tähtijoukoiksi

Tähtijoukoiksi is a Finnish term that translates to "star clusters" or "star groupings" in English. In astronomy, it refers to a collection of stars that are gravitationally bound together. These stars typically form from the same giant molecular cloud and thus share a similar age and chemical composition. Astronomers classify star clusters into two main types: open clusters and globular clusters.

Open clusters are generally younger and less densely populated. They contain a few hundred to a few thousand stars and are often found in the spiral arms of galaxies, including our own Milky Way. The Pleiades and the Hyades are well-known examples of open clusters. These clusters tend to disperse over time as gravitational interactions with other stars and gas clouds loosen their bonds.

Globular clusters, on the other hand, are much older, more massive, and more tightly bound. They can contain hundreds of thousands to millions of stars packed into a spherical region. Globular clusters are typically found in the halo of a galaxy. They are among the oldest stellar systems in the universe, with ages often exceeding 10 billion years. Omega Centauri and Messier 13 are prominent examples of globular clusters. Their dense, spherical nature suggests a strong gravitational cohesion that has lasted for eons. Studying both types of star clusters provides valuable insights into stellar evolution, galaxy formation, and the history of the universe.