The seven sisters refer to The Pleiades (M45) star cluster. One of the most beautiful open clusters I know of. It is in the Constellation Taurus and it kind of resembles a small dipper in a way. Some people have mistaken this as the Little Dipper. There are more than 30 stars in this cluster, but only seen through a scope or good binoculars. The seven sisters refers to the 6 or seven stars that can be seen with the naked eye. Most folks can only pick out six. On a clear and dark night it is possible to see all seven. There are many names for this cluster. Also this cluster (M45) is known for the reflection nebulosity that are in front of the stars. Hence the beauty of this object.