Cetus, the Sea Monster, is a southern constellation that is visible in the fall. It is also often called the Whale. Cetus is located in the region of the sky called the "Sea" or the "Water" that is home to Aquarius (the Water Bearer), Pisces (the Fishes) and Eridanus (the River), which are all water-related constellations. Although Cetus is not technically an ecliptic constellation because the line of the ecliptic does not actually go through it, the ecliptic lies just 8.5 arcminutes away from one of its northwest corners. Because the Sun subtends an apparent angle of 30 arcminutes, part of the Sun does pass through that corner of Cetus. This currently occurs on March 27 and March 28. The planets can also pass through Cetus. In Greek mythology, Cetus is the sea monster who was killed by Perseus when he rescued the Princess Andromeda, who had been chained to a rock for the monster. Andromeda's mother, the queen Cassiopeia, had angered Poseidon, the sea god, by claiming that Andromeda was more beautiful than Poseidon's Nereids, the sea nymphs. To appease Poseidon, Cassiopeia and her husband Cepheus, the king, had to sacrifice Andromeda to Cetus, who had been sent by Poseidon to ravage their land. Andromeda was rescued by Perseus, who happened to be passing by. Perseus later married Andromeda.