If you guessed that I was referring to the Pleiades, you are correct.  The small open star cluster, Messier 45, is about 440 Light Years from Earth, relatively close for a star cluster.  We are able to see it with the naked eye in Autumn and Winter here in the Northern Hemisphere. The stars in the Pleiades are young and bright blue, meaning they are very massive and hot.  By young, I mean somewhere around a hundred Million Years, about 40 times younger than the Sun.  The smears of blue in the above photo show that the cluster is still...