Starwatch: the Garnet Star, Cepheus’s red gem, is a thing of beauty

Known as Cepheid variables, stars in constellation are used to measure distances to nearby galaxies

This week, we’re going to concentrate on an often overlooked northern constellation. Cepheus is named after the king of ancient Aethiopia in Greek mythology. Part of the Perseus myth, Cepheus is married to Cassiopeia and is the father of Andromeda, the princess whom Perseus saved from the sea monster Cetus.

Cepheus is one of the 48 constellations listed by the astronomer Ptolemy in the second century. The constellation is easy to miss as it contains only moderately bright to faint stars, but its shape is distinctive once located.

The brightest star is Alderamin, derived from the Arabic phrase meaning “right arm”, which means that the king is upside down on the sky, or facing away from us.

The most significant star is Delta Cephei (∂ Cep). Located almost 1,000 light years away from Earth, it was observed to pulsate by John Goodricke in 1784. Such pulsating stars, called Cepheid variable stars, are now used to measure distances to nearby galaxies. The most beautiful star is the Garnet Star, so-called because of its deep red colour.

The chart shows the view looking north-north-west from London at 20.00 GMT on 14 March. Unfortunately, the constellation is not visible from much of the southern hemisphere.