M45, the Pleiades in Taurus, is probably the most known open cluster over the entire sky. Seven stars are normally visible with unaided eye under dark skies, so the cluster is also referred to as The Seven Sisters or The Seven Virgins. Very young in astronomical terms, the cluster is surrounded by the gas cloud from which are born the stars. The gas reflect the blue light emitted by the hot stars, and of consequence it appear on the pictures with this color.