Odd Star

Globular clusters are huge groups of stars held together in a spherical formation by their mutual gravitational attraction.  Because such clusters are physical associations, all the stars in a given cluster are about the same age.

Messier 4 is  a well-known globular cluster among astronomers, amateur and professional.  Recently, however, professiomal astronomers have found an odd star in M4.  While the cluster is made up of older stars, one star seems much younger.  Astronomers tell the age of stars by their chemical composition.  The star in question still has a component of lithium, an element that is usually used up early in a star's life.  So, either this star is very young, or its lithium is somehow replenished.  Either way, it's interesting.