"Cetus" is a constellation in the southern sky, but clearly visible in the northern sky too. Its name refers, in Greek mythology, to a sea monster or, in other words, the "whale". It is located in the region of the sky known as "the Water", along with other watery constellations such as Aquarius, Pisces, and Eridanus.
To rescue Cepheus' daughter, Andromeda from the gods' anger due to Cassiopeia' boast (see constellation Andromeda), Phoenix used a ship called "Whale".
Its star Omicron Ceti belongs to the "long period variables", which change brightness from 3rd to 4th magnitude over a period of 332 days.