Cluster Full of Black Holes May Be Spitting Out Stars
An anonymous reader shares a report: As we carefully map the stars of our Milky Way, we’re able to identify features that tell us of its history. These include local details, such as the stars that have passed through an area from which something would be able to detect Earth. And it includes far larger structures, like the trails of stars left behind by smaller galaxies that have merged with our own. But one feature we’ve discovered has been a bit confusing: trails of stars that are too small and thin to have come from a galaxy collision. There are dozens of them that we’ve not identified a source for. Their size suggests they came from a globular cluster, but there’s no obvious mechanism for these clusters to eject stars at a rate sufficient to generate this sort of stream. Now, a team of researchers has suggested a not-so-obvious mechanism: Over time, clusters may become dominated by black holes that eject all the stars.

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.

Read more of this story at Slashdot.

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