Optical photograph of M45, the Pleiades open star cluster. The brighter stars of the cluster are embedded in a distinctive blue halo, caused by their starlight reflecting off dust particles in the cold gas around them. Only 400 light years from Earth, the Pleiades consists of some 300-500 stars, six or seven of which (insthe seven sistersins) are visible to the naked eye. 10 Jan, 1986. 6-inch, f/4 RFT, 15 mins, Fuji 400-D pushed to 1600.