The Pleiades, or Seven Sisters, is the most well-known star cluster in the night sky. It’s what’s known as an ‘open cluster’, which is a group of stars that form from the same huge cloud of dust and gas. As the cloud collapses under gravity, temperatures rise and stars begin to take shape, becoming loosely bound by their mutual gravitational attraction.
The Pleiades contains some 3,000 stars, all less than 100 million years old, making them mere babies compared to our Sun’s 4.6 billion years. The cluster’s name possibly comes from the Ancient Greek word plein, meaning ‘to sail’, because the first appearance of the cluster in the dawn sky each year heralded the start of the sailing season. It’s thought that the name Pleiades was later used in Greek mythology for the seven daughters of the titan Atlas and the sea nymph Pleione.
In the night sky, the Pleiades sits within the constellation of Taurus. It’s actually possible to see up to 14 of the stars with the naked eye in areas with no light pollution. You can see the Pleiades between October and April, but the best month to look for it is November, when it can be seen for the entire night.
To find the Pleiades, first locate the three stars in Orion’s Belt. During November, look above the eastern horizon from around 10pm. Draw an imaginary line going through the belt from left to right, and continue this line through Orion’s bow. This will direct you to the brightest star in Taurus: Aldebaran.
Past Aldebaran, in the same direction, is the Pleiades. It’s easily recognisable, because the positions of its five brightest stars make it look like a tiny version of the Plough. Once you’ve found it, grab a pair of binoculars if you have one, and take a closer look to reveal more of the cluster’s stars.
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