From the April 2010 issue

Why don’t globular clusters ultimately collapse, rather than getting old and stable?

Stefano Odoardi, Denver
By | Published: April 26, 2010
m80 globular cluster
One of the densest globular clusters in the Milky Way, M80 is located roughly 28,000 light-years from Earth and holds hundreds of thousands of stars.

What keeps these clusters from collapsing is the angular momentum of the stars as they orbit the cluster’s center of mass. It’s the same physics that keeps the solar system from collapsing.