Open Clusters as a Record of the Past

The Galactic open cluster population has long been used as a probe of the structure of the Galactic disk and a timeline for studying its evolution. With ages that range up to 12 billion years and positions that span a large range of Galactocentric distances, the open clusters provide a broad sample with which to investigate issues such as the history of star formation in the Galaxy, the chemical evolution of the disk, and the competing influences of cluster formation and disruption that mold the properties of the current cluster population. This revised version was published online in July 2006 with corrections to the Cover Date.