Monday, December 10, 2012

Know Your Seven Sisters

This is a great time to view the Seven Sisters open star cluster in the night sky. Look high in the west for a small cloud the size of the full moon. Upon closer examination your eye can catch the individual stars in the cloud and you can start counting. 1, 2, 3, 4, 5, 6... and maybe 7 stars (if you have really good eyesight) in the cluster.
These are the Seven Sisters, or Pleiades (their family name). They are the children of a Titan named Atlas (the guy that holds up the world) and a sea-nymph named Pleione. The names of the Seven Sisters are: Alcyone, Maia, Taygeta, Celaeno, Merope, Sterope, and Electra. On a clear night you can see Alcyone, Maia, Taygeta, Merope, and Electra along with one or both of their parents.
Most people with 20/20 vision can only make out 6 stars in the cluster. What happened to the 7th? One legend says that in the ancient Greek days (2500 years ago) they could see all seven. But one star suddenly got dimmer. To explain this phenomenon, the Greeks believed that one of the sisters (Electra in some stories, Merope in others) was sad and covered her face with her hands - thus shielding her beautiful light from the world.
With any binoculars you can see much more than 7 stars in the cluster. In total the cluster contains over 1,000 members resting about 440 light years away that were all formed from the same nebula. Click on the pictures for close-up views. Try to find them tonight and see how many you can catch.

"Seven Sisters" a painting by Helen Gerro