Stories in the Sky

Our clear skies make for ideal conditions for star-watching. Last night the Diary was out as usual, spurred by a 'phone call from Tony Swift at Branault (for which many thanks), who said that there were signs of an aurora along the northern horizon. Nothing visible this side, sadly, but caught a couple of a fierce shooting star, and saw the constellation Cassiopeia high in the sky - and thereby hangs a good tale.

Cassiopeia was Queen of Ethiopia, married to King Cephus, and mother to the beautiful Andromeda. Unfortunately, a nasty sea monster, Cetus, was threatening their kingdom and had to be bought off by regular meals of fair Ethiopian maidens.

After a while the populace began to get a bit annoyed that their daughters were being eaten while beautiful Andromeda sat safely at home sipping sherbet in the palace. So, sadly, Cassiopeia and Cephus finally agreed that their child should be chained to a rock as a sacrifice to Cetus.

At this point, every Victorian painter who was worth his salt was on the scene to capture the action, resulting in hundreds of images of naked Andromeda and a rather scrawny monster cluttering up our museums. But most of the paparazzi left hurriedly when Cetus turned up, so they missed the climax of the story - the unexpected arrival of that great Greek hero, Perseus - who, of course, slew the monster, won the maiden, and married her.

Perseus is also famous for slaying the Medusa, another beautiful lady who so upset the goddess Athena that she turned her hair into serpents and made her face so terrible that anyone looking at it would be turned to stone - a problem Perseus got round by carrying a shield polished into a mirror.

To celebrate this, the star Algol is imagined as the eye in the Medusa's head, which Perseus is carrying - in fact, he used the head to turn the evil Cetus to stone. Algol is an 'eclipsing binary star', two stars, one dark, one light, whirling round each other with a period of two days and 21 hours so, from Earth, the Medusa's eye appears to wink at us.