Starwatch: track Cetus, the sea monster, sprawling across the night sky

This week, track down the constellation Cetus, variously referred to as the whale or sea monster. It is one of the faint constellations, but it sprawls across the sky, taking up roughly 1,230 square degrees, which makes it the fourth largest of the 88 modern constellations. Although it lacks bright stars, there is something hypnotic about tracing its faint outline across the sky. The chart shows the view looking south-southeast from London on 17 November at 20:00 GMT. However, the view will not change much all week. Since it lies close to the celestial equator, Cetus is visible in northern and southern hemispheres. In classical Greek mythology, Cetus represents the sea monster sent by Poseidon to wreak havoc on the kingdom of King Cepheus and Queen Cassiopeia. To protect their daughter, Andromeda, the hero Perseus turned Cetus into stone with the head of the gorgon Medusa. The constellation does contain one true astronomical gem: Omicron Ceti or Mira. This variable star rises and falls in brightness every 330 days or so. At its faintest, it is invisible to the naked eye. It is now close to its minimum brightness, so star watchers should keep an eye open for it to return to visibility in the coming months.