A new study using NASA's Chandra X-ray Observatory indicates that globular clusters might be surprisingly less mature in their development than previously thought. Globular clusters are dense bunches of up to millions of stars that are found in the outskirts of galaxies, including the Milky Way. Understanding the nature of globular clusters is important as they are thought to contain some of the first stars to form in a galaxy.
Most estimates of their ages range from 9 to 13 billions of years old. A study of 13 globular clusters in the Milky Way shows that three of them have unusually large number of X-ray sources, or X-ray binaries, suggesting the clusters are middle-aged. Previously, these globular clusters had been classified as being in old age because they had very tight concentrations of stars in their centers, another litmus test of age used by astronomers.
The implication is that most globular clusters, including the other ten from the study, are not in middle age as previously thought, but are actually in adolescence. Besides improving the understanding of the basic evolution of globular clusters, this result has implications for understanding stellar interactions in dense environments. It also removes the need for exotic mechanisms - some involving black holes - that were thought to be needed to prevent the many middle-aged clusters from collapsing into old age.
