M45 the Pleiades, or Seven Sisters is an open star cluster containing middle aged hot stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky. The cluster is dominated by hot blue and extremely luminous stars that have formed within the last 100 million years. Dust that forms a faint reflection nebulosity around the brightest stars was thought at first to be left over from the formation of the cluster. For technical details look here : http://astrofarma.gr/en/m45
Farmakopoulos Antonis