tähtiryhmää

Tähtiryhmää is a Finnish term that translates to "star cluster" in English. Star clusters are groups of stars that are gravitationally bound together. They are a common sight in the night sky and are of great interest to astronomers for understanding stellar evolution and the structure of galaxies.

There are two main types of star clusters: open clusters and globular clusters. Open clusters are younger, less densely populated, and typically contain a few hundred to a few thousand stars. They are often found in the disk of galaxies, such as our own Milky Way. Globular clusters, on the other hand, are much older, more massive, and densely packed, containing tens of thousands to millions of stars. They are usually found in the halo of galaxies.

The stars within a cluster are generally thought to have formed at roughly the same time from the same giant molecular cloud. This shared origin makes star clusters valuable for studying stellar evolution because astronomers can observe stars of different masses that have aged together. By comparing stars within a cluster, scientists can learn how stellar properties change with mass and age.

The study of star clusters has contributed significantly to our understanding of the universe's age and composition. For instance, the oldest globular clusters are among the oldest objects in the Milky Way, providing clues about the early history of our galaxy.