The Pleiades nebulosity is caused by a chance encounter between an open cluster of stars and a molecular cloud . The Pleiades can be seen without binoculars from even the depths of a light-polluted city . The Pleiades contains over 3000 stars, is about 400 light years away, and only 13 light years across. Quite evident in the above photograph are the blue reflection nebulae that surround the bright cluster stars. Low mass, faint, brown dwarfs have recently been found in the Pleiades .
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