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 . Open clusters like M50, shown above , typically contain hundreds of stars , many of which are bright, young, and blue. M50 lies about 3000 light-years from Earth and is about 20 light years across.
Open clusters tend to have irregular shapes and are mostly found in the plane of our Galaxy .
Many stars like our Sun were formed in open clusters . The stars in this cluster all formed together about 150 million years ago. The bright young stars in M11 appear blue. Open clusters , also called galactic clusters, contain fewer and younger stars than globular clusters . Also unlike globular clusters, open clusters are generally confined to the plane of our Galaxy .