Why are Open Clusters useful as temporal markers for Milky Way star formation history?
Because all stars formed simultaneously from the same material, they act as snapshots showing when and where star formation occurred recently.
The utility of open clusters for studying the Milky Way's evolution stems directly from their synchronized birth. Since all stars within an open cluster originate from the collapse of a single giant molecular cloud at virtually the same moment, they share identical initial chemical compositions and, critically, the exact same age. This uniformity allows astronomers to use these clusters as precise 'temporal markers.' By observing their distribution and age within the spiral arms, researchers can reconstruct the history of when and where star formation has recently taken place across the galactic disk.
