OB Association
Quick Summary
An OB association is a large, loose grouping of stars, primarily young, massive stars of spectral types O and B. These stars are significantly brighter than the Sun, with luminosities about 100,000 times greater. OB associations are considered the birthplaces of most stars, with about 90 percent originating in such groups.1
These associations are much more spread out than star clusters, as their members have not yet dispersed far from their common origin. They are typically found in the spiral arms of galaxies and can span hundreds of light-years in diameter, though they contain a relatively small number of stars, usually between 10 and a few hundred. The stars within an OB association are generally no more than 10 million years old, as massive stars consume their fuel rapidly.1
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