rd century B.C.); and catalogued by Ptolemy (10 stars), Tycho Brahe (10 stars), and Hevelius (14(14 stars). ry Delphini is a double star: a yellowish of magnitude 4, and a bluish of magnitude 5.