How do globular clusters differ from open clusters?

Globular clusters and open clusters differ significantly in their physical characteristics, age, and distribution within the galaxy.

Key Differences

• Structure and Size: Open clusters are generally loose, unsymmetrical groups containing from a dozen to a few thousand stars. In contrast, globular clusters are dense, symmetrical, and roughly spherical systems that contain thousands to hundreds of thousands of stars.12
• Age: Open clusters are typically young, often ranging from a few million to a few hundred million years old, though some can reach several billion years. Globular clusters are very ancient, with ages typically around 11 billion years.134
• Galactic Distribution: Open clusters are strongly concentrated along the plane of the Milky Way, often tracing the galaxy's spiral arms. Globular clusters, however, are typically found in the galactic halo and show little to no concentration toward the galactic plane.1356
• Stellar Population: Open clusters contain stars of various spectral classes and are often associated with gas and dust. Globular clusters are characterized by their ancient stellar populations and are notably associated with RR Lyrae stars, a type of variable star that is conspicuously absent from open clusters.16