Explanation: A globular cluster is a system of about one million stars that together orbit a galaxy. One of the brightest globular clusters in our Milky Way galaxy is the pictured M15, the fifteenth object on Messier's list of diffuse objects on our sky. Most stars in globular clusters are older and redder than our Sun, which is about 5 billion years old.

For more information on M15 see The Electronic Universe Project's write-up.

Many images of Messier objects can be found in The Electronic Universe Project's The Galaxy Gallery: Messier Objects.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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