Star clusters come in two main types. Open clusters are collections of some of the youngest stars in the galaxy. These stars all form at about the same time, and are a good representation of the distribution of created star types. Globular clusters are collections of some of the oldest stars in the galaxy. Globular clusters can contain hundreds of thousands of stars in a "glob" that is only a few tens of light years across. More details about the different cluster types are included on the individual image pages.