Composition:
Population I Stars
Lifespan
100 million yearsNumber of stars
1,000 to 10,000Notes:
Open (or galactic) clusters are physically related groups of stars held together by mutual gravitational attraction. They are believed to originate from large cosmic gas/dust clouds in the Milky Way, and to continue to orbit the galaxy through the disk. In many clouds visible as diffuse nebulae star formation takes still place at this moment, so that we can observe the formation of new young open star clusters.Example (on left): M44.
