Keith Wilson has had a lifelong interest in the night sky and has written for space and astronomy publications in the UK and USA. He lives under the dark night skies of the Isle of Gigha.
By Keith Wilson
Look high up towards the south-east in the early November night sky and you will find the star cluster known as the Pleiades or ‘seven sisters’.
The nickname ‘seven sisters’ comes from Greek mythology. The Pleiades were the seven daughters of Atlas, a Titan who held up the sky.
This cluster of stars in the constellation of Taurus are much younger than our Sun and contain several thousand stars although a powerful telescope is needed to see them all.
They were all born together in a huge cloud of dust and gas. When the cloud collapsed, temperatures rose and the stars began to take shape held together loosely by gravity.
You can use the constellation Orion in the south-east to help you find the Pleiades. Find the three stars in a row that make up Orion’s belt. Draw an imaginary line upward through these stars to the bright star Aldebaran then keep the line going and you will see the Pleiades cluster.
Although the star cluster is nicknamed the ‘seven sisters’, most people see just six, not seven Pleiades stars. This may be due to the seventh brightest star in the cluster being a complicated star which causes the star to vary in brightness.
The Pleiades stars were used as a method for testing eyesight in ancient times; a soldier who could see at least seven was given the job of scout or archer!
Over time, the Pleiades have served as a calendar for many civilizations. The Greek name Pleiades probably comes from a word meaning to sail.
In the ancient Mediterranean world, the day that the Pleiades cluster first appeared in the morning sky before sunrise announced the opening of the navigation season.
The Zuni of New Mexico call the Pleiades the ‘seed stars’, because the cluster’s disappearance in the evening sky every spring signalled the seed-planting season.
The Pleiades also have a spooky connection – the pagan All Hallow’s Eve – which evolved into our own Hallowe’en – was set to take place when the Pleiades star cluster reached its highest point in the night sky at midnight.