- a star cluster is a large group of stars whose members are held together by mutual gravitational attraction.
- not to be confused with galaxies that are also gravitationally bound groups of stars.
- to distinguish these space objects, keep in mind that galaxies are way more massive.
- a typical (globular) star cluster contains a mass of 100,000 Suns, while the Milky Way galaxy has nearly 1 trillion solar masses.
Star clusters are divided into two main types:
– globular and open ones.
– the difference between them is significant.
What is a globular Cluster?
Globular clusters are old, usually spherical groups of stars that can contain from a few thousand to a million members.
What is an Open Cluster?
Open clusters, on the contrary, are much younger and smaller;
– they contain hundreds or thousands of stars.
– these star clusters tend to lose a gravitational bound over time and spread out, becoming loosely clustered.
– due to this, they are more irregular in shape.
– you can notice this by observing the Pleiades (M45), Hyades, or Beehive Cluster (M44).