Delphinus, the Dolphin

Delphinus, the Dolphin, is a small northern constellation, one of Ptolemy's forty-eight, its compact group of stars forming a pleasing figure of a leaping dolphin near the celestial equator, beside the Milky Way. In Greek myth it is the dolphin sent by Poseidon to persuade the sea-nymph Amphitrite to become his queen, rewarded with a place in the sky, or the dolphin that rescued the poet Arion. Two of its stars bear the curious names Sualocin and Rotanev, a nineteenth-century astronomer's Latinised name spelled backwards. In astronomical tradition the constellation is a pattern of stars rather than a zodiac sign, and its watery nature groups it among the water-associated figures. These are the features of Delphinus as the classical and modern traditions describe it, distinct from any astrological reading of the small region of sky it occupies.

Delphinus is generally reckoned the more securely ancient of the sky's two small water-creature figures near Aquila and Pegasus, distinguishing it from later seventeenth-century additions in the surrounding sky; it appears already in Aratus's third-century-BCE Phaenomena, one of the oldest surviving descriptions of the constellations, centuries before Ptolemy's own systematic catalogue.