The whale constellation, also known as Cetus, is a large constellation located in the southern sky. It is one of the 88 modern constellations and was first catalogued by the Greek astronomer Ptolemy in the 2nd century. Cetus is associated with the mythological figure of the sea monster sent by Poseidon to devour Andromeda. The constellation contains several stars and deep sky objects, including the spiral galaxy Messier 77.