Tähtiryhmiä

Tähtiryhmiä refers to star clusters, which are groups of stars that are gravitationally bound to each other. These celestial groupings are common throughout the universe and are classified into two main types: open clusters and globular clusters. Open clusters are typically younger, less dense, and found in the disk of galaxies, often containing a few hundred to a few thousand stars. They are generally more loosely organized and tend to disperse over time. Examples of open clusters include the Pleiades and the Hyades.

Globular clusters, on the other hand, are much older, denser, and more spherical in shape. They contain hundreds of thousands to millions of stars and are typically found in the halo of galaxies, orbiting the galactic center. These ancient structures are thought to have formed early in the history of a galaxy. The stars within globular clusters are very tightly packed, and they are very stable, remaining bound for billions of years. The Hercules Cluster (M13) and Omega Centauri are well-known examples of globular clusters.

The study of star clusters is important in astronomy for several reasons. Because the stars within a cluster are generally formed at roughly the same time from the same material, they provide valuable insights into stellar evolution. By observing stars of different masses within a cluster, astronomers can study how stars change throughout their lifespans. Their distances and ages can also be determined more easily than for individual, isolated stars, making them crucial for understanding the structure and history of the Milky Way and other galaxies.