M 45 is commonly referred to as
the Pleiades, also the Seven Sisters. In Japanese culture, it is
known to as Subaru ("coming together"). It lies in the
constellation of Taurus. At a distance of 425 light years, it is
one of the closest star clusters to us. It is composed of type B
stars that are between 75 and 150 million years old, approximately
1/50 the age of our sun.
It was believed that the nebulae
around the stars were remants of the star cluster formation. We
now know that this nebulosity is unrelated dust through which the
stars' light passes.