SAGITTA (" the arrow " or " dart ")  , in astronomy, a constellation of the northern hemisphere, mentioned by Eudoxus (4th century B.C.) and Aratus (3rd century B.e.), and catalogued by Ptolemy, Tycho Brahe and Hevelius, who each described 5 stars . The fable was that this constellation was one of the arrows with which Hercules killed the vulture which gnawed the liver of Prometheus . S . Sagittae is a short period variable, period 8.38 days, range in magnitude 5.6 to 6.4 .