High in the sky at the moment are the beautiful Seven Sisters. That’s the popular name for the Pleiades star cluster (pronounced ‘Ply-adeez’), the brightest and most prominent star cluster in the sky. If you’ve found Orion, follow the three stars of Orion’s Belt upwards and you come to a bright star called Aldebaran, in the constellation of Taurus, the Bull. Keep going and you meet the Seven Sisters.
Even if your sky is light-polluted, the Pleiades stand out, despite none of them being particularly bright. Together they form a hazy patch of light that attracts the eye, and with reasonable eyesight you should be able to see that there are several stars there. But seven? Some people can easily count more, particularly in a dark sky. And in fact nine of them have names, given in ancient Greek times.
So how come there are Seven Sisters? Seven was always thought of as a good number, and it sort of fits the number that you can see. The girls themselves are those on the right, while Atlas and Pleione are their parents, keeping an eye on them. Well, you couldn’t trust those Ancient Greeks.
In fact the cluster has been attracting people’s attention for thousands of years. Star patterns on the most ancient of art, such as the cave paintings in Lascaux, France, are thought to be of the Pleiades.
All stars are created as members of a cluster within starbirth regions such as the Orion Nebula, but like many families they drift apart over time. The Pleiades are a particularly young cluster, so we still see them as a compact group. Long-exposure photos show them as seeming to be enveloped in blue mist. This is caused by patches of dust through which they happen to be passing, and the blue colour is a reflection of the colour of the very hot stars themselves.