Pleiades Star Cluster - Astronomy Picture of the Day http://antwrp.gsfc.nasa.gov/apod/ap950620.html "The Pleiades star cluster, M45,... consists of many bright, hot stars that were all formed at the same time within a large cloud of interstellar dust and gas. The blue haze that accompanies them is due to very fine dust which still remains and preferentially reflects the blue light from the stars."