Sterrenhopen

Sterrenhopen, the Dutch term for star clusters, are gravitationally bound assemblies of stars that originate from the same molecular cloud and share a common origin. They range in age from a few million to several billion years. In astronomy, star clusters are typically categorized into two main types: open star clusters and globular clusters. Open clusters are relatively young, loosely bound, and contain tens to thousands of stars that lie primarily in the disks of galaxies. Globular clusters are older, densely packed, and contain hundreds of thousands to millions of stars distributed in roughly spherical halos around galactic centers.

Formation and evolution: Most stellar clusters form inside giant molecular clouds when regions collapse under gravity. Over time, internal dynamics and external tidal forces erode and disperse open clusters, although some survive for several hundred million years. Globular clusters are among the oldest objects in galaxies, with ages exceeding 10 billion years.

Properties: Clusters provide laboratories for stellar evolution because their stars share age and chemical composition. Their distance is often determined by main-sequence fitting or other techniques using the cluster's Hertzsprung-Russell diagram. They appear as visible fuzzy patches in distant galaxies, while many nearby open clusters resolve into individual stars with telescopes.

Distribution and examples: In the Milky Way, thousands of open clusters are known, concentrated in the spiral arms; globular clusters populate the halo. Notable examples include the Pleiades and Hyades as nearby open clusters, and M13 or Omega Centauri as well-known globular clusters.

See also: star cluster, open cluster, globular cluster, Hertzsprung-Russell diagram.