Sometimes stars form in groups.  A star cluster is a congregation of stars that have a stronger gravitational attraction for each other, due to the fact that they are closer in proximity to each other compared to the general field of stars in the galaxy.  Clusters range from rich aggregates (Globular Clusters) of many thousand of stars to loose associations (Open Clusters) of only a few stars.  Scientists have found that all Globular Clusters are very old--perhaps 10 billion years.  They are tens of thousand of light years away from us.  Globulars are generally located in a halo above and below the plane of our galaxy.  Open Clusters, on the other hand, have a wide range of ages and may even be forming now.  They are not very distant from us-- within a few hundred light years.  Open Clusters are found in the spiral arms of our Galaxy.

To view the details on each Cluster, including how I imaged it, just click on the name or the image.