This video shows the movement of blue straggler stars in globular clusters over time. Blue straggler stars are blue, bright stars, with a higher mass than the average for a cluster, and they are expected to sink towards the centre of a star cluster over time. Those closest to the cluster core are the first to migrate inwards, with more distant blue stragglers progressively moving inwards over time.
A new study using the NASA/ESA Hubble Space Telescope and the MPG/ESO 2.2-metre telescope at the ESO La Silla Observatory has shown that not all globular clusters evolve at the same rate. While all globular clusters are old (over 10 billion years), the stellar distribution within some remains youthful, with the blue straggler stars spread throughout the cluster. Others have aged prematurely, with the stars all located in the centre.
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NASA, ESA, L. Calçada, F. Ferraro (University of Bologna)