Pleiades open cluster. The Pleiades open star cluster (NGC 1432), or "seven sisters", lies about 400 light years away in the constellation of Taurus. The cluster contains hundreds of stars in a spherical volume of space about 100 light years in diameter. Six of these are easily visible to the naked eye, five of which are shown in this photograph. The stars in the cluster range from old red stars to hot young blue stars. The six brightest are all young stars under 50 million years old. The blue haze around some of the stars is caused by a nebula of dust that reflects the stars' light.