Pleiades: The Seven Sisters Star Cluster

Pleiades - The Seven Sisters

Pleiades - The Seven Sisters

The Pleiades are an open star cluster found in the constellation Taurus and make their appearance in the night sky of the northern hemisphere in late autumn.  This small, bright blue star cluster is also referred to as The Seven Sisters.  How did they get their name?

The name, Pleiades, comes from ancient Greek mythology.  The Pleiades were the seven daughters of the titan Atlas and Pleione, who was a sea nymph.  The Pleiades, were themselves, nymphs.  Their names are Maia (the oldest), Electra, Taygete, Alcyone, Celaeno, Sterope, and Merope.  In the Pleiades star cluster, six of the stars shine brightly.  The seventh, which shines faintly is named after Merope who as legend has it was shamed because she had an affair with a mortal!  The star cluster most likely got this name because it was visible during the summer months in the Mediterranean where the ancient Greeks lived.

A nebula visible in the Pleiades

A nebula visible in the Pleiades

The Messier classification for this object is M45.  It contains roughly 1,000  bodies many of which are brown dwarfs.  The age of this young cluster is estimated to be between 75 and 150 million years and it is one of the nearest star clusters to Earth – lying a mere 135 parsecs (440 light years) away.  The Pleiades are moving too.  The image at the right shows a faint reflection nebula around the stars which was originally thought to be a remnant of the original cluster formation.  Current information indicates that the Pleiades are just passing through a dusty region of the universe.

If your eyesight is keen and the observing conditions are perfect, you would be able to see 14 stars with the naked eye.  Normally, you can see six.  How many can you count?

Image source:  NASA and STScI

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