Globular clusters are dense groups of stars that orbit the Milky Way together. They’re held in association by their mutual gravity. Complex interactions will inevitably eject some of the stars, but not at an appreciable rate, which makes the clusters extremely long-lived. The researchers started their work, however, by looking at an unusual globular cluster called Palomar 5. It has both extended tails of lost stars, and its total mass is relatively small, making it diffuse compared to other clusters we’ve studied. The lower density makes it easier for Palomar 5 to lose stars, but it could also have been caused by past star loss, creating a bit of a chicken-and-egg problem. So, the researchers decided to model globular cluster evolution and try to find a model that could produce something that looks like Palomar 5. The researchers created a model that takes a cluster of stars and models their gravitational interactions with each other and the Milky Way as they orbit the galactic center. Thanks to some help from a cluster of GPUs and the right software, they were able to run these simulations for billions of years. By changing the parameters, they could find which factors were associated with clusters that ended up looking like Palomar 5.
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